1
Q
What are abiotic factors?
A
Non-living components of an ecosystem that affect other living organisms
2
Q
How is temperature an abiotic factor?
A
- Each species has a different optimum temperature
- The further away from the optimum, the fewer can survive
- Ectothermic animals can grow faster
3
Q
How is light intensity an abiotic factor?
A
- LDRs are dependent on it
e.g. greater light intensity = more photosynthesis = more seeds = higher population = more animals can be supported
4
Q
How is pH an abiotic factor?
A
- Enzymes are dependent
- Impacts active shape
5
Q
How is water and humidity an abiotic factor?
A
- In scarce water, only species adapted to dry conditions will increases/maintain populations
- Increased humidity affects transpiration rates
6
Q
How is oxygen availability an abiotic factor?
A
- In aquatic habitats, it is beneficial to have fast flowing cold water as it has high concentrations of oxygen
- Water logged soil has less oxygen
7
Q
How are edaphic factors abiotic?
A
- Soil provides minerals need for growth, water for photosynthesis and anchorage for the roots
8
Q
What are biotic factors?
A
Environmental factors associated with living organisms in an ecosystem that affect each other
9
Q
What are examples of biotic factors?
A
- Competition
- Food
- Territory
- Breeding partners
10
Q
What is an ecosystem?
A
Made up of all the living organisms that interact with one another in a defined area and also the physical factors present in that region
11
Q
What is a producer?
A
Makes its own food (through photosynthesis)
12
Q
What is a carnivore?
A
Only eats other animals
13
Q
What is a herbivore?
A
Only eats plants
14
Q
What is an omnivore?
A
Eats both animals and plants
15
Q
What is a primary consumers?
A
Eats producer (usually herbivore)
16
Q
What is a secondary consumers?
A
Eats primary consumer (usually carnivore)
17
Q
What is a trophic level?
A
Position or stage that something occupies in a food chain
18
Q
What do the arrows in a food chain show?
A
Direction of energy transfer
19
Q
What is biomass?
A
The mass of living material present in a particular place or in a particular organism
20
Q
How do you measure biomass?
A
- Biomass present in each organism multiplied by the number of organisms in that trophic level
- Either by measuring dry mass or mass of fresh material
21
Q
What are the pros and cons of measuring the mass of fresh material?
A
- Easiest method
- Unreliable as mass of water varies greatly
22
Q
What are the pros and cons of measuring the dry mass?
A
- Most accurate
- Organisms are killed and put in an oven at 80°C to evaporate the water
23
Q
What are the units for biomass?
A
Area of land = g/m2
Area of water = g/m3
Each trophic level = kJm-2yr-1 (allows for seasonal changes)
24
Q
What is ecological efficiency?
A
Efficiency with which biomass or energy is transferred from one trophic level to the next
25
What is the efficiency of producers?
- Producers convert 1-3% of sunlight into chemical energy and then biomass
- Not all available solar energy is used for photosynthesis
- Energy lost of photosynthetic reactions
26
Why is not all available solar energy used for photosynthesis?
- 90% is reflected
- Some is transmitted
- Some has an unusable wavelength
- Other limiting factors of photosynthesis
27
How do you calculate net production?
Net production = gross production - respiratory losses
Net production = energy available to pass onto the next level
Gross production = total solar energy that plants convert to organic matter
Respiratory losses = 20-50% of energy for respiration
28
What is nitrogen fixation?
- Nitrogen gas -> nitrogen containing compounds
- Azobacter/Rhizobium bacteria contain nitrogenase enzyme to convert nitrogen and oxygen into ammonia
29
What is Azobacter?
- Nitrogen fixing free living bacteria
- Produce ammonia from nitrogen gas
- Make amino acids
- Release them when they die
30
What are mutualistic bacteria?
- Live in root nodules on peas and beans (legumes)
- Obtain carbohydrates from plants and plants get amino acids from bacteria
31
What is ammonification?
- Production of ammonia from organic compounds (e.g. urea, proteins, nucleic acids)
- Saprobiotic microorganisms (fungi and bacteria) feed on these to release ammonia into the soil
32
What is nitrification 1?
- Ammonium ions -> nitrite ions (NO2-)
- Oxidation
- Releases energy
- Done by Nitrosomonas bacteria
33
What is nitrification 2?
- Nitrite ions -> nitrate ions (NO3-)
- Requires oxygen so occurs in soil with air pockets
- Done by Nitrobacter bacteria
34
What is denitrification?
- Occurs when soil becomes waterlogged
- Anaerobic bacteria carry out denitrification
- Soil nitrates -> nitrogen gas
- Reduced nitrogen compounds for plants
35
What is the carbon cycle?
- Plants remove CO2 from the air by photosynthesis
- Animals eat plants so C is passed along the food chain
- Respiration of animals releases CO2
- Combustion of fossil fuels releases CO2
- Soil bacteria and fungi decompose dead organisms which releases CO2
- Their remains form fossil fuels
36
What are the short term fluctuations in carbon?
- More CO2 at night
- Less in summer
37
Why have there been increased CO2 levels?
- Combustion of fossil fuels releases CO2 locked up millions of years ago
- Deforestation removes photosynthesising biomass which reduces the volume of CO2 removed
38
What is the greenhouse effect?
1. Heat from the sun is reflected from the Earth's surface
2. When it reaches the atmosphere some rays pass through
3. Other rays are trapped in by greenhouse gases
39
What is global warming?
The average increase in average temperature over the last century
40
How is methane produced?
- Decomposers break down dead remains of organisms
- Microbes in primary consumers digest food that has been eaten
- Levels have doubled due to more extraction of fossil fuels, more decaying waste, more cattle and permafrost melting
41
What are the consequences of global warming?
- Changes in temperature and precipitation
- Failure of current crops
- Natural plant distribution change, therefore food chains affected
- Timing of the seasons
- Melting of polar ice caps -> changing sea levels
- Flooding of low lying areas, major cities and fertile land
- Increased frequency of extreme weather (storms, floods, droughts)
- Alter niches available in a community -> loss of species
- We don't know
42
What is succession?
The process of ecosystem change over time
43
What is a pioneer species?
First plant to colonise a land
44
What are the features of pioneer plant species?
- Small species
- Fast growing
- Ability to fix nitrogen
- Produce large quantities of seeds/spores
- Seeds are easily dispersed over long distances
- Rapid germination of seeds
- Self-pollinating or asexual reproduction
- Tolerate extreme conditions
45
What are the features of a climax plant species?
- More species than pioneer community
- Larger species
- Unable to tolerate extreme environments
- Require soil with ample water and minerals
- Dominant species
- Slow growing
46
What are the features of pioneer animal species?
- Few species, if any
- Most small species
47
What are the features of climax animal species?
- Larger species
- More herbivore species
- Carnivore species present
- Longer food chains
48
What are the features of marram grass?
- Deep roots
- Tolerates salty environment
- Only found on sand dunes
49
What is the order of primary succession?
1. Colonisers (e.g. lichens, mosses)
2. Pioneers (e.g. grasses, ferns)
3. Herbaceous plants (e.g. weeds)
4. Shrubs (e.g. shrubs, bushses)
5. Climax (e.g. trees)
50
What is the process of primary succession?
- Colonisers colonise the rock/bare ground which releases minerals which enables other species to survive
- As plants die and decompose the soil deepens so large plants (pioneers and herbaceous plants) can now survive, increasing stability
- Diversity increases when shrubs outcompete smaller plants and become the dominant species
- Soil is now rich and deep enough to support larger climax trees, making it stable
51
What is a climax community?
- Final and stable
- Not subject to further succession
E.g. rainforest
52
What is deflected succession?
- A community that remians stable only because human activity prevents succession to run its course
- Many places need to be actively managed to compete against succession
E.g. sheep grazing, mowing golf courses
Biology A Level Content
flashcards
Decks in class (25)
# Cards
-
2.1.1 Cell Structure45
-
2.1.2 Biological Molecules68
-
2.1.3 Nucleotides and Nucleic Acids32
-
2.1.4 Enzymes36
-
2.1.5 Biological Membranes25
-
2.1.6 Cell Division, Cell Diversity and Cellular Organisation64
-
3.1.1 Exchange Surfaces44
-
3.1.2 Transport in Animals65
-
3.1.3 Transport in Plants60
-
4.1.1 Communicable Diseases, Disease Prevention and the Immune System102
-
4.2.1 Biodiversity70
-
4.2.2 Classification and Evolution58
-
5.1.1 Communication and Homeostasis38
-
5.1.2 Excretion as an Example of Homeostatic Control94
-
5.1.3 Neuronal Communication59
-
5.1.4 Hormonal Communication63
-
5.1.5 Plant and Animal Reponses120
-
5.2.1 Photosynthesis45
-
5.2.2 Respiration52
-
6.1.1 Cellular Control50
-
6.1.2 Patterns of Inheritance78
-
6.1.3 Manipulating Genomes73
-
6.2.1 Cloning and Biotechnology64
-
6.3.1 Ecosystems52
-
6.3.2 Populations and Sustainability44
