classification

Question 1

state the meaning of the term phylogeny and explain how phylogeny is related to classification (3)

Answer 1

the study of evolutionary relationships between organisms
it is the basis of modern classification
the closer the evolutionary relationships the closer the taxanomic grouping eg gorillas and chimpanzees are closely grouped

Question 2

state the name given to the evolution of a new species (1)

Answer 2

speciation

Question 3

fossils provide strong evidence that organisms have evolved over time
describe other types of evidence that support the theory of evolution (6)

Answer 3

similarities shown in dna in the nucleotide base order
as this means they must share a common ancestor
also in cytochrome c
an example is chimps and humans
proof of evolution within human history eg mrsa resistance to antibiotics

Question 4

state the role of a gene (1)

Answer 4

code for more than one polypeptide

Question 5

explain how the structure of DNA allows replication (5)

Answer 5

• double stranded and each strand acts as a template
• h2 bonds break and form easily between bases
• between the bases there is complementary base pairing
  eg purines are only able to bind to pyrimidines
• and h2 bonding is different between A-T and G-C eg AT has 2h bonds and GC has 3h bonds

Question 6

describe how it is possible to use selective breeding to improve the overall disease resistance of a crop eg potatoes in both short and long term
include precautions to avoid disease susceptibility (7)

Answer 6

• cross breed with disease resistant variety
• test the offspring for disease resistance eg germinate the seeds and expose the disease to see if they die or not
• then select the best offspring
• interbreed the best offspring
• continue this process for many generation
• but avoid interbreeding to preserve genetic diversity
• and regular cross with a wild variety and preserve rare varieties incase they are needed in the future

Question 7

why might plants be affected b the environment to a greater degree than animals?

Answer 7

plants do not move and therefore cannot change their environment as easily as animals and are therefore more
likely to be exposed to environmental factors for prolonged
periods

Question 8

why are studies of twins (identical and non-identical) useful to scientists?

Answer 8

• identical twin studies help us understand to what degree characteristics are affected by environmental and genetic factors
• non-identical studies are not as useful but can also show how different combinations of genes can manifest

Question 9

why do you think it is difficult for scientists to agree on how much a characteristic is determined by genetic or environmental factors?

Answer 9

because so man are caused by a combination of the two, it’s difficult to investigate and fully control the factors - identical twin studies have been the best at investigating nature vs nurture