The Organism in the Environment Practice Questions

Sand dunes are a coastal habitat. Marram grass grows on the dunes, and rabbits and sand lizards feed and shelter there.

Cleaner wrasse are small fish that live on coral reefs. They remove small animals from the skin and gills of much larger fish and eat them. The large fish stay still and allow the cleaner wrasse to feed.

A student estimated the number of daisy plants growing on a school field. The field has an area of $600\text{ m}^2$.

The student counted the number of daisy plants in five $1\text{ m} \times 1\text{ m}$ quadrats.

Barn owls hunt field voles on farmland. Scientists estimated the number of field voles and the number of barn owls on one farm over six years.

Kelp is a large seaweed that forms underwater 'forests' along rocky coasts. Sea urchins graze on kelp, and sea otters eat sea urchins. Many species of fish shelter and feed among the kelp.

Scientists use mark and recapture to estimate the size of animal populations. Animals are caught, given a harmless mark and released. After a period of time the habitat is sampled again, and the number of marked animals in the second sample is counted.

The population can be estimated using this equation:

$\text{population size} = \dfrac{\text{number marked in the first sample} \times \text{size of the second sample}}{\text{number recaptured in the second sample}}$

A student used this method to estimate the number of woodlice living under a log pile. She caught and marked 48 woodlice. Two days later she caught 60 woodlice, of which 16 were marked.

A group of students investigated the plants growing across a well-used footpath in a park. They laid a tape measure at right angles to the path and placed a quadrat at $0.5\text{ m}$ intervals, starting at the centre of the path. In each quadrat they estimated the percentage cover of grass and of ribwort plantain.

A gardener investigated competition between radish plants. She sowed different numbers of radish seeds in identical trays of soil. After eight weeks she harvested all the radishes from each tray and calculated the mean mass of one radish.

On a rocky shore, different seaweeds grow in bands at different heights up the shore. Near the low tide mark the rocks are covered by sea water nearly all the time. Near the high tide mark the rocks are uncovered for many hours each day, so the seaweeds dry out and the temperature changes more.

A scientist wants to find out how the percentage cover of bladder wrack seaweed changes from the low tide mark to the high tide mark, and whether abiotic factors can explain the pattern.

A conservation team estimated the number of green-winged orchid plants growing in a meadow. The meadow has an area of $1.5$ hectares ($1$ hectare $= 10\,000\text{ m}^2$).

The team used ten quadrats, each $0.5\text{ m} \times 0.5\text{ m}$, placed at random positions in the meadow.