Exam (elaborations)
2024 AQA A LEVEL BIOLOGY- POPULATIONS PAST PAPER EXAM WITH CORRECT ANSWERS
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2024 AQA A LEVEL BIOLOGY- POPULATIONS PAST PAPER EXAM WITH CORRECT ANSWERS
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2024 AQA A LEVEL BIOLOGY-POPULATIONS PAST PAPER EXAM
WITH CORRECT ANSWERS
Define niche. - CORRECT-ANSWERSHow an organism fits into its
environment, including where it lives, its role and all abiotic and biotic
factors.
Define ecosystem - CORRECT-ANSWERSA group of interrelated organisms
and their physical environment in a particular area.
State three assumptions of the capture-recapture technique. - CORRECT-
ANSWERSmarking does not affect probability of recapture
marking persists over trapping period/marks do not wear/wash off
the population remains constant over the sampling period
the samples consitute an accurate cross section of the population/sexes/ages
etc
Explain why 'throwing quadrats' is not an acceptable sampling technique. -
CORRECT-ANSWERSwill not provide a random sample
because of 'handedness'/subjectivity/bias/differences between samplers'
throwing ability
Outline how you would use random sampling to estimate the number of
dandelion flowers in a square lawn. - CORRECT-ANSWERSset up grid using
tapes at right angles/along two sides of lawn
generate random/numbers for use as co-ordinates
using accurate technique e.g. computer/tables
place quadrat at intersection
count number of dandelions in the quadrat
repeat at least 10 times and calculate the mean density per quadrat area
calculate daisy population in total lawn area
Describe how the surface area of a leaf can be measured. - CORRECT-
ANSWERSlay leaf flat on graph paper and draw round margin
count up total number of squares included
count up total number of ½ squares included and add into total
multiply by two to get total surface area (both sides of leaf)
, Samples of mud were collected using large spoons. Nets were used to
sample organisms in the open water and in the weeds. Suggest two possible
sources of error in the sampling methods used. - CORRECT-ANSWERSunequal
sampling intensity/unequal sample sizes/only part of microhabitat sampled
To determine total biomass, quadrats were used to collect the heather
samples.
Describe the procedure you would have used to place these quadrats. -
CORRECT-ANSWERSPlacing quadrats at random
(method of) marking area out with grid/using tapes
acceptable method of generating random numbers e.g.
table/calculator
Give one organic compound in which the nitrogen will be found in the
heather plants. Give one ion in which the nitrogen will be found in the soil. -
CORRECT-ANSWERS(i) proteins/nucleic acids/amino acids/ATP/nucleotides
(ii) ammonium/nitrate/nitrite
Explain how bare ground may, over a long period of time, become forest. -
CORRECT-ANSWERSColonisation/pioneer species/examples from
fig/seeds/fruits
soil formation/improvement/change by organism
succession/
process repeated to climax community/forest
diversity is reduced
Explain how bare, cleared land could once again become forest. - CORRECT-
ANSWERS(Before clearing) soil exists / already produced
(After clearing) recolonisation by new plants / seeds
(Brings about) change in environment / soil
(Allows) succession
(Leading to) climax (community)
Some of the soil used to determine bacterial numbers was collected from the
surface of the soil store. Describe how you would ensure that this soil was
collected at random. - CORRECT-ANSWERSTapes / string / axes laid out at
right angles / grid area
Method of obtaining random co-ordinates
Explain why one community is gradually replaced by another during
succession. - CORRECT-ANSWERSchange in habitat/environmental conditions
by the species present
making it less suitable for existing species/more suitable for other species
reference to competition
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