Energy and Ecosystems

Question 1

What is an ecosystem?

Answer 1

All the organisms living in an area and their interactions with the abiotic conditions.

Question 2

What are producers?

Answer 2

Organisms that make their own food.

Question 3

How does energy enter an ecosystem?

Answer 3

Plants use energy from the sun to make glucose and other sugars during photosynthesis. They are then used for respiration and the rest to make other biological molecules that make up the plant biomass.

Question 4

How is energy transferred in an ecosystem?

Answer 4

When organisms eat other organisms.

Question 5

Define what biomass means.

Answer 5

The mass of carbon that an organism contains or the dry mass of tissue per unit of area.

Question 6

Why do we use dry mass when measuring the biomass of an organism?

Answer 6

The water content of organisms varies so using the dry mass makes sure we get an accurate result.

Question 7

What apparatus do we use to measure the biomass of an organism?

Answer 7

calorimeter

Question 8

How does calorimetry work?

Answer 8

A sample of the biomass is burned and the energy released is used to heat a known volume of water. The change in temperature of the water is used to calculate the chemical energy present in the biomass.

Question 9

What is the gross primary production?

Answer 9

The chemical energy stored in a plant’s biomass in a given volume, in a given time.

Question 10

What is primary productivity?

Answer 10

When GPP is expressed as a rate.

Question 11

What is the net primary production?

Answer 11

The chemical energy stored in a plant’s biomass after respiratory losses.

Question 12

What is the NPP used for?

Answer 12

It is the energy available for plant growth and reproduction. It is also available for the organisms in the next trophic level.

Question 13

Why does some of the energy in a consumer’s food not get transferred to the next trophic level?

Answer 13

1. Some of the energy is lost in respiration.
2. Not all parts of the organism are eaten.
3. Some of the energy in faeces and urine.

Question 14

How is the net production of consumers calculated?

Question 15

How do you measure the percentage efficiency of energy transfer?

Answer 15

net production of trophic level / net production of the next trophic level x 100

Question 16

What are food chains?

Answer 16

simples lines of energy transfers

Question 17

What are food webs?

Answer 17

These show all the food chains in an ecosystem and their interactions.

Question 18

What are trophic levels?

Answer 18

each stage in a food chain

Question 19

What are decomposers?

Answer 19

organisms that break down dead or decomposing material which allows them to be recycled.

Question 20

How do farmers increase the amount of energy available for human consumption?

Answer 20

They increase the NPP of crops by reducing the amount of energy lost to other organisms. They increase the NP of livestock by reducing the energy lost through respiration and other metabolic processes.

Question 21

How do farmers decrease the energy lost to other organisms from crops?

Answer 21

1. Pesticides
2. Biological agents.

Question 22

How do pesticides help in making sure the NPP of crops stays high?

Answer 22

1. Insecticides kill insects that feed on and damage crops. This means that the crops lose less biomass and the NPP does not decrease.
2. Herbicides kill weeds that compete with the crops for sunlight and food. With more sunlight and food the crops photosynthesise more and more biomass is produced.

Question 23

How do biological agents help in making sure the NPP of crops stays high?

Answer 23

1. Parasites kill insects and reduce their ability to function.
2. Pathogenic bacteria and viruses can be used to kill pests.

Question 24

How do farmers decrease the energy lost through respiration in the livestock?

Answer 24

1. They keep them in small cages which means they move less and that decreases the rate of respiration.
2. They are kept in warm places so they lose less energy in generating body heat.