B14 Variation and Evolution

Question 1

what is variation?

Answer 1

the differences of the characteristics of individuals in a population

Question 2

what are the three main causes of variation in a population?

Answer 2

• alleles that an individual has inherited (genetic causes)
• environment
• a combination of genes and evironment

Question 3

what is genetic variation due to?

Answer 3

mutations of the DNA

Question 4

what can happen rarely with a mutation?

Answer 4

it can lead to a completely new phenotype

Question 5

what can a beneficial mutation and a change in phenotype lead to?

Answer 5

it can lead to a rapid change in the species

Question 6

what is natural selection?

Answer 6

an organism which has a characteristic which makes it better adapted to the environment is more likely to survive and reproduce. the offspring may also have the alleles for the advantageous characteristics so are more likely to survive and spread the characteristic through the population.

Question 7

what is evolution?

Answer 7

the change in the inherited characteristics of a population over time through a process of natural selection

Question 8

how can two populations become two completely separate species?

Answer 8

they become so different in phenotype that they are no longer able to interbreed and produce fertile offspring

Question 9

what are some examples of selective breeding?

Answer 9

• domestic dogs - bred to have a gentle nature
• food crops - disease resistant
• animals - produce more meat/milk
• plants - produce larger flowers

Question 10

how do you carry out selective breeding?

Answer 10

• select the characteristics you want from a mixed population
• breed the parents with the selected characteristics together
• select the desired characteristics from the offspring and breed them together
• continue to do this so all the population have the desired characteristic

Question 11

how do you get inbreeding?

Answer 11

when closely related plants or animals are bred together

Question 12

what can inbreeding cause?

Answer 12

some breeds to be prone to disease or inherited defects

Question 13

what happens during genetic engineering?

Answer 13

genes from one organism are cut out and transferred to a different organism.
this means the genome of the second organism is modified

Question 14

what is a good example of genetic engineering?

Answer 14

bacteria which have been genetically modified to contain the human insulin gene and produce human insulin

Question 15

what are GM crops?

Answer 15

crops which have been genetically modified to have enhanced characteristics such as greater yields

Question 16

What characteristics can crops be genetically modified to have?

Answer 16

greater yields
disease or pest attack resistance
bigger or better fruits
herbicide resistance

Question 17

what are some concerns for GM crops?

Answer 17

if they are harmful for wild flowers and insects
some people feel that more research should be done on the health effects of eating gm crops

Question 18

what is gene therapy?

Answer 18

using genetic modification to treat inherited diseases

Question 19

what are the steps of genetic engineering?

Answer 19

• identify the gene you want to transfer
• use enzymes to isolate the gene
• transfer the gene into a plasmid from bacteria
• the desired gene is transferred into the target organism

Question 20

what is a vector?

Answer 20

a plasmid or virus which transfers DNA from one organism to another

Question 21

when is a gene transferred in the life cycle of an organism?

Answer 21

at an early stage of the organism’s development to ensure all of the cells receive the transferred gene.

Question 22

what is a clone?

Answer 22

a genetically identical organism to the parent organism

Question 23

what is the advantage of cloning plants?

Answer 23

we know exactly what the clone’s characteristic will be as the clone is genetically identical to the parent

Question 24

what do you do when you take cuttings from a plant?

Answer 24

you remove a small piece of the plant and dip the end into rooting powder that contains hormones to promote roots to grow

Question 25

when does taking cuttings work well (in what situations)?

Answer 25

when you want a few genetically identical plants

Question 26

what happens during tissue-culture?

Answer 26

the plant which you want to clone is divided into hundreds of tiny pieces which contains a small number of cells

Question 27

What happens once the tiny pieces of plant are divided during tissue culture?

Answer 27

they are incubated with plant hormones that stimulates growth into fully-grown clones

Question 28

why must the conditions for tissue-culture be sterile?

Answer 28

we don’t want to introduce any microorganisms

Question 29

when is tissue-culture used?

Answer 29

in commercial plant nurseries
to preserve rare species

Question 30

How does cloning animals work? (With embryos)

Answer 30

Lots of eggs from a top quality cow are fertilised with the sperm from a top quality bull.
At early stages of development, the embryos are split and transplanted into surrogate mothers.
The offspring produced are genetically identical to each other