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)