B14 - Variation and Evolution

Question 1

What is variation, and what can cause it? Give examples of characteristics that are affected by these causes:

Answer 1

-differences in the phenotypes of individuals in a population

-genetic causes (eye colour)
-environmental causes (scars)
-combination of both (height)

Height is both because you might have the genes that cause you to be tall, but because they are malnourished they don’t grow.

Question 2

Explain 2 reasons behind the genetic causes of variation within a population:

Answer 2

-mutations (rarely, it can produce a new phenotype that is suitable to an environmental change, and this leads to a relatively rapid change in the species)

-sexual reproduction due to the fusion of gametes, causing mixing of genetic info

Always say the reason for sexual reproduction causing variation
Mutations usually have no effect on phenotype

Question 3

What is evolution?

Answer 3

the gradual change in the inherited characteristics of a population over time through the process of natural selection, which may give rise to the formation of new species

Question 4

What does the Theory of Evolution state the origin of all living species is?

Answer 4

the Theory of Evolution states that all species of living things evolved from simple life forms from over 3 billion years ago

Question 5

What distinguishes 2 different species?

Answer 5

the species are different if they can’t interbreed to produce fertile offspring

Question 6

Describe, generally, how natural selection drives evolution:

Answer 6

-variation present in population due to mutations/sexual reproduction

-environment changes
-the better-adapted variants survive in new environment and reproduce more, while others die
-favourable alleles are passed on to the next generation

In a question, use this model answer but apply it to the context of the situation

Question 7

What is selective breeding?

Answer 7

the process by which humans breed plants/animals for favourable genetic characteristics

Question 8

Name 4 things that humans may want from selective breeding:

Answer 8

-animals with more meat/milk
-disease/drought resistance in crops
-domestic dogs with gentle nature
-large/unusual flowers

Question 9

How can you selectively breed in a population? Why might this be a bad thing?

Answer 9

-choose parents with the desired characteristics and breed them
-the offspring will show variation for the characteristic
-only breed the offspring with the desired characteristics
-repeat over multiple generations until all offspring show the desired characteristic

-inbreeding means some breeds are more prone to certain diseases and recessive disorders

Question 10

Why might you want to selectively breed cats?

Answer 10

-so they don’t have any specific genetic defects
-to make them more docile
-aesthetic reasons (eg more fluffy)

Question 11

What is genetic engineering?

Answer 11

the process of modifying the genome of an organism by introducing a gene from another organism to give it a certain desirable characteristic

Question 12

Give some reasons why people might be concerned about genetic engineering:

Answer 12

-ethics of designer babies
-lack of control over genes spreading into other wildlife

Add in points about GM crops if necessary

Question 13

Give some examples of where genetic engineering has been used:

Answer 13

-GM crops
-bacteria (to produce insulin for treating T1 diabetes)

Everyone with T1 takes insulin, but only some with T2 take it

Question 14

What are the pros and cons of GM crops?

Answer 14

-disease/drought/herbicide/insect resistant
-larger crop yield
-better nutritional value

-new technology, effects on human health has not been fully explored, and it may cause some side effects

Always say side effects as the rest of it alone won’t get any marks

Examples include golden rice, sugar beets, and bananas

Question 15

Describe the process involved in genetic engineering:

Answer 15

-use enzyme to isolate the required gene
-insert into virus or bacterial plasmid (vector)
-insert into bacteria
-bacteria multiply and develop with the desired characteristics

Bacterial plasmids are only used for engineering bacteria, whilst viruses are used for engineering plant cells. Specify the one needed in your answer

Question 16

Name 4 methods of cloning:

Answer 16

-cuttings
-tissue culture
-embryo transplant
-adult cell cloning

Question 17

What is the method of cuttings?

Answer 17

a simple cloning method used to produce many identical plants from a parent plant, by cutting and replanting its meristems

Question 18

What is tissue culture?

Answer 18

the process of using small groups of cells from part of a plant to grow multiple identical plants

Question 19

Describe the steps involved in tissue culture:

Answer 19

-scrape tissue sample from leaf
-place in agar with nutrients + auxins
-grows into many small plantlets
-transfer into soil

Question 20

What is an embryo transplantation?

Answer 20

the process of splitting apart cells from a developing animal’s embryo before they become specialised, then transplanting the identical embryos into other surrogate mothers

Foster is a mother that takes care of an animal in its upbringing, and is different to a surrogate which actually gives birth to the animal

Question 21

Describe the process of adult cell cloning:

Answer 21

-remove nucleus of unfertilised egg cell and replace it for the nucleus from an adult body cell (eg skin cell) from the animal you want to clone
-stimulate egg cell with an electric shock to divide and form an embryo
-once it develops into a ball of cells, insert it into a surrogate mother to continue its development

This process starts off similarly to therapeutic cloning

Question 22

State some pros of cloning in general:

Answer 22

-can preserve endangered species
-organ harvesting could overcome donor shortage
-can combat aging

Question 23

State some cons of cloning in general:

Answer 23

-reduced gene pool (fewer different alleles in population)
-ethical issues (eg experiments on human cloning)
-unknowns about new tech (eg meat produced may be unfit for human consumption, may cause side effects)