Evolution

Question 1

Three conditions for evolution by natural selection

Answer 1

• Heritable characteristics
• Characteristics vary between indiciduals
• Differential fitness between individuals (e.g. survival -> reproduction)

Question 2

Def of evolution

Answer 2

Change in allele frq (genetic change) over time in a population

Question 3

Does natural selection operate on pehnotypes or genotypes?

Answer 3

Phenotypes

Question 4

What type of evolution is the cause of consistent adaptation?

Answer 4

Natural selection

Question 5

A way to show natural selection (think E.coli)

Answer 5

In a dish, increasing levels of antibiotic as you get closer inwards to the dish
Produces increasingly resistant bacteria

Question 6

Types of evidence for evolution

Answer 6

• Fossils
• Imperfection (bad design)
• Biogeography
• Molecular genetics
• Natural selec in action

Question 7

Missing Link

Answer 7

• 380M yrs ago, fish like fossils
  -360M yrs ago, amphibian like fossils
• Must’ve been something in between
• 2004 research by Neil Shubin
  Looking for something to fill that 370M yr old gap
• Found Tiktaalik roseae
• had very small developing limbs, had ability to pull itself out onto land
• one example of paleantology being predictive and not retrospective

Question 8

Evidence of evolution visible in the human body now

Answer 8

• Plica Semilunaris - skin in corner of eye- remnant of reptilian past, have no use for it but not incovenient enough to get rid of
• Vestigial muscle called palmaris longus - as primates, would help climb trees
• Darwin’s tubercle - used to move ears about
• Goosebumps - stay warm, when adrenaline released made them look more intimidating (hence why emotions give us goosebumps)

Question 9

Example of bad design

Answer 9

• LEFT RECURRENT LARYNGEAL NERVE
• from Broca’s area to larynx
• Loops around aorta, 1m long even tho distance from brain to larynx in <30cm
• even longer in larger necked animals
• First evolved from fish directly from brain to gills
• over generations, gradually lengthened
• Laryngial’s location remained the same, but brainchial arch function changed over time into the aorta
• was easier to lengthen during each small step rather than a major rewiring

-evolution has no foresight

Question 10

Type of fossils that showed evidence for evolution

Answer 10

Trilobites
Extinct around 250M yrs ago
- preserved well due to thick shell
- showed clear signs of evolution over relatively short periods

Whales
- fossils show rear limbs that have pretty much no use but bones still there

Question 11

Biogeography - Oceanic islands

Answer 11

Oceanic islands
- native species have vry specific adaptations
- on near land, species are similar but not identical
- modern island biodiversity is affected by humans - tourism

Question 12

Convergent evolution

Answer 12

• distantly related species showing similar adaptation due to similar selection pressure
  but in diff environments
• often diff underlying genetic factors

Question 13

Marsupial distribution

Answer 13

Marsupials
- pouched mammals
- found distributed across world in australias and americas
- 80 M yrs ago started in Americas, travelled across antarctica to Australias

• continents moved -> can predict on basis of continental movement and found fossils of marsupials in Antarctica
• none in africa as it had split off before relocation

Question 14

examples of covergent evolution

Answer 14

• placentals and marsupials

e.g. flying squirrel and sugar glider
have similar features
but not same common ancestor

mole and marsupial mole
similar features
not common ancestor

North american porupine
crested porcupine

• their last common ancestor was 45M yrs ago and it didnt have quills!

so all found saem adaptation

Question 15

convergent evolution in plants

Answer 15

CACTI in N and S america
EUPHORBS in asutralia

• both succulents - stems store water, small leaves, spines etc.
• but two completely diff families
• (not very specific local adaptations as human intervention means theyre both in wrong ecosystem)

Question 16

examples of completely unique adaptations

Answer 16

duck billed platypus:
lays eggs + makes milk
no fossils like it

elephants:
- only ones in fossil records to have trunks (unsure why)

kangaroos:
- only animal uses hopping as primary way of locomotion

stegasaur:
only one to have big plates

Question 17

evolution we can see in ‘real time’: peppered moth

Answer 17

Used to be lighter in colour (typica)
During indusstrial revolution: trees covered in smoke/soot (carbonaria)
- darker moths that are more well adapted appeared

after clean air act:
lighter form reappeared (typica)

1950s, they experimented
- released both types
- took photos of birds coming to eat darker coloured ones cuz were’nt camo

BUT
might not have been the perfect example
so they repeated the experiment more rigorously
got same resultd

Question 18

humans creating selection pressures: Green Fritillary bulb

Answer 18

• used in chinese medicine
• humans harvest bulbs on moutainside
• usually bright green
• green ones easily picked, camofalgued ones left behind
• so majority of them are now darker
• humans act inadvertantly as selective agent

Question 19

lizards in hurricane wooooooo

Answer 19

researchers measure liazards of caribbean island
- hurricane irma hits
- returned a few weeks later
no reproduction could’ve taken place
- remeasured
- now avg lizard had bigger toe pads, longer arms and shorter hind legs

so shift in population characeteristics

• those wihtout the charecteristics died in storm
• shows natural selec NOT evolution
• 2020 study found offspring of these also had larger pads

shows evidence for evo

Question 20

molecular genetics as evidence

Answer 20

• DNA is sole & universal carrier of genetic code
• this in itself shows existence of common ancestor, cuz everyone uses DNA
• can track evo by compaing genetic sequences or proteins

Question 21

the molecular clock

Answer 21

• genetic diff accumulate at constant rate

e.g. evolutionary tree of cytochrome c gene (in all eukaryotes)
shows consistence between molecular data and morphologica tree

can be used to to say how long ago lineages seperated

Question 21

the molecular clock

Answer 21

• genetic diff accumulate at constant rate

e.g. evolutionary tree of cytochrome c gene (in all eukaryotes)
shows consistence between molecular data and morphologica tree

can be used to to say how long ago lineages seperated

Question 22

surprises shown in ancestory through DNA sequences

Answer 22

hippo more closely related to whale than it is to a pig or rhino

Question 23

evolutions of birds

Answer 23

• mass extinction of dinos: all non aviator species died
• ancestors of chickens and ostriches used to be around first

but sudden change, skies were now free so free reign for then to evolve

Question 24

whales and the olfactory gene

Answer 24

cetaceans moved back to live in the water noses shifted into spouts, didn't need nose to breathe researchers compared olfactory recpetors in - dwarf spermwhale - porpoise - sea lion - dog found in cetaceans 68% were pseudogenes so non functional (in others, it was much less) no selection pressure to select against non working sense of smell cuz didnt matter

Question 25

lactase persistence and evolution

Answer 25

- usually after weaning, lactase production disappears - lactase perisistance levels highest in europe (pastoralist radiotions = looking after animals) - human agriculture had influence - not massive selec pressure, so lactose intolerance still exists possibly during times of famine, where people already weak, lactose intolerance lead to more sickness and death and people who could drink milk etc. had an extra source of food

Question 26

neutral theory

Answer 26

genetic code is redundant - some mutations in codon do not change amino acid (lots of combos of genes produce same AA) synonymous chnages many DNA seq are not genes have no function (junk) - frq of these change and mutate but arent selected for so = selectively neutral provide best molecular clocks cuz mutations randomly accumulating