paper 2

Question 1

name given to all of the organisms living in the same habitat

Answer 1

a community

Question 2

what happens to the shape of a lens when focusing on a near object

Answer 2

becomes wider

Question 3

what is tissue culture

Answer 3

a group of cells are grown into
a new organism

Question 4

milk contains lipids
the lipids are broken down when milk decays
explain why the pH changes more quickly when the temperature is higher

Answer 4

enzymes are more active
lipids are broken down more quickly
fatty acids produced more quickly (which changes pH)

Question 5

explain how the production of thyroxine causes an increase in body temperature

Answer 5

thyroxine increases basal metabolic rate
respiration releases energy

Question 6

describe how muscles in the iris help the person to see clearly when moving from a dimly-lit area to a brightly-lit area

Answer 6

• (muscles in the iris) contract
• reduce size of pupil
• reduces (amount of) light
  entering

Question 7

give reason the farmer used a large number of chickens

Answer 7

reduce the effect of
anomalies

Question 8

describe how carbon and nitrogen in compounds in the leaves are recycled and used by living trees

Answer 8

microorganisms / bacteria / fungi (cause decay) respiration by microorganisms
* production / release of carbon dioxide
* carbon dioxide is released into the air
carbon dioxide taken in by stomata / leaves
* carbon dioxide used in photosynthesis
* making glucose
release of nitrate (ions) into the soil
* nitrate (ions) taken in (by roots)
* nitrate (ions) taken in by active transport
* nitrate (ions) for making amino acids

Question 9

give two reasons why an increase in the diversity of trees in the rainforest leads to an increase in animal diversity

Answer 9

different types of food
available
different types of habitat available

Question 10

explain why the lack of FSH in the woman’s blood caused underdeveloped breasts

Answer 10

(lack of FSH causes) lack of
oestrogen (production)
breast development is
dependent on oestrogen (from
follicles)

Question 11

describe how meiosis produces cells that are genetically different

Answer 11

random chromosome from
each pair (of chromosomes)
moves to one end of the cell

Question 12

explain how our understanding of evolution has developed due to:
fossil evidence
increased understanding of the mechanisms of genetic

Answer 12

• fossils show evidence of life in the past
• fossils show change over time
• fossil record shows development of species over time
  gaps in fossil record are being filled in with new evidence
• observation of chromosome behaviour during cell division
• chromosome behaviour and Mendel’s units work in similar ways
• structure of DNA worked out
• gene mechanism in determining protein synthesis worked out