Evolution Flashcards
What was JP Lamarck’s theory for how evolution occured?
Desire incurred physical change - for example, a giraffe has a long neck because it’s short necked ancestors desired the fruits at the top of the tree, so the next generations had long necks.
What is evolution?
the genetic change in allele frequency over time in a population
what is the only consistent force that incurs evolution?
natural selection
what is the evidence for evolution?
- fossils
- imperfection in modern organisms
- molecular genetics
- being able to observe natural selection in action via timelapses of bacteria
what is an example of “bad design” as proof of evolution?
humans - left recurrent pharyngeal nerve
- distance from brain to larynx is only 30cm, but this nerve is 1m long, as it loops all the way around the aorta.
- this is due to the layrnx evolving from the brachial arch, and while the brachial arch changes over time with evolution, the nerve stays in the same place.
what is the correct word to describe the action of natural selection?
“tinkering”
what is convergent evolution?
distantly related species show similar adaptations due to similar selection pressures, but often with different underlying genetic factors.
what are some examples of animals NOT displaying convergent evolution?
- kangaroos hopping for locomotion
- elephants having a prehensile trunk
what are some examples of natural selection in action?
- lizards in a hurricance
- lizards before hurricane irma were measured, and after they were measured again. On average, it was discovered that the remaining lizards had longer arms, bigger toe pads, and shorter hind legs.
how do molecular genetics prove evolution?
- DNA is the sole universal carrier of the genetic code
- evolution can be reconstructed by showing the change in allele freq. in a species
- shows existence of a universal common ancestor
what is LUCA?
- Last Universal Common Ancestor
- all life can be traced back to LUCA
what is eukaryogenesis?
- a one time event, probably around two billion years ago
- (probably) archaebacterium engulfed a heterotrophic eubacterium, which eventually became mitochondria
what is speciation?
biological definition - a population of reproducing organisms that is isolated from other populations
what are the problems with the biological definition of speciation?
- doesn’t apply to organsims that can reproduce asexually
- doesn’t apply to extinct organisms (dinosaurs)
- difficult with bacteria that have horizontal gene transfer
what is allopatric speciation?
via physical isolation, one population of a species becomes a different species
what is stabilising selection?
selection acts against both extreme phenotypes and favours the intermediate - bell curve is thin and in the middle of the graph
what is disruptive selection?
two extreme phenotypes are selected for, whereas the intermediate is selected against - curve has peaks on far left and far right of graph and dip in the middle of the graph
what is directional selection?
when individuals with one specific phenotype on one side of the mean are selected for - curve is shifted to the far left or the far right
what is genetic drift?
the process by which random effects can cause major changes in small populations - e.g. in a small field of red and white flowers, by chance, only the red ones reproduce - leads to the next generation only having red flowers
- process can occur via a founder effect/ bottlenecking event where population is drastically reduced
in what environment does sympatric speciation occur?
when there are no physical barriers seperating a population, and all members are in close proximity to one another.
sympatric speciation seems to occur spontaneously
what are some genetic factors regarding speciation?
- requires a sampling effect (e.g. genetic drift or genetic bottlenecking event) combined with long periods of time
- essentialy random events
- speciation = branching process - 1 species can give rise to more than 2 others
what are some prezygotic barriers (barriers before mating) to prevent interbreeding?
PRE mating attempt
- habitat isolation - if two individuals are geographically isolated
- temporal isolation - timing of critical reproductive events prevents organisms from interbreeding
- behavioural isolation - courtship behaviour is different, which leads to no mating attempt occuring - negative rizz between species :(
POST mating attempt
- mechanical isolation - genitals are different shapes, and do not fit together, resulting in mating being impossible
- gametic isolation - egg and sperm both join together but no zygote is created due
what are some postzygotic barriers (barriers after mating) to prevent interbreeding?
-reduced hybrid viability - hybrids are produced but fail to develop to reproductive maturity
-reduced hybrid fertility - hybrids are produced but fail to produce functional games (hybrid is sterile)
- hybrid breakdown - F1 hybrids are fertile, but F2 hybrids fail to develop properly
what is Fitness?
the relative probability of survival + reproduction of a given genotype
i.e. capability of passing down your genome