Variation and Evolution - Finished Flashcards
What is variation?
Difference between individualsof the same species
What are the two types variation?
Continuous
Discontinuous
What is the definition of continuous variation?
Anywhere on a sliding scale of measurement
Lots of seperate genes interacting) (genes intending with environment
What is the definition of discontinuous variation?
Cannot be measured (categoric) or cannot be measured on a sliding scale (discrete)(single gene)
Examples of heritable differences?
Eye colour, height
Examples of non heritable differences?
Scars
What ios interspecific competition?
Competition between members of different species
Lion vs. Leopard
Lion vs. Zebra
What is intraspecific competition?
Competition between members of the same species
Lion vs. Lion
Most severe type of competition = every resource is the same
What are selective agents?
resources that affect an individuals ability to survive
What does the normal distribution of selection pressures look like?
few at the extremes of a feature (extremely tall/short) most organisms close to average
What are selection pressures?
Lots of competition for resources
What does a directional selection pressure look like on a graph?
(example = drop in temperature)
graph moves to the right. average getting further right as well.
Supports evolution = Population has changes over time / adapted to changes in the environment (selection pressures)
What does a stabilising selection pressure look like on a graph?
Graph moves inwards, extreme populations get smaller.
Bad to be at the extremes/ good to be average
No support for evolution - no change in the population
Disadvantage - less genetic variation, less chance to respond to changes in the environment
Creates a smaller gene pool
What is the definition of a gene pool?
All of the genes/represented alleles present in the population
What does a disruptive selection pressure look like on a graph?
Graph begins to decrease at the average. Splits in 2
Bad to be average
Supports evolution = Changes the population, splits in two
What is speciation?
The formation of a new species.
If one genotype/allele is lost hen the whole populations gene pool can be rapidly altered
What are speciation mechanisms?
Isolation mechanisms
Ways of stopping gene flow between populations/maintaining reproductive isolation
What is allopatric speciation?
Geographical isolation
Separation by Rivers/Mountains
What is Sympatric speciation?
Non Geographical isolation
Separation of species due to:
Mechanical isolation (incompatible isolation)
Behavioural isolation (displays/courtship)
Both allopatric speciation and sympatric speciation are pre zygotic what does that mean?
STOP fertilisation from happening
What does Post Zygotic speciation mean?
Fertilisation is possible BUT further fertilization in future generations is not.
Lion + Tiger = Liger
Horse + Donkey = Mule
What is the definition of Hybrid sterility?
2 different species interbred together
non homologous pairs from the parents mean offspring are sterile
What is the definition of genetic drift?
Variations in allele frequency that occur as a result of random chance
WHat is the founder principle?
A new population is established by individuals with gene pools unrepresentative of the other populations
What was Darwin’s Theory of Evolution?
Organisms reproduce at a high rate (more than is needed to replace themselves) - This leads to overpopulation which is a problem with a finite food supply.
Some organisms due to variation will have a selective advantage over others (cope with finding food better). These are more likely to survive and reproduce which would pass on the suitable alleles.
What does Darwins Theory of Evolution show?
Variation within a population
