Variation and selection

Question 1

Describe variation

Answer 1

the differences between
individuals of the same species

Question 2

What continuous variation results in?

Answer 2

in a range of phenotypes between two extremes

Question 3

state examples of continuous variation;

Answer 3

body length and body mass

Question 4

What discontinuous variation results
in

Answer 4

results in a limited number of phenotypes with no
intermediates

Question 5

state examples of discontinuous variation

Answer 5

examples include;
ABO blood groups
seed shape in peas
seed colour in peas

Question 6

what is discontinous variation caused by?

Answer 6

usually caused by genes only

Question 7

what is continuous variation caused by?

Answer 7

caused by both genes and the environment

Question 8

Define a mutation

Answer 8

a genetic change

Question 9

Describe gene mutation

Answer 9

a random change in the base sequence of DNA

Question 10

How are new alleles formed?

Answer 10

by mutations

Question 11

states the sources of genetic variations in populations

Answer 11

mutation
meiosis
random mating
random fertilisation

Question 12

What increase the rate of mutation

Answer 12

ionising radiation and some chemicals

Question 13

Define an adaptive feature

Answer 13

an inherited feature that helps an organism to survive and
reproduce in its environment

Question 14

state examples of natural selection

Answer 14

• genetic variation within populations
• production of many offspring
• struggle for survival, including competition
  for resources
• a greater chance of reproduction by
  individuals that are better adapted to the
  environment than others
• these individuals pass on their alleles to the
  next generation

Question 15

Define an adaptation

Answer 15

the process, resulting from natural selection, by which populations become more suited to their environment over
many generations

Question 16

State an example of natural
selection

Answer 16

the development of strains of antibiotic
resistant bacteria

Question 17

Outline the differences between natural and
artificial selection

Question 18

Explain the development of strains of antibiotic resistant bacteria

Answer 18

This process is an example of natural selection because it involves the survival and reproduction of individuals with traits that confer a survival advantage.
In this case, the antibiotic resistance gene is the advantageous trait that allows bacteria to survive and reproduce in the presence of antibiotics. As a result, antibiotic-resistant strains of bacteria become more common in populations over time, demonstrating the process of natural selection in action.

Question 19

Outline how selective breeding by artificial
selection is carried out over many generations to
improve crop plants and domesticated animals

Answer 19

(a) selection by humans of individuals with
desirable features
(b) crossing these individuals to produce the
next generation
(c) selection of offspring showing the desirable
features