Origin of Species Flashcards
Human Influence on Speciation:
What happens when humans expand into another organism’s habitat?
What do the organisms have to do as a result?
What is formed as a result?
Cause the species to be divided.
These groups now have to evolve and adapt to the new environmental situations.
Different species are formed.
Human Influence on Speciation:
What may happen resulting from humans taking land and resources away from organisms?
Humans, in this case, are called the ______ species. The other organisms are the _______ species.
Extinction.
Invasive, indigenous
Genetic Drift:
What is the definition?
When the frequency of an allele changes as a result of chance over a number of generations.
Genetic Drift:
Genetic drift is the result of ________ effect, ________ effect, and recurring _______ ________.
Why is this the case?
bottleneck effect
founder effect
population sizes
The species is more prone to changes in alleles.
Genetic Drift:
Larger populations are _______ prone to dramatic changes in alleles.
less
Genetic Bottleneck:
What is the definition?
Why does it contribute to genetic drift?
Dramatic, often temporary reduction in population size.
Only a few survive, resulting in a smaller gene pool. Thus, future generations will be less genetically diverse and will reflect the genetics of the survivors. Alleles from the original population are lost.
Genetic Bottleneck:
What are three examples of events that can cause this?
Habitat destruction
environmental disaster
natural disaster
over-hunting of species
Founder Effect:
How does this occur and what happens?
Why does it contribute to genetic drift?
Occurs when a few individuals separate from the original population, and establish a new population.
Alleles that were found in the original population may not occur in the new population, different mixture/distribution of alleles.
Disruptive Selection:
What is it?
When natural selection favours the extreme variations of a trait over the intermediate.
Give an example of disruptive selection.
Camouflage in rabbits. In an environment of black and white rocks, black rabbits and white rabbits would be camouflaged (favoured by natural selection). Grey rabbits would be seen by predators (selected against).
Sexual Selection:
What is sexual selection? What does it result in?
When a trait is favoured that specifically enhances the mating success of an individual
Results in sexual mating behaviours
Sexual Selection:
What are the most common forms of this?
What is the significance of the traits passed down generations?
Female mate choice–based on physical traits and behaviours
Male-vs-male competition
The favoured traits may not always be the most beneficial–can hinder the individual (easier prey)
What is natural selection?
Traits are determined by the environment and if individuals can survive to reproductive age in that environment.
Beneficial traits are favoured, and harmful traits are selected against. This creates a stronger species.
What is an example of natural selection?
Rats that lived in trees needed to be the right size and weight. Too heavy and they would break the branches and fall off. Natural selection brought the species’ weight and size down
What is directional selection? Give an example.
When more extreme trait variations are favoured by natural selection.
Hummingbirds living in an area with long flowers. Birds with the extreme trait for longer beaks will flourish more than the others because they can reach the nectar more effectively.
