Organisms and their environment

Question 1

what is the principal source of energy

Answer 1

the sun principle source of energy input to biological systems

Question 2

describe the flow of energy through living organisms

Answer 2

1. light energy from the sun is trapped
2. energy stored as chemical energy in organisms
3. it eventually transfers to the environment

Question 3

what is a food chain

Answer 3

showing the transfer of energy from one organism to the next, beginning with a producer

Question 4

example of simple food chains

Answer 4

flower (producer) –> caterpillar (primary consumer) –> sparrow (secondary consumer) –> eagle (tertiary consumer)

Question 5

what is a food web

Answer 5

a network of interconnected food chains and interpret food webs

Question 6

what is a producer

Answer 6

an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

Question 7

what is a consumer

Answer 7

an organism that gets its energy by feeding on other organisms. May be classed as primary, secondary, tertiary and quaternary according to their position in a food chain.

Question 8

what is a herbivore

Answer 8

an animal that gets its energy by eating plants

Question 9

what is a carnivore

Answer 9

an animal that gets its energy by eating other animals

Question 10

what is a decomposer

Answer 10

an organism that gets its energy from dead or waste organic material

Question 11

what is a trophic level

Answer 11

the position of an organism in a food chain, food web or ecological pyramid

Question 12

the human negative impact on food chains and webs

Answer 12

• over-harvesting of food species - this can reduce the amount of food available for other animals
• introducing foreign species to a habitat- this increases competition and can interfere with the food chain

Question 13

what is a pyramid of numbers

Answer 13

shows the number of organisms at each trophic level

Question 14

what is a biomass pyramid

Answer 14

shows the total dry mass of organisms at each trophic level

Question 15

Advantages of using a pyramid of biomass rather than a pyramid of numbers

Answer 15

1. pyramids of biomass take into account the size of organisms
2. less misinterpreted
3. range of number may be enormous

Question 16

explain transfer of energy in food chains

Answer 16

the transfer of energy from one trophic level to another is insufficient because of gestion, excretion, respiration and production of inedible bones and shells

Question 17

why do food chains have fewer than 5 trophic levels

Answer 17

because biomass transfers are not 100% efficient and so there isn’t enough energy to support 6 trophic levels

Question 18

why is it more efficient to eat crop plants than to eat livestock

Answer 18

it is more efficient for humans to eat plants directly as every step in the chain loses 80- 90% and this can maximise the amount of energy gained as there is 1 transfer

Question 19

describe a population

Answer 19

a group of organisms of one species, living in the same area, at the same time

Question 20

what is a community

Answer 20

all of the populations of different species in an ecosystem

Question 21

what is an ecosystem

Answer 21

a unit containing the community of organisms and their environment interacting together

Question 22

the factors affecting the rate of population growth

Answer 22

1. organisms are adapting to the environment and there are few organisms
2. food supply is abundant, birth rate is rapid and death rate is low
3. population levels out due to a factor in the environment such as a nutrient becoming limited. Birth rate = death rate
4. death rate > birth rate because food supply is short or metabolic wastes have built up to toxic levels