Ecosystems

Question 1

Producers are

Answer 1

plants which photosynthesise to produce food

Question 2

Consumers are

Answer 2

animals that eat plants or other organisms

Question 3

Decomposers are

Answer 3

generally bacteria or fungi which break down dead organic matter and help to recycle nutrients. This includes detritivores (like woodlice) which break up larger chunks of dead material and increase the surfaces area for bacteria and fungi

Question 4

The environment is

Answer 4

the sum of the non-biological (abiotic) components of an ecosystem. For example the water and soil in a pond or the soil and air in a forest.

Question 5

A habitat is

Answer 5

where a specific organism lives

Question 6

A population is

Answer 6

all the organisms belonging to a particular species in an ecosystem

Question 7

A community

Answer 7

is all the organisms in an ecosystem, ie all the different populations combined

Question 8

Quadrats

Answer 8

are square frames usually 1m squared used to collect data of organisms which do not move< (plants) or do not move much, (snails).

Question 9

To do a good quadrat sampling you must

Answer 9

Lay out two 10m tape measures at right angles, creating a grid. Generate two random numbers between 1 and 10. Position the quadrat using the coordinates and count the number of daises for example. Repeat with 9 more quadrats in the same area and calculate the average of the daises per m squared.
If you are comparing two areas, then do the other area and plot a bar graph comparing them.

Question 10

An environmental gradient means

Answer 10

how the population size varies with a distance from a path, or with altitude up a slope or with distance from the shore line.

Question 11

To measure along an environmental gradient

Answer 11

you must create a transect, which means sample at set intervals along a line. Lay out a tape measure along the gradient that you are investigating (perpendicular to the shoreline for example), place your quadrat at set intervals (every 5m) along the transect. Count the number of individuals of the species you are investigating and plot a graph.

Question 12

A trophic level

Answer 12

an organism’s position in a food chain

Question 13

When an organism eats another organism, various things happen to the food

Answer 13

Waste- bits get dropped, some are indigestible. Respiration- the food is respired to release energy and CO2 is produced. Building new biomass, the food is used to produce new cells/tissues in the consumer.

Question 14

When a primary consumer eats a primary producer

Answer 14

it wastes or uses up in respiration 90% of the mass of the plant on average. Only 10% goes into making the consumer larger. A secondary consumer cannot use the food that has been wasted already so only the 10% used in growth is passed along. Secondary consumers then waste 90% of what they receive and store 10%. Overall then, a tertiary consumer will store 0.1% of the mass of the primary producer (10% of 10%). This is why tertiary consumers are rare because there is not enough biomass in an ecosystem for it.

Question 15

Pyramids of numbers

Answer 15

represent the numbers of organisms in each trophic level in a food chain, irrespective of its mass. It often goes up in a pyramid shape (getting smaller at the top) unless there is an oak tree at the bottom, or a parasite at the top.

Question 16

Pyramids of biomass

Answer 16

show the total mass of the organisms in each trophic level, irrespective of numbers. These always go up in a pyramid shape (largest at bottom, getting smaller).

Question 17

Why do these pyramids form this shape?

Answer 17

Because not all the materials in the grass for example end up as rabbit for example.
Some parts are not eaten (roots), some parts are indigestible, some of the materials form excretory products and many of the material are respired to release energy with the loss of carbon dioxide and water.

Question 18

When answering questions on food webs always justify your answer. In a garden where slugs and snails both eat lettuce and are both eaten by thrushes. If the snails became extinct, what would happen to the slugs?

Answer 18

The number of slugs would fall because the thrushes will have no snails to eat and will eat more slugs. That is correct but there are other possibilities. For example, the number of slugs would rise because there would be less competition for food with snails. So the best thing to do is to combine the answers:
The number of slugs would most likely stay the same, as although more would be eaten by thrushes, there would be less competition with snails so they would reproduce more quickly.