Key Area 7: Evolution Flashcards
What is evolution?
Evolution is the gradual change in the characteristics of a population of organisms over successive generations as a result of variation in the population’s genome.
What is natural selection?
natural selection is a non-random increase in frequency of DNA sequences that increase survival and non-random reduction in the frequency of deleterious sequences.
What are the three different types of natural selection?
Stabilizing, Directional, or Disruptive
When does stabilising selection occur?
It occurs when the average phenotype is selected for and extremes of the phenotype range are selected against.
When does directional selection occur?
It occurs when one extreme of the phenotype range is selected for.
When does disruptive selection occur?
It occurs when the extreme phenotypes are selected for.
Describe natural selection in prokaryotes.
Prokaryotes can exchange genetic material horizontally, resulting in faster evolutionary change than organisms that only use vertical gene transfer.
What is vertical gene transfer?
from parent to offspring/one generation to the next.
What is horizontal gene transfer?
genes are transferred between individuals in the same generation.
What is a species?
a species is a group of organisms that can successfully interbreed to produce fertile offspring.
What do species have in common
have a similar anatomy and physiology
share a common chromosome complement and gene pool (gene pool-total of all genes in a population).
interbreed to produce fertile offspring.
What are the two types of speciation?
Allopatric and sympatric.
When does allopatric speciation occur?
When gene flow between two (or more) populations is prevented by a geographical barrier.
When does sympatric speciation occur?
When two (or more) populations live in close proximity in the same environment but still become genetically isolated due to a behavioural or ecological barrier.
Example of a geographical barrier?
Rivers, mountain ranges, desert, sea etc.
