Organisms and their environment

Question 1

The Sun is the

Answer 1

principal source of energy input to biological systems.

Question 2

The flow of energy through

Answer 2

living organisms, including light energy from the Sun and
chemical energy in organisms, is eventual transfer to the environment.

Question 3

A food web

Answer 3

is a network of interconnected food chains.

Question 4

A producer

Answer 4

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

Question 5

A consumer

Answer 5

an organism that gets its energy by feeding on other organisms

Question 6

Consumers may be classed as

Answer 6

primary, secondary, tertiary and quaternary
according to their position in a food chain.

Question 7

A herbivore

Answer 7

is an animal that gets its energy by eating plants

Question 8

A carnivore

Answer 8

is an animal that gets its energy by eating other animals

Question 9

A decomposer

Answer 9

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

Question 10

Advantages of using a pyramid of biomass rather than a pyramid of numbers to
represent a food chain:

Answer 10

in a pyramid of numbers one large individual is shown in the same way as
one very tiny individual ;
biomass indicates how much food there is, available / left ;
biomass is an indicator of the energy available ;
pyramid of biomass is pyramid shaped whereas a pyramid of numbers is not
always

Question 11

A trophic level

Answer 11

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

Question 12

Advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain:

Answer 12

it shows how much energy is available
it shows how much energy is passed through per meter square
other pyramids are not very informative, because we cannot be sure that one
gram of biomass for one species contains the same quantity of energy as one
gram of biomass of a different species.

Question 13

Transfer of energy from one trophic level to another is often not efficient because

Answer 13

energy is lost between tropic levels. Energy is lost in respiration, movement,
muscles contraction, heat. Energy is lost in faeces, urine. Not all animal or plant is
digestible. Only 10% of the energy is transferred. As we move up the food chain
lesser and lesser energy is available to support a population. Therefore a food chain
is not longer than 5 tropic levels.

Question 14

nitrogen fixation occurs by

Answer 14

lightning or by bacteria in root nodules, they convert
nitrogen from air into ammonia.

Question 15

ammonia is converted to

Answer 15

nitrate ions in the process of nitrification, by nitrifying
bacteria.

Question 16

the plant absorbs nitrate ions from

Answer 16

the soil.

Question 17

plant produce amino acids and protein from

Answer 17

nitrate ions

Question 18

animals feed and digest

Answer 18

protein.

Question 19

deamination of protein occurs in

Answer 19

animals and they excrete it as urea.

Question 20

bacteria decompose plant and animal proteins into

Answer 20

ammonium ions.

Question 21

ammonium ions are converted to

Answer 21

nitrogen in the process of denitrification, by
denitrifying bacteria.

Question 22

A population

Answer 22

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

Question 23

A community

Answer 23

all of the populations of different species in an ecosystem.

Question 24

An ecosystem

Answer 24

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

Question 25

Factors affecting the rate of population growth for a population of an organism

Answer 25

food supply
competition
predation
disease