B17 - Organising an Ecosystem

Question 1

What is biomass?

Answer 1

The amount of biological material in an organism

Question 2

What is the carbon cycle?

Answer 2

The cycling of carbon through the biotic and abiotic components of an ecosystem

Question 3

What are decomposers?

Answer 3

Microorganisms that break down dead or undigested organic material. They are important in nutrient cycling

Question 4

What is a primary consumer?

Answer 4

Animals that eat producers

Question 5

What is a producer?

Answer 5

Organisms that produce organic molecules from simple inorganic materials and use them as an energy source. Examples include green plants and algae

Question 6

What is a secondary consumer?

Answer 6

Animals that eat the primary consumer

Question 7

What does the arrow in a food chain represent?

Answer 7

The direction of energy flow

Question 8

What are the first 4 stages of a food chain?

Answer 8

Producer -> Primary Consumer -> Secondary Consumer -> Tertiary Consumer
1st Trophic Level -> 2nd Trophic Level -> 3rd Trophic Level -> 4th Trophic Level

Question 9

Why are food chains limited to 4 / 5 trophic levels?

Answer 9

Poor energy efficiency means food chains are limited in size as little energy is passed between stages.

Question 10

What are examples of producers?

Answer 10

Green plants and algae

Question 11

What are the advantages of being a herbivore?

Answer 11

The food does not move, it cannot escape instead it stays still

Question 12

What are the disadvantages of being a herbivore?

Answer 12

Cellulose is very difficult to break down and digest. Herbivores must use a variety of techniques to break down and access the cell contents. They must also eat a lot of plant mass to find and eat enough plant material to provide them with the nutrients they need

Question 13

What are the advantages of being a carnivore?

Answer 13

Food is high in protein and fat and relatively easy to digest

Question 14

What are the disadvantages of being a carnivore?

Answer 14

Food is in the form of other animals, therefore the food must be caught before it can be eaten

Question 15

What are prey?

Answer 15

Consumers which are eaten

Question 16

Describe how the populations of predators and prey in a community change over time?

Answer 16

The numbers of predators and prey rise and fall in cycles

Question 17

Explain this predator prey graph:

Answer 17

• If there is a plentiful supply of food available (possibly due to a warm summer with lots of rain), the prey animal grow and reproduce successfully, and more offspring survive, so population increases
• As prey number increases, there is a plentiful supply of food available for the predators, so predators can reproduce successfully, and more offspring survive, so predator population increases
• The high number of predators eat a large proportion of the prey animals, so the population of the prey falls
• With fewer prey animals, there is less food for the predators, so the predator population falls as fewer offspring survive
• Due to a reduction of the population of predators, and the good food supply that results from fewer animals, prey population increases as more offspring survive.
• The cycle then repeats itself

Question 18

In what circumstances is this graph true?

Answer 18

In a stable community - if a change occurred within the community (e.g. a drought) or a new predator arrived, then predator prey cycles would begin to change

Question 19

What adds new biomass into an ecosystem?

Answer 19

Photosynthesis

Question 20

What are 2 examples of decomposers?

Answer 20

Bacteria and Fungi

Question 21

Explain the recycling of materials in an ecosystem (decay cycle)

Answer 21

Producers are eaten by consumers. The excretion from the consumers and the bodies of the consumers when they die are broken down by decomposers which digest both the dead animals, plants and waste. They use some nutrients to grow and reproduce but release carbon dioxide, water, and mineral ions as waste products. This returns mineral ions to the soil and carbon to the atmosphere. The mineral ions can then be taken up through plant roots and carbon dioxide into producers during photosynthesis.

Question 22

Explain the water cycle:

Answer 22

• The sun heats the earths surface causing water to evaporate from lakes, rivers, and the sea. This forms warm moist air. Water is also released back into the atmosphere through transpiration and respiration in animals
• As moist air rises it cools, condensing back into a liquid and forming clouds
• The water droplets are then precipitated back to earth as snow, rain, or hail
• Surface run off and percolation return water to bodies of water and plants

Question 23

What is percolation?

Answer 23

The movement of water through gaps in soils and rocks

Question 24

How is water released in animals?

Answer 24

• Respiration
• Decay
• Urine
• Faeces
• Sweat

Question 25

How is water released in plants?

Answer 25

Transpiration

Question 26

Explain the carbon cycle:

Answer 26

• Carbon is stored as organic compounds in green plants.
• This carbon can then be transferred to organic compounds in consumers through feeding. It can also be transferred to organic compounds in dead organisms as the plant dies. It may also be directly released back into the atmosphere through respiration
• Organic compounds in consumers may then be returned directly to the atmosphere through respiration or to organic compounds in a dead organism as the consumer dies
• Organic compounds in dead organisms may then be released into the atmosphere through decay and decomposition - releasing CO2 through respiration in microorganisms. However, it may become a carbon compound in fossil fuels
• Fossil fuels can then undergo combustion to return the carbon to the atmosphere in the form of CO2
• Photosynthesis from green plants can remove CO2 from the environment, storing it in organic compounds. Carbon dioxide can also dissolve is seas and lakes and be used to make shells in marine life

Question 27

What do plants use carbon from carbon dioxide for?

Answer 27

Making glucose, which can then be used to make starch, proteins, carbohydrates, and lipids

Question 28

What is the word equation for photosynthesis?

Answer 28

Carbon Dioxide + Water -> Glucose + Oxygen

Question 29

What is the word equation for respiration?

Answer 29

Glucose + Oxygen -> Carbon Dioxide + Water

Question 30

What is the word equation for combustion?

Answer 30

Fuel + Oxygen -> Carbon Dioxide + Water

Question 31

What does the water cycle do?

Answer 31

Provide fresh water for plants and animals on land before draining into the seas

Question 32

Why are scientists fearful that the carbon cycle may not be able to support itself in the years to come?

Answer 32

Due to increased carbon dioxide emissions by humans

Question 33

What 3 factors affect decay and decomposition?

Answer 33

• Temperature
• Moisture
• Oxygen

Question 34

How does temperature affect decay and decomposition?

Answer 34

The speed at which things decay depends on the temperature as the enzyme controlled chemical reactions in decomposer microorganisms works faster in warm conditions. In cold conditions the reactions slow down as there are fewer collision, therefore reducing the rate of reaction. If the temperature is too high then the enzymes in decomposer organisms will become denatured.

Question 35

How does moisture affect decay and decomposition?

Answer 35

Most microorganisms grow faster in moist conditions as moisture makes it easier for them to digest their food and prevents them drying out

Question 36

How does oxygen affect decay and decomposition?

Answer 36

Although some microorganisms are anaerobic, most decomposers respire aerobically. This means they need oxygen to break down food and transfer energy, grow, and reproduce. Therefore decay is more rapid in aerobic conditions with a plentiful supply of oxygen.

Question 37

How do gardeners use decomposition?

Answer 37

Gardeners provide optimal conditions for decomposition in order to maximise rapid decay of waste material. Compost produced by the decay of waste organic matter is used as a natural fertiliser

Question 38

What is compost?

Answer 38

A brown crumbly substance produced by aerobic decomposition of waste organic matter and is used as a natural fertiliser as it has high nutrient levels

Question 39

How does making compost kill weed seeds and speed up the decomposition process?

Answer 39

Compost is made by the decomposition of waste organic matter when the decomposers are respiring aerobically. This means they transfer energy to the environment around them which can kill off weed seeds and speed up the decomposition process.

Question 40

What happens when bacteria decompose waste material in anaerobic conditions?

Answer 40

They produce methane

Question 41

What is methane used for?

Answer 41

Fuel

Question 42

How does a biogas generator work

Answer 42

Plant and animal waste is placed in biogas generators. The conditions in the biogas generators are controlled to be kept in anaerobic conditions. Anaerobic decay form bacteria then produces methane which can be used as a fuel

Question 43

What are the advantages of biogas generators?

Answer 43

• Produces Methane as a fuel

* Reduces amount of waste