CB4 Natural Selection and evolution of humans

Question 1

What are 2 causes of genetic variation?

Answer 1

Random mutations producing new alleles, sexual reproduction producing different combinations of alleles.

Question 2

What is a selection pressure? Give an example.

Answer 2

A factor affecting the survival and / or reproduction of an organism e.g. predation, competition for resources, competition for breeding partners, disease, environmental conditions, poisons.

Question 3

Which organisms are most likely to survive / reproduce following a selection pressure?

Answer 3

The best adapted / those with advantageous alleles.

Question 4

What does evolution of a species mean?

Answer 4

Changes in the appearance / alleles of a species over time.

Question 5

What is an antibiotic?

Answer 5

A substance that kills bacteria, often by damaging their cell walls.

Question 6

What does it mean if a bacteria is resistant to antibiotics?

Answer 6

The antibiotic does not kill the bacteria.

Question 7

What are 3 characteristics that change over the course of human evolution?

Answer 7

Skull capacity / brain size increases, bipedalism (walking upright on 2 legs), shorter arms / longer legs.

Question 8

What happens to stone tools used by human ancestors over the course of human evolution?

Answer 8

Increase in complexity, sharper blades, smaller size.

Question 9

What are 2 methods for dating fossils?

Answer 9

Recording the layer of rock the fossils were found in, using radioactive minerals.

Question 10

What are the steps to natural selection?

Answer 10

1. A selection pressure is present 2. Variation exists within the population so some characteristics are advantageous and other disadvantageous. 3. Organisms with advantageous characteristics are more likely to survive and reproduce. 4. The genes for the advantageous characteristics are inherited by their offspring. 5. Over many generations the percentage of the population with this characteristic increases.