Life on Earth - Evolution of Species

Question 1

Mutation

Answer 1

a random change to an organisms genetic material

Question 2

Mutagenic agent

Answer 2

An environmental factor that can increase the rate of mutation eg. radiation (UV, X-rays) and chemicals (mustard gas)

Question 3

Natural Selection Definition

Answer 3

Process by which individuals best adapted to the environment survive and pass their genes onto succeeding generations

Question 4

Natural Selection Stages

Answer 4

1. Sexual reproduction produces many offspring
2. Inherited variation means that organisms are different from each other
3. Struggle for survival:
   - death from disease
   - death due to inability to survive environmental conditions
   - death from predation
   - death due to inability to
   compete for scarce food or other resources
   The fittest survive
4. Mating and offspring produced (favoured forms of genes passed on)
5. Offspring struggle to survive again
6. The cycle repeats over and over

Question 5

Speciation Definition

Answer 5

The formation of a new species

Question 6

Speciation Stages

Answer 6

1. Large freely interbreeding population of one species
2. Isolation by barrier (geographical, ecological, or behavioural). The barrier creates sub-populations
3. different mutations arise in both populations (some of these confer “selective advantage”)
4. Natural selection occurs over a very long period of time, and the sub-populations habe become suited to their environments
5. The two populations can no longer interbreed to produce fertile offspring therefore speciation has occurred. The populations are now different species

Question 7

Isolating Mechanisms and Examples

Answer 7

Geographical - oceans mountains, deserts
Behavioural - breeding calls, mating dance
Ecological - different habitats, pH or salinity (salt concentration)

Question 8

What is the importance of variation?

Answer 8

Allows species to adapt to changing environmental conditions

Question 9

Evolution

Answer 9

Process involving natural selection that has transformed life on earth from its earliest beginnings to its present diverse state