Energy transfer in Ecosystems

Question 1

The total mass of living material in a specific area at a given time. Usually measured in gm-2. Fresh mass is quite easy to assess, but varies depending on the water content. Measuring dry mass overcomes this problem but the organism must be killed, it is usually only a small sample and may not be representative.

Answer 1

Biomass

Question 2

Calorimetry

Answer 2

The chemical energy store in a dry mass can be estimated using this technique. When a sample of dry material is weighed and then burnt in pure oxygen within a sealed container (bomb). The bomb is surrounded by a water bath and the heat of combustion causes a temperature rise. This can be used to work out the energy released from the mass of burnt biomass.

Question 3

Photosynthetic organism that manufacture organic substances using light energy, water, carbon dioxide and mineral ions.

Answer 3

Producer

Question 4

An organism that obtains its energy by feeding on (consuming) other organisms. Primary consumers eat producers. Secondary consumers eat primary consumers. Tertiary consumers eat secondary consumers.

Answer 4

Consumer

Question 5

When saprobionts release enzymes externally which break down large biological molecules into smaller ones which are then absorbed by digestion or active transport.

Answer 5

Extracellular digestion

Question 6

Trophic level

Answer 6

Each stage in a food chain

Question 7

GPP

Answer 7

Gross primary production which is the total quantity of the chemical energy store in plant biomass, in a given time. Plants use 20-50% of this energy in respiration.

Question 8

NPP

Answer 8

Gross primary production – respiratory losses. The chemical energy store which is left when these losses to respiration have been taken into account. This is available for plant growth and reproduction and available to other trophic levels in the ecosystem (such as consumers and decomposers).

Question 9

Taken away from GPP to calculate NPP.

Answer 9

Respiratory losses

Question 10

Food chain

Answer 10

Describes a feeding relationship in which the producers are eaten by primary consumers, which are eaten by secondary consumers, which are then eaten by tertiary consumers. These could then be eaten by quarternary consumers. Each stage is referred to a trophic level.

Question 11

How food chains link together in a habitat to form a food web.

Answer 11

Food web

Question 12

A pyramid drawn with bar lengths proportional to the numbers of organisms present

Answer 12

Pyramid of Number

Question 13

A pyramid drawn with bar lengths proportional to the mass of plants/animals

Answer 13

Pyramid of Biomass

Question 14

Pyramid of Energy

Answer 14

A pyramid drawn with bar lengths proportional to the energy stored in organisms

Question 15

Productivity

Answer 15

The rate of generation of biomass in an ecosystem. Usually measured in units of mass per area put unit time (gm-2y-1). Farming practices try to improve this by increasing yields by increasing the efficiency of energy transfer along the food chains which produce our food.

Question 16

Intensive farming

Answer 16

A type of farming which uses processes, such as using confined spaces to restrict movement, keeping the environment warm and excluding predators, to try and make energy conversion more efficient by ensuring that as much energy from respiration as possible goes into growth rather than other activities or other organisms.

Question 17

Can be calculated by dividing the energy available after the transfer by energy available before the transfer x 100.

Answer 17

Percentage Efficiency

Question 18

(Energy available after the transfer / energy available before the transfer) x 100

Answer 18

Energy Transfer

Question 19

Controlling pests by introducing predators

Answer 19

Biological Control

Question 20

Selective Breeding

Answer 20

Breeding of organisms by human selection of parents for certain characteristics