Life On Earth

Question 1

What are two factors that can affect an ecosystem?

Answer 1

The two factor groups are:

• Abiotic factors - caused by non-living
• Biotic factors - caused by living things

Question 2

Examples of biotic factors

Answer 2

• Disease
• Grazing
• Predation
• Food availability

Question 3

Examples of abiotic factors

Answer 3

• Light intensity
• pH of soil or water
• Moisture
• Temperature

Question 4

What must biologists do when studying an ecosystem?

Answer 4

When studying an ecosystem biologists must:

1. Collect a sample of organisms (e.g. Using quadrats or pitfall traps)
2. Identify the organisms (using a key)
3. Measure the abiotic factors

Question 5

Sources of error for quadrats, pitfall traps and light meter

Answer 5

The source of error for quadrats is that it may not be placed randomly so the whole area may not be sampled.

The source error for a pitfall trap is that the organisms could escape and potentially get eaten by predators.

The source of error for a light meter is the you could be shading the probe.

Question 6

Habitat

Answer 6

A habitat is the place where an organism lives.

Question 7

Population

Answer 7

Population is all the living things in one species

Question 8

Community

Answer 8

A community is all the living things of all species in an ecosystem

Question 9

Ecosystem

Answer 9

An ecosystem is all the habitats and the whole community

Question 10

Producer

Answer 10

Producer is an organism that makes its own food (plants)

Question 11

Consumer

Answer 11

A consumer is an organism that needs to eat

Question 12

Niche

Answer 12

A niche is the role an organism plays in the community. It includes what resources the organism uses and how it interacts with other organisms

Question 13

Biome

Answer 13

A biome is a region of the planet that is made up of similar temperatures and rainfall. The ecosystems are also similar.

Question 14

What happens if a food web is disturbed?

Answer 14

If a food web has few links the effect of removing a species could be severe. However, if the food web has many links the removal may not be as drastic as the remaining consumers would have other sources of food.

Question 15

What energy is used by the consumer and how much is passed onto the next level?

Answer 15

Only the energy that is in the organisms body when it is eaten and digested can be used by the consumer. 10% of the energy is passed onto the next level.

Question 16

Ways energy can be lost

Answer 16

• Movement
• Heat
• Undigested food
• Uneaten remains
• Faeces

Question 17

Food chain pyramids

Answer 17

Food chains are represented by pyramid diagrams. The simplest is the pyramid of numbers - this doesn’t take into account the size of the organism. The pyramid of biomass takes size into account - Biomass is the total mass of all living matter in a population. The pyramid of energy shows the total energy in a population that is available for the next consumers - this clearly shows the 90% lost at each level.

Question 18

Nutrients and recycling them

Answer 18

Plants need nutrients for healthy growth. Nutrients are taken into the plant by its root system. The main nutrients are:

• Nitrogen (N) - used to make protein, need for healthy leaves
• Phosphorus (P) - needed for healthy roots
• Potassium (K) - needed for healthy roots flowers and fruit

Recycling nutrients is important because it gets rid of waste and returns the nutrients to the soil to be used again by plants.

Question 19

Nitrogen cycle

Answer 19

Nitrogen cycle