B17: Organising an ecosystem

Question 1

What is the producer?

Answer 1

Every food chain starts with a producer - in most food chains the producer is a green plant.
The source of all biomass in a community.

Question 2

Why are producers important in food chains?

Answer 2

They synthesise complex molecules and produce all the biomass in a community.

Question 3

What is biomass?

Answer 3

e.g. glucose.
Molecules that pass down the food chain into other organisms

Question 4

What are primary consumers?

Answer 4

Organisms that eat the producers.

Question 5

What are secondary consumers?

Answer 5

The animal that eats the primary consumer.

Question 6

What is a predator?

Answer 6

Consumers that kill and eat other animals

Question 7

What is a prey?

Answer 7

The animal that is being eaten by the predator

Question 8

What would the predator-prey graph look like for 2 animals?

Answer 8

Put population against time.
Wavy - prey is generally higher, with more fluctuation, whereas predators are generally lower, with less fluctuation in numbers. The numbers of predators and prey rise and fall in cycles - only true in a STABLE COMMUNITY.
When there are more foxes, it means more rabbits are eaten, so population of rabbits falls. Now less rabbits are available, so fox population falls. Now rabbits can grow in population and rinse and repeat

Question 9

What are the two sampling techniques?

Answer 9

Random sampling
Sampling along a transect

Question 10

Describe the process of random sampling

Answer 10

Used to compare the numbers of organisms in different areas. This is done using a quadrat (a wooden or plastic square). A quadrat is placed on the ground and the number of organisms inside the quadrat are then counted - can be used to sample plants or slow-moving animals. The quadrat is placed at random locations across the area (can use random numbers to select the different locations), the count the numbers of each organism in the quadrat. Do this a few times until you have sampled a large number of random locations, which produces more valid results.

Question 11

What is the equation to find the total population size in an area?

Answer 11

Total population size = (total area /area sampled) *number of organisms of that species counted in the sample

Question 12

Describe the process of sampling along a transect

Answer 12

Used when we want to investigate whether the numbers of species change across a habitat e.g. a sand dune. Place transect so it runs across the habitat we are looking at. Then use a quadrant to count the number of organisms at intervals on the transect.
Investigation should be carried out a number of times to get valid results.

Question 13

What is a transect?

Answer 13

A line e.g. a rope or tape measure

Question 14

Where does the carbon cycle start?

Answer 14

With CO2 in the atmosphere - the only way that carbon can enter the carbon cycle is through photosynthesis.

Question 15

How does CO2 return back to the atmosphere?

Answer 15

Aerobic respiration, carried out by every living organism.

Question 16

Describe the carbon cycle

Answer 16

Plants and algae take in CO2 from the atmosphere in photosynthesis. Carbon is used to make carbohydrates, fats and proteins, which make up the cells of the plants and algae. These respire, so some carbon dioxide is released back into the atmosphere.
They can be eaten by animals, and these animals can be eaten by more animals. Now the carbon that was in the plants becomes part of the carbohydrates, lipids and proteins in the cells of animals. Animals respire and release CO2. Animals release waste, and eventually, animals and plants die. Now there is carbon in waste and dead remains, which are broken down by decomposing microorganisms e.g. bacteria and fungi, which respire and release CO2 back into the atmosphere.
If decomposers cannot function properly, carbon in dead remains is converted to fossil fuels over millions of years. However, humans have been burning large amounts of fossil fuels, which releases CO2 back into the atmosphere.

Question 17

Why are decomposers important?

Answer 17

They cycle materials through an ecosystem, as well as returning carbon to the atmosphere as CO2.
They also release mineral ions into the soil.

Question 18

Under what conditions can decomposers not function effectively?

Answer 18

Lack of oxygen

Question 19

Describe the water cycle

Answer 19

Energy from the sun causes the water from the sea to evaporate from its surface. Water vapour travels into the air and cools down. When it cools, it condenses to form clouds, which then falls to the ground as precipitation, including rain and snow.
All forms of precipitation contain fresh water.
Once the water hits the ground, some of it evaporates back into the atmosphere as water vapour, and some passes through rocks and forms aquifers. A lot of water forms rivers or streams. Water in rivers and streams eventually drains back into the sea

Question 20

How do living organisms play a role in the water cycle?

Answer 20

Plants take up water in their roots, and passes out of the stomata (transpiration)
Animals take in water through drinking and their food. They release this water in faeces and urine and when they exhale.

Question 21

What are the conditions required for decomposition?

Answer 21

Temperature - warm (decomposers use enzymes to break down materials, which work faster in warm conditions. If conditions are too hot, then the enzymes will denature and decomposers can die). Compost tends to be warm anyway, as decomposers release energy when they carry out aerobic respiration
Water - microorganisms work faster when compost is moist, as many of the chemical reactions in decay use water.
Oxygen - decomposers carry out aerobic respiration, which requires a good supply of oxygen. Gardeners can use a gardening fork to mix compost regularly to introduce oxygen into the centre. This also breaks up large clumps, and increases the surface area for decomposers to act on. In absence of oxygen, decomposing microorganisms carry out anaerobic decay, producing a mix of gasses e.g. methane (biogas)

Question 22

Describe how compost is made

Answer 22

Gardeners put dead plant material into a compost heap. Bacteria and fungi then break decompose plant material and produce compost. Gardeners and farmers use the compost as natural fertiliser, as it is very rich in minerals needed for plant growth.

Question 23

What is biogas used for?

Answer 23

Small-scale biogas generators are used to provide fuel for homes. These often use plant materials, such as food waste or manure.
Biogas is produced under anaerobic conditions/