variation and selection

Question 1

variation

Answer 1

the differences between individuals of the same species

Question 2

continuous variation

Answer 2

results in a range of phenotypes between two extremes
- body length, body mass

Question 3

discontinuous variation

Answer 3

results in a limited number of phenotypes with no intermediates
- ABO blood groups, seed shape + colour in peas

Question 4

difference between continuous and discontinuous variation

Answer 4

discontinuous depends on genes only but continuous is caused by both genes and environment

Question 5

mutation

Answer 5

genetic change

Question 6

how are new alleles formed

Answer 6

mutation

Question 7

stuff that increase rate of mutation

Answer 7

• ionising radiation
• some chemicals (mutagens)

Question 8

gene mutation

Answer 8

change in the base sequence of dna

Question 9

adaptive feature

Answer 9

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

Question 10

adaptive features of xerophytes

Answer 10

• sunken stomata reduces water vapour loss
• thick leaves and stem to absorb more water
• long roots to reach water in soil
• small leaves to reduce surface area for evapration

Question 11

adaptive features of hydrophytes

Answer 11

• small roots as they can absorb from tissues as well
• large stomata
• flat broad leaves to float

Question 12

natural selection

Answer 12

• there is genetic variation among a population
• as many offspring are produced
• there’s a struggle for survival due to competition for resources
• there’s a greater chance of reproduction by individuals that are better adapted
• they pass on their alleles to the next generation

Question 13

selective breeding

Answer 13

• humans select individuals with desirable features
• they are crossed to produce the next generation
• offspring with desirable features are selected

Question 14

why selective breeding

Answer 14

to improve crop plants + domesticated animals

Question 15

adaptation

Answer 15

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

Question 16

example of natural selection

Answer 16

development of strains of antibiotic resistance

Question 17

differences between natural and artificial

Answer 17

• natural occurs naturally but artificial occurs with human intervention
• natural takes a long time artificial takes less time
• results in adapted individuals but results in useful features to humans that aren’t necessarily adapted

Question 18

causes of variation

Answer 18

• meiosis
• random mating
• random fertilisation
• mutation