T6 variation and evolution

Question 1

what is variation

Answer 1

differences in the characteristics of individuals in a population

Question 2

what are the causes of variation within a species

Answer 2

genetics

environment

Question 3

what is genetic variation

Answer 3

variations in the genotypes of organisms of the same species due to the presence of different alleles

creates differences in phenotypes

Question 4

what creates genetic variation in a species

Answer 4

spontaneous mutations

sexual reproduction

Question 5

3 types of gene mutation

Answer 5

insertion

deletion

substitution

Question 6

how may a gene mutation affect an organisms phenotype

Answer 6

neutral mutation doesn’t change the sequence of amino acids, protein structure and function same, no effect

mutation may cause minor change in phenotype

may completely change the sequence of amino acids, resulting in a non-functional protein, severe changes to phenotype

Question 7

consequence of a new phenotype caused by a mutation being suited to an environmental change

Answer 7

rapid change in the species

Question 8

what is evolution

Answer 8

gradual change in the inherited trains within a population over time

occurs due to natural selection which may result in the formation of a new species

Question 9

outline the theory of natural selection

Answer 9

all species of living things have evolved from simple life forms that first developed more than 3 billion years ago

1. genetic variation exists due to spontaneous mutations
2. selection pressures exist
3. random mutation gives an organism a selective advantage
4. organism is better adapted to the environment and survives
5. organism reproduces, passing on its beneficial alleles
6. frequency of advantageous alleles increases

Question 10

how do two populations become different species

Answer 10

when their phenotypes become different to the extent that they no longer interbreed to produce fertile offspring

Question 11

outline main steps in selective breeding

Answer 11

1. identify desired characteristic
2. select parent organisms that show the desired traits and breed them together
3. select offspring with desired traits and breed them together
4. process repeated until all offspring have the desired traits

Question 12

examples of characteristics selected for in selective breeding

Answer 12

disease resistance in crops

higher milk or meat production in animals

large flowers

Question 13

advantages of selective breeding

Answer 13

creates organisms with desirable features

Question 14

where is selective breeding useful

Answer 14

medical research

sport eg horse racing

agriculture

Question 15

outline the disadvantages of selective breeding

Answer 15

reduction in the gene pool (becomes harmful is sudden environmental change occurs)

inbreeding results in genetic disorders

development of physical problems

potential to unknowingly select harmful recessive alleles

Question 16

what is genetic engineering

Answer 16

modification of the genome of an organism by the insertion of a desired gene from another organism - genes from chromosomes of humans and other organisms can be cut out and transferred to cells other organisms

enables the formation of an organism with beneficial characteristics

Question 17

what is a use for genetically modified bacteria cells

Answer 17

produce human insulin to treat diabetes mellitus

Question 18

describe the effects of genetic engineering

Answer 18

increased crop yields for growing population

useful in medicine possibly to overcome some inherited disorders

GM crops produce scarce resources (golden rice produces beta-carotene (source of VA in body))

Question 19

risks of genetic engineering

Answer 19

long-term effects of consumption of GM crops unknown

negative environmental impacts

late-onset health problems in GM animals

GM seeds are expensive, LEDC may be unable to afford or may become dependent on businesses that sell them

Question 20

what is bacillus thuringiensis (Bt)

Answer 20

insect larvae are harmful to crops

bacterium which secretes a toxin that kills insect larvae

Question 21

how is genetic engineering used to protect crops against insects

Answer 21

gene for toxin production in Bt can be isolated and inserted into the DNA of crops

Bt crops now secrete toxin which kills any insect larvae that feed on it

Question 22

benefits of Bt crops

Answer 22

increased crop yields

lessens need for artificial insecticides

Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it

Question 23

risks of Bt crops

Answer 23

long term effects of consumption unknown

insect larvae may become resistant to toxin

killing reduces biodiversity

Question 24

describe the process of genetic engineering

Answer 24

1. DNA is cut at specific base sequences by restriction enzymes to create sticky ends
2. vector DNA cut using the same restriction enzymes to create complementary sticky ends
3. ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA
4. recombinant DNA mixed with and taken up by target cells

Question 25

what is a vector

Answer 25

structure that delivers the desired gene into the recipient cell

Question 26

how can plants be cloned

Answer 26

taking plant cuttings

tissue culture

Question 27

what is tissue culture

Answer 27

using small groups of cells from part of a plant to grow identical new plants

Question 28

describe how plants are grown using tissue culture

Answer 28

1. select a plant showing desired characteristics
2. cut multiple small sample pieces from meristem tissue
3. grow in a petri dish containing growth medium
4. transfer to compost for further growth

Question 29

what must be ensured when preparing tissue culutres

Answer 29

aseptic conditions to prevent contamination by microorganisms

Question 30

what does the growth medium contain

Answer 30

nutrients and growth hormones

Question 31

advantages of growing plants by tissue culture

Answer 31

fast and simple process

requires little space

enables growth of many plant clones with same desired characteristics

useful in preservation of endangered plant species

Question 32

disadvantages of growing plants by tissue culture

Answer 32

reduction in gene pool

plant clones often have a low survival rate

could unknowingly increase the presence of harmful recessive alleles

Question 33

brief overview of plant cuttings method of plant cloning

Answer 33

older but simpler method than tissue culture

gardeners use this method to produce many identical new plants from a parent plant

Question 34

detail the process of plant cuttings method of plant cloning

Answer 34

1. branch is cut off from the parent plant
2. lower leaves of the branch are removed and the stem is planted
3. plant hormones are used to encourage new root development
4. plastic bag covers the new plant to keep it warm and moist
5. new roots and a new plant is formed after a few weeks

Question 35

what does embryo transplanting involve

Answer 35

pre-specialised cells from a developing animal embryo are spilt apart

resulting separate but identical embryos are transplanted into host mothers

Question 36

describe how adult cell cloning is performed

Answer 36

1. nucleus removed from unfertilised egg cell
2. nucleus from adult body cell is inserted
   into the egg cell
3. electric shock stimulates the nucleated egg to divide and it forms an embryo
4. embryo cells contain the same genetic information as the adult body cell
5. when the embryo is a ball of cells, inserted into the uterus to continue developing