Unit 3 - Key Area 6 - Adaptions, Natural Selection and Evolution Flashcards
What are mutations?
A mutation is a random change to genetic material. Mutations may be neutral or confer an advantage or a disadvantage to survival.
Mutations are spontaneous and are the only source of new alleles.
What is a mutant?
A mutant is an organism who’s genetic material has changed.
What effect do environmental factors have on mutations rate?
Environmental factors such as radiation and some chemicals can increase the rate of mutation.
Mutations can lead to cells becoming cancerous which would be of a disadvantage to an organism.
Name chemical mutagenic agents
Mustard Gas
Colchicine
Caffeine
Formaldehyde
Name radiation mutagenic agents
X-Rays
UV Light
Gamma Rays
What are adaptations?
New alleles produced by mutation can result in plants and animals becoming better adapted to their environment.
What happens to organisms over time?
Over time, Variation within a population makes it possible for a population to evolve in response to changing environmental conditions.
What are selective pressures?
If conditions are favourable, a species may produce more offspring than the environment can sustain.
Some organisms die because of factors such as predation, food shortage or disease. These are selection pressures.
What is natural selection?
Natural selection or survival of the fittest occurs when there are selection pressures.
The best adapted individuals in a population survive to reproduce passing on the favourable alleles that confer the selective advantage.
These alleles increase in frequency within the population.
What is speciation?
Speciation occurs after part of a population becomes isolated by an isolation barrier.
What are isolation barriers?
Geographical (seas, rivers, mountains, deserts)
Ecological (temperature, water level, pH, salinity)
Behavioural (sex cells unable to fuse, unsuccessful mating displays, flowering at different times of year)
How do isolation barriers change species?
Natural Selection selects for different mutations in each group due to different selection pressures.
Each sub-population evolves until they become so genetically different that they are two different species.
