5.2

Question 1

What is the difference between evolution and natural selection

Answer 1

natural selection is a theory to explain how evolution takes place

Question 2

What is meant by variation

Answer 2

the difference between individuals of the same species

Question 3

what can cause variation among members of the same species

Answer 3

can be caused by differences in genes or by differences in the environment

Question 4

Explain how mutations cause variation

Answer 4

-random changes to the base sequence of a gene
- usually harmful, often neutral, rarely beneficial
- the original source of variation
- produces new alleles which enlarges the gene pool of a population

Question 5

explain how meiosis causes variation

Answer 5

• crossing over (in P1) produces new combination of alleles
• random orientation of bivalents (in M1) results in independent assortment of chromosomes
• every gamete produced is genetically different

Question 6

explain how sexual reproduction causes variation

Answer 6

• the fusion of male and female gametes
• offspring have a combination of alleles from 2 different parents

Question 7

what leads to variation between individuals in a species

Answer 7

mutations, meiosis, sexual reproduction

Question 8

How is adaptation a mechanism for evolution

Answer 8

adaptations are characteristics that make an individual suited to its environment and way of life
eg. melanie fix moths, giraffes long neck

Question 9

what are acquired characteristic

Answer 9

characteristics that are developed over an organisms lifetime eg. strong muscles in tennis players right arm

these characteristics cannot be passed on because they aren’t associated with changes to gene therefore can’t be inherited by offspring

Question 10

Explain overproduction as a mechanism for evolution

Answer 10

species tend to produce more offspring than the environment can support

the result of having too many offspring and not enough resources is competition for resources (animals: food, territory, shelter) (plants: light, space, water)

THIS LEADS TO STRUGGLE FOR SURVIVAL

Question 11

Explain differential survival and reproduction as a mechanism for evolution

Answer 11

• individuals that are better adapted tend to survive and produce more offspring while less well adapted tend to die or produce fewer offspring eg. melanistic moths

Question 12

outline the mechanism by which characteristics are passed to offspring

Answer 12

inheritance

heritable characteristics are passed on from parents in their genes
in sexual reproduction, gametes containing half the genetic material of the parents are produced
when two gametes fuse to form a zygote, the new individual contains genes from both parents

Question 13

what characteristics cannot be inherited

Answer 13

acquired characteristics can’t be passed on because they don’t change an organisms genes

Question 14

explain how adaptations and differential survival can change the characteristics of a species

Answer 14

• better adapted individuals are more likely to survive and reproduce to pass on genes for their beneficial characteristics to offspring
• individuals that are less better adapted have lower survival rates and lower reproductive success
• this leads to an increase in proportion of individuals in a population with character which make them well adapted

Question 15

what is the biochemical process behind the change in characteristics of a species

Answer 15

• a change in the characteristics of a species is caused by changes in the frequency of alleles in the populations gene pool

Question 16

Overview of natural selection

Answer 16

• there is variation between individuals of a species
• some individuals are better adapted to their environment than others
• there is overproduction of offspring which leads to struggle for survival
• the individuals with better adapted characteristics are more likely to survive and reproduce
• the genes for the useful characteristics are passed on to the next generation

Question 17

explain industrial melanism in the peppered moth

Answer 17

Question 18

explain how antibiotic resistant bacteria evolve

Answer 18

• there is variation between bacteria, where some have a mutation which makes them antibiotic-resistant
• the antibiotic-resistant bacteria are better adapted to their environment because they’re not killed by antibiotics
• there is overproduction of offspring (bacteria have rapid generation time)
• the antibiotic-resistant bacteria are more likely to survive and reproduce
• the genes for the antibiotic-resistance characteristic is passed on to the next generation

Question 19

Why has antibiotic resistance evolved so rapidly

Answer 19

• widespread use of antibiotics
• rapid reproduction of bacteria
• huge population sized of bacterial colonies which increases the chances of a gene for antibiotic resistance being formed by mutation
• the transmission of antibiotic resistant genes between bacteria via plasmids

Question 20

what can be done to reduce the prevalence of antibiotic resistant bacteria

Answer 20

• reduction if use of unnecessary antibiotics reduces the selection in favour of bacteria which are resistant, so the percentage of resistant bacteria in the population will fall