Key Area 6 - Evolution Of Species Flashcards
What is a mutation?
A random change to genetic material. Mutations are spontaneous and random, and are the only source of new alleles in a population
How can a mutation be an advantage to an organism?
By improving their phenotype to make them better adapted to surviving and reproducing in the environment they live in.
How can a mutation be a disadvantage to an organism?
For example, by causing a change to an essential enzyme that stops it from working.
What is a neutral mutation?
One which has no effect on the organism’s chances of surviving to reproduce
What environmental factors can increase the rate of mutation?
Radiation or some chemicals (known as mutagenic agents)
What does variation allow a population to do?
To adapt as a whole to changing environmental conditions over time, and results in the long-term survival of the species.
Why do organisms produce more offspring than the environment can support?
As some may die out die to predation, lack of food or disease
What are environmental selection pressures?
The factors that make some individuals better at surviving to reproduce than others (e.g predation, disease, lack of food) - when these pressures are present, natural selection occurs
How is selective advantage passed onto offspring?
Individuals best adapted to selection pressures pass on the alleles that give the selective advantage to the next generation (the “fittest” individuals). These alleles will have increases in frequency in the population
What is an adaptation?
A characteristic possessed by an organism which makes it well suited to its environment
What is speciation?
The formation of a new species
Explain the process of speciation
- Individuals in a population are able to interbreed freely
- Isolation barrier causes the population to be separated - no longer able to interbreed freely
- Different mutations occur in each sub-population. Natural selection occurs with different selection pressures changing each sub-population over many generations
- If isolation barrier is removed and sub-populations can no longer interbreed to produce fertile offspring, then speciation has occurred. This is because sub-populations are now so genetically different after many generations of evolution that interbreeding is not biologically possible
What is an isolation barrier?
A barrier which splits a population into sub-populations. Can be geographical (e.g oceans, mountains, deserts), ecological (e.g individuals don’t encounter each other because of differences in their ecological niches), or behavioural (individuals do not breed with each other as a result of differences in their behaviours).
