key area 6 - evolution of species

Question 1

what is evolution

Answer 1

evolution is the gradual change if species overtime which can lead to
- a change withing a species
- the production if a new species

Question 2

what is a mutation?

Answer 2

a mutation is a random change to an organisms genetic material (DNA). Mutations are spontaneous and are the only source of new alleles. Mutations are therefore an important source of variation in population.

Question 3

what are the environmental factors that can increase the natural rate of mutation?

Answer 3

• radiation eg UV radiation, x rays
• chemicals e.g mustard gas

Question 4

what is the effect of variation in a population?

Answer 4

new alleles produced by mutation can result in plants and animals becoming better adapted to their environment. Variation within a population makes it possible for a population to evolve over time in response to changing environmental conditions.

Question 5

what is the sequence of events that occurs during the evolution process?

Answer 5

1. species produce more offspring than the environment can sustain
2. natural selection or survival of the fittest occurs when there are selection pressures
3. the best adapted individuals in a population survive to reproduce, passing on favourable alleles that confer the selective advantage.
4. these alleles increase in frewuency within the population

Question 6

what is speciation?

Answer 6

sometimes evolution can result in the formation of new species. this process is called speciation

Question 7

what is the order if sequence of events that occurs during speciation

Answer 7

1. speciation occurs after part of a population becomes isolated by an ISOLATION BARRIER. this can be geographical, ecological ( diff levels of abiotic factors eg pH) behavioural ( diff mating behaviours)
2. different MUTATIONS occur in each sub population
3. NATURAL SELECTION selects for different mutations in each group, due to different selection pressures.
4. each sub population evolves until they are so genetically different that they are two different species (SPECIATION)

Question 8

why do we need so many species

Answer 8

1. food species for us
2. important source of medicines
3. raw materials e.g wood