Lecture 8 - natural selection & adaptions

Question 1

What type of individuals leave more offspring?

Answer 1

better adapted individuals survive longer & mate more frequently

• poorly adapted individuals due sooner or fail to mate so leave fewer offspring

Question 2

What are the 3 ingredients for natural selection?

Answer 2

1. variability - individuals vary in most traits
2. heritability - variation is passed on via inheritance
3. competition & fitness - individuals compete for limited resources

Question 3

What is variation?

Answer 3

commonly observed that there is variation within a species - not all individuals are alike & there is even variation between parent & offspring

Question 4

What are 2 types of variation?

Answer 4

• continuous - continuous range of variation in handing intensity
• discrete - e.g. discrete colour morphs

Question 5

What is heritability?

Answer 5

• individuals inherit their characteristics from their parents
• the basis for this inheritance is genetic
• i.e. variation is not completely random, but has a deterministic genetic basis

Question 6

What are epigenetics?

Answer 6

describes changes to RNA due to the environment, leading to faster evolution

Question 7

Why is mendelian inheritance important?

Answer 7

because it doesn’t produce a directional change in gene frequency:

P generation: S = 0.5 s = 0.5
F1 generation: S = 0.5 s = 0.5
F2 generation: S = 0.5 s = 0.5

Question 8

What is competition?

Answer 8

There is a finite amount of resource available to members of a species & this means that some individuals are successful & others are not

• consequently not all individuals in a population are able to survive to reproduce
• ecological competition is the consequence of limited amounts of resources

Question 9

What are examples of resources?

Answer 9

include food, water, shelter, space or mates

Question 10

What is fitness?

Answer 10

a measure of reproductive success of an individual
- if an individual pass on copies of 100% of their genes to the next generation, on average, the fitness = 1.0

Question 11

How does an organism achieve a fitness = 1.0?

Answer 11

diploid organisms need to produce at least 2 offspring

Question 12

Why is colour important for mushrooms?

Answer 12

• relationship between thermoregulation and colour
• darker ones absorb more heat, whereas white ones don’t absorb heat so warm up slowly.
• lighter mushrooms in the south, darker in the north

Question 13

What are 2 different types of selection?

Answer 13

• natural selection
• sexual selection

Question 14

What is fecundity & fertility?

Answer 14

number of offspring that can be produced in one cycle

Question 15

How can some behaviours only be explained from the perspective of sexual selection?

Answer 15

e.g. large feathers - attracts attention which makes it more vulnerable to predation, however it attracts a mate

Question 16

When does selection occur?

Answer 16

when genotypes differ in their ability to pass genes on the next generation

Question 17

What happens if a genotype is successful?

Answer 17

its genes will increase in frequency

Question 18

What happens if a genotype is unsuccessful?

Answer 18

its genes will decrease in frequency

Question 19

What are 3 different types of selection?

Answer 19

• directional selection
• stabilising selection
• disruptive selection

Question 20

What is directional selection?

Answer 20

• selection generates a long-term change in a trait
• e.g. evolution of feet in horses - digits to hoof
• e.g. the evolution of long necks in giraffe

Question 21

What is stabilising selection?

Answer 21

• selection against extreme trait values
• e.g. eyespots in butterfly’s provide defence against predators
• selection against eye spots that are too large or small
• the spots mimic an eye so predator doesn’t eat them

Question 22

What is disruptive selection?

Answer 22

• selection for multiple optimum trait values
• e.g. 2 different groups with 2 peaks & no intermediates - evolved to 2 different optima - e.g. depending on what seeds are available for birds