The Living Environment

Question 1

What does the term ‘ecology’ mean?

Answer 1

Ecology is the science of ecosystems. It is the scientific study of the distribution and quantity of the organisms, and their interactions with their environment.

Question 2

On what islands did Charles Darwin undertake research?

Answer 2

The Galapagos Islands.

Question 3

Describe what a habitat is.

Answer 3

This is a place where an organism lives e.g. a pond. It supplies the needs of the organism such as food, water, oxygen and nutrients.

Question 4

Describe what a population is.

Answer 4

A group of organisms of the same species e.g. a shoal of fish, oak trees in a wood and the human inhabitants of a town.

Question 5

Describe what an ecosystem is.

Answer 5

A biological community of interacting organisms and their physical habitat.

Question 6

Describe what a community is.

Answer 6

The sum total of all the populations of plants, animals and micro-organisms living in the ecosystem together.

Question 7

Describe what biodiversity is.

Answer 7

The range of animals and plants in a given area.

Question 8

Describe what a consumer is.

Answer 8

An organism that obtains its energy by eating other organisms.

Question 9

Describe what a producer is.

Answer 9

Plants that begin food chains by producing food using the sun’s energy through the process of photosynthesis.

Question 10

Describe what an autotroph is.

Answer 10

An organism that has the ability to produce its own food by converting the sun’s energy into chemical energy by the process of photosynthesis. Autotrophs are the producers in food chains. Green plants (including algae and plankton) are referred to as autotrophs.

Question 11

Explain how green plants create food and energy.

Answer 11

Green plants absorb light energy using chlorophyll, a green pigment which is found in cells in their leaves. They use it to react carbon dioxide with water to make simple sugars such as glucose which provide food and energy for the plant to grow.

Carbon dioxide + Water = Glucose + Oxygen

Question 12

Describe what a heterotroph is.

Answer 12

An organism that cannot produce its own food. Heterotrophs are consumers as they must consume plants or other animals in order to stay alive and grow. There are three main categories: herbivores, carnivores and omnivores.

Question 13

What is a herbivore?

Answer 13

Herbivores (e.g. sheep) eat plant or vegetable matter only.

Question 14

What is a carnivore?

Answer 14

Carnivores (e.g. lions) consume meat only.

Question 15

What is an omnivore?

Answer 15

Omnivores (e.g. pigs) eat a mixture of plant and animal matter.

Question 16

Describe what interdependence is.

Answer 16

When two or more organisms are reliant on one another.

Question 17

Describe what respiration is.

Answer 17

The chemical change that takes place inside living cells, which uses glucose and oxygen to produce the energy organisms need to live. Carbon dioxide is a by-product of respiration.
Glucose + Oxygen = Carbon dioxide + Water + Energy

Question 18

Describe what a food chain is.

Answer 18

A sequence of organisms, each of which feeds on a type of organism from the preceding food level.
In a food chain, the direction of arrow indicates the transfer of energy (energy flow).

Almost all food chains within an ecosystem are interconnected showing the interdependence between species, and form complex food webs.

Question 19

State the different feeding or trophic levels.

Answer 19

• Primary producers include green plants, algae, and blue-green bacteria
• Primary consumers are herbivores which feed on green plants e.g. caterpillars
• Secondary consumers fed on primary consumers, e.g. spiders
• Tertiary consumers are at the top of the food web e.g. owls. They eat animals from all 3 levels below them, although may concentrate specifically on secondary consumers

Question 20

Describe what a niche is.

Answer 20

A niche is the role or function of an organism in an ecosystem.

Question 21

Describe what detritus is.

Answer 21

Detritus includes partly broken down dead plant and animal material, such as fallen leaves, seeds and berries, animal faeces and dead organisms. This material still has critical value to the flow of energy within an ecosystem and supports populations of detritivores and decomposers.

Question 22

Describe what detritivores are.

Answer 22

Detritivores are organisms which feed on partly broken down dean plant and animal matter (detritus), e.g. wood lice and earthworms.

Question 23

Describe what decomposers are.

Answer 23

Decomposers are micro-organisms which chemically break down waste materials and dead organisms using enzymes, e.g. bacteria and fungi. They also put nutrients into the ecosystem.

Question 24

Describe what energy loss in ecosystems means.

Answer 24

Technically energy is not “lost” but converted to other forms such as heat and sound energy. Within ecosystems, energy is said to be “lost” when it is not made available to the trophic level above. Generally only 10% of the energy consumed by an organism is made available to the next trophic level, and food chains can usually sustain no more than six energy transfers before all the energy is used up.

Question 25

State the two main reasons why energy is lost in ecosystems.

Answer 25

• Animals use up energy to build up their body weight. However when some of this is eaten by a predator, some parts may have no nutritional value such as cellulose, bones, skin or horns. These are left uneaten or expelled as undigested waste or faeces, and as a result energy is effectively “lost” from the food chain.
• Energy gained by a consumer in its food is used for moving around, and in warm blooded animals such as mammals, for keeping warm. Only a tenth of the energy taken in is used for building up body tissue, with most being lost as heat or through respiration.

Question 26

Describe what ecological productivity is.

Answer 26

The productivity of an ecosystem is the rate of production or the amount of organic matter (biomass) formed or accumulated per unit area in unit time.

Question 27

What is the definition of biomass?

Answer 27

The mass of living material.

Question 28

Describe what gross productivity is.

Answer 28

Gross productivity is the measure of all photosynthesis, or creation of chemical energy, that occurs in an ecosystem.

Question 29

Describe what net productivity is.

Answer 29

Net productivity is the energy which is left after losses as a result of respiration, growth, heat and movement.

Question 30

How would you calculate the net productivity.

Answer 30

If a plant makes 100 molecules of glucose from photosynthesis but only uses 35 molecules to grow, the net productivity is 65 molecules, which is available to consumers.

Question 31

Explain what an endotherm is.

Answer 31

Endotherms are organisms which can control their internal body temperature (e.g. mammals and birds). They have high metabolic rates and have to eat frequently to obtain energy.

Question 32

Explain what an ectotherm is.

Answer 32

Ectotherms are organisms that cannot control their internal body temperature and rely on their external environment for temperature control (e.g. invertebrates, most fish, reptiles and amphibians). They have lower metabolic rates and feed less regularly. Physical activity is restricted to certain times of the day (night time).

Question 33

What are the four primary ecological events which affect the density of a population?

Answer 33

There are four primary ecological events which affect the density of a population: births, deaths, emigration (organisms moving away) and immigration (organisms moving in).

Question 34

How do you calculate the change in population density?

Answer 34

Change in population density = (births + immigrants) – (deaths + emigrants)

Question 35

Describe what the carrying capacity is in an ecosystem.

Answer 35

The maximum number of individuals of a species that can be supported by an ecosystem. If the population of a species exceeds the carrying capacity, death rates may exceed reproduction and a population crash may result.

Question 36

Describe what a density dependent factor is.

Answer 36

These include rates of predation, the competition between species of the same population and with other species, rates of disease and symbiotic relationships such as parasitism.

Question 37

Describe what a density independent factor is.

Answer 37

These are conditions which will affect an ecosystem, regardless of the number of species within a particular area including weather related events such as heavy rainfall, freezing temperatures and factors such as a decrease in the concentration of oxygen (aquatic ecosystems) and the risk of fire.

Question 38

Describe what inter-specific competition is.

Answer 38

The competition which occurs between organisms of different species for a common resource within an ecosystem.

Question 39

Describe what intra-specific competition is.

Answer 39

The competition between organisms within the same species for a common resource in an ecosystem.

Question 40

Describe what symbiosis is.

Answer 40

Members of two different species having a type of ecological interaction that affects both populations.

Question 41

Describe what parasitism is.

Answer 41

An interaction between two species where one organism benefits and causes harm to the other organism.

Question 42

Describe what commensalism is.

Answer 42

A type of relationship between two organisms where one organism benefits but the other is unaffected.

Question 43

Describe what mutualism is.

Answer 43

A type of relationship where both organisms benefit from the proximity of one another.