p2 exam questions Flashcards
some of the leaves from the gardener’s strawberry plant die. the dead leaves fall off the plant onto the ground. the carbon in the dead leaves is recycled through the carbon cycle. explain how the carbon is recycled into the growth of new leaves.
- carbon compounds in dead leaves broken down by microorganisms
- microorganisms respire and release the carbon from the leaves as carbon dioxide
- plants take in the carbon dioxide released for use in photosynthesis to produce glucose
- glucose produced is used to make amino acids / proteins / cellulose
- which are required for the growth of new leaves
suggest two factors that may have caused the extinction of the siberian rhinoceros
- drought
- ice age / global warming
- volcanic activity
- asteroid / meteor collision
- new predators
- new disease
- competition for food
- competition for mates
- lack of habitat
give two control variables the student should use in the milk investigation
- volume of milk
- exposure to oxygen
- sterilise test tubes
- treatment of milk before investigation
- freshness / age of milk (at start)
- time of day pH was measured
suggest two reasons the different types of milk took different lengths of time to reach pH 5
- different concentrations of lipid
- different concentrations of protein / carb / sugar
- different types of bacteria present
- may have been pasteurised by a diff process
- different starting pH
dead plant material in compost heap and biogas generator doesn’t decay completely. explain why a farmer might spread the remaining dead plant material onto his fields
- so plants grow faster
- decays further and releases mineral ions
“light intensity affects the number of dandelion plants that grow in an area”
plan an investigation to test this hypothesis
- place quadrat
- large number of quadrats used
- how randomness achieved e.g., along transect
- quadrats placed at regular intervals along transect
- transect running through areas of different light intensity
- for each quadrat count number of dandelions and measure light intensity
- compare data
describe how the students could sterilise the flask in a school lab
- heating
- to over 100
describe how bacteria change organic matter into carbon dioxide and inorganic mineral ions
digestion:
- enzymes released
- role of enzymes
- substrates & products
absorption:
- by diffusion / active transport
deamination:
- amino acids -> ammonia
respiration:
- produces carbon dioxide
- release of energy allows other processes to take place
human land use
- crops for food
- increasing population requires more food
- farming crops for biofuels
- peat use as compost
- peat use as fuel
give two reasons why the total biomass of the daphnia in the pond is different from the total biomass of the algae
- non-digestable parts of algae
- not all absorbed
- lost in urine / urea
- used in respiration
- algae not all eaten
- some algae decompose
evaluate evidence for and against the theory that an increase in the concentration of carbon dioxide in the atmosphere causes an increase in air temperature
for:
- overall increased temperature
- co2 traps long-wave radiation / IR / heat
against:
- in some years, temp falls while CO2 rises
- many large and small rises and falls in temp
- other unknown factors may be involved in temp change
- correlation /= cause
give two possible effects of a rise in the earth’s temperature
- changes in climate e.g., droughts, flooding
- rise in sea levels
- reduce biodiversity
- change in migration patterns
- may change distribution of species
what structure causes the change in the size of the pupil and how
- iris
- muscle contraction
explain why more water was lost by breathing during the race
- more energy needed
- so more aerobic respiration
- so increased breathing rate
suggest two advantages of asexual reproduction for bluebells
- many offspring produced
- takes less time
- more energy efficient
- genetically identical offspring
- successful traits propagated
- only one parent is needed
explain why sexual reproduction is an advantage for bluebells
- genetic variation in offspring
- so better adapted to survive
- and colonise new areas by seed dispersal
- many offspring so higher probability some will survive
scientists want to produce a type of cattle that makes large volumes of low-fat milk. describe how the scientists selectively breed them
- find female with lowest fat in milk and highest milk yield
- find male whose female offspring have highest milk yield and lowest fat in milk
- cross the best female with the best male
- select best offspring from each generation and repeat for several generations
explain why a long-sighted person has difficulty seeing near objects clearly
- eyeball is too short or lens cannot be thickened enough
- so light focuses behind retina
describe how spectacle lens can correct long-sightedness
- convex lens
- light rays refracted more
- light rays focused on retina
in tissue culture cloning, give a reason for each of the following steps
- several groups of cells are scraped off the leaf
- nutrients added to the agar jelly
- hormones are added to the agar jelly
- plant cells are kept in sterile conditions
- plant cells kept at 20C
- so many plants can be produced
- for respiration
- so roots / shoots develop
- to prevent entry of microorganisms
- so optimum / good growth
explain two biological reasons why most doctors think a kidney transplant is a better method than dialysis
- changes in concentrations of urea minimised
- so less chance of causing damage to body cells
- not repeatedly puncturing skin
- so less chance of infection
suggest three ways the scientist could maintain a high rate of reproduction in the bacterial culture
- add more sugar
- add more amino acids
- add more oxygen
- increase temperature
- remove toxins
- stir the culture
explain the advantage of making crop plants resistant to herbicide
- kills weeds but doesn’t affect crops
- less competition for light / water / minerals / ions
- so crops have higher yield
explain how making dog food from insects could improve human food security in the future
- less land required
- so more spaces for crops for humans
- less methane from animals therefore less global warming
- therefore less harmful effects of global warming on human food production
