Biology Practice Paper Review
Key answers and reasoning from the mixed biology exam paper covering cells, systems, photosynthesis, genetics and ecology.
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Questions Covered in This Set
11 cards to master
Which organelle is in plant cells but not animal cells?
The chloroplast (site of photosynthesis). Plant cells also have a cell wall and permanent vacuole.
Define osmosis.
The movement of water across a partially permeable membrane from a dilute solution (high water potential) to a concentrated solution (low water potential).
Word equation for aerobic respiration, and where does it occur?
Glucose + oxygen → carbon dioxide + water (+ energy released); mainly in the mitochondria.
Product of anaerobic respiration in human muscle?
Lactic acid (no oxygen used, less energy released; in yeast it would be ethanol + carbon dioxide).
Give two adaptations of the small intestine for absorption.
Villi/microvilli for large surface area; thin one-cell wall for short diffusion distance; rich blood supply to keep a steep gradient; long length for more absorption time.
What is homeostasis? Give an example.
Maintaining a constant internal environment despite external change — e.g. body temperature, blood glucose, or water/ion balance.
Why destarch a plant (48 hours in the dark) before a starch test?
To remove starch already stored, so any starch found afterwards must have been made by photosynthesis during the experiment.
Two brown-eyed parents have a blue-eyed child — genotypes and probability?
Both parents are Bb. Punnett square gives BB, Bb, Bb, bb, so the chance of a blue-eyed (bb) child is 1/4 = 25%.
In the pondweed and lamp experiment, name the variables.
Independent = distance from lamp; dependent = number of bubbles (rate of photosynthesis); controlled = temperature, CO₂ concentration, same piece of pondweed.
If disease kills most rabbits, what happens to grass and foxes?
Grass increases (less grazing); fox population falls because there is less food/prey available.
What does natural selection above all require?
Variation within a population, so that better-adapted individuals survive, reproduce and pass on their alleles.
