Ch 18 - (Variation & Selection)

Question 1

Define Variation.

Answer 1

differences between individuals of the same species

Question 2

What is phenotypic variation?

Answer 2

difference in features between individuals of the same species

Question 3

How are the differences in phenotypic variation caused?

Answer 3

differences in genes, which is genetic variation

Question 4

What are the 2 types of phenotypic variations?

Answer 4

1.Continuous Variation

2. Discontinuous Variation

Question 5

What is continuous variation?

Answer 5

• very many small degrees of difference for a particular characteristic between individuals
• they are arranged in order and can usually be measured on a scale

Ex- height, mass, finger

Question 6

What is discontinuous variation?

Answer 6

distinct differences for a characteristic

Question 7

How is phenotypic variation caused?

Answer 7

1. It can be genetic - controlled entirely by genes
2. environmental - caused entirely by the environment in which the organism lives

Question 8

What are examples of genetic variation in humans?

Answer 8

• blood group
• eye colour
• gender
• ability to roll tongue
• whether ear lobes are free or fixed

Question 9

What are characteristics of all species affected by?

Answer 9

environmental factors such as climate, diet, accidents, culture and lifestyle

Question 10

What is discontinuous variation caused by?

Answer 10

genetic variation alone

Question 11

What are mutations?

Answer 11

genetic changes

Question 12

What do mutations lead to?

Answer 12

• o effect on the phenotype
• development of new alleles and so new phenotypes and if they do, most have a small effect
• harmful changes (Ex- sickle cell anaemia)

Question 13

What do alleles give an individual?

Answer 13

survival advantage over other members of the species

Question 14

How do mutations happen?

Answer 14

spontaneously and continuously

Question 15

How can the frequency of mutations be increased?

Answer 15

1. Ionising radiation (e.g. gamma rays and X - rays) - which can damage bonds and cause changes in base sequences
2. non-ionising radiation (e.g. ultra-violet) - can also damage bonds and cause changes in base sequences
3. Certain types of chemicals - for example chemicals such as tar in tobacco

Question 16

What can increased rates of mutations lead to?

Answer 16

cancerous

Question 17

What re the ways in which genetic variation happens?

Answer 17

1. Mutations:
   - random genetic changes to the base sequence of DNA

• New alleles form through these random changes to
  DNA

2. Meiosis
   - New allele combinations form through segregation
3. Random mating
   - Which partnerships form for sexual reproduction
4. Random fertilization
   Which sperm and egg combinations occur during sexual reproduction

Question 18

What are adaptive features?

Answer 18

inherited functional features of an organism that increase its fitness

Question 19

what is fitness?

Answer 19

probability of an organism surviving and reproducing in the environment in which it is found

Question 20

What is hydrophytes?

Answer 20

Plants adapted to live in extremely wet conditions

Question 21

What are common adaptations in hydrophytes?

Answer 21

1. Large air spaces in their leaves
2. Small roots
3. Stomata

Question 22

What does Large air spaces in their leaves do as an adaptation for hydrophytes?

Answer 22

for flotation, to keep the leaves close to the surface of the water where there is more light for photosynthesis

Question 23

What does Small roots do as an adaptation for hydrophytes?

Answer 23

extract nutrients from the surrounding water through their tissues

Question 24

What does stomata do as an adaptation for hydrophytes?

Answer 24

open all the time and mainly found on the upper epidermis of the leaf where they can exchange gases much more easily with the air

Question 25

What is xerophytes?

Answer 25

Plant adapted to live in extremely dry conditions

Question 26

What are common adaptations in xerophytes?

Answer 26

1. Thick waxy cuticle 2. Sunken stomata 3. Leaf rolled 4. Small leaves: 5.Extensive shallow roots 6.Thickened leaves or stems

Question 27

What does thick waxy cuticle do as an adaptation for xerophytes?

Answer 27

- the cuticle cuts down water loss in two ways: 1. it acts as a barrier to evaporation and also the shiny 2. surface reflects heat and so lowers the temperature

Question 28

What does Sunken stomata do as an adaptation for xerophytes?

Answer 28

- stomata may be sunk in pits in the epidermis - moist air trapped here lengthens the diffusion pathway - reduces the evaporation rate

Question 29

What does Leaf rolled do as an adaptation for xerophytes?

Answer 29

- stomata inside and an inner surface covered in hairs - traps moist air and prevents air movement across stomata - reduces transpiration

Question 30

What does Small leaves do as an adaptation for xerophytes?

Answer 30

- small, needle-shaped leaves - reduce the surface area and therefore the evaporating surface

Question 31

What does Extensive shallow roots do as an adaptation for xerophytes?

Answer 31

allow for the quick absorption of large quantities of water when it rains

Question 32

What does thicken leaves or stems do as an adaptation for xerophytes?

Answer 32

contain cells that store water

Question 33

What results in natural selection?

Answer 33

individuals that have the best adaptive features are the ones most likely to survive and reproduce

Question 34

What do individual species show?

Answer 34

range of variation caused by differences in genes

Question 35

What happens when species reproduce?

Answer 35

- produce more offspring than the environment is able to support - competition for food and other resources which results in a ‘struggle for survival’

Question 36

Which individuals have a high chance of survival and to reproduce?

Answer 36

characteristics most suited to the environment

Question 37

What does more chances of survival and reproduce lead to?

Answer 37

- alleles resulting in these characteristics are passed to their offspring at a higher rate - next generation, will hv greater number of individuals with the better adapted variations in characteristics

Question 38

Who is survival of the fittest?

Answer 38

theory of natural selection was put forward by Charles Darwin

Question 39

What happens if environment does not changes in adaptation?

Answer 39

selection does not change

Question 40

what happens if environment changes in adaptation?

Answer 40

- a chance mutation produces a new allele, - selection might now favor individuals with different characteristics or with the new allele

Question 41

What Favours individuals when environment does not change?

Answer 41

same characteristics as their parents

Question 42

What happens to individual that survive and reproduce?

Answer 42

- different set of alleles that they pass on to their offspring - change in the characteristics of the species - it will produce evolution

Question 43

Define evolution.

Answer 43

change in adaptive features of a population over time as a result of natural selection

Question 44

What does natural selection result in?

Answer 44

process of adaptation

Question 45

What happens as a result of evolution?

Answer 45

populations of organisms become better suited to their environment

Question 46

What does selective breeding mean?

Answer 46

elect individuals with desirable characteristics and breed them together

Question 47

Why does the selective breeding process not stop?

Answer 47

not all of the offspring will show the characteristics you want so offspring that do show the desired characteristics are selected and bred together

Question 48

Does selective breeding process hv to be repeated?

Answer 48

repeated for many successive generations

Question 49

What happens in natural selection?

Answer 49

- occurs naturally - results in development of populations with features that are better adapted to their environment and survival - usually take a longer time to occur

Question 50

What happens in artificial selection?

Answer 50

- only occurs when humans intervene - results in development of populations with features that are useful to humans and not necessarily to survival of individual - take less time as only individuals with the desired features are allowed to reproduce