Measuring the size and distribution of populations of organisms | Exit Quiz | Oak National Academy

What means to give an approximate value, for example, when sampling the population of fish in a lake?

(a)  

Answer explanation

To estimate means to give an approximate value, for example, when sampling the population of fish in a lake.

What is the image an example of?

• a pyramid of numbers

• a pyramid of biomass

• a classification key

• a food web

Answer explanation

The correct answer is a classification key. These are used to identify organisms by answering questions relating to physical characteristics.

The image shows a sample of organisms found from a pond. Why has the net been emptied into a white tray which contains water?

• The white tray helps the organisms to see each other.

• It helps you to be able to identify organisms as the white makes them stand out.

• The water makes sure that they stay alive after being caught.

• The white tray helps to create an environment that is similar to the habitat.

Answer explanation

When surveying ponds and aquatic habitats, using a white tray helps you to be able to identify organisms as the white of the tray makes the organisms stand out. The water is important to keep the organisms alive.

When carrying out a mark-release-recapture experiment what do you need to remember to do?

• Mark the organisms with something that is harmful.

• Mark the organisms with a bright mark so you can see them.

• Mark the organisms with a mark that means the organism doesn't stand out.

• Capture more organisms as soon as marked individuals are released.

Answer explanation

The correct answer is that you should mark the organisms so that they don't stand out. That means that predators won't spot them easily. The other examples will all cause harm or bias results.

100 beetles were caught and marked in a mark-release-recapture experiment. Two days later in a second catch 80 beetles were caught. 40 of these were marked. What is the population of beetles?

• 2

• 20

• 200

• 2000

Answer explanation

There were 100 beetles in the first sample and 80 beetles in the second sample. 40 of these were marked. 100 × 80 = 8000 8000 ÷ 40 = 200 The population size of beetles in this habitat is 200.

30 woodlice were caught and marked in a mark-release-recapture experiment. Two days later in a second, 15 woodlice were caught. 5 of these were marked. What is the population of woodlice?

• 300

• 45

• 90

• 145

Answer explanation

There were 30 woodlice in the first sample and 15 woodlice in the second sample. 5 of these were marked. 30 × 15 = 450 450 ÷ 5 = 90 The population size of woodlice in this habitat is 90.