Adaption & speciation (Lucy)

Question 1

Are adaption & speciation the same thing?

Answer 1

Not necessarily

Adaption can happen in species whereas speciation is how new species arise

Question 2

How can adaptions happen within a species?

Answer 2

There can be variation within a species for a trait (such as colour, flowering time & growth rate)

Question 3

Give an example of an experiment on adaptions:

Answer 3

Climatic selesction on shell colour in Capaea nemoralis (type of snail)

Question 4

How was the experiment on Capaea nemoralis conducted?

Answer 4

Denim was stuck to the shells of the snails

The rate of fading tells the researcher whether the snail has been more in shade or sun

Snails were either yellow or brown & they all had different amts of bands on them

Question 5

What were the results of the experiment on Capaea nemoralis shell colour?

Answer 5

Found that the lighter in colour (yellow morphs) snails spent more time in the sun

& also the snails with fewer bands spent more time in the sun

Denim was most faded on these

Question 6

Give 2 examples of adaptions occurring quickly:

Answer 6

• Antibiotic resistance in bacteria
• Pesticide resistance in insects (this is slower than bacteria tho)

Question 7

How can antibiotic resistance occur quickly in bacteria?

Answer 7

New mutations arise & are selected for the population

This happens so quickly bc they spread rapidly on plasmids

Question 8

How can pesticide resistance occur quickly in insects?

Answer 8

Selection for resistant types already in the pop at very low freq –> ‘standing genetic variation’

If a pesticide is applied to a pop, it will wipe out the non-resistant individuals, the survivors (resistant) will reproduce & form the next generation of resistant individuals

Question 9

What happens to the amount of resistant speciesif more pesticides are added to plants?

Answer 9

The numebr of resistant species will increase

Question 10

Give an example of an insect that is resistant to pesticides:

Answer 10

The Colorado potato beetle, Leptinotarsa decemlineata

Resistant to a wide range of insectecides

Question 11

If pesticides are removed from plants what happens to the number of resistant insects & why?

Answer 11

Remove the pesticide = no. resistant insects decreases

This is bc if resistance is costly then there will be selection favouring the non-resistant types IF pesticide treatment is removed

Question 12

What 2 factors can affect the relative “fitness” of different variants in species?

Answer 12

• The abiotic environment (e.g. temperature, presence of pesticide)
• The biotic environment (e.g. presence of other species, abundance of own species eg frequency dependence)

Question 13

What are conspicuous polymorphisms thought to be influenced by?

Give an example

Answer 13

External factors such as preadtors

e.g. Predation of Cepaea (snails) by birds

Question 14

How does birds predation of Capaea influence influence the snails polymorphisms?

Answer 14

Birds have an innate preference for brown but also learns which morph is most common & preferentially predates on that

Predators are known to favour common morphs in many cases = rare morphs having an advantage

Brown snail no. will decrease & become rare

Pink & yellow more popular so the preference of birds shift to the popular one

This happens in a cycle

Question 15

How is the polymorphism in the Hawaiin spider maintained?

Answer 15

Thru frequency dependent selection

Question 16

What happens as a morph becomes less rare?

Answer 16

It loses its advatage & a stable equilibrium can result

Question 17

What is negative frequency dependent selection?

Answer 17

Fitness DECREASES as a morphs becomes more common

It keeps variation in the population

(This was alos written on this slide but not sure how to put it onto a fc = Not just predation - variation in Major Histocompatibility Complex thought to be maintained by host-pathogen co-evolution)

Question 18

What is an example of balancing selection?

Answer 18

Negative frequency dependent selection (Positive is also an example)

Question 19

What is negatvie freuqency dependent selection proposed to explain?

Answer 19

Persistence of colour morphs in some spiders and snails for example

Question 20

What is postive frequency dependent selection?

Answer 20

Fitness of a morph INCREASES as it becomes more common - would eliminate the rare morph

e.g. rare morph so rare it can’t find a mate

Remove variation from the population

Question 21

Give an example of how positive frequency dependent selection removes variation from the population?

Answer 21

Warning colouration to advertise unpalatableness & thus deter predators

When a morph is common, it’s more likely that birds will have already learned to avoid it

When a morph is rare, birds will not yet have learned to avoid it. An individual of a rare morph is therefore more likely to get eaten (i.e. gets killed while educating the bird)

The fitness of each morph is positively frequencey dependent

Question 22

Are benficial adaptions always more frequency?

Answer 22

No

There may be thresholds in terms of actual number rather than freq –> so 1 individual with the trait in question is needed per group regardless of grp size

e.g. colour vision in New World primated

Question 23

Give an example of frequencey in a New World priamte with colour vision:

Answer 23

New World Monkey species

Males in most New World Monkey species are always dichromatic

Females are EITHER dichromatic (see blues & greens) or trichromatic (see blues, reds & greens) –> depends on the number of different opsin alleles they carry on their X chromosome

Question 24

How is the opsin carried in male and female monkeys?

Answer 24

• S opsin, carried by males & females on chromosome 7
• M and L are 2 opsin alleles at the same locus on the X chromosome (males have one, female two)

(Female can have 3 alleles)