1
Q
Define ecology
A
the study of inter-relationships between organisms and their environment
2
Q
What sort of factors does the environment include?
A
- Biotic factors: Living factors
2. Abiotic factors: Non-living or physical factors
3
Q
Examples of biotic factors
A
Predation, competition, number of mates, disease, prey and predator numbers
4
Q
Examples of abiotic factors
A
Soil pH, water availability, space, rainfall, nutrients, light intensity
5
Q
Define the biosphere
A
The biosphere is the regions of the surface (land) and atmosphere (air) and earth occupied by living organisms
6
Q
Describe the biosphere (3 points)
A
- Shaped by interactions within organisms and environment
- An interconnected network
- Involved in the study of ecology
7
Q
Define ecosystem
A
An ecosystem is all the interacting biotic and abiotic factors in an area
8
Q
What are the two main components of an ecosystem
A
- The flow of energy
- The cycling of elements
9
Q
Different ecosytem cycles and what they are
A
Water cycle – cycling of water (H and O) through the water cycle
Respiration – transfer of energy and elements
Nutrient cycles – nutrients contain elements (nitrates and phosphates) are recycled in pond
Photosynthesis – plants utilising the suns energy and converting some to ATP/chemical energy
Decay – decay of material releases CO2
10
Q
What is a habitat
A
A habitat is where the community (different organisms in the same place) is found
11
Q
Within each habitat there are smaller microhabitats, what are these?
A
- A habitat which is of small or limited extent
- Differs in character from surrounding habitat (own microclimate)
12
Q
What are the different microhabitats present in a mature fruit tree?
A
- Leaves, flowers and fruits (different microhabitats throughout year (seasons) and fruit and flowers in specific times of year)
- Bark (Lichens and mosses grown on the bark (habitat for them) and different depending on position, shelter age and light intensities = different conditions
- Lichens and mosses (provide microhabitat for small insects)
- Canopy deadwood (micro-organisms involved in decay found)
- Plants colonising the tree base/surface (millipedes, woodlice and caterpillars)
13
Q
What is a population?
A
A population is a group of interbreeding organisms of one species in a habitat
14
Q
.A number of ______ can be found within each ecosystem
A
species
15
Q
.Members of the same species group together forming a ________
A
population
16
Q
.Different _____ group together to form different populations
A
species
17
Q
Population boundaries are difficult to define because organisms move, explain this in more detail
A
- All herons can breed with one another so form a population
- Woodlice on a rotting log on one side of the pond could breed with woodlice on the other side of the bond
- If interbreeding is unlikely = two populations
18
Q
A community is …
A
… all the populations of different species living and interacting in a particular space at the same time
19
Q
In the pond ecosystems, the community would consist of:
A
- Frogs
- Herons
- Bacteria
- Bull rushes
- Trees
- Grass
- Fish
- Worms
- Insects
- Fungi
- Snails
20
Q
What is an ecological niche?
A
An ecological niche is how an organisms fits into its role within the environment
21
Q
What does an ecological niche include?
A
- Where it lives and what it does
- The biotic and abiotic factors required for an organisms survival
22
Q
Why do no two organisms occupy the same niche?
A
- Different tolerance levels to environmental factors
- Best adapted species survives and reproduces
- At the expense of the weaker species (if conditions remain stable)
- Competitive exclusion principle (two species competing for the same limited resource cannot coexist at constant population values as one will always outcompete the other)
23
Q
What is population size?
A
Population size is the number of individuals within a population
24
Q
What is exponential growth?
A
- Growth rate is proportional to time
- As time increases, the variable being recorded increases
- At an exponential rate
- But most population growth in the wold does not follow this trend
25
What is most population growth like?
1. Slow growth – initially a small number of individuals to reproduce
2. Rapid growth – increased number each reproducing
Population doubles, increasingly steep curve
3. Stable state, no growth – rate of growth declines until roughly stable, the population reaches its carrying capacity
26
What is carrying capacity?
the number of organisms which an ecosystem can support without environmental degradation
27
A limiting factor is ...
... an environmental condition that limits the growth, abundance, or distribution of an organism or a population of organisms in an ecosystem
28
Why do limiting factors matter?
Limiting factors prevent the population growing exponentially
29
What are the main limiting factors?
- Disease
- Predators
- Water/Humidity
- Oxygen
- Competition
- Food
- Light
- Shelter
- Waste accumulation
- Temperature
- pH
30
How are all of the population limiting factors limiting population?
Disease Mutation = no antigens, no memory cells
Predators New adaptations, introduction of species, competition
Water/humidity Transpiration, photosynthesis, osmotic lysis, drought tolerance (GM)
Oxygen Respiratory rate, haemoglobin, tertiary structures, affinity
Competition Intra and inter specific, food webs
Food New sources, global warming, monocultures, deforestation
Light Light intensity – photosynthesis, transpiration, food production
Shelter Shade tolerance, competition
Waste accumulation Mutations for tolerance, pH changes = enzymes
Temperature Enzymes, transpiration, all metabolic processes
pH Enzymes, tissue fluid, mutations, O2 affinity, metabolic processes
31
Describe the growth rate in bacteria
.Quick/rapid growth
.Asexual reproduction
.Less complex
.Binary fission
32
Describe the growth rate in humans
.Slow growth/stabilises
.Sexual reproduction
.Long development
.Few offspring
33
Describe the growth rate in cats
.Middle term
.Long gestation
.Multiple births
34
Is the rate of population change between species the same?
No
35
When should you use logarithmic scales?
.Rapid growth
| .Long period of time
36
Why should you use logarithmic scales?
.Reduces wide-ranging quantities to tiny scopes
| .Clearer pattern shown
37
If log x (y) = z then ...
... x^z = y
38
A new pond has formed and some algae cells have been found.
Predict what will happen and explain why you think this.
Hint, it is summer, there are no nutrients in water, there are no limiting factors, they reproduce asexually
• They reproduce asexually
- Reproduction is quick so number rapidly increases
• It is summer
- High rate of photosynthesis = growth occurs quickly
• There are nutrients in the water
- Mineral ions used up by increasing population.
• There are no limiting factors BUT this changes
- Algae on surface block light reaching deep into the pond.
- Fewer ions or sunlight available for algae
- Other species arrive better adapted to different abiotic factors
- Increase competition and/or predation.
- Changing seasons = temperature drop and lower light intensity
- Algae population decrease
39
Describe the human population growth with figures
The human population has doubled in the last 50 years. Now over 7 billion. If this rate continues we will double our population in the next 40 years!
40
What factors are increasing human population growth?
- Health Care – Fewer people are dying/aging population
- Infrastructure and resources – More houses/workplaces/stability
- Economy – More money for medical care, houses, food
- Food availability (Agricultural Revolution) – Better nutrition/growth
- Better quality of life – Better hygiene, fewer diseases
- Industrial Revolution
41
.Human population growth does not follow the usual _______ shape
sigmoidal
42
For human population growth, the exponential phase is still continuing rather than plateauing, why?
- Birth rate outweighs death rate
| - Immigration outweighs emigration
43
Population growth =
(births + immigration) - (deaths + emigration)
44
Percentage population growth rate =
(Population change during time period / population at start of period) x 100
45
Birth rate is affected by:
* Contraception
* Money
* Culture and Religion
* Social Pressures
* Politics (Education and Taxes)
46
Death rate is affected by:
* Age of population
* Life expectancy at birth
* Food supply and range
* Natural Disasters and War
* Water and Sanitation
47
What is a population pyramid?
.Age and gender profiles are displayed graphically by stacked bars which represent the % age of males and females in each age group
48
What do population pyramids give information on?
.They give information on future trends of populations, for example how many females of child bearing age
49
In a population pyramid with a narrow base and wide apex what can you deduce
Lower birth rate = narrower base.
Lower mortality rate = more elderly people so apex is wider.
Applies to certain economically more developed countries (Japan)
50
In a population pyramid with a wide base and narrow apex what can you deduce?
High birth rate = wider base.
Fewer old people = narrow apex.
Typical of economically less developed countries.
51
In a population pyramid with an in balance birth and death rate what can you deduce?
Birth rate and death rate are in balance
No change in population size.
Typical of economically developed countries.
52
As countries develop economically, their human populations display a pattern of growth known as what?
demographic transition.
53
Demographic transitions can be divided into 4 stages depending on what?
- Death Rate - Birth Rate - Total population
54
What are the four stages in demographic transition and describe them
1. Small and stable – high birth rate, high death rate
2. Early expansion – high birth rate, decreasing death rate
3. Late expansion – decreasing birth rate, low death rate
4. Large and stable – low birth rate, low death rate
55
Draw a demographic transition
check notes
56
What is a predator?
A predator is an organism that feeds on another organism (prey)
57
Predators have evolved to become better adapted for capturing their prey, give some examples of adaptations
- Faster
- Better camouflage
- Sense of smell/eyesight
- Claws/teeth
- Agile
58
What is a prey?
A prey is an organism that is attacked/eaten by another organism
59
Prey have evolved to become better adapted for escaping predators, give some examples
- Camouflage
- Concealing behaviour
- Speed
- Protective features
60
Explain how prey become adapted for escaping their predators.
New mutations occur within the prey population, those with mutations that are advantageous to escaping the predators survive and reproduce and their alleles are passed on at the expense of the less advantageous alleles.
61
What is a stable community?
A stable community is where all the species and environmental factors are in balance so that population sizes remain fairly constant
62
Draw and label a graph that shows the effect of change in temperature on a stable community
Check notes
63
Describe predator prey cycles
* Predator and prey populations determine one another’s growth
* The size of one population has a direct impact on the others
* This is a cyclic relationship (recurring in cycles)
64
Describe the predator prey cycle graph
1. The pattern shown is that whenever the prey rises to a peak in population size, the population size of the predator grows soon after (but not to the size of the prey), then then as soon as the population size of the prey starts to drop again, soon the population of the predator will as well, this pattern continues multiple times.
65
Explain the predator prey cycle graph
2. This pattern exists as, since the population of the prey rises, then the predators have more food to eat, so they have more chance of survival, so they can reproduce more, so their populations increase, which means they need more food to maintain their population, so they eat more prey, so the population size of the prey falls, so the predators have less food, so they have less chance of survival, so they reproduce less, so their population falls as well, and now since theirs less predators to eat the prey the prey have a higher chance of survival and so their population rises again and the cycle starts again.
66
A relationship that is described as cyclical is …
a. Evolving or recurring in cycles – changes in population size
b. Recurrence in cycles – as one population changes it directly affects another
67
Cyclical relationships can also be a result of what?
a. Climatic changes
| b. Disease
68
The severity of a population crash can be increase or decreased depending on what? Explain each point
1. The number of food sources relied upon (If only one food source is relied upon, and it is destroyed, the population will crash/die. If it has other options its likelihood of survival is higher)
2. Genetic diversity (Increased probability that there is an advantageous allele in the population)
3. Availability of mates (Those with advantageous allele or those who survive can breed easily and increase the population size rapidly. Lack of mates means the population cannot increase)
4. Gestation time (asexual or sexual) (Can lots of offspring be produced very quickly after a crash or decline to re-build the population quickly?)
5. Intensity of change (Has the environment significantly changed i.e. a drought or is it a period of prolonged dryness that can be survived?)
69
How can climate change affect cyclical relationships? draw and label a graph
Check notes
70
Discuss the advantages and disadvantages of using lab studies to investigate predator prey relationships
Advantages –
• Control group for comparison
• Investigate multiple factors i.e. is it food availability, poaching or both
• Difficult to count all organisms in the wild so data is unreliable
Disadvantages –
• Results in extermination of the prey which would not happen in nature. Why?
• Habitats are varied in the wild (could have an effect)
• Area the organisms can travel is much larger
• Prey can escape predation
71
Competition arises when ...
... 2 or more individuals share any resource that are insufficient to satisfy their requirements
72
What do animals compete against?
space, mates, food and minerals, light, territory and water
73
There are two types of competition, what are they? With examples
1. Intraspecific (same species) i.e. mates
| 2. Interspecific (different species) i.e. space/food
74
Why is intraspecific competition important?
• The availability of resources determines the population size as the greater the availability, the larger the population size as there are more resources to grow and breed
75
Some oak trees have just started to grow. They are competing for light, water and nutrients. Only some survive. Which will survive and why?
* Mutation occurs
* Mutation is advantageous (causes leaf to have larger leaves or extended roots)
* Organisms is better adapted to access the requirements for photosynthesis
* Organisms grows and survives to reproduce
* Frequency of allele increases in subsequent generations
* At the expense of the smaller leaved plants
76
Examples of intraspecific competition
1. Limpets, competing for algae (food)
2. Oak trees, many small trees, some grow and block light, smaller ones dies, left with few large, dominant oaks
3. Robins, breeding territory, females only mate with males with territory, each territory only supports one family, scarce food, territories become larger
77
What occurs in interspecific competition?
* Populations of 2 different species initially occupy the same/very similar niche BUT…..
* One will normally have a competitive advantage over the other so….
* Best adapted survives and breed
* Population increases at the expense of the weaker, less adapted species, resulting in…..
* Complete removal of the weaker species
78
What is the competitive exclusion principle?
No two species competing for limited resources can co-exist (or occupy the same niche) as one will always eliminate the other
79
Example of competitive exclusion principle
* Red : Native to UK
* Grey : Introduced from America
* 2.5 million grey squirrels and only 160,000 red.
80
Describe and explain the relationship between red and grey squirels
* More grey squirrels, less red squirrels as competing for food, habitats and space
* Number of predators increase, grey squirrels do not increase in number as predators eat grey squirrels but the ones alive still outcompete red
* As predation decreases, population of red squirrels decrease and grey squirrels growth slows, grey squirrels are not eaten but more competition within grey
81
It is often difficult to prove that competition is the factor affecting population sizes, why?
1. Many other factors involved (abiotic)
2. A causal link has to be established
3. Often a time lag (population change may be due to competition that took place many years earlier)
4. Data on population sizes are hard to obtain and not always reliable
82
What is abundance?
the number of individuals of a species in a given space
83
How do we measure abundance?
.Study small sections of the habitats in detail
84
Sample methods include:
- Random sampling in the form of frame quadrats and point quadrats
- Systematic sampling along transects
85
What do quadrats do?
investigate the difference between two or more sites
86
Three key factors need to be considered when using quadrats:
1. The size of the quadrat to be used
2. The number of sample quadrats to record within the study area
3. The position of each quadrat within the study area
87
Why the size of the quadrat being used is important –
.Size of the species being studied
.Size of the area being studied
.Are species evenly distributed or clustered in small groups? If not, a large number of small quadrats is representative
88
Why the number of sample quadrats to record within the study area is important –
.Larger sample = more reliable the results
.Number of species present in the sample area
.Larger number of different species in the sample, the greater the number of quadrats required to produce valid results
89
Why the position of each quadrant within the study area is important –
.Sampling must be random
90
To ensure that observer bias is minimised, you must generate the positioning of your quadrats in what way?
Randomly
91
How do you do random sampling with quadrats?
1. Two long tape measures at right angles along 2 sides of the study area.
2. Use coordinates by using random numbers from a table/computer
3. Place a quadrat at the point of intersection
4. Repeat multiple times
92
Sampling with quadrats must be random in order to –
- Avoid sampling bias
- Ensure data obtained is valid
- Produce statistically significant results
93
You have been provided with frame quadrats of varying sizes:
- 0.5m2, 1m2 or 4m2
Using this equipment, suggest how you could use a frame quadrat to investigate the effect of grazing animals on the number of plants growing in a field. (5 marks)
1. Choose a quadrat of appropriate to the size - plants are quite small but area is quite large so 1m2 would be most suitable
2. Choose 2 fields close together as this minimises soil, climatic and other abiotic differences
3. One site is regularly grazed, the other is not
4. Take random samples at many sites in each field either by dice, random number generator, co-ordinates out a hat
5. Place the quadrat on the ground and record the names and numbers of the different species present
6. Repeat to increase reliability and calculate a mean
94
What are point quadrats and how are they used?
* Horizontal bar supported by 2 legs.
* Pins are dropped through holes in the top
* Each species the pin touches is recorded.
95
Difficulties of using quadrats include –
.Difficult to identify and count every organism
.Time consuming
.May damage the habitat.
.Difficult to avoid introducing an element of personal bias
.No indication of pattern
96
Advantages and disadvantages of point quadrats?
```
+ Smaller organisms
+ Small areas or specific detail
-Tedious
-Hard to use
-Time consuming
```
97
Economic Advantages –
.Construction sites, less environmental costs
.Finding the optimum conditions for horticulture
.Finding the optimum conditions for agriculture
98
Systematic sampling studies what?
The distribution of a species
99
When is systematic sampling important?
.Gradual changes occur across a habitat
.Transitions within communities occur
.Zonation is present
100
What are the two types of transect?
.Belt transect
| .Line transect
101
What is a line transect and how does it work?
.String or tape
.Organisms over which the line passes are recorded
.Usually using a quadrate
102
What is a belt transect and how does it work?
.Strip or meter wide tape
.Second placed parrall to the first
.Species between the two belts are recorded
103
Line Transect Adv and DisAdv –
.Limited Time (Quick)
.Easily shows species range along the transect
.Clear visual of how species change
.Harder to see the range across a large area
.Less data collected
104
Belt Transect Adv and DisAdv –
.More data
.Tells you more about the abundance AND range of individual species at different points along the line
.Shows changes/distribution more clearly as more data
.Dominance of one species can be determined
.Larger area covered
.Time Consuming
105
.Transects show what?
change in the number of species over a given area
.It is not a comparison between two area
.It is used to show a trend
106
How to use a transect?
1. Place a transect (tape measure) down across a given area
2. Place a quadrat down at equal or random intervals along the transect
3. Carry out a second transect in a different part of the sample are but still close by your first sample, so that there is not too much variance in the environment as to change the results massively
4. Calculate a mean across the 3 transects studied and display your results in a table
5. Plot a graph and describe the pattern shown
107
Abundance is ...
... the number of individuals in a given space
108
Frequency is what?
.The likelihood of a particular species occurring in a quadrat
109
Percentage cover is what?
.Estimate of the area within the quadrat that a particular plant species covers
110
Equation for per quadrat?
Per quadrat = (number of squares species occurs / number of squares in total) x 100
111
Adv and disadv for frequency?
Often expressed as a %
Useful where a species is easier to count
A quick idea of the species present
Lacks information on the density
No detailed information distribution of a species
Can be quite time consuming
112
Adv and disadv for percentage cover?
Useful when a species is abundant or difficult to count
Data can be collected quickly
Gives a representation of distribution/density
Less useful where organisms occur in overlapping layers
Can be less precise
Often subjective
113
What does mark, release, recapture method entail?
1. A specific number of animals are caught, marked and then released
2. After some time, a given number of animals are collected randomly
3. The number of marked animals counted
114
Estimated population =
(total number in 1st sample x total number in 2nd sample) / number of marked individuals recaptured
115
4. Not all organisms will have equal chance of being caught as ...
... they might have different adaptations to make them more camouflaged/escape
116
Mark, release, recapture is the best option when
- Live organisms
- Large areas to sample
- Focus of one species
117
The mark, release, recapture method is based on a number of assumptions, list them along with why the assumptions are important:
1. Proportion of marked to unmarked in the second sample is the same as the proportion of marked to unmarked in the whole population – results not due to different sizes of sample
2. Marked individuals distribute evenly – results are valid and not in clusters
3. The population has a definite boundary – you are studying the whole population
4. Markings are nontoxic and makes it no more conspicuous – do not injure of reduce the survival chances
5. Population is constant e.g. not breeding season – ‘new’ individuals would not be marked
6. Markings cannot be rubbed off during the investigation – population size in second sample is not reduced = valid
118
Why is mark, release, recapture useful for measuring abundance with organisms?
When organisms can move, hide, and are difficult to find and identify
119
What are the disadvantages of the mark, release, recapture method?
Time consuming (need to leave time)
Risk of predation changing sample size
Disturbance of habitat
Trauma or injury to the organism (ethics)
120
What is meant by positive cooperativity?
1. The binding of the first oxygen to haemoglobin makes the binding of the second and then third easier
121
What is meant by the term competitive exclusion principle?
3. Organisms will compete for the same resources, the better adapted will survive at the expense of the weaker
122
Succession is what?
the change in species in an area over time
123
Is succession fast or slow?
It can be either
124
Does succession occur in plants or animals?
Both
125
Where is succession seen?
- Seen in a range of environments:
.Silt/mud deposits at estuaries
.Lakes/ponds created by land subsiding
.Sand forming dunes
126
At each stage in succession, certain species change the environment so ...
it becomes more suitable for other species with different adaptations
127
What is a pioneer species and climax community?
Pioneer species (a species colonises an inhospitable area, the first one)
Climax community (stable community, very little/no change, the last one)
128
Pioneer Species tend to have what characteristics?
1. Reproduce asexually
2. Produce large quantities of wind dispersed seeds or spores
3. Can tolerated/are adapted to survive in harsh conditions i.e. low light intensities, low/high pH
4. Short dormancy or fast germination
5. Photosynthesise
6. Are nitrogen fixing
129
Why does pioneer species have those characteristics?
.They reproduce asexually so that they do not rely on another species to increase its population size
.They produce large quantities of wind dispersed seeds or spores so that they can spread to remote areas and without the need for other organisms
.The can tolerate harsh conditions so that they can survive and reproduce when no other organism can
.They have short dormancy/fast germination so that they can reproduce/increase in number quickly
.They can photosynthesise so that they do not rely on food sources
.They are nitrogen fixing so they improves soil quality in when few nutrients
130
(S) Explain the process of succession, using both animals and plants as an example of this (6 marks)
1. Pioneer species colonises inhospitable area
2. Reproduces = increases
3. Changes the conditions/a species makes the conditions less hostile;
4. New/primary coloniser is better competitor/pioneer species outcompeted; Example = Lichens
5. Pioneer species grows, dies and nutrients are recycled via decay
6. Increase in secondary coloniser, changing abiotic factors further
7. Better adapted/tertiary species increases and secondary decreases
8. Process continues until a climax community is formed
9. Few if any new species are replaced
131
What is the process of succession?
1. Pioneer Species
Colonises harsh environment
Reproduce and increase population size
Changes the environment – nitrogen fixing
Improve soil quality
2. Primary Coloniser – for example Lichens who colonise bare rock and can survive desiccation (extreme dryness)
New species better adapted
Outcompete pioneers
New community forms
Continue to change the environment (abiotic factors) to make it less hostile
3. Secondary Coloniser
Weathering of the rock creates sand and soil
Lichens die and decompose
Nutrients are recycled
Nutrients support small plant species
• The quality and quantity of the soil improves
• Rock erosion continues and plant species die and decompose.
• The smaller plants again change and improve the abiotic factors
• The area can support larger species: grasses, shrubs then trees.
• Continues until the climax community is reached.
132
Animal populations establish and grow in the _______ process
Cessionary
133
Describe animal succession?
Animals are still reliant on the pioneer plant species
Lichen dies and provides food for detritus feeders Mosses and grasses provide food and habitat for insects Secondary consumers feed on the insects Flowering plants and trees support reptiles, mammals and birds
They are still reliant on lichens to provide primary colonisers with food
134
Climax communities have dominant _____ and ______ species
plant
| animal
135
If an area of land has experienced land clearance or a natural disaster the area returns to its climax community but:
- It does it much faster as the seeds and spores are already present therefore it does not begin at a pioneers species
- The climax community will be different as there are different abiotic factors
136
Define preservation
Maintaining individuals, populations and ecosystems in their current state without the exploitation of their natural resources
137
Define conservation (and the two types)
```
Allowing ecosystems to evolve (change) naturally, without resources being overused, there is active human management and two forms:
- Ex-situ:
Individual endangered species in zoos
Outside natural habitat
- In-situ:
Whole ecosystems and landscapes
Within habitat
Monitoring succession
```
138
Why do we manage succession?
* Allows ecosystems to evolve naturally
* No detrimental effects on any stage of succession
* Enables maximum diversity and ecosystems
139
Explain the stage of succession that should be of greatest focus to conservationists.
1. Mid Succession
2. Not dominated by one species (low diversity)
3. Not a very hostile environment
4. Can support multiple species, more habitats/food sources = higher biodiversity
140
Why is the stage of succession that should be of greatest focus to conservationists not the climax community?
- Dominated by one species
- High competitive element
- Competitive exclusion principle
- Low Biodiversity
141
How does burning heathlands manage succession?
1. SOME areas are burnt = Prevent succession
2. Prevents dominance/climax community
3. Older forms are less palatable and less nutritious
4. New heather and other new species can grow
5. Biodiversity is increased
142
Burnt vs Unburnt areas create more:
- Habitats
- Food sources
- Species
143
How is succession controlled in moorlands? Why?
* Grazing by sheep and/or periodic burning
* Maintains low growing plant populations
* Provide plentiful food sources for grouse
* Increases number of grouse
* Happy hunters!
144
Explain what may happen to moorland if sheep grazing and burning of vegetation ceased? (3 marks)
1. Moorland would undergo secondary succession
Moorland would reach its climax community
Community would be dominated by deciduous oak woodland (one species)
Reduction in biodiversity
145
Suggest how conservation and leisure could be managed (2 marks)
2. Hunters pay to shoot/only allowed at given times
| Payments control and coordinate conservationist burning the land
146
Discuss the importance of studying and understanding conservation and enhancing biodiversity
- Money - Medicines
- Tourism - Wood
- Food - Horticulture
- Removal of CO2
147
Define genepool
all the alleles of all the genes of all the individuals in a population at a given time at a given time
148
What is natural selection?
the process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted.
149
Phenotypic variation is a result of:
1. Genetic factors
| 2. Environmental factors
150
Why does genetic variation occur?
1. Meiosis
2. Sexual reproduction
3. Main factor – Mutations
All can result in selection occuring
151
.Most traits are normally distributed, what does this mean?
.The most common result (mode) is near the average (mean) and the middle value (mode)
152
.When selection occurs, the normal distribution curve may what?
Change shape
153
Directional Selection, what is it with example
* Change in environment
* Changes the mean
* Extreme is selected for
* Antibiotic Resistance
154
Stabilizing Selection, what is it with example
* Selection against both extremes
* Phenotypic variation decreases
* Environment has remained stable
* Birth Weight
155
Differences between the reproductive successes of individuals affects the allele frequency in populations, explain how. (6 marks)
1. Random mutation of alleles within the gene pool
2. The new allele has an advantage in a SPECIFIC environment
3. The individuals are better adapted/obtain resources
4. These individuals grow rapidly and live longer compared to other alleles
5. Reproduce passing on this allele.
6. Offspring survive better and reproduce
7. The advantageous allele increases at the expense of the individuals with the less advantageous allele.
8. Change in the allele frequencies in a population occurs = Evolution
156
Selection pressures are what?
environmental factors that limit the population of a species
157
Give the features of selection pressures
* Determine the frequency of all the alleles within the gene pool
* Vary from time to time and place to place
158
Every organism is subject to selection so ...
... certain factors may increase the chances of selection occurring
159
Examples of selection pressures
dation, competition, disease, natural disasters
160
2. The bacteria population’s normal distribution curve shifted in the direction of a population that has a greater resistance to antibiotics. Explain why. (6 marks)
2. A spontaneous mutation results in a different protein structure, a new enzyme breaks down the antibiotic. Bacteria with the mutation survived. Antibiotic resistance bacteria multiply, this creates an increased frequency of antibiotic resistant alleles at the expense of the non-resistant population.
161
All species have the potential to increase their number ________
exponentially
162
’The rate increases in proportion to ...
... the growing total number or size’
163
Evolution only occurs by natural selection if ....
organisms reproduce and have sufficient resources and genetic variation is present within the population and phenotypic variation is present within the population (greater diversity = adapt to change)
164
In order for populations to survive and increase exponentially they must ...
have a high reproductive success and a suitable population size to minimise intraspecific competition
165
Factors that make exponential growth unlikely could be ...
high death rates from predators, low parental investment and lack of resources
166
```
Death rates are not random, how are the following death rates influenced:
Turtle
Arctic fox
Hedgehog
eagle
human
```
Turtle – some food sources, some camouflage
Arctic Fox – Not camouflaged, too warm in summer, some possible food
Hedgehog – lots of food sources, camouflage, hibernation, adapted to predators
Eagle – plenty of food sources, adapted to hunt, suitable habitats
Human – not camouflaged, ability to hint but possible limited food sources
167
.Death rates within a population will not be completely random / exponential growth is unlikely to occur because organism will…
- Be better adapted to the environment i.e. Camoflagued
- Suited to prevailing conditions i.e. Catch food
- Resit disease
168
Variation is essential because ...
- Changing environments - New diseases
| - New predators - New competitors
169
Great tits are small birds. Natural selection influences the number of eggs laid by the Great tits. Explain why great tits that lay fewer than 3 eggs per nest or more than 14 eggs per nest are at a selective disadvantage. (3 marks)
1. When high number of eggs, each individual young will receive less food; reference to mortality rates to disease / predators for
2. low numbers of eggs; so in both cases low number of offspring will reach maturity / survive;
3. so less likely to pass on genes / alleles;
170
Selection pressures are what?
environmental factors that limit the population of a species
171
Difference between directional and stabilizing selection?
```
Stabilizing Selection –
.Selection pressure against both extremes
.(Mean remains the same)
Directional Selection –
.Selection pressure for an extreme
.(Mean changes)
```
172
The selection pressure may change too frequently for _____to occur, so both must be over prolonged periods
evolution
173
What is disruptive selection?
.Least common form of selection
.Opposite to stabilizing selection
.Favors the extremes at the expense of the intermediate phenotypes
174
When will disruptive selection occur?
When an environmental factor i.e. temperature takes two or more distinct forms. Summer – warm, Winter = cold
175
Explain the example: Fur Length, in disruptive selection
* 5 degrees in winter (long fur). 15 degrees in summer (Short fur)
* Result: Two different species, each activie in each season
* One active in summer so only breed with others active in summer, producing short haired cubs.
* One active in winter only breed with those active in winter
176
Why is it important/what impact will it have? (disruptive selection)
* Most important for causing evolutionary
| * Could result in two distinct species
177
Coho salmon example disruptive selection
* Large males and small males have a selective advantages
* Small males sneak up to females so reproduce and pass on their alleles
* Large males' fierce competitors so attract the females and reproduce passing on their alleles
* Intermediate sized is selected against as has no selective advantage
178
What is the hardy weinberg principle?
A mathematical equation used to calculate the frequencies of the alleles of a gene in a population
179
The hardy weinberg principle is a ______ analysis
statitical
180
What does the hardy weinberg principle established what?
- Establishes the frequency of the dominant and recessive alleles
- Establishes the frequency of carriers (heterozygotes) in a population
181
The total frequency of alleles for a gene in a gene pool with only one dominant and recessive alleles will =
1 (100%)
182
In the equation p+q = 1, what do p and q represent?
Dominant allele = p
| Recessive allele = q
183
The frequency that A combines with A in the zygote is
p x p = p2
184
The frequency that a combines with a in the zygote is
q x q = q2
185
The frequency that A combines with a in the zygote is
p x q = pq
186
The frequency that a combines with A in the zygote is
q x p = qp
187
P2 + 2pq + q2 =
1
188
What is p2?
the frequency/ number of individuals in that population that are homozygous dominant (AA)
189
What is 2pq?
the frequency/number of individuals that are heterozygous (Aa or aA)
190
What is q2?
the frequency / number of individuals in that population that are homozygous recessive (aa)
191
The Hardy Weinberg formulae is based on the principle that:
The proportion of dominant and recessive alleles of any gene in a population remains from one generation to the next
192
Key conditions of The Hardy Weinberg formulae ?
- No new mutations arise
- The population is isolated (no gene flow / flow of alleles into or out of the population)
- There is no selection bias
- Population studied is large
- Mating is random
193
Why are the conditions in the hardy Weinberg principle important?
- No new mutations arise – no introduction of new alleles
- The population is isolated (no gene flow / flow of alleles into or out of the population) – movement encourages interbreeding which reduces genetic differences between populations
- There is no selection bias – natural selection = advantageous alleles favoured
- Population studied is large – prevents the effects of random events affecting allele frequencies or changes due to chance
- Mating is random – prevents the selection of particular alleles, selective breeding would alter allele frequencies
194
What is speciation?
The formations of two populations from one
195
What are the types of speciation?
Allopatric speciation and sympatric speciation
196
Explain how oxygen is loaded, transported and unloaded in the blood. (6 marks)
.Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
. Loading / uptake / association in lungs;
.at high p.O2;
.Unloads / dissociates / releases to respiring cells / tissues
.at low p.O2;
.Unloading linked to higher carbon dioxide (concentration);
197
Selection pressures are ...
... environmental factors that limit the population of a species
198
Stabilising selection is caused by ...
... selection pressure against both extremes, and so the mean remains the same
199
Directional selection is caused by ...
... selection pressure for an extreme, and so the mean changes
200
Tell me about disruptive selection
- Selects against the average phenotype
- Favours the extreme phenotypes
- Can lead to speciation
201
.Speciation is what?
the evolution of new species from existing species
202
What does speciation enable?
.It enables evolutionary change and diversity
203
Speciation occurs due to:
- Reproductive isolation
- Genetic differences (mutations)
- Geographical isolation
o Differences in two populations gene pools
204
What are the two forms of speciation?
Allopatric Speciation:
| Sympatric Speciation:
205
WHat is allopatric speciation?
.More common
.Different locations
.Geographic separation
206
WHat is Sympatric Speciation:
.Less common than allopatric
.Same location
.Reproductive isolation
207
How does allopatric speciation occur –
.Each species will have its own range, within which there will be a number of other populations of that species
.Populations can still interact and interbreed
.Unless a barrier occurs, preventing migration between populations of the same species
.The environments of each new range may be different
.Different mutations occur in each range
.Due to different selection pressures, different mutations are favoured
.No gene flow can occur and so changes in allele frequency occur
.Eventually they will be unable to interbreed even if the barrier is removed
208
Define Adaptive radiation
The diversification of a species into forms adapted to different ecological niches
209
Allopatric Speciation key points
```
.More common than sympatric
Different locations
.Geographic seperation
.Physical barrier i.e. Lake, desert, mountain area
.Takes millions of years
```
210
Sympatric Speciation key points
.Less common than allopatric
.Same locations
.Reproductive isolation
.Breeding seasons or food preference
211
Apple maggot fly sympatric specxiation example explanation
1. Only lay eggs inside Hawthorns Fruits (native to North America)
2. Apple trees introduced
3. Some flies lay eggs in apples
4. Mates are found by searching site where they were raised
5. Raised in apples, mate with flies raised in apples
6. Mutations may result in two new species
212
two examples of sympatric speciation
apple maggot fly, seasonal breeding
213
Why is speciation more likely in small populations?
In a small populations there will be:
- A small variety of alleles (lower genetic diversity)
- Not equal chance of each allele being passed on OR if a muation occurs....
- One allele/mutation is passed on very quickly
- Increase in allele frequency
- Speciation is more likely
214
What is genetic drift?
Genetic drift is genetic change due to chance, eg. By chance fewer decesendents of one phenotype are left behind after some organisms of a species get stamped on
215
On islands in the Caribbean, there are almost 150 species of lizards belonging to the genus Anolis. Scientists believe that these species evolved from two species found on mainland USA.
Explain how the Caribbean species could have evolved. (6 marks)
1. Geographic(al) isolation;
2. Separate gene pools /no interbreeding/gene flow
3. Variation due to mutation;
4. Different selection pressures / different abiotic / biotic conditions / environments / habitats
5. Different(ial) reproductive success / selected organisms (survive and) reproduce
6. Leads to change / increase in allele frequency
216
What are the steps to scientific research?
1. Observation
2. Hypothesis (Null hypothesis, Alternative hypothesis)
3. Experimentation
4. Results Analysis
5. Further Research
217
Null Hypothesis:
.There will be no significant difference between two sets of data
218
Alternative Hypothesis:
.There will be a significant difference between two sets of data
219
Statistical Testing –
a mechanism for making quantitative decisions about a process or processes
220
Chi-squared test used for?
comparing observed and expected values
221
When is a two sample t test used for?
looking for significant differences between two sets of data
222
When is a Pearson’s correlation coefficient used for?
is there a significant correlation between 2 variables?
223
What is the level of probability?
The level of probability that you can accept or reject your null hypothesis (significant or due to chance)
224
What does you calculated chi squared value tell you?
Calculate a chi squared value
Compare your calculated value with a critical value
At a 0.05 level of probability
95% confidence the difference is significant
5% probability it is due to chance
225
Degrees of Freedom, what are they with example
.The number of variables that are free to change
.Calculated by number of categories (n) – 1
.Example: 3 categories – 1 = degrees of freedom is 2
226
How to analyse chi-squared results
.Conduct your statistical test = calculated chi squared value
.Compare calculated chi squared and critical values
.If your Chi squared value is higher than the critical value at 0.05 probability, reject the null hypothesis and the results are not due to chance.
If your value is LESS, ACCEPT null hypothesis.
If your value is GREATER, REJECT null hypothesis.
227
What does Harry Robinson remind us?
Harry Robinson - HR - Higher Reject, for the chi test
228
What are the steps to a statistical analysis?
1. Formulate a Null Hypothesis
2. Select the appropriate statistical test
3. Carry out the calculation
4. Determine the degrees of freedom
5. Compare your calculated value to the critical value calculated at 0.05
6. Compare the calculated value with the critical value:
a) Higher than the critical value = difference is not due to chance = reject the null hypothesis
b) Lower than the critical value = difference is likely due to chance = accept the null hypothesis
229
What does a chi-squared test allow us to do?
.Identify significant differences between observed and expected results
.Measure the degree of deviation between them
.Determine if differences present between data sets (2+) are significant or due to chance
230
When can we use the chi-squared test?
.Data is categorical Phenotypes i.e. eye colour, gender, location
.The portion of numbers expected in each category is known
.The number in each category is greater than 5
231
Chi-squared test formula
Chi-squared = Sum ( (observed result – expected result)^2 / expected result)
232
What does the funny E mean?
sum of
233
For the chi-squared test, what is 'o'?
observed result
234
For the chi-squared test, what is 'E'?
Excepted result
235
What is disruptive selection?
Selective pressures against the intermediate trait
236
Examples of disruptive selection
fur length (medium against)
Colour or rabbit (white against)
237
What is speciation?
Speciation is the formation of two species from one
238
Where is sympatric speciation?
Sympatric Speciation = Same place
239
Exampels of sympatric speciation?
Examples are mayflies or seasonal breeding
240
Where does allopatric speciation?
away from species
241
Key points of allopatric speciation
1. Geographic(al) isolation
2. Separate gene pools / No gene flow
3. Variation caused by a mutation
4. Different selection pressures
5. Different(ial) reproductive success
6. Change in allele frequency.
242
What is genetic drift? What does it do?
* Genetic Change due to CHANCE dissapearance of certain alleles
* In small populations
* Increases liklihood of speciation
243
Steps of genetic drift?
1. Smaller population, fewer alleles, less diversity
2. By chance, one allele is not passed on
3. By chance fewer decedents of one phenotype are left
244
What is an isolating mechanism?
* Way in which a population becomes separated
| * Required for speciation to occur
245
How does ecological (habitat choice) act as isolating mechanism?
Inhabit different areas (within the same area), individuals rarely meet or cross paths/mating grounds
246
How does temporal (breeding seasons) act as isolating mechanism?
Breeding seasons do not coincide, may not be fertile at the same time, no interbreeding
247
How does hybrid sterility act as isolating mechanism?
Different chromosome number, fusion of gametes cannot produce viable gametes, horse (2n = 64), donkey (2n = 62) = mule 63 – no pairing
248
How do behavioural differences act as isolating mechanism?
Courtship behaviors are different, no attracted to one another scent, different mating rituals
249
What does conservation entail?
• Allowing ecosystems to evolve naturally
• Without resources being overused or exploited
• Active human management
Ex situ vs in situ
250
What is succesion?
* Gradual change
* Each species changes the conditions for the next
* Conservation of middle stages
* Maintains more habitats, food sources, diversity
251
What are the steps to succession?
Pioneer species (inhospitable area) Intermediate stages (highest diversity) Climax community (domination of one species)
252
What is an example of management of succession? What problems arise from this?
Example, burning heathlands –
1. SOME areas are burnt = Prevent succession
2. Prevents dominance/climax community
3. Older forms are less palatable and less nutritious
4. New heather and other new species can grow
5. Biodiversity is increased
Problems? This can be costly as hunters pay a charge to hunt
253
Stages of population growth
Slow growth rapid growth carrying capacity
254
When is it best to use logarithmic scales? Why?
Best to use with rapid growth or when studying a long period of time
• Reduces wide-ranging quantities to tiny scopes
• Clearer Pattern shown
255
Example of when to use logarithmic scale
• Bacterial Growth
256
When do you use a two sample t test?
.Looking for significant differences between 2 sets of data
257
The two sample t test tells you if there is a statistically significant difference between two means when:
- The sample size is less than 25
| - The data is normally distributed
258
Two sample t test equation
T = (x1 – x2) / (root( (s1^2 / n1) + (s2^2 / n2) ))
259
In the two sample t test, what does x1 mean?
mean of first sample
260
In the two sample t test, what does x2 mean?
mean of second sample
261
In the two sample t test, what does s1 mean?
standard deviation of first sample
262
In the two sample t test, what does s2 mean?
standard deviation of second sample
263
In the two sample t test, what does n1 mean?
number of measurement sin fist sample
264
In the two sample t test, what does n2 mean?
number of measurements in second sample
265
What does standard deviation show?
.How much the data deviates from the mean
| .Average distance between each of the data points and the mean
266
How much data lies within 1 and 2 s.d
68% of the data lies within 1 s.d
| 95% of the data lies within 2 s.d
267
Standard deviation equation and meaning of letters
```
S = root( ( sum( x-mean(x) )^2 ) ) / (n-1) )
X = each score
N = the number of values
```
268
What does Chi Squared test allow us to do?
.Identify significant differences between observed and expected results
.Measure the degree of deviation between them
.Determine if differences present between data sets (2+) are significant or due to chance.
269
What conditions must apply for the chi-square test?
.Data is categorical (e.g. Phenotypes i.e. eye colour, gender or location)
.The portion of numbers expected in each category is known
.The number in each category is greater than 5
270
Chi squared test formula and meaning
χ^2=∑((O-E)^2/E)
Σ Sum of
O Observed result
E Expected result
271
Step by step chi squared test
1. Formulate a Null Hypothesis
2. Select the appropriate statistical test
3. Carry out the calculation
4. Determine the degrees of freedom (n-1)
5. Compare your calculated value to the critical value calculated at 0.05
6. Compare the calculated value with the critical value:
1. Higher than the critical value = difference is not due to chance = reject the null hypothesis
2. Lower than the critical value = difference is likely due to chance = accept the null hypothesis
272
T-Test, what to do step by step?
1. Formulate a Null Hypothesis
2. Select the appropriate statistical test
3. Carry out the calculation
4. Determine the degrees of freedom (n-1)
5. Compare your calculated value to the critical value calculated at 0.05
6. Compare the calculated value with the critical value:
a) Higher than the critical value = difference is not due to chance = reject the null hypothesis
b) Lower than the critical value = difference is likely due to chance = accept the null hypothesis
273
What does the T-Test tell you? with conditions
.If there is a statistically significant difference between two means when…..
.The sample size is less than 25
.The data is normally distributed
274
Standard deviation formula and meaning of each part
root( (sum (x - mean(x))^2 ) / (n-1) )
x = each score
n = the number of values
275
T test formula and meaning of each part
t = (x1 - x2) / root( (s1^2 / n1) + (s2^2 / n2) )
```
x1 = mean of 1st sample
x2 = mean of 2nd sample
s1 = S.D of 1st sample
s2 = S.D of 2nd sample
n1 = no. measurements in 1st sample
n2 = no, measurements in 2nd sample
```
276
T test, when to accept or reject:
.If t is HIGHER than the critical value = REJECT the null hypothesis = there is a significant difference between both samples, differences are not due to chance
.If t is LOWER than the critical value = ACCEPT the null hypothesis = differences between the samples are not significant and are likely due to chance
277
What do you use correlation coeficient for?
to find if there is a significant correlation between 2 variables
278
When do you use correlation coefficient?
.If there is a significant correlation
.If the correlation is positive or negative
.Compares data which from two values
.May be visible on a graph
279
Correlation coefficient (r) =
( sum(XY) – ( ( (sum(x)) x (sum(y)) )/n ) ) / root( ( sum(x^2) – ( (sum(x) )^2 /n ) ) x ( sum(y^2) – ( (sum(y) )^2 /n ) ) )
280
What is n, in the correlation coefficient?
the number of values of x and y
281
Where will r, the correlation coefficient, always lie?
r will always be between -1 and 1
282
For r, the correlation coefficient, the closer to +1, the ...
stronger the positive correlation
283
For r, the correlation coefficient, the closer to 0, the ...
the weaker the correlation
284
For r, the correlation coefficient, the closer to -1, the ...
stronger the negative correlation
285
Student got an r value of 0.324, what is the relationship?
Weak positive correlation
286
Student got an r value of -0.963, what is the relationship?
.Strong negative correlation
287
Statistical Analysis Steps
1. Formulate a Null Hypothesis
2. Select the appropriate statistical test
3. Carry out the calculation
4. Determine the degrees of freedom
5. Compare your calculated value to the critical value calculated at 0.05
6. Compare the calculated value with the critical value:
a) Higher than the critical value = difference is not due to chance = reject the null hypothesis
b) Lower than the critical value = difference is likely due to chance = accept the null hypothesis
288
Why population growth might differ between countries
- Access to medical care
- How much money people in the country have
- How developed the country is, e.g. water quality
- Benefits systems
- Religious beliefs, contraception
- Education, contraception
- Social pressures
- Availability of contraception
- Culture
- Age of population
- Life expectancy low at birth
- Natural disasters and war
- Sanitation
289
Features of a Pioneer Species –
- Reproduce asexually
- Reproduce quickly (short gestation period)
- Produces lots of offspring
- Movement of offspring
- Doesn’t rely on other organisms
- Adapted to harsh environments
- Photosynthesise
- Are nitrogen fixing
290
Define preservation
maintaining individuals, populations and ecosystems in their current state without the exploitation of their natural resources
291
Define conservation
allowing ecosystems to evolve (change) naturally, without resources being overused
292
Differences between line transect and belt transect
Line Transect
.String or tape
.Organisms over which the line passes are recorded
.Usually using a quadrat
Belt Transect
.Strip or metre wide tape
.Second placed parallel to the first
.Species between the two belts are recorded
293
Adv and Disadve of line transect vs belt transect
Line - .Limited time (quick)
.Easily shows species range along the transect
.Clear visual of how species change
.Harder to see the range across a large area
.Less data collected
Belt -
.Mora data
.Tells you about the abundance and the range of individual species at different points along the line
.Shows changes/distribution more clearly as more data
.Dominance of one species can be determined
294
Assumptions for mark, release and recapture and why they are important?
1. Proportion of marked to unmarked in the second sample is the same as the proportion of marked to unmarked in the whole population – so results not due to different sizes of sample
2. Marked individuals distribute evenly – so results are valid, representative and not a result of clusters
3. The population has a definite boundary – so you are studying the whole population/habitat
4. Markings are nontoxic and makes it no more conspicuous – so it does not injure them or reduce their survival chances
5. Population is constants (not breeding season) – ‘new’ individuals would not be marked/representative
6. Markings cannot be rubbed off during the investigation – so that the population in second sample is not reduced
295
What is the HardyWeinberg Principle
The Hardy-Weinberg principle is a mathematical equation used to calculate the frequencies of the alleles of a gene in a population.
Classed as a statistical analysis
- Established the frequency of the dominant and recessive alleles
- Established the frequency of carriers (heterozygotes) in a population
296
What principle is hardy-weinberg based on?
The proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next
297
What conditions is the hardy weinberg princple based on? Why are these important?
- No new mutations arise, so no introduction of new alleles
- The population is isolated, so no movement which encourages interbreeding which would reduce genetic differences between populations
- There is no selection bias, natural selection = advantageous alleles favoured
- Population studied is large, prevents the effects of random events affecting allele frequencies or changes due to chance
- Mating is random, prevents the selection of particular alleles – selection breeding would alter allele frequencies
298
Explain each part of the hardyweinberg principle
p = dominant allele
q = recessive allele
p2 + 2pq + q2 = 1
p2 is frequency of individuals that are homozygous dominant (AA)
2pq is frequency of individuals that are heterozygous (Aa or aA)
q2 is the frequency of individuals that are homozygous recessive (aa)
1 = all the alleles present must add up to 1 or 100%
299
Define Gene
A segment of a nucleic acid that carries the code for a particular polypeptide or fRNA
300
Define locus
The location of a specific gene on a chromosome
301
Define amino acid
Monomers which make up proteins, coded for by 3 nucleotides
302
Define triplet
3 bases code for 1 amino acid
303
Define genetic code
The sequence of bases on mRNA which codes for amino acids
304
Define degenerate code
Base combinations that lead to the same amino acid
305
Define non-overlapping
Each of the amino acids that are coded for are distinct from the bases of adjacent amino acid codes
306
Define universal
The same in all living organisms and cells
307
Define exons
A part of DNA which codes
308
Define introns
A part of DNA which doesn’t code
309
Define chromosomes
Structures found inside the nucleus which hold genetic information
310
Define chromatid
One of the two strands of a chromosome, held together by the centromere, after DNA replication, before division
311
Define histones
Proteins found in the nucleus of eukaryotes which DNA coils around
312
Define allele
A version of a gene
313
What are the rules for calculating inheritance?
- Choose a letter to represent the trait you are investigating (B for blue eyes)
- Choose letters that are different lower case and capitals (Gg not Ww)
- Capital = dominant, lower case = recessive
- Label parents and their phenotypes (parent 1 = brown eyes)
- Label gametes the parents produce and circle them
- Draw a Punnett square
- Label the gender of each parent
- Always write the dominant allele first
- Work out the cross
- State the phenotypes
- Calculate the ration
314
What is a monohybrid cross?
a cross in which the alleles of only one gene are involved
- Inheritance of a single gene
- Used to determine the dominance relationship between two alleles
- The cross begins with the parental (P1 or P) generation
315
What is always the expected ration when heterozygotes are crossed?
3:1
316
In diploid organisms, characteristics are determined by alleles that occur in ____
pairs
317
Only one of each pair of alleles can be present in a single _____ in diploid organisms
gamete
318
What do dihybrid crosses do?
- Consider the inheritance of two characteristics at the same time
- Shows how two characteristics, determined by 2 different genes, located on different chromosomes, are inherited
319
How did Mendel use Peas to investigate bihybrid inheritance?
```
Pea plants varied in two ways:
1. Seed colour
2. Seed shape
Yellow and round = dominant
Green and wrinkled = recessive
So there were 4 possible combinations:
1. R and Y
2. R and G
3. W and Y
4. W and G
Or by genotype
1. RY
2. Ry
3. rY
4. ry
1 and 4 are homozygous, dominant and recessive respectively
```
He bread these two to produce a plant with 100% chance of RrYy (heterozygous for both characteristics, so all round and yellow), Mendel then crossed these two over
That means there was a ratio of RY:Ry:rY:ry of 9:3:3:1
320
what is Mendel’s Law of Independent Assortment –
Each member of a pair of allels may combaine randomlu with either of another pair
321
The gene for colour and gene for shape are on ________ chromosomes
different
322
WHat is codominance?
When both alleles are expressed in the phenotype
| - Neither allele is dominant nor recessive, they are both equally dominant
323
Explain how snapdragons are an example of codominant alleles
- One allele codes for an enzyme that catalyzes the synthesis of a red pigment in flowers
- The other allele code for an altered version of the enzyme that doesn’t produce the red pigment – flowers remain white
1. Homozygous for allele 1 – pigment produced – red flowers
2. Homozygous for allele 2 – no enzyme activity so no pigment – white flowers
3. Heterozygous – single functioning allele so only produces enough pigment to make the flowers pink
324
Rules of codominant writing
We can’t use upper and lower case letters as this implies dominant/recessive
- We use different letters instead
o R = red
o W = white
- Letters should be superscript to the letter that represents the gene in question:
o C = colour
325
What are mutiple alleles with example
- Multiple alleles have more than two alternate forms of a single gene, located at the same loci of homologous chromosomes
- Polygenetic traits (eye colour) are determined by several genes at different gene loci
- Multiple alleles are involved in the determination of a single train by codominance
- E.g.
o Human blood groups
o 3 alleles associated with he immunoglobulin gene (gene I)
o Gene I dictates the presence of a certain antigen on the cell surface of red blood cells
326
The allele is I^A, what is the antigen produced, possible genotypes, blood group, and diagram?
A
IAIA and IAIO
A
check notes
327
The allele is I^B, what is the antigen produced, possible genotypes, blood group, and diagram?
B
IBIB, IBIO
B
Check notes
328
The allele is I^O, what is the antigen produced, possible genotypes, blood group, and diagram?
Neither
IOIO
O
Check notes
329
The allele is I^A I^B, what is the antigen produced, possible genotypes, blood group, and diagram?
A and B
IAIB
AB
Check notes
330
- For red blood cells, there are 3 alleles, but only 2 can be present in an individual, why?
- This is because there are only two homologous chromosomes, so only 2 gene loci
331
- IA and IB are codominant
- IO is recessive to both
- This gives rise to ___ possible blood groups
4
332
Which are the blood groups, and which is the most common?
A, B, AB, O
O is the most common – 48%
333
If you have which antigen, your blood is positive?
Rhesus (Rh) D antigen
334
Receiving blood from the wrong group can be life threatening, why? How can this be counteracted?
- The antibodies will attack the cells
- BUT
- As group O red blood cells have no antigens, it can safely be given to any other group
335
Explain the antibodies associated with each red blood cell type
- A antigens on the red blood cells with anti-B antibodies in the plasma
- B antigens with anti-A bodies in the plasma
- O antigens but both anti-A and anti-B antibodies in the plasma
- Both A and B antigens so no antibodies
336
What is Recombinant DNA Technology? What does it produce?
- Transferring DNA fragments from one organism to another
- Produces transgenic organisms
- Produces genetically modified organism
- Produces large quantalities of a required protein
337
Process of producing proteins from recombinant dna technology?
1. Isolation of the DNA fragment that carries the desirable gene
2. Insertion of the DNA fragment into a vector
3. Transformation (moving DNA into a host cell)
4. Identification of the host cells that have successfully taken up the gene by using gene markers
5. Growth/cloning of the population of host cells
338
Why is it possible to use differing organisms in recombinant dna technology?
genetic code is universal
| - Mechanisms involved in transcription/translation are universal
339
What is the difference between chromosomes and chromatids?
* Before replication, one chromosome is composed of one DNA molecule
* Following replication, each chromosome is composed of two identical DNA molecules (i.e. DNA replication increases the amount of DNA but does not increase the number of chromosomes)
* The two identical copies – each forming one half of the replicated chromosome – are called chromatids
* During the later stages of cell division, these chromatids separate longitudinally to become individual chromosomes
340
Desxribe the human Karyotype
- 46 chromosomes
- 23 pairs
- 22 of the 23pairs have homoglous partners which are identical
- 23rd pair are sex chromosomes (X and Y)
341
Which of XX, and XY is male and femal?
XY – male
| XX – female
342
What is the ratio of offspring for reproduction of males and females? (in terms of x and y chromosomes)
Offspring – 2x XX, 2x XY
Phenotype – 2x male, 2x female
Ratio – 1:1
343
- Genes found on either X or Y are _______
sex-linked
344
Which is longer, x or y?
X
345
Some genes found on x do not have a _______ on Y?
Homologous equivalent
346
- Recessive characteristics found on those people will be more frequent in men, why?
This is because they have no homologous series on Y that could carry the dominant allele
347
What is hemophillia?
- X-linked genetic disorder (defective gene on X)
- Blood does not clot correctly
- Leads to excess bleeding following a cut or persistent internal bleeding
- Fatal if not treated
Fatalities have selectively reduced the gene in the population to approximately 1 in 20,000
348
Why is hemophillia rare in females?
- Have two x chromosomes
| - Hemophiliac females used to die at the onset of puberty
349
Is hemophilia recessive or dominant?
Recessive
350
What does the recessive hemophilia allele code for?
codes for an alternative sequence which results in a faulty protein
351
What do pedigree charts allow us to do?
- Allow us to trace inheritance of sex-linked characteristics
352
Methods used to identify a gene include:
- mRNA cDNA using reverse transcription
- Using restriction endonucleases to cut out desired gene
- Making the gene in a gene machine
353
Draw the process of HIV replication
CHECK NOTES
354
What are the steps of HIV replication?
1. HIV binds to helper T cells
2. Protein capsid fuses
3. Reverse transcriptase converts HIV RNA to DNA
4. The new DNA moves into the nucleus to create mRNA
5. New viral proteins and HIV made
6. HIV bud away from the helper T cell
355
How is reverse transcriptase used in recombinant DNA?
1. Protein producing cell with large amounts of relevant mRNA is selected
2. Desired genes mRNA is extracted
3. Reverse transcriptase forms a single-stranded complementary copy of DNA (cDNA) from mRNA = template strand
4. Hydrolysis of the mRNA isolates cDNA
5. DNA polymerase forms DNA on the template cDNA
6. Desire gene is formed
7. Could be inserted into plasmids
356
What is a restriction endonuclease?
- A restriction enzyme
- Cutes DNA at a specific sequence of bases – recognition sequence
- Has two results
o Producing ‘blunt ends’
o Producing ‘sticky ends’
357
Why are sticky ends more useful?
- Are a palindrome
o Same forward and backward
- 4 unpaired bases are opposite
- Recognition sequence is 6 bp palindromic sequence
o 6 because restriction endonuclease recognizes a 6 base pair sequence
o Complementary to plasmid
358
What is the gene machine?
- Used to create the gene required
- Synthesizes DNA fragments from scratch
- No need for a pre existing DNA template
359
How does the gene machine work?
1. Desired protein identified
2. Base sequence determined
3. Amino acid order determine
4. Amino acid sequence helps work out complementary mRNA codons
5. mRNA used to produce complementary DNA
360
What are the steps involved in the gene machine?
1. The DNA sequence is designed (if not known) and fed into the computer
2. First nucleotide is fixed to a support
3. Nucleotides are added in correct order
4. Protecting groups are added to ensure bases are added at the right place
5. Compurers design oligonucleotides
a. Short sections of single stranded DNA
6. Protecting groups are removed and oligonucleotides joined
7. Double strands are formed to replicate a gene
8. Gene is inserted into a plasmid
9. Vector (bacteria) stores, replicates, and transfers the gene
10. New gene is checked for mistakes
11. Bacteria carrying suitable gene are cloned
361
What is amplification?
Once a DNA fragment containing the desired gene you need is isolated you need to:
- Clone it
- Produce enough of it for medical or commercial use
362
How is amplification done?
Two main methods:
1. In vivo – transferring into a host cell using a vector
2. In vitro – polymerase chain reaction
363
What are the 5 main stages of in vivo amplification?
In vivo amplification involves the same 5 steps:
1. Isolation
2. Insertion
3. Transformation
4. Identification
5. Growth
364
What does isolation and insertion require?
- Restriction endonuclease
- Complementary sticky ends
- A vector
- A plasmid
365
Steps of isolation and insertion
1. Desired gene (from a human) is cut at the recognition site with a restriction enzyme
2. The section of DNA from E.coli (bacteria) is cut using the same restriction enzyme at the same recognition site
3. Complementary sticky end is produced
4. Complementary base pairing occurs
5. Weak hydrogen bonds form
6. DNA ligase reforms the sugar-phosphate backbone
366
Explain why the same restriction endonuclease enzyme must be used (4 marks)
1. Cuts at the same base sequence
2. Ensures sticky ends are complementary
3. Only cuts at specific recognition site
4. Ensures DNA fragment can insert into the plasmid
367
Fr transcription to take place you also require (for amplification
- RNA Polymerase
- Transcription factors to bind near gene
- Promoter region: initiates transcription
o Tells RNA polymerase where to bind
- Terminator: releases RNA polymerase
368
What is transformtion?
- Introducing recombinant plasmids into a host
- Mixing bacterial cell and plasmid in a medium containing
o Calcium ions
o Ice cold
369
Why are those conditions needed for transformation?
1. Ice cold calcium chloride solution
Increases permeability
2. Heat shock
Encourages uptake
370
Problems with transformation
1. Less than 1% take up the plasmids
2. Some plasmid close before the new DNA is added
3. Some DNA joins to form its own plasmid
371
What are the main methods of identification?
Using a second, separate gene on the plasmid that is easily identifiable –
1. Resistant to an antibiotic
2. Make a fluorescent protein
3. Produce an enzyme whose action can be identified
372
Explain autosomal linkages
When 2 or more genes are carried on the same autosome = autosomal linked
• All linked genes stay together during meiosis
• This means they will pass into the gamete together
• Meaning they will pass into the offspring together
• They do not follow Mendel’s Law of Independent Assortment as each allele is not free to mix with either allele from another pair
373
Predict the genotypes of offspring of GgNn and GgNn if GN and gn are autosomal linked
GGNN
GgNn
GgNn
ggnn
374
Gene markers that code for antibiotic resistance can be used to identify the uptake of recombinant plasmids. Explain how and what are the problems with this (4 marks)
1. Bacterial cells are grown in a medium containing antibiotic
2. Plasmids taken up, have resistance so survive
3. Any that do not will die
Problems –
Plasmids may be taken up but close before gene is inserted
OR
1. Second antibiotic resistance gene is cut when new gene is incorporated
2. Bacteria with required gene are not resistant
3. Grown in medium containing antibiotic 2
4. Those with required gene die
375
What is replica plating?
One or more secondary petri plates are inoculated with the same colonies of microorganisms from a primary plate, reproducing the original spatial pattern of colonies
376
Steps of replica plating
1. The bacteria is gown on agar treated with ampicillin (antibiotic)
2. Colonies grow if resistant to ampicillin (the bacteria that took up the plasmid)
3. A replica plate is now made by pressing the agar of one petri-dish, onto the agar of a new petri-dish, transferring bacterial cells from each colony onto the new agar
4. Second agar plate is treated with antibiotic 2
5. Colonies are allowed to develop
6. Missing colony did not have resistance, must be a colony containing cells with the plasmid
377
Which genetic cross has 3:1 ratio?
monohybrid two heterozygous
378
Which genetic cross has 9:3:3:1 ratio?
dihybrid two heterozygous
379
Which genetic cross has 1:1:1:1 ratio?
blood group (heterozygous A and B) or sex linkage (carrier female and normal male)
380
Which genetic cross has 1:2:1 ratio?
Codominant heterozygous
381
What does epi mean?
upon/over
382
What is epistasis?
- Epistasis describes a condition whereby one gene controls the expression of another gene
- Or
- When an allele of one gene affects or masks the expression of another in the phenotype
383
Ratio for crossing over AaBb and AaBb where a dominant B means A works and a recessive bb means A doesnt work
9:4:3
384
Explaination of epistemic genes
- The expression of gene B affects the expression of gene A
- bb = no melanin/white
- If there is no melanin then gene A cannot be expressed
- This means AA, Aa, and aa, will all produce white fur if bb is present
- If B is present in the genotype, melanin is produced
- If A and B are produced then melanin and banded are produced, so agouti
- If B is found with aa, then melanin I produced but bands are not, black
385
How does epistemic genes affect biochemical oathways
- Some genes act in sequence by coding for specific enzymes in a pathway
- Dominant alleles code for the functional form of the enzyme
- Recessive homozygotes would disrupt the pathway
- The presence of one non-functional gene will affect the other as failure to express one gene will result in no pigment being made
386
Explain how antibiotic resistance aids in the identification stage of in vivo amplification?
1. Select a plasmid with two antibiotic resistant genes
2. Insert the DNA fragment in an antibiotic gene
3. Grow bacteria on an agar plate containing antibiotic 2
4. replica plating
5. Missing colony did not have resistance, and so must be a colony containing cells with he plasmid, you compare this with the first plate, and identify the desired cells to clone
387
A plasmid may be used as a vector. Explain what is meant be a vector in this context. (2 marks)
Something which carries foreign DNA molecules into another cell.
388
Molecular biologists often use plasmids which contain antibiotic resistance genes. Explain the reason for this. (2 marks)
Acts as a marker gene, which allows the detection of cells containing the plasmid.
389
How can fluoresence aid in the identification stage of in vivo amplification?
How?
- Organisms such as jellyfish can produce green fluorescent protein (GFP)
- GFP is introduced into bacterial plasmids
- Required gene is inserted in the middle
What?
- Hybrid plasmid is inserted into host (bacterial cell)
- Any cells that successfully took up plasmids will not fluoresce
- These are collected and cloned
390
How can enzyme markers be used in the identification stage of in vivo amplification?
- Desired gene inserted into a gene coding for an enzyme i.e. lactase
- Colorless substrate Xgal lactase blue
- Bacteria are grown in a medium containing Xgal
- Bacteria with plasmid cannot produce lactase
- Cannot convert colour to blue
- Colorless spots identified and cloned
391
What is in vitro cloning?
- Copying DNA fragments outside of living organisms
- Fully autonamted
- Fast and efficient
- Highly used in forensic science
392
What is the main method of in vitro cloning?
- PCR (polymerase chain reaction)
- DNA sequence is exponentially amplified
- Thousands/millions of copies of DNA segment
393
What is required for in vitro cloning?
1. DNA fragment – specimen of interest that needs to be copied
2. DNA Polymerase – enzyme that joins nucleotides together
3. Primers – short nucleotide sequence that has bases complementary to one end of the DNA fragments
4. Nucleotides – contain the 4 DNA bases and are used to join to the DNA fragments
5. Thermocycler – automated machine that controls the temperature during the PCR cycle
394
Describe the process of PCR
1. DNA Fragments, DNA polymerase, and primers are mixed and put in the thermocycler
2. Temperature increased to 95’C which causes the hydrogen bonds to break which separates the DNA strands
3. Cooled to 55’C which causes the primers to anneal to the complementary bases at the ends of the DNA fragments
4. Primers stop DNA strands from re-joining
5. Primers provide the starting sequence for DNA polymerase, which can only join nucleotide onto an existing chain
6. DNA polymerase beings DNA copying
7. It begins at the primer until it reaches the end of the fragment
8. Temperature increases to 72’C, which is the optimum temperature for DNA polymerase
395
Key poitns of PCR
- Produces 2 copies of the original double stranded fragment
- One cycle takes about 2 minutes
- More than 100 billion copies can be made in a few hours
- Process is repeated
396
Polymerase works in PCR because ...
o It is taken from bacteria in hot springs
o Its an extremophile
o It is thermostable (works functionally in high temperatures)
397
Why is it good to locate genes?
- Identify genes responsible for diseases
- Infer treatments
- Allow early diagnosis
- Recombinant gene technology
398
What are the two main methods for locating genes?
- Labelled DNA probes
| - DNA hybridization
399
Summarize the process of DNA hybridization for locating genes
1. Double stranded DNA is heated
2. The single stranded DNA is mixed with a labelled DNA probe (marker)
3. The solution is cooled so the complementary bases can anneal DNA hybridisation
4. The marker on the probe identifies the gene present
400
What is a DNA probe and what is it used for?
- Short, single-stranded sections of DNA fragments
- Bind to complementary sections on other DNA strands
- Labelled so easily identifiable
401
DNA probe methods
- Fluorescently labelled
- Radioactively labelled
- Isotope 32P
- IDd using X-ray film
402
To identify a disease causing mutation you need to:
- Screen for mutated genes
- Create a probe complementary to mutated gene
- Sequence the mutant gene
o DNA sequencing is used to determine the nucleotide order of the mutant allele
403
How do you identify a mutant allele?
1. DNA sequencing determines the nucleotide order
2. DNA fragments complementary to the mutant gene are made
3. The DNA fragment is radioactively/fluorescently labelled (DNA probe)
4. PCR used to copy the DNA probe
5. PCR used to copy the DNA prove
6. DNA from the patient is heated to make it a single strand
7. The probe is added
8. DNA prove will bind if complementary mutant DNA is present
9. Sample is washed to remove any unattached proves
10. Labeled DNA fragments labelled are identified
404
What is genetic counselling?
A service that help individuals to:
- Understand a screenings emotional, psychological, medical and economic consequences
- Get more accurate testing and understand results of this
- Help make more appropriate and informed decisions
405
Why do genetic counselling?
- Family history
- High probability of having children with the disorder
- Increased risk/risk factors
406
What is a microarray?
- A collection of microscopic DNA spots
- Attached to a solid tile
- In a known position
407
Why is a microarray useful?
It is a lab tool used to:
- Detect the expression of different gees
- At the same time (simultaneously)
- Identify multiple genetic disorders
408
Steps for microarray use
1. Identify different disease causing genes
2. Amplify the DNA probes using PCR
3. Attach them to a glass slide
4. Extract the DNA/RNA you want to test (from different areas of the genome)
5. Add a label to this so that it can be identified
6. Add this to your slide
7. Complementary DNA in the donor will bind to probes
8. Wash the array to remove any unbound sample fragments
9. Expose to UV light
10. Any DNA bound to the probe will fluorescence
409
Micro array positive result
If the fluorescent spot contains the probe for the mutated gene, the sample donor has that genetic disorder.
410
How can microarrays be used?
A microarray can be very useful for identifying:
- Cancer causing mutations
- People at risk of genetic diseases
- The most effective medicines
411
What are the two Tumour Supressing Genes
- One alleles of the tumour suppressing gene = can survive
| - Both alleles of the tumour supressing gene = tumour may develop
412
How can microarrays help?
- Identify people at risk
- Ensure they cut down on mutagens
- Regular check ups
413
How is genetics linked to medicine?
- Genotypes affect the effectiveness of some drugs
- Dosages can be controlled, making it
o Cheaper
o More effective
o Reduces harm
Cancer screening could show:
- Oncogene mutations
o Determine the type of cancer = the best drug or chemo to use
- Gene changes
o Predict likely benefit from different treatments
- Single cancer cells
o Could cause a relapse
Other Examples:
- Painkillers
o Effectiveness linked to activating enzyme levels
- Vitamin E
o Reduces risk of cardiovascular disease in some diabetic patients, increases it in others
414
What is a mutation?
- A change to the structure or quantity of DNA
415
WHat are the two types of mutations?
- There are 2 categories of mutation
o Gene mutation
o Chromosome mutation
416
What is a gene mutation?
- A change to one or more of the bases
- A change to the order of the bases
- Can happen during DNA replication
417
What is a chromosome mutation?
- Change to the structure or number of chromosomes
o Polyploidy
Change in whole set, usual when organism has 3 or more sets (plants
o Non-Disjnction
When homologous pairs don’t separate during meiosis, gametes end up with more or fewer chromosomes
418
Explain substitution
- One base is replaced with another
- 3 possible outcomes
o A stop codon is formed
Polypeptide chain formation is stopped prematurely
o Different amino acid formed
Polypeptide different by one amino acid
Protein may have different shape (active site)
o Different codon produce by codes for the same amino acid
419
Explain deletion
- Deletion of base
- Can have a huge impact
- Frameshift left
- Reading frame shifts so all triplets are changed
- All amino acids are different
- Worse if deleted base is at the start of a sequence
420
Effects of addition and deletion of bases
Addition of a base –
- Similar to deletion if its one base – frameshift tight
- If 3 bases (or a multiple of 3 bases) area added there will be no frameshift and so the change less dramatic
Duplication of a base –
- One or more bases repeated
- Frameshift right
421
Explain inversion mutation
- A group of bases separate from the sequence and re-join in the same place but in inverted order
- The base sequence is reversed
422
Explain translocation mutation
- A group of bases separate from one chromosome and join another
- Usually have a marked effect
- Translocation between chromosomes 9 and 22 causes leukaemia
423
Crossing Over Vs Translocation
- Translocation is a mutation, crossing over is not
- Translocation result in a change in the genetic information between non-homologous chromosomes
- Crossing over simple swaps genetic material between homologous chromosomes unchanged
424
Causes of Mutations
- Spontaneous
o No outside factors involved, usually during DNA replication
- Natural mutation rate = 1 or 2 mutations per 100,000 genes per generation
- Mutagenic agents/mutagens increase this
o Chemicals
Nirogen dioxide affects transcription
Benzopyrene (tobacco) inactivates tumour suppressor genes
o High energy ionising radiation
Alpha and beta particles
Xrays
UV
All disrupt DNA Structure
425
What is genetif fingerprintin?
Genetic fingerprinting is a forensic diagnostic tool which uses analysis of DNA to identify individuals
426
What is genetic fingerprinting useful for?
```
It is useful for:
- Forensic science
- Genetic relationships
o Paternity testing
- Genetic variation/diversity
- Medical diagnosis
- Plant and animal breeding
o Identify organism the desired genes
o Identify paternity (pedigrees)
o Prevent interbreeding
```
427
Why is everyone’s genome unique?
- Genomes contain repetitive, non-coding bases (introns)
- Contain repeated sequences called variable number tandem repeats (VNTRs)
- VNTRs number and length gives a unique pattern
- Close related = more similar the VNTRs
428
Steps of genetic fingerprinting
1. Extraction
2. Digestion
3. Separation (gel electrophoresis)
4. Hybridization
5. Development
429
Describe extraction for DNA fingerprinting
- DNA is extracted from a sample (blood, hair, semen, skin)
| - Amplified using PCR or cells broken down to release DNA
430
Describe digestion for DNA fingerprinting
- Restriction endonucleases
| - Cut close but not within the target DNA (VNTR)
431
What is gel electrophoresis and how does it work?
```
What is Gel Electrophoresis?
- Separates DNA fragments by size
How does it work?
- Agar gel with electrical current running through it
- Fragments are labelled
- Small fragments travel further
- Final position can be viewed
```
432
Why is everyone’s genome unique?
- Short sequences of non-coding DNA
- Repeat in tandem (end to end)
- Number of repeats varies
- Length varies
433
Steps of genetic fingerprinting?
1. Extraction – cell lysis and/or PCR
2. Digestion – restriction endonuclease
3. Separation – gel electrophoresis
4. Hybridization – labelled probe
5. Development – UV or radioactive analysis
434
Describe the steps of gel electrophoresis
1. DNA sample added to well
2. Power source turned on and DNA migrates through the gel
3. The fragments are separated by size
4. Smallest move further
435
How do you analyze gel electrophoresis?
- Control = DNA ladder
- Sample from scene
- Suspects DNA
- Comparisons made
- Criminal identified
436
What is southern blotting?
- A lab technique
- Transfer’s electrophoresis-separated DNA fragments
- To a filter membrane (nylon sheath)
- Prepares fragments for hybridization
- Enables identification
437
Steps of southern blotting simplified
1. Nylon membrane
2. Absorbent paper
3. Exact position of fragments
4. DNA probes
5. Hybridization
6. Analysis and identification
438
Steps of southern plotting
1. DNA fragments produced on gel
2. Placed in alkali to separate double strands
3. Thin nylon membrane laid over gel and covered with absorbent paper sheets
4. Paper draws up the liquid containing the DNA by capillary action, DNA fragmens fix to the nylon in the same position as the gel
5. DNA fragments are fixed to the nylon using UV light, nylon is peeled off
439
What is hybridizarion?
- Radioactive/fluorescent DNA probes are added to label the VNTRs (hybridization)
- Specific probes bind to complementary sequences
- Washed to remove excess probes
- Membrane is dried
440
What is development?
- Nylon sheet is placed under X-ray film
- Radioactive probes on the DNA fragments expose the film
- Produces visible pattern of light and dark bands
- Pattern is unique
- Distribution analyzed
441
Whole process of genetic fingerprinting
- Extraction
- Digestion
- Separation
o Including Southern Blotting
- Hybridization
- Development
o Including Analysis
442
- For forensic science, DNA matches are not enough to convict a suspect, why?
o The DNA may have been left on some other, innocent occasion
o The DNA may belong to a very close relative
o The DNA sample may have been contaminated after the crime, either by the suspects DNA or by chemicals which affect the action of the restriction endonuclease used in preparing the fingerprint
o The calculation used to suggest the probability of a DNA match is based on the assumption that the binding pattern DNA is randomly distributed within the community, but in the case where small religious or ethnic groups tend to have partners within their own community
443
What are stem cells?
- Undifferentiated cells that can mature into any type of cell
- All specialised cells originally came from stem cells.
- Stem cells divide to become new cells, which then become speciailised.
444
What is self-renewal?
Self-renewal – the ability to go through numerous cycles of cell division while maintaining the undifferentiated state.
445
What is an embryonic stem cell?
early stages of development, very flexible
446
What is an adult tissue stem cell?
found in fetus adult, specific to a particular tissue/organ, allow self-regeneration only
447
What are the locations of somatic stem cells?
- Blood vessels
- Skin
- Heart
- Liver
- Gut
- Bone marrow
- Peripheral blood
- Skeletal muscle
448
What is a totipotent stem cell?
o Can produce all cell types (embryo and placenta)
| o Only present during the first few cell divisions
449
What is a pluripotent stem cell?
o Can become body cells found in an embryo but not the placenta
o Can divide in unlimited numbers so used in medicine
450
WHat is a multipotent stem cell?
o Found in adults
o Give rise to several different types of specialised cells, but are restricted to a certain organ or tissue types e.g. blood cells
451
WHat is a unipotent stem cell?
o Found in adults
| o Can only make one type of cell e.g. epidermal skin cells
452
Why are totipotent cells useful?
- Totipotent cells have the ability to develop into any cell found in the human body and during its development
- Useful during embryo development, as we start off as a single cell, but are eventually a collection of millions of different cell types
453
Why are embryonic stem cells important?
- Embryonic stem cells are important because they can differentiate into any type of cell
- For the first few weeks, the developing embryo contains unspecialised cells, these are embryonic stem cells
454
How do cells become specialised?
Specialised cells all contain the same genetic information.
1. A cell becomes specialised as different genes are expressed, and so only some DNA is translated into proteins
2. All cells in the body do not make all of the products they are genetically capable of, as it would be a waste of resources
455
How are cells specialised, in depth?
1. Some genes are permanently expressed
2. Some genes are never expressed
3. Some switch on and off
4. Differentiated cells produce different proteins as a result
Essentially:
Gene expressed mRNA transcribed and translated into proteins proteins modify the cell cell becomes specialised for a particular function
Genes switched off mRNA not transcribed protein not produced
456
How are genes prevented from expressing themselves?
1. The prevention of transcription (therefore no mRNA)
| 2. Break down of mRNA before translation
457
Describe cardiomyoctes
unipotent
- Heart muscle cells
- Originally thought they were unable to divide to replicate themselves in mature mammals
- Now thought that we have unipotent stem cells in the heart that can replace the old/damaged cardiomyocytes
458
How can stem cells help heart attacks?
- A heart attack occurs when the coronary arteries are blocked
- With no blood flow, the cells die, causing cardiac tissue to die
- Once these tissues are lost, they cannot be replaced, thus causing permanent damage
- Current research has shown that it may be possible to repair damaged cardiac tissue with stem cells
- Human embryonic stem cells can differentiate into cardiomyocytes under appropriate conditions
459
How are human embryonic stem cells used?
- Cells can be taken from the early stages of an embryo, grown in vitro, and induced to develop into tissues
460
Descrbe parkinson's disease
- Degenerative neurological disorder that affects the body’s motor system
- It is caused by a lack of dopamine made by brain cells
- 10 million sufferers
461
What are iPS cells?
1. iPS cells are induced pluripotent stem cells that are produced from unipotent cells
462
How are iPS cells geneticallly altered?
2. They are genetically altered so that they have the characteristics of embryonic stem cells (pluripotent), this is done by inducing genes and transcriptional factors to be expressed (switches on ‘off’ genes)
3. Since the genes can be ‘switched on’ it shows that adult stem cells retain the genetic information that was present in the embryonic stage
463
What are interesting about iPS cells?
4. iPS cells are similar to embryonic stem cells, capable of self-renewal, and have the potential to divide indefinitely
464
Why could iPS cells be useful?
5. They could be useful as they replace embryonic stem cells in research and treatment, as well as removing ethical complications
465
Do mature plants have stem cells?
6. Mature plants have many totipotent cells, this allows them to form clones from a single cell
466
For stem cell research
- Huge potential to cure debilitating disease
- Wrong to allow suffering when it can be relieved
- Embryos are created for other purposes (IVF) so why not stem cells
- Embryos of less than 14 days are not recognisably human and so do not command the same respect as adults or fetuses
- There is no risk of research escalating or including fetuses because of current legislation
- Adult stem cells are not as suitable as embryonic stem cells and it may be many years before they are, in the meantime many people will suffer unnecessarily
467
Against stem cell research
- It is wrong to use humans, including potential humans, as a means to an end
- Embryos are human, they have human genes, and deserve the same respect and treatment as adult humans
- It is a ‘slippery slope’ to the use of older embryos and fetuses for research
- It could lead to research and development of human cloning and, although banned in the UK, the information gained could be used elsewhere
- It undermines respect for life
- Adult stem cells are an available alternative and energies should be directed towards developing these
468
What does in vivo have which in vitro doesn't?
Can add a gene to a different organism via a vector
Little risk of contamination as restriction endonuclease is specific
Isolates specific genes
Very accurate/mutation rate is low
Contaminated in In Vivo will not be taken up by the plasmid due to specific sticky ends
469
What does in vitro have which in vivo doesn't?
```
Very fast (in vitro takes weeks)
Forensic analysis – produce samples quickly from a tiny specimen
Does not require living cells
No time consuming culture needed
Only need a DNA sequence
```
470
How does RNA polymerase Stop?
- When RNA polymerase reaches a stop triplet, it detaches – the production of pre-mRNA is complete
471
What is a splieosome?
RNA-protein complex made up of small nuclear ribonucleoproteins (snRNPs)
472
Draw a diagram to show ho w spliceosome works
check notes
473
Describe tRNA –
- The open-end of a tRNA molecule is the amino acid attachment site
- The opposite end is the anticodon loop
- The anticodon loop consists of 3 unpaired bases
- These bases vary, giving tRNA specificity to amino acids
474
What forms the peptide bonds in translation?
Peptide bonds are formed with the enzyme peptidyl transferase and ATP in translation
475
The ribosome loves along the mRNA until it reaches a stop codon, there it detaches due to what?
The ribosome loves along the mRNA until it reaches a stop codon, there it detaches due to the presence of a release factor.
476
How does the adrenaline second messenger model work? Draw a diagram
check notes
477
How does the epinephrine second messenger model work? Draw a diagram
check notes
AQA A Level Biology
flashcards
Decks in class (19)
# Cards
-
Topic 1 - Biological molecules309
-
Topic 2 - Cells355
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Topic 3 - Organisms exchange substances with their environment334
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Topic 4 - Genetic Infomation, variaton and relationships between organisms183
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Topic 5 - Energy transfers in and between organisms403
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Topic 6 - Organisms respond to factors in the external or internal environment300
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Topic 7 - Genetics, population, evolution and ecsystems477
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MIX43
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Topic 5 - Respiration50
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Essay1
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Exam Questions I've Gotten Wrong34
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Immune Response74
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PAper 1B356
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Paper 2A part 1330
-
Paper 2A Part 2148
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Paper 2B Part 1132
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Paper 2B Part 2107
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Paper 3A363
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Paper 3B243
