evolution Flashcards
Darwins theory of natural selection
Sailed on the HMS beagle
- Natural selection: populations change over time and individuals with traits best suited to the environment will survive and reproduce.
This is called the Survival of the Fittest
Darwin calls this Natural Selection:
It is important to note that Darwin did not use the word Evolution he used Descent with Modification
- Descent with Modification- theory that natural selection does not demonstrate progress but results in the ability to survive local environmental conditions
Homologous
Similar internal anatomy, differnet function. (Common ancestor)
Ex. Bat wing & Human arm
Analogous
Similar function, different anatomy. (No common ansestor )
Ex. Bat wing & Butterfly wing
Vestigial structures
Non functioning versions of structures that were once useful and functioning to an organism’s ancestor. Ex. Goosebumps show we used to have a lot of body hair to keep warm, Tail-bone shows us, humans at some point had a tail
Adaptation
Mimicry and camouflage
Mimicry
Harmless species mimic harmful species, or species that predators don’t like. Ex. The Viceroy butterfly will mimic the Monarch butterfly because predators won’t eat monarchs as they don’t taste very good.
Camouflage
Organisms use their appearance to blend in with their surroundings
Fitness
Refers to a species ablilty to produce viable offspring in a gene pool
Pre - zygotic:
Prevention of mating
Behavioural isolation
behaviours that prevent other species from recognizing or selecting them for mating
Temporal isolation
Two species that live in the same habitat but have different mating season
Habitat isolation
Two species that live in same general area but in different habitats
Post - zygotic
Prevention of fertilization
Hybrid inviablilty
Death in the womb
Hybrid breakdown
They can have babys, but that offspring is weak and as the generations go on, they get weaker and weaker showing consequences
Hybrid infertilitity
Offspring can’t have babies
Stabilizing Selection
favours an intermediate phenotype and selects against extreme variants of the phenotype - Ex weight of human babies
Directional Selection
favours phenotypes at one extreme over the other - This type of selection is common during times of environmental change - Ex: colour of pepper moths or antibiotic resistant bacteria
Disruptive Selection
favours extreme phenotypes rather than intermediate phenotypes - Sometimes intermediate phenotypes are completely eliminated from the population - Ex: Male coho salmon - > Very large phenotype (4500 grams or more) are better at fighting for access to females’ eggs and very small phenotype (~ 500 grams) are better at “sneaking” & fertilizing females’ eggs
Survival of the fittest
organisms compete for limited resources. Organisms with favourable traits that help them survive will have an increased chance of reproduction. If they reproduce, a growing number of the population will have these traits in later generations
