Evolution Flashcards
Three conditions for evolution by natural selection
- Heritable characteristics
- Characteristics vary between indiciduals
- Differential fitness between individuals (e.g. survival -> reproduction)
Def of evolution
Change in allele frq (genetic change) over time in a population
Does natural selection operate on pehnotypes or genotypes?
Phenotypes
What type of evolution is the cause of consistent adaptation?
Natural selection
A way to show natural selection (think E.coli)
In a dish, increasing levels of antibiotic as you get closer inwards to the dish
Produces increasingly resistant bacteria
Types of evidence for evolution
- Fossils
- Imperfection (bad design)
- Biogeography
- Molecular genetics
- Natural selec in action
Missing Link
- 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
Evidence of evolution visible in the human body now
- 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)
Example of bad design
- 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
Type of fossils that showed evidence for evolution
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
Biogeography - Oceanic islands
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
Convergent evolution
- distantly related species showing similar adaptation due to similar selection pressure
but in diff environments - often diff underlying genetic factors
Marsupial distribution
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
examples of covergent evolution
- 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
convergent evolution in plants
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)
examples of completely unique adaptations
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
evolution we can see in ‘real time’: peppered moth
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
humans creating selection pressures: Green Fritillary bulb
- 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
lizards in hurricane wooooooo
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
molecular genetics as evidence
- 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
the molecular clock
- 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
the molecular clock
- 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
surprises shown in ancestory through DNA sequences
hippo more closely related to whale than it is to a pig or rhino
evolutions of birds
- 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
whales and the olfactory gene
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
lactase persistence and evolution
- 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
neutral theory
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
