Evolution

Question 1

How are experimental methods used to test adaptations?

Question 2

Describe an in vitro experiment used to show evolution n E coli

Answer 2

• E coli in petri dishes of nutrients, left to replicate and aliquots taken
• up to 7000 generations,
• up to 35,000 generations, new biosynthetic pathways (citrate)

Question 3

Why are microbes a good model for evolution?

Answer 3

• easily propagated
• rapid generation
• large population sizes
• single/mixed genotype
• phenotypes easily detected
• whole genomes sequenced
• direct genetic manipulations possible

Question 4

What are the basics that need to be ascertained before a trait is deemed adaptive?

Answer 4

• variation in a trait
• heritability of a trait
• trait utility
• fitness consequences of altering a trait
• correspondence between trait and a specific niche

Question 5

What is human induced selection?

Answer 5

humans having an extreme effect on environment

Question 6

What is urban selection? Give an example

Answer 6

novel ecosystems with increase noise and light pollution adaptation, new diets, altered hydrology and surface cover
eg. Anolis lizard from Puerto Rico, found in cities had longer legs and increased lamellae under feet to better use smooth surfaces and buildings

Question 7

Define Co- evolution

Answer 7

the evolution of reciprocal adaptations of two or more species that have prolonged close interactions
- expected in mutualism, predation, competition

Question 7

Give an example of co evolution in host-pathogen interactions

Answer 7

• Flax Rust, both flax and flax rust have multiple genes for resistance and virulence
• The flax’s immune receptors recognize the rust’s effectors, which favors changes in the rust that allow it to escape recognition. This leads to the development of new resistant crop varieties, which in turn leads to the evolution of new rust varieties

Question 7

What is an ‘arms race’?

Answer 7

an innovation of one species leads to a counter innovation in the other

Question 7

Why are Mullerian mimics likely to exhibit reciprocal evolutionary patterns?

Answer 7

Both species involved are unpalatable so have an opportunity to affect the evolution of each others colour patterns

Question 8

What is Mullerian mimicry

Answer 8

multiple species that are dangerous, poisonous, or unpalatable to predators evolve to look similar to each other.

Question 9

Describe the 2 step step process of co -evolution in mimicry

Answer 9

• an initial major gene mutation occurs to make the less protected species look like the more protected species
• minor gene mutations in both species refine the mimicry

Question 10

What is Batesian mimicry

Answer 10

Batesian mimicry is a form of biological resemblance where a harmless organism imitates the warning signals of a harmful organism. The mimic gains protection because predators mistake it for the harmful model and leave it alone

Question 11

Give an example of frequency dependent selection

Answer 11

Batesian mimicry whereby a palatable species imitates the warning signals of a unpalatable species, under positive selection

Question 12

Define adaptive radiation

Answer 12

the spread of new species of common ancestry into different niches, involving an excess of cladogenesis over extinction

Question 13

What is cladogenesis?

Answer 13

type of branching evolution, the splitting of an ancestral species into several new species

Question 14

What is anogenesis?

Answer 14

type of phyletic evolution, the transformation of an ancestral species to a new species

Question 15

Define convergent evolution

Answer 15

process whereby organisms not closely related independently evolve similar traits as a result of having to adapt similar environments or ecological niches

Question 16

Define divergent evolution

Answer 16

process whereby single ancestral species diversifies into multiple descendant species that adapt to different environments or lifestyles

Question 17

Give some intrinsic factors that promote adaptive radiation

Answer 17

• metabolic and physiological opportunities eg. crassulacean acid metabolism, endosymbiosis, toxins
• developmental opportunities eg. hox genes and segmentation, wings, flight dispersal

Question 18

Give some extrinsic factors that promote adaptive radiation

Answer 18

• empty habitats - lack of competition
• novel environments (man-made)
• intensity of selection
• founder effects
• ecological release

Question 19

What is ecological release

Answer 19

occurs when a species expands its niche within its own habitat or into a new habitat where there is little competition for resources which remain abundant

Question 20

What are the 3 major stages put forward by Streelman and Danely in vertebrate evolution for adaptive radiation

Answer 20

• divergence of lineages into different major habitats
• morphological specialisation leading to trophic differentiation within habitats
• sensory communication diversification - sexual selection

Question 21

Define evolution

Answer 21

a gradual change in allele frequency

Question 22

Describe 4 postulates of evolution by natural selection from Darwin's theory

Answer 22

- individuals within species are variable - some of the variations are passed onto offspring - in most generations, more offspring are produced than can survive - survival and reproduction are not random; individuals with the highest reproductive success are those with the most favourable conditions

Question 23

Explain the meaning behind the term 'Survival of the fittest'

Answer 23

- Populations have tremendous growth potential - Populations tend to remain stable - Resources are limited - There is a 'struggle for existence' in which most offspring produced die -Individuals vary and variation is heritable - The best adapted (most 'fit') for their environment organisms survive and pass their beneficial traits onto their offspring -Thus the population changes over time

Question 24

Define genetic drift

Answer 24

the chance of difference in transmission of alleles, leading to fluctuations in allele frequency

Question 25

Give some key principles of genetic drift (4)

Answer 25

- it most strongly affects rare alleles - it has a greater influence on rare alleles than selection - it is the primary mechanism for increasing rare recessives - responsible for changing frequencies of neutral mutations

Question 26

Define the founder effect

Answer 26

where drift in small populations can produce bias allele frequencies