The image below shows a head louse.

Head lice are tiny insects that feed on blood from the human scalp.

When a head louse bites the human scalp, the louse benefits but the human is harmed.

What term is used for this type of interaction between organisms?

Head lice have short legs and large claws.

These are traits which allow them to cling to their host's hair.

What is the name given to a trait that helps an organism survive and reproduce in its environment?

The photograph below shows a bee.

Bees collect nectar and pollen from flowers.

As they do this, they become covered in pollen.

When they move to another flower, some of the pollen is transferred to this other flower.

The relationship between plants and bees is beneficial for both parties.

What term is used for this type of interaction between organisms?

Suggest what the bees and the plants each gain from their relationship.

Bee populations are rapidly declining around the world due to habitat loss, pollution, and the use of pesticides, among other factors.

In the USA, there was a honey bee decline from about 6 million hives in 1947 to 2.4 million hives in 2008.

Calculate the percentage decrease in bee hive numbers from 1947 to 2008.

Suggest why conserving bees is important.

The Dead Sea is the most saline lake on Earth, with a salt concentration over 10 times higher than that of sea water.

It is such a harsh environment that only microorganisms from the Archaea domain are able to survive.

Salt concentration is an example of an abiotic factor that affects the growth of organisms.

State two other abiotic factors.

Give two biotic factors that affect the growth of organisms.

Animals in a habitat compete with each other.

Great tits and blue tits are two bird species that compete with each other.

What is meant by the term habitat?

Give two factors for which great tits and blue tits may compete.

The graph shows changes in the populations of the two bird species in a woodland between 2006 and 2022.

Describe the changes in the population of great tits between 2014 and 2018.

Suggest an explanation for changes in the population of great tits between 2014 and 2018.

Squirrels feed on the leaves of oak trees.

Red-tailed hawks feed on the squirrels.

What do we call animals, like the red-tailed hawk, that eat other animals, such as the squirrel?

The graph below shows how the numbers of squirrels and red-tailed hawks change over a period of time.

What happens to the number of red-tailed hawks after the number of squirrels decreases?

Suggest a reason for your answer.

The scientists collected the data in the graph above using sampling techniques.

Suggest why the data collected may not be accurate.

A healthy garden will support several species of ladybird.

The photograph below shows a ladybird.

Ladybirds are natural predators of greenflies, as represented in the food chain below.

oak tree  →  greenfly  →  ladybird  →  blue tit

Many of the ladybirds in the garden died.

Explain what is likely to happen to the number of greenflies in the garden.

Give two factors that may limit the number of ladybirds.

Population and community are terms used to describe the organisms in an area.

Describe the difference between the terms 'population' and 'community'.

Explain why a garden is not a stable community.

The photograph below shows loggers cutting down trees in a forest.

Describe the effects of cutting down trees on the biotic and abiotic factors of the forest ecosystem.