More evidence for Evolution by Natural Selection - Lecture 2

Question 1

What is biogeography?

Answer 1

Distribution of organisms around the planet

Question 2

What are oceanic islands?

Answer 2

○ No immediate ability of physical contact
○ Native species: plants, birds, arthropods with specific adaptations
○ Modern island biogeography increasingly affected by humans e..g rats from ships

Question 3

How did marsupials end up in Australia?

Answer 3

○ In the cretaceous period (65 million years ago), South America, Antarctica and Australia were connected so they could easily traverse

Question 4

What is convergent evolution?

Answer 4

Distantly related species show similar adaptations due to similar selection pressures, but often with different underlying genetic factors

Question 5

What are some examples of convergent evolution?

Answer 5

Placentals and marsupials:
○ Anteater and banded anteater
○ Flying squirrel and sugar glider
○ Mole and marsupial mole
North American porcupine and Crested porcupine:
○ Both have adapted their hair to produce large, spiky quills
○ Regulatory genes are different
Cacti and Euphorbs (different families):
○ Cacti in Americas
○ Euphorbs in “Old world”
○ Both are succulents

Question 6

How are trees an example of convergent evolution?

Answer 6

○ Tree-ness has evolved and disappeared repeatedly in separate lineages
○ Common ancestor of a nettle and a strawberry was a tree
○ Common ancestor of a maple tree and mulberry tree was not a tree

Question 7

What is carcinisation?

Answer 7

○ A type of convergent evolution
○ Relatives of squat lobsters and hermit crabs have evolved a crab shape○

Question 8

What are some examples that do not show convergent evolution?

Answer 8

○ Duck-billed platypus: Males have venomous glands
○ Elephants: Only organism with trunks
○ Kangaroos: Only animals bound for long distances
○ Stegosaurus: Large backplates

Question 9

How are moths examples of natural selection?

Answer 9

○ Mutation in moths: some light and some dark
○ During industrial evolution, trees turned black due to the smoke
○ Dark moths survived more than the light moths

Question 10

How do humans cause selection?

Answer 10

Fritillary bulbs:
○ Harvest bulbs on the mountainside and only collected the bright coloured ones
○ Darker bulbs were the only survivors as we didn’t notice
Hunting:
○ Heavy poaching of elephants led to an increase in tuskless females

Question 11

What did the “lizards in a hurricane” show?

Answer 11

○ Average lizard after the hurricane had bigger toe pads, longer arms, shorter hind legs
○ Shows natural selection not evolution
○ Later study showed that the offspring had larger pads, strongly suggesting evolution

Question 12

What is the molecular clock?

Answer 12

○ Pair of species are compared for the same protein
○ Coding differences highly correlated with divergence
○ Genetic differences appear to accumulate at a constant rate

Question 13

What are some surprises found from the molecular clock?

Answer 13

○ A hippo is more closely related to a whale than it is to a pig or rhino
○ Rapid diversity of birds after the extinction of the dinosaurs - recent evolution of caracara and bowerbirds

Question 14

What happened to the olfactory receptor genes in cetaceans (whales, porpoises and dolphins)?

Answer 14

○ Majority does not work
○ 68% of OR genes are psuedogenes - non-functional

Question 15

How is lactase persistence evidence of selection?

Answer 15

○ Lactase persistence levels highest in Europe and in regions with strong pastoralist traditions (sheep and cattle farmers)
○ People were consuming milk long before the appearance of the relevant alleles
○ Advantage came during periods of famine or pathogen exposure

Question 16

What is neutral theory?

Answer 16

○ Most variation at the molecular level does not affect fitness
○ Mutations in these parts of the genome should not be selected and should evolve randomly
○ Non-coding regions provide the best molecular clocks