Evolution Of Species Flashcards
Mutation
A random change to genetic material and is the source of new alleles in a population
What can mutations be?
-Neutral
-Advantageous
-Disadvantageous
What factors can increase the chance of a mutation?
-Radiation e.g. sun beds
-Some chemicals e.g. those found in cigarettes
What impact does new alleles have on plants and animals?
New alleles produced by mutation allow plants and animals to adapt to their environment
Adaptation
An inherited characteristic that makes an organism well suited to survive its environment
What impact does variation have within a population?
Variation within a population make it possible for the population to evolve over time, in response to changing environmental conditions
What happens when a species produce more offspring than an environment can sustain?
Natural selection or survival of the fittest occurs when there are selection pressures
What is natural selection (or survival of the fittest) within a population?
The best adapted individuals in a population survive and reproduce, passing on the favourable alleles that confer a selection advantage. The less well adapted organisms die before they reproduce
What are examples of selection pressures?
-Temperature : some organisms may be adapted to colder temperatures
-Predators : some organisms may be adapted to camouflage and avoid predators
Stages of natural selection
- Species produce more offspring than the environment can sustain
- Variation exists between members of a species
- Those who survive reproduce, passing on their favourable alleles that give a selection advantage
- This happens over many generations and these alleles increase in frequency within the population
What is speciation?
The evolution of new species from pre existing ones
When does speciation occur?
When populations become isolated from eachother by a barrier and interbreeding is prevented
What are the 3 types of isolation barriers?
-Geographical e.g. mountains, oceans and rivers
-Ecological e.g. differences in temperature or pH
-Behavioural e.g. different breeding times, different courtship mechanisms
What role does natural selection have in speciation?
After a population becomes isolated, different mutations can occur in each sub poph. Natural selection selects for different mutations in each group due to selection pressures
Each sub population evolves until they become so genetically different, they are 2 different species
Stages of speciation
Isolation barriers
Mutations
Natural selection
Speciation
I Must Not Smoke
Speciation stage 1 : isolation barriers
Part of a population becomes isolated by an isolation barrier
Speciation stage 2 : mutations
Different mutations occur in each sub population
Speciation stage 3 : natural selection
NS selects for different mutations in each group due to different selection pressures
Speciation stage 4 : speciation
Each sub population evolves until they can no longer interbreed to produce fertile offspring - they are different species
