Food Chains And Energy Transfer

Question 1

Organisms in any ecosystem rely on a source of energy to carry out all their activities- ultimate source of this energy for almost all organisms is

Answer 1

Sunlight (conserved as chemical energy by plants)

Question 2

Most plants use sunlight in making organic compounds from carbon dioxide in the air or water that surrounds them- these organic compounds include sugars, most of which are used by the plants as respiratory substrates. The remainder is used to make other groups of biological molecules. These biological molecules form

Answer 2

The biomass of plants, that is the means by which energy is passed between other organisms

Question 3

Organisms can be divided into 3 groups according to how they obtain their energy and nutrients:

Answer 3

• producers
• consumers
• saprobionts

Question 4

What are producers?

Answer 4

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

Question 5

What are consumers?

Answer 5

Organisms that obtain their energy by feeding on (consuming) other organisms than using energy of sunlight directly

Question 6

Animals are consumers. Those that eat producers (green plants)=

Answer 6

Primary consumer (first in chain of consumers)

Question 7

Those animals eating primary consumers=

Answer 7

Secondary consumers

Question 8

Those eating secondary consumers=

Answer 8

Tertiary consumers

Question 9

Secondary and tertiary consumers are usually predators but they may also be

Answer 9

Scavengers or parasites

Question 10

What are saprobionts (decomposers)?

Answer 10

Group of organisms that break down the complex materials in dead organisms into simple ones; in doing so, they release valuable minerals and elements in a form that can be absorbed by plants and so contribute to recycling (majority of this work is carried out by fungi and bacteria)

Question 11

Describe and explain concept of food chain

Answer 11

• a food chain describes a feeding relationship in which producers eaten by primary consumers
• these in turn are eaten by secondary consumers
• then eaten by tertiary consumers
• in a long food chain, the tertiary consumers may in turn be eaten by further consumers called quaternary consumers

Question 12

Each stage in a food chain is referred to as a

Answer 12

Trophic level

Question 13

What’s the benefit of food webs rather than food chains?

Answer 13

In reality, most animals don’t rely on a single food source and within a single habitats, many food chains will be linked together to form a food web

Question 14

What is biomass?

Answer 14

The total mass of living material in a specific area at a given time

Question 15

Fresh mass is quite easy to assess but the presence of varying amounts of _____ makes it unreliable

Answer 15

Water

Question 16

How is problem of varying amounts of water in fresh mass overcome?

Answer 16

Measuring mass of carbon or dry mass overcomes this problem, but because the organism must be killed, it is usually only made on a small sample and this sample might not be representative

Question 17

Biomass is measured using dry mass per area in a given time- more specifically it is measured in

Answer 17

Grams per square where an area is being sampled, for example on grassland or a seashore
(Where a volume is being sampled e.g. in a pond or ocean, it is measured in grams per cubic metre

Question 18

Chemical energy store in dry mass can be estimated using a

Answer 18

Calorimetry

Question 19

Explain how bomb calorimetry works

Answer 19

• a sample of dry material is weighed and then burnt in pure oxygen with a sealed chamber called a bomb
• the bomb is surrounded by a water bath and the heat of combustion causes a small temp rise in this water
• as we know how much heat (energy) is required to raise the temperature of 1g of water by 1 degree Celsius, we can calculate the energy released from the mass of burnt biomass in units such as KJkg^-1