Adaptations, Interdependence & Competition Practice Questions

A hedgerow grows between two fields. The hedgerow contains hawthorn shrubs, bramble plants, woodmice, snails and many species of insect.

The desert kangaroo rat lives in hot, dry deserts in North America.

Deep sea vents are cracks in the ocean floor, several kilometres below the surface, where very hot water rich in dissolved chemicals escapes from the rocks. Communities of bacteria live around these vents.

Mayfly nymphs are insects that live in streams. They take in oxygen from the water.

Students sampled the same stream at five sites, A to E. Site A was highest up the stream and site E was lowest down, where the stream flowed slowly through open fields.

Their results are shown in Table 2.

Table 2

Site	Mean water temperature in °C	Dissolved oxygen in mg/dm³	Mean number of mayfly nymphs per sample
A	9.5	11.2	38
B	11.0	10.1	31
C	13.5	8.6	19
D	16.0	7.2	10
E	18.5	6.3	4

A woodland contains a shrub called spindle.

• Spindle flowers are pollinated by only one species of moth.
• The caterpillars of this moth feed only on spindle leaves.
• Spindle berries are eaten by thrushes, which disperse the seeds in their droppings.

A farmer sprayed insecticide on a field next to the woodland. All the moths in the woodland were killed.

The white-clawed crayfish is native to rivers in the UK. The American signal crayfish was brought to the UK and escaped into rivers.

• Both species live on river beds and feed on the same small animals and plant material.
• Both species shelter in holes in the river bank.
• The signal crayfish is larger and grows faster than the white-clawed crayfish.
• The signal crayfish carries a fungus called crayfish plague. The fungus does not harm the signal crayfish, but it kills the white-clawed crayfish.

The Arctic fox lives on tundra where the mean winter air temperature is $-25\ ^\circ\text{C}$ and the ground is covered in snow.

The fennec fox lives in the Sahara desert where the mean daytime air temperature is $38\ ^\circ\text{C}$ and the ground is pale sand.

Table 3 shows some features of the two foxes.

Table 3

Feature	Arctic fox	Fennec fox
Mean body mass in kg	4.0	1.2
Mean ear length in cm	6	12
Mean thickness of fur in winter in mm	50	8
Colour of fur	white	pale sandy

Two species of barnacle live attached to rocks on a rocky shore. Barnacles feed only when they are covered by sea water. The higher up the shore a barnacle lives, the longer it is exposed to the air each day.

• Chthamalus is small and can survive being dried out for long periods.
• Semibalanus is larger and grows much faster. It grows over and crushes any Chthamalus next to it, but it dies if it dries out.

Scientists measured the mean percentage cover of each species at five heights up the shore. Their results are shown in Table 4.

Table 4

Height above low tide mark in m	Mean cover of Chthamalus in %	Mean cover of Semibalanus in %
0.5	0	62
1.5	4	55
2.5	26	18
3.5	48	2
4.5	51	0