Man and his environment Part 1

Question 1

Population

Answer 1

A group of organisms of the
same species living together
in a particular habitat.

Question 2

Community

Answer 2

A group of populations
that live and interact
with one another in a
particular habitat.

Question 3

Ecosystem

Answer 3

A community of
organisms interacting
with one another and
with the abiotic
environment.

Question 4

Habitat

Answer 4

The place

where an organism lives

Question 5

What do organisms need to survive

Answer 5

• All organisms require energy and nutrients for growth,

maintenance, reproduction and locomotion.

Question 6

Whats a food chain

Answer 6

A linear network of links in which

organisms transfer energy by eating and being eaten.

Question 7

Food web

Answer 7

All possible feeding relationships in a community.

• Made up of a network of food chains in an ecosystem.

Question 8

Describe relationship between Predator and prey

Answer 8

• Population of prey is high → A lot food for predators →
Predator population ↑.
• Population of predator is high → Prey are killed faster
than they can reproduce → Prey population ↓
• Less food (prey) is available → Predator population ↓.
• Predator population is low → Prey population recovers
and ↑ again.
• Predator now have more food (prey), predator
population ↑ again.

Question 9

Describe Parasite-Host relationship

Answer 9

• An organism (parasite) depends on another
organism (host) for food, harming it and possibly
causing death.
• The parasite lives on or in the body of the host.

Question 10

Producer-Consumer relationship

Answer 10

Producers/Autotrophs use sunlight or chemical
energy to manufacture complex organic materials
from simple inorganic molecules.

Consumers/Heterotrophs cannot make their own
food, thus feed on plants and animals for food.

Question 11

What do decomposers do and are they consumers

Answer 11

Decomposers are consumers. They break down organic materials
externally into simple molecules and absorbed e.g.
fungi, bacteria

Question 12

What do consumers get from eating other organisms and how are they used

Answer 12

By eating other organisms, consumers gain a source of
energy (ATP from cellular respiration) and biomolecules
from the food ingested.
• The energy is used to carry out cellular processes.
• The biomolecules are used to build new biomass of the
consumers, resulting in growth.

Question 13

How does energy flow in a food chain

Answer 13

Energy flows in one direction in a food chain. It is

linear or non-cyclic.

Question 14

How is energy lost in food chain

Answer 14

Organisms use energy for life processes e.g. cell division,
photosynthesis, cellular respiration, active transport.

• Exothermic chemical reactions release energy as heat

Question 15

How much energy is passed on to next trophic lvl

Answer 15

10%

Question 16

Why are food chains short?

Answer 16

• As you move up a food chain, both the energy
available and biomass decrease.
• As less energy becomes available to the higher
trophic levels, they can sustain a smaller population
of individuals (hence smaller biomass).

Question 17

Biomass

Answer 17

The total amount of organic matter in

living organisms in a given area or ecosystem.

Question 18

Whats an ecological pyramid

Answer 18

a diagram that shows the relative
amount of energy or biomass or organisms contained
within each trophic level of a food chain or web

Question 19

How can the pyramid of no. be inverted

Answer 19

Pyramid may be inverted if
• Consumer is parasitic
• Producer is a single large organism

Question 20

Advantages of Pyramid of no.

Answer 20

Data easy and fast to collect
using sampling counts.

Good for comparing changes
in ecosystem at different
times of the year

Question 21

Disadvantages of pyramid of no. (3)

Answer 21

Numbers may be too large
to measure accurately.

Producers may vary in size.
Pyramid may be inverted if
consumer is parasitic, or
producer is a single large
organism.

Does not take into account
juvenile or immature forms.

Question 22

Pyramid of biomass

Answer 22

show the total mass of organisms at each trophic level at a
particular time.
It takes into account the size of the organism

Question 23

How find biomass

Answer 23

There are 1000 rabbits in a given area at one time.
• Anaesthetise 10 rabbits, then kill them.
• Dry the dead rabbits in an oven at 100°C until a
constant mass is obtained (to remove water).
• Multiply the mass by 100

Question 24

How explain inverted pyramid of biomass of phytoplankton as producer

Answer 24

Pyramid of biomass does not take into account the rate of
reproduction (productivity) and rate of consumption of organisms.
• Phytoplankton reproduce quickly enough to replace the individuals
consumed by zooplankton.

Question 25

Advantages of pyramid of biomass

Answer 25

Eliminates problem

of size differences.

Question 26

Disadvantages of pyramid of biomass

Answer 26

Data labour-intensive and costly to
collect. Involves killing the organism.

Organisms of same mass may have
different energy content.

Does not take into account rate of
reproduction or consumption of
organisms. Pyramid may be inverted
if producer has high turnover rate.

Question 27

Pyramid of energy

Answer 27

shows the total energy available at

each trophic level over a period of time e.g. 1 year.

Question 28

Advantages of pyramid of energy

Answer 28

Takes into account
productivity.

Eliminates problem of mass
differences.

Pyramid will never be
inverted.

Question 29

Disadvantages of pyramid of energy (2)

Answer 29

Data labour-intensive and
costly to collect. Involves
killing the organism.

Difficult to assign an
organism in a trophic level.

Question 30

Nutrient cycle

Answer 30

Nutrient cycle is the
movement of chemical
nutrients in the
environment.

Question 31

Importance of nutrient cycles

Answer 31

• The nutrient cycles are
nature’s recycling system.
• Ecosystems employ
decomposers and
detritivores to recycle
mineral nutrients for use
by living organisms.
• Without them, nutrients
will remain locked up in
dead organisms. Over long
periods of time, they turn
into fossil fuels.

Question 32

CO2 carbon cycle: Photosynthesis

Answer 32

Photosynthesis: Green plants absorb atmospheric CO2
to
manufacture carbohydrates (e.g. glucose). When
herbivores feed on plants, the digested carbon compounds
become assimilated as part of their bodies.

Question 33

CO2 carbon cycle: Dissolution

Answer 33

CO2 dissolves in the sea water and is used by

phytoplankton and algae in photosynthesis.

Question 34

Carbon cyle: Respiration

Answer 34

Living organisms break down carbon

compounds (e.g. glucose) to release energy and CO2

Question 35

Carbon cycle: Combustion

Answer 35

Carbon compounds in dead organisms may
be deposited as fossil fuels. Fossil fuels are burned to
release energy and CO2
.

Question 36

Carbon cycle: Combustion

Answer 36

Carbon compounds in dead organisms may
be deposited as fossil fuels. Fossil fuels are burned to
release energy and CO2
.

Question 37

Carbon cyclee decomposition

Answer 37

Decomposers break down dead organisms
and waste products into simple organic and inorganic
substances, including CO2