Natural Selection & Genetic Modification

Question 1

Why are the cells from birds described as eukaryotic?

Answer 1

• they have membrane-bound organelles

Question 2

The three domain classification system was suggested for..

Answer 2

• genetic analysis
• based on DNA/genetics
• domain theory is based on genetics
• differences between coding & non-coding DNA

Question 3

The domain that plants belong to is..

Answer 3

Eukarya

Question 4

What happens in a chloroplast?

Answer 4

• oxygen produced
• sunlight absorbed by chlorophyll

Question 5

Describe the evidence how Ardi ramidus inhabited Earth earlier than Homo habilis

Answer 5

• differences in structural features of fossil (smaller cranial capacity)
• Ardi would be deeper in rock layer than Homo (stone tools)

Question 6

Suggest an explanation for the extinction of Homo habilis

Answer 6

• out-competed by Homo erectus
• for resources essential for survival/due to presence of a new selection pressure

Question 7

Define evolution

Answer 7

• Evolution is the change of inherited characteristics through natural selection.
• these changes occur because genes mutate

Question 8

Describe how the thinner beak of species A is a result of evolution

Answer 8

• variation in beak shape/mutations occured that changed shape of beak
• thinner beaks more suited to environment
• birds with thinner beaks more likely to survive
• more birds with thinner beaks reproduced + passed on alleles for thinner beaks
• occurs over many generations

Question 9

Describe how stone tools & fossils can be dated to find out how old they are

Answer 9

• compare with other tools/fossils (that have already been dated)
• from the layer of rock it was found in/how deep down each was found
• radiometric dating

Question 10

Explain how bacteria has become resistant to Colistin

Answer 10

• people don’t finish their course
• natural selection/evolution occurs
• some bacteria has mutation /
genetic variation
• resistant bacteria survive / resistant bacteria reproduce

Question 11

The theory of evolution suggests…

Answer 11

new species evolve over many generations

Question 12

Explain how bacteria developed resistance to antibiotics

Answer 12

• by natural selection/evolution
—> mutation in bacterium / variation in population
• only resistant bacteria survived treatment by antibiotics / survives when people don’t finish course
• resistant bacteria reproduce
• offspring inherit resistance

Question 13

State how the use of antibiotics contributes to bacteria developing resistance to antibiotics

Answer 13

People not completing their course of antibiotics / overuse of antibiotics

Question 14

Describe how structure of limbs provide evidence for evolution

Answer 14

• pentadactyl limb
• suggests a common ancestor
• that also had a pentadactyl limb
• structure has been adapted to different functions

Question 15

Describe the theory of evolution by natural selection

Answer 15

• organisms in a species have variation / mutations
• there is a selection pressure / competition for resources (food)
• organisms most adapted to environment survive
• reproduction leads to offspring inheriting characteristics
• repeated over generations

Question 16

Explain how MRSA bacteria have evolved to become resistant to antibiotics (6 marks)

Answer 16

• bacteria reproduce rapidly generating a large population
• variation in bacterial population
• some bacteria develop resistance to antibiotics through mutation
• bacteria resistant to antibiotics survive
• antibiotic resistance is inherited
• non-resistant bacteria doesn’t survive

Question 17

Explain why having less brightly coloured feathers increases the survival rate of females

Answer 17

• they are camouflaged
• therefore they’re less likely to be eaten by predators
• more likely to get food from prey

Question 18

Suggest why it’s more important for the survival rate in female birds to be higher than male birds

Answer 18

• females produce offspring/lay eggs
• one male bird can reproduce with many female birds
(increases population of birds)

Question 19

State how fossils can be dated

Answer 19

• location in rock layer
• radiometric dating
• stratigraphy

Question 20

Describe reasons why the anatomy of pentadactyl limbs suggests that bats & cats evolved from a common ancestor

Answer 20

• same bone structure
• common ancestor had pentadactyl limb structure / similar limb structure

Question 21

Scientists can sequence genes from different organisms.
Describe how genetic analysis provides evidence for evolution

Answer 21

• compare genes/sequence of genes from different organisms
• closely related organisms have similar sequences / organisms with similar genes share a common ancestor

Question 22

Describe how scientists can produce a genetically modified bacterium that produces penicillin (4)

Answer 22

• use restriction enzymes to remove the gene & cut plasmid
• use ligase enzymes to join DNA molecules together
• cut the gene from the genome of the fungus & extract a plasmid from bacteria
• insert recombinant plasmid back into bacteria

Question 23

Describe how cattle can be selectively bred to produce cattle that can survive high temperatures & have good meat quality

Answer 23

• breed cattle with better characteristics
• select offspring with desired characteristics & breed them
• repeat over many generations

Question 24

Describe how drought-resistant crops plants can be produced

Answer 24

• genetic variation - some plants will be more adapted to drought conditions & these can be selected
• cross-pollinate these plants & grow seeds under drought conditions
• select offspring & repeat over many generations

Question 25

Describe how racehorses alive today have been selectively bred to run faster (3)

Answer 25

• breed two animals that can run fast
• select offspring that can run fast
• repeat process over many generations

Question 26

Explain how bacteria can be genetically engineered to produce human insulin (6 marks)

Answer 26

• gene that codes for human insulin is identified
• in human DNA
• this is removed using a restriction enzyme
• plasmid of a bacterial cell is removed
• using lysosomes/lysozyme
• using same restriction enzyme
• leaving complementary sticky ends
• human gene is inserted into bacterial plasmid
• using ligase enzyme
• plasmid returns to bacterial cell
• bacterial cell multiplies

Question 27

Explain how enzymes are used to produce a genetically modified plasmid in a bacterial cell (3 marks)

Answer 27

• plasmid & gene are cut using restriction enzymes
• these enzymes produce complementary sticky ends/base pairs
• gene is inserted into plasmid using ligase

Question 28

Explain advantages of producing genetically modified crop plants

Answer 28

• less crop damage
• so higher yield
• so more food for people

• crop plants less likely to have diseases that are spread by insects
• so less pesticides/insecticides used

• more profit
• so more income for developing countries

increases yield
• can be produced in a shorter time period
• production is cheaper/easier to extract
• takes up less space than growing plants

Question 29

Explain disadvantages of producing genetically modified crop plants

Answer 29

Less variation

• concerns about long term effects
• GM crops can cause diseases to humans
• GM crops could trigger allergic reactions

• genes could be transferred to other species/weeds
• so weeds could grow out of control

• reduced gene pool
• insects will evolve so crops are no longer resistant to insect pests

• concerns over genetically modified yeast being manufactured illegally
• may not be as effective/identical
• concerns over GM organisms entering environment

Question 30

ExplIn one advantage of producing genetically modified crops that produce toxic chemicals in their leaves (2 marks)

Answer 30

• kills insects/pests/pathogens
• less damage to crops / increases crop yield
• no need to use insecticides/pesticides

Question 31

If GM crops have a large yield…

Answer 31

Less land is needed to grow GM crops