Biology - Ecosystems

Question 1

What is the order of a food chain?

Answer 1

-Producers
-Primary consumer
-Secondary consumer
-Tertiary consumer

Question 2

What is interdependence?

Answer 2

In a food web, changes in the population of one organism have an affect on the population of other organisms.

Question 3

How do producers transfer energy to the primary consumer.

Answer 3

They use light energy from the sun to convert carbon dioxide from the air and water from the soil into glucose and oxygen. The glucose made can be eaten by other organisms so that they can use it for respiration which releases the energy stored in the glucose. This energy can then be used for their life processes.

Question 4

What is a pyramid of number?

Answer 4

A pyramid of number shows the population at each stage in a food chain. It is drawn as a bar chart with the bars stacked on top of each other. The wider the bar, the more organisms it represents. The producer always goes at the bottom.

Question 5

What is a pyramid of biomass?

Answer 5

A pyramid of biomass represents the mass of organisms at each trophic level. A pyramid of biomass is always shaped like a pyramid.

Question 6

What is biomass?

Answer 6

Biomass is the dry mass of a living organism in an area at a particular time.

Question 7

How much energy on average is passed on to the next trophic level?

Answer 7

10%

Question 8

What are some ways energy gets passed out of the food chain?

Answer 8

-It is released as heat during respiration.
-It is used for life processes eg. movement.
-In faeces or remains in dead organisms.

Question 9

What is the equation for percentage efficiency of energy transfer?

Answer 9

Efficiency =( Energy tranferred to the next level / Total energy in ) x100

Question 10

What are some examples of pollutants?

Answer 10

-Pesticides - used by farmers to prevent pests eating their crops
-Heavy metals - used in industry

Question 11

What is bioaccumulation?

Answer 11

The build up of toxins at higher trophic levels.

Question 12

How do pollutants enter the food chain?

Answer 12

-The pollutant is washed into rivers and lakes.
-It enters the food chain by adhering to or being absorbed by producers.
-When the producer is eaten, the pollutant it contains is passed onto the next trophic level as it is persistent. It remains in the body tissues of the organism because it is not easily broken down.
-The pollutant continues to accumulate, increasing in concentration, as it moves up the food chain.
-By the time it reaches the top carnivore, the pollutant will have accumulated to such an extent that it becomes toxic, causing reduced fertility or even death.

Question 13

What happens when sewage gets into rivers?

Answer 13

If untreated sewage gets into rivers, micro-organisms decompose it. They dramatically increase in number and use oxygen from the water for aerobic respiration. As a result there is less oxygen dissolved in water, so aquatic organisms such as fish and insects may be unable to survive.

Question 14

What is leaching?

Answer 14

It is the washing of chemicals into rivers or lakes by rainwater.

Question 15

How do nitrate fertilisers affect the food chain?

Answer 15

-Increased nitrates in the water increase the growth of algae and plants.
-The algae form a bloom over the water surface, preventing sunlight reaching other water plants.
-These plants die because they are unable to carry out photosynthesis without light.
-Microbes such as bacteria increase in number as they decompose the dead plants, using and reducing the oxygen content in the water during respiration as they do so.
-The low oxygen levels can cause aquatic insects and fish to suffocate, and eventually the lake may be left completely lifeless.

Question 16

What is an indicator species?

Answer 16

An indicator species is an organism whose presence or absence is used by scientists to determine if an area is polluted.

Question 17

What are lichens?

Answer 17

An organism that is part fungus and part algae or cyanobacteria. Lichen grow in exposed places such as rocks and can be used as an indicator species for air pollution.

Question 18

How are lichens used to determine pollution in the air?

Answer 18

Lichens are commonly used to determine air pollution as many species will only grow in areas which are free of air pollutants such as those produced by traffic.

Question 19

How are invertebrates used to determine pollution in the water?

Answer 19

Some organisms can tolerate high levels of pollution, whereas others will not be found in polluted areas.

Question 20

What are the 4 stages of the carbon cycle?

Answer 20

1) Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
2) Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
3)Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die.
4)Dead organisms are decomposed by bacteria and fungi, and the carbon in their bodies is returned to the atmosphere as carbon dioxide. Under some conditions, decomposition is prevented and fossilisation takes place. Combustion of these fossil fuels returns carbon dioxide to the air.

Question 21

What are the 5 stages of the nitrogen cycle?

Answer 21

1)Nitrogen-fixing bacteria found in root nodules and free living in the soil convert nitrogen gas into nitrates.
2)Plants absorb nitrates from the soil and use these to make proteins. Consumers feed on the plant and nitrogen is transferred.
3)Animals urinate urea which releases nitrogenous compounds into the soil. Bacteria in the soil make an enzyme called urease which converts this urea into ammonia. Nitrifying bacteria convert the ammonia into nitrates which plants can now absorb.
4)Decomposers break down the protein in the dead bodies of animals and plants, converting it into ammonia. Nitrifying bacteria then convert the ammonia into nitrite, and then nitrates.
5)Denitrifying bacteria in the soil break down nitrates and return nitrogen gas to the air. This occurs in anaerobic conditions.

Question 22

How can farmers prevent denitrification?

Answer 22

-Plough the soil regularly to encourage aerobic conditions (get oxygen in).
-Drain any waterlogged areas.
-Rotate crops by planting leguminous plants every few years. These have root nodules filled with nitrogen-fixing bacteria that can convert nitrogen gas directly from the air into nitrogenous compounds the plants can use, increasing soil fertility.

Question 23

What do the arrows in the food chain represent?

Answer 23

The arrows between each organism in the chain always point in the direction of energy flow from the food to the feeder.

Question 24

What is bioaccumulation?

Answer 24

The build up of toxins at higher trophic levels.