Ecosystems and Communities

One single living thing.

All the organisms of the same species living in the same place at the same time.

All the populations of the different species living in the same place.

A community of living organisms together with the non-living parts of their surroundings.

Individual organism, population, community, ecosystem.

A community, because it has several species.

Organisms in a community depend on each other, for example for food, shelter and pollination.

Other species depend on it for food or other needs, so the effects spread.

A relationship in which the parasite benefits and the host is harmed.

Tapeworms and fleas.

It takes water and mineral ions from the tree, weakening it.

A relationship in which both organisms benefit.

Sugars (a food supply) and a home.

Nitrogen compounds that it can use to make proteins.

The cleaner gets food, and the larger fish loses its parasites.

The flower is pollinated, and the bee gets nectar and pollen.

Name each level of organisation shown, and say what each contains.

Individual: one organism. Population: all the organisms of one species in the same place. Community: all the populations of the different species in the same place. Ecosystem: the community plus the non-living factors such as light, water and temperature.

Name each relationship, and say which organisms benefit and which are harmed.

Mistletoe on a tree is parasitism: the mistletoe benefits and the tree is harmed. Root nodules are mutualism: the plant gets nitrates and the bacteria get sugars. A cleaner fish and a big fish are mutualism: the big fish is cleaned and the cleaner gets food.

A non-living part of the environment.

A living part of the environment, such as a predator or a competitor.

Temperature, light, water and pollutants.

Competition and predation.

Light limits photosynthesis and so the number of producers, and consumers depend on producers.

Sensitive species die, so the number of species falls.

Light, water, mineral ions and space.

Food, water, mates, territory and shelter.

Its population declines and it may die out from the area.

An animal that kills and eats other animals.

The prey population.

Predators need time to breed and increase once the food supply has increased.

Energy is lost at each trophic level, so the prey cannot support as many predators.

More predators eat more prey.

Change divided by the original value, multiplied by 100.

Factors that increase them balance the ones that decrease them.

Sort the factors in the picture into abiotic and biotic, and name each one.

Abiotic (non-living): temperature, pollutants, water and light. Biotic (living): competition (for food) and predation (a predator eating prey).

Describe and explain the pattern in the graph.

The prey peak comes first and the predator peak comes later, because predators increase once there is plenty of prey. More predators then eat more prey, so the prey fall, and then the predators fall as food runs short. The cycle repeats, and there are fewer predators than prey.

A square frame that marks out a known area to sample.

Counting every organism would take too long and damage the habitat.

Use random numbers as coordinates along two tape measures laid at right angles.

To avoid bias, so every part of the area has the same chance of being sampled.

A larger sample is more representative, so the results are more reliable.

When conditions change gradually across a habitat, such as from shade to light.

At regular intervals along a line, such as every 5 m.

A light meter for light intensity, and a moisture meter for soil moisture.

The percentage of the quadrat that a species covers.

The total divided by the number of values.

Mean per quadrat multiplied by the field area divided by the quadrat area.

\(100 \div 0.25 = 400\).

It is based on a sample, not on counting every organism.

Any of: too few quadrats, bias in placing them, misidentifying species, or uncontrolled variables.

Use more quadrats, repeat the transect, and control the variables.

The crosses rise from the lower left to the upper right.

No, other factors may be involved.

Each square is 1% of the area, so percentage cover is easy to count.

Describe how to place quadrats at random in a study area.

Lay a tape measure along each of two sides at right angles. Use random numbers as coordinates along each tape, place a quadrat where they meet, and record what is in it. Repeat for many quadrats.

Describe what this belt transect shows, and why it is used.

Quadrats are placed at regular intervals along a line running away from the tree. It shows how the organisms change as the light intensity increases from the shade into the open, so each quadrat can be linked to an abiotic factor.

A feeding stage in a food chain.

The producers.

The mass of living material in organisms.

The water content of organisms varies, so dry mass gives a fair comparison.

Heat from respiration, waste (faeces and urine), and parts that are not eaten.

Heat released by respiration.

About 10%, although it varies.

Organisms cannot use heat in the surroundings to build biomass.

They keep a constant body temperature higher than their surroundings.

Less energy and less biomass are available at each higher level.

Too little energy is left to support another population.

There is more biomass at each lower level, because energy is lost at every step.

(energy transferred to the next level \(\div\) energy available) \(\times\) 100.

\(400 \div 5000 \times 100 = 8\%\).

\(30 \div 250 \times 100 = 12\%\).

The crops are a shorter food chain with fewer energy losses.

The top (tertiary or final) consumer.

In the surroundings as heat, with some in the dead material that decomposers break down.

Name each trophic level, and say why the pyramid is this shape.

From the bottom: producer, primary consumer, secondary consumer and tertiary consumer. It narrows because energy is lost at each trophic level (as heat, waste and uneaten parts), so there is less biomass at each higher level.

Describe what happens to the energy at each stage in this food chain.

About 10% of the energy is passed on at each step, and the other 90% is lost to the surroundings. It is lost as heat from respiration, in waste such as faeces and urine, and in parts that are not eaten, such as bones and roots.