Ecosystems

Question 1

What is a community?

Answer 1

All the organisms of different species living in a habitat

Question 2

What is a population?

Answer 2

All the organisms of one species in a habitat

Question 3

What is a habitat?

Answer 3

The place where an organism lives

Question 4

What is an ecosystem?

Answer 4

A community of organisms along with all the non-living conditions

Question 5

How does temperature affect communities?

Answer 5

(for example) the distribution of bird species in Germany is probably changing because of a rise in average temperature, e.g. the European Bee-Eater bird is a Mediterranean species now found in parts of Germany.

Question 6

How does amount of water affect communities?

Answer 6

E.g. daisies grow best in soils that are slightly damp. If the soil becomes waterlogged/too dry the population of daisies will decrease.

Question 7

How does light intensity affect communities?

Answer 7

e.g. As trees grow and provide more shade, grasses may be replaced by fungi or mosses which are better able to cope with the lower light intensity.

Question 8

How do levels of pollutants affect communities?

Answer 8

e.g. lichen are unable to survive if concentration of the air pollutant sulfur dioxide is too high

Question 9

How does competition affect communities?

Answer 9

Organisms compete with other species and members of their own species for resources. e.g. red & grey squirrels live in the same habitat and eat the same food. Competition with the greys means that in many areas there isn’t enough food for the reds so the population of reds is decreasing.

Question 10

How does predation affect communities?

Answer 10

e.g. if the number of lions (predators) increases, then the number of gazelles (prey) decreases as more of them are eaten by lions. This causes number of lions to decrease (less food) so number of gazelles increases (fewer predators) so number of lions increases again. This is a predator-prey cycle

Question 11

How does the interdependence of organisms in an ecosystem allow for survival?

Answer 11

Organisms depend on each other for food, shelter etc in order to survive and reproduce. This is known as interdependence. It means that a change in the population of one species can have a knock on effect for other species in the ecosystem.

Question 12

What is mutualism?

Answer 12

A relationship between two organisms from which both organisms benefit. e.g. bees and flowering plants have have a mutualistic relationship. Bees get food and plants’ pollen gets spread.

Question 13

What is a parasitic relationship?

Answer 13

one organism lives very closely with a host species (in or on them). The parasite takes what it needs to survive but the host doesn’t benefit. E.g. fleas.

Question 14

How do you estimate population size with quadrats?

Answer 14

Using a 1m^2 quadrat, count the number of individuals in a random square metre. Repeat and calculate the average number of individuals per square metre. Extrapolate.

Question 15

What energy transfers occur between trophic levels?

Answer 15

Some energy is used at each stage by organisms to stay alive, i.e. in respiration, which transfers energy for all life processes (movement etc). A lot of energy is transferred to surroundings by heat. The rest is stored as biomass. Some of this biomass energy (as not all of an organism is eaten) is transferred to organisms in the next trophic level.

Question 16

Why are food chains limited in length?

Answer 16

So much energy is lost at each stage that there isn’t enough left to support organisms after four or five trophic levels.

Question 17

How do energy transfers determine the shape of a pyramid of biomass?

Answer 17

A pyramid of biomass shows how much the organisms at each level of a food chain weigh if added up. Since biomass is a store of energy, this also shows how much energy there is at each stage of the food chain. Therefore, as not all the energy is tranferred, there is almost always a pyramid shape.

Question 18

How is efficiency of energy transfer or % of biomass transfer calculated?

Answer 18

Energy transferred to next level/energy available at previous level x 100
To calculate % biomass transfer substitute ‘biomass’ for ‘energy’

Question 19

How do you calculate the effect of abiotic factors on the distribution of organisms?

Answer 19

Use a belt transect: Mark out a line from one extreme to the other (e.g. shade to sun). Collect data from quadrats at regular intervals (no. organisms or percentage cover). You could also collect other data e.g. height of plants. Repeat, find means and plot graphs to establish correlation (distance vs number of organisms/percentage cover).

Question 20

Name an indicator species which indicates clean water and explain why it does

Answer 20

Stonefly larvae and freshwater shrimps. They are sensitive to the concentration of dissolved oxygen in the water. If raw sewage/ fertilisers containing nitrates are released into a river, microbes in the river increase and use up oxygen.

Question 21

Name an indicator species which indicates dirty water and explain why it does

Answer 21

Blood worms and sludgeworms. They have adapted to live in polluted conditions.

Question 22

Name an indicator species which indicates clean air and explain why it does

Answer 22

Bushy lichen and blackspot fungus (on rose leaves) need clean air with low levels of sulfur dioxide (a pollutant)

Question 23

Name an indicator species which indicates polluted air and explain why it does

Answer 23

Crusty lichen can survive in high levels in sulfur dioxide

Question 24

Advantages of indicator species

Answer 24

Simple and cost effective.

Question 25

Disadvantages of indicator species

Answer 25

Can’t give accurate figures for extent of pollution. There may be other factors playing a role in the presence or absence of a species from an area. Sometimes non-living indicators are better.

Question 26

How are indicator species used to measure pollution?

Answer 26

A simple survey (is the species present?) is quick but does not show extent of pollution whereas counting number of individuals allows rough comparisons of extent of pollution.

Question 27

What non-living indicators can be used to investigate extent of pollution?

Answer 27

Dissolved oxygen meters and chemical tests are used to accurately measure concentration of dissolved oxygen in water and show how level of water pollution is changing. Electronic meters and laboratory tests are also used to accurately measure concentration of sulfur dioxide in air to show how air pollution is changing.