SCSA Biology Science as a Human Endeavour

1 mark for each correct point (any 6 of):

• Identifies the need to identify/isolate a suitable gene • States that it must be a gene that produces an enzyme that digests oil
• Describes choosing a suitable bacterium for genetic modification (one that can survive in aquatic environments)
• Explains the use of the same restriction enzyme to remove the gene from the host and insert it into a plasmid
• Describes amplifying the target gene (in a plasmid or by polymerase chain reaction (PCR))
• States that the gene is inserted into the bacteria/target organism
• Describes transforming the bacteria using heat shock or another relevant method
• States the need to check the ability of the bacteria to reproduce/produce the gene product

1 mark for each correct point (any 2 of):

• Explains that genes from other species can be used or outcomes not possible via natural processes can be achieved
• States that (after development) it is easy/fast to produce/supply transgenics in large quantities
• States that microorganisms are easy to transport/handle/store

1 mark for each correct point (any 2 of):

• Explains that transgenic organisms could have a negative impact on other organisms/the environment or oil-digesting bacteria could take over/displace natural bacteria
• Identifies the risk of gene transfer to other organisms
• States that it is a fairly new technology, so there may be unknown effects, it may not be effective, or development can be very expensive

1 mark for each correct point (any 2 of):

• Describes mutation as a permanent change to DNA or a change in DNA structure
• States that it changes one allele to another or creates new alleles
• Identifies that it occurs at random

1 mark for each correct point (any 3 of):

• Explains that mutations can have deleterious effects on individuals, can result in the death of individuals, or can have neutral, advantageous, or disadvantageous effects (depending on the mutation)
• States that mutations have a limited effect on allele frequencies (because the rate of mutation is low)
• Identifies mutation as the source of all genetic variation/alleles/biological diversity • Explains that other evolutionary processes are dependent on this variation or that populations cannot evolve without genetic variation

1 mark for each correct point (any 2 of):

• Describes genetic drift as the random death of individuals, selection of gametes, or founder effect
• States that it involves random/chance changes in allele frequencies
• Identifies that it has the biggest effect in small populations

1 mark for each correct point (any 3 of):

• Explains that it leads to a loss of diversity/alleles or can result in the loss of advantageous alleles
• States that it places populations at risk of extinction
• Explains that this risk is due to increased inbreeding, inability to adapt, or susceptibility to pathogens

dominant – only one copy of allele is needed for an individual to show phenotype or heterozygote will show phenotype

autosomal – alleles are on autosomal chromosomes or alleles are not on sex chromosomes or two alleles are present in both males and females

0.25/25%/1 in 4

Must use specified notation for alleles (T,t).

Only one in four offspring will have tt genotype or three in four offspring will have one copy of T/dominant allele.

DNA sequencing or (comparative) genomics

compare genomes/DNA sequences of affected and unaffected sheep

controlled/influenced by the alleles at many genes/by many genes

trait shows many different phenotypes in a population or trait shows continuous variation/a normal distribution in a population

(breeding sheep is a) natural process

artificial selection changes allele/gene frequencies gradually

Identifies/extracts a herbicide resistant gene (in another species)

States that the gene is inserted into the crop species

1 mark for each correct point (up to 3) for one of the following mechanisms:

• Natural selection (Describes excessive spraying of herbicides to kill weeds; Explains that natural selection favours herbicide resistant individuals in weed species; States that over time, herbicide resistant individuals become common or the entire species is herbicide resistant)
• Gene is transferred to another species (Describes gene flow occurring between the transgenic crop and weed/related wild species; Explains that this transfers the resistant gene/traits to the weed/wild relative; States that this gives the weed/wild relative herbicide resistance)
• Crop species becomes a weed (States that the crop species becomes a weed; Explains that the crop species spreads to a new area or it is impossible to remove the crop species from the field; States that the herbicide is not effective at removing the crop/weed species or it cannot be controlled outside of its intended use)

1 mark for each correct point (up to 3) for one of the following mechanisms:

• Natural selection (Describes excessive spraying of herbicides to kill weeds; Explains that natural selection favours herbicide resistant individuals in weed species; States that over time, herbicide resistant individuals become common or the entire species is herbicide resistant)
• Gene is transferred to another species (Describes gene flow occurring between the transgenic crop and weed/related wild species; Explains that this transfers the resistant gene/traits to the weed/wild relative; States that this gives the weed/wild relative herbicide resistance)
• Crop species becomes a weed (States that the crop species becomes a weed; Explains that the crop species spreads to a new area or it is impossible to remove the crop species from the field; States that the herbicide is not effective at removing the crop/weed species or it cannot be controlled outside of its intended use)

1 mark for each correct point (any 4 of): Defines fossils as preserved remains/traces of organisms; States that most fossils are from extinct organisms; Explains that this shows organisms were different in the past; States that fossils include intermediate/transitional forms; Explains that this shows how a trait has (gradually) changed through time or how an organism has changed from its ancestor

1 mark for each correct point (up to 2) for one of the following limitations: Gaps (Identifies gaps in the fossil record or that the fossil record is incomplete; Explains that fossilisation is rare, most organisms do not leave fossils, most fossils are not found, or fossils are destroyed), Organism bias (Identifies that the fossil record is biased towards certain taxa/types of organisms; Explains that some organisms are more likely to fossilise than others, such as organisms with hard structures being more likely to fossilise than soft-bodied organisms), Environmental bias (Identifies that the fossil record is biased towards certain environments; Explains that organisms in aquatic environments are more likely to fossilise than those in terrestrial environments), Age bias (Identifies that the fossil record is biased towards younger organisms; Explains that older fossils are more likely to have been destroyed than younger fossils), Morphological bias (Identifies that most fossil evidence is morphological; Explains that there is only limited information about other aspects of the biology of extinct species, such as genetics, behaviour, or physiology)

1 mark for each correct point (up to 2) for one of the following limitations: Gaps (Identifies gaps in the fossil record or that the fossil record is incomplete; Explains that fossilisation is rare, most organisms do not leave fossils, most fossils are not found, or fossils are destroyed), Organism bias (Identifies that the fossil record is biased towards certain taxa/types of organisms; Explains that some organisms are more likely to fossilise than others, such as organisms with hard structures being more likely to fossilise than soft-bodied organisms), Environmental bias (Identifies that the fossil record is biased towards certain environments; Explains that organisms in aquatic environments are more likely to fossilise than those in terrestrial environments), Age bias (Identifies that the fossil record is biased towards younger organisms; Explains that older fossils are more likely to have been destroyed than younger fossils), Morphological bias (Identifies that most fossil evidence is morphological; Explains that there is only limited information about other aspects of the biology of extinct species, such as genetics, behaviour, or physiology)

1 mark for each correct point (up to 2) for one of the following limitations: Gaps (Identifies gaps in the fossil record or that the fossil record is incomplete; Explains that fossilisation is rare, most organisms do not leave fossils, most fossils are not found, or fossils are destroyed), Organism bias (Identifies that the fossil record is biased towards certain taxa/types of organisms; Explains that some organisms are more likely to fossilise than others, such as organisms with hard structures being more likely to fossilise than soft-bodied organisms), Environmental bias (Identifies that the fossil record is biased towards certain environments; Explains that organisms in aquatic environments are more likely to fossilise than those in terrestrial environments), Age bias (Identifies that the fossil record is biased towards younger organisms; Explains that older fossils are more likely to have been destroyed than younger fossils), Morphological bias (Identifies that most fossil evidence is morphological; Explains that there is only limited information about other aspects of the biology of extinct species, such as genetics, behaviour, or physiology)