Chapter 19: Organisms and their environment

Question 1

What is the ultimate source of energy for biological systems on earth?

Answer 1

The Sun.

All living things depend directly or indirectly on plants for their food, so also depend indirectly on sunlight.

Question 2

How do plants harness solar energy?

Answer 2

By photosynthesising and then transforming it into chemical energy for organisms that eat them as well as subsequent organisms in the food chain.

Question 3

What is a food chain?

Answer 3

A diagram that shows the transfer of energy from one organism to the next beginning with a producer.

Question 4

Define producer.

Answer 4

An organism that makes its own food.

Question 5

Give an example of a producer?

Answer 5

A plant

Question 6

Define consumer.

Answer 6

A living thing that eats other plants and animals

Question 7

Define interdependence in biological terms.

Answer 7

The way in which living organisms depend on each other in order to remain alive, grow and reproduce

Question 8

Define primary consumers.

Answer 8

Animals that eat the plants

Question 9

Define secondary consumer.

Answer 9

animals that prey on the plant-eaters

Question 10

Define tertiary consumers

Answer 10

Animals that feed on secondary consumers

Question 11

Define quaternary consumers

Answer 11

Animals that are at the top of the food chain

Question 12

Define herbivore.

Answer 12

Animals that feed on plants

Question 13

Define carnivore.

Answer 13

Animals that eat other animals

Question 14

Define omnivore.

Answer 14

Animals that eat both plants and animals

Question 15

Define predator.

Answer 15

A carnivore that kills and eats other animals

e.g. foxes

Question 16

Define scavengers.

Answer 16

Carnivores that eat the dead remains of animals killed by predators.

Question 17

Define decomposers.

Answer 17

Organisms that feed on dead and decaying matter, such as dead leaves.

e.g fungi and bacteria

Question 18

Describe the effects of over-harvesting.

Answer 18

Over-harvesting causes the reduction in umbers of a species at a certain level in the feeding community.

This means that other groups within the community who rely on that species as a food source often must look to a different species as food.

This increases competition.

Question 19

What happens when a foreign species in introduced to a habitat?

Answer 19

Can have a similar effect as over-harvesting.

The introduced organism may be better at exploiting a food source than a species natural predator.

This leads to the natural predator becoming endangered.

If introduced to an area which a native animal has no natural predator, this can lead to extinction.

Question 20

What is a pyramid of numbers?

Answer 20

A way of showing the population size at each trophic level.

Question 21

What is a regular pyramid of numbers?

Answer 21

Where the number of consumers is smaller that the producer, showing a typical pyramid shape

Question 22

What is an inverted pyramid of numbers?

Answer 22

The producer is much larger in size than the consumers so there only needs to be one of them to support the food chain.

Question 23

What is a pyramid of biomass?

Answer 23

A way of showing the biomass at each trophic level.

Question 24

What are the advantages of using biomass over numbers?

Answer 24

They are more accurate indication of how much energy is passed on at each trophic level

They make it easier to compare the food value of a small number of large organisms with a large number of small organisms.

Question 25

What is a pyramid of energy?

Answer 25

A model that shows the flow of energy from one trophic level to the next.

The pyramid is always upward with a large energy base at its base.

Question 26

What are the advantages of the pyramid of energy?

Answer 26

1. Takes account of the rate of production.
2. Their productivity is directly comparable
3. Relative energy chain within an ecosystem can be compared
4. Different ecosystems can be compared
5. No inverted pyramids.
6. Input of solar energy can be added.

Question 27

Define tropic level.

Answer 27

A level or position in a food chain/web occupied by a group of organisms that have a similar feeding mode.

Question 28

How is energy transferred as it goes up each trophic level?

Answer 28

1. Energy decreases as energy is lost as heat when organisms from one trophic level are consumed by organisms from the next level.
2. Energy transfer is efficient as the entire organism isn’t completely consumed or digested.
3. Transfer of energy from primary to secondary consumers is more efficient as a greater proportion of the food is digested and absorbed.
4. Short food chains are more efficient than longer ones in providing energy to the top consumer in the food chain.

Question 29

How do some farmers maximise meat production?

Answer 29

by reducing movement of their animals and keeping them warm in winter.

This means less stored energy is wasted by the animals

Question 30

Describe and State the stages of the carbon cycle.

Answer 30

1. Photosynthesis - plants absorb CO2 and change it to glucose
2. Feeding - herbivores eat the plants which are then changed into fats and proteins in animal tissue. Carnivores then eat the herbivores passing the carbon up the food chain
3. Respiration - animals produce CO2 as a waste product of respiration, which returns carbon to the atmosphere.
4. Decomposition - microorganisms feed on the dead and decaying plants and animals and their waste, taking up the carbon from these animals. These animals also release CO2 into the atmosphere as they break down
5. Fossilisation - The remains of the dead animals are buried and their remains leach into the ground depositing carbon
6. Combustion - the burning of fossil fuels releases CO2 back into the atmosphere.

Question 31

Describe and state the stages in the nitrogen cycle.

Answer 31

Question 32

State the roles of microorganisms in the nitrogen cycle.

Answer 32

Bacteria:

nitrogen-fixing bacteria convert atmospheric nitrogen to nitrates

bacteria of decay convert decaying nitrogen waste to ammonia

nitrifying bacteria, which convert ammonia to nitrates/nitrites

denitrifying bacteria, which convert nitrates to nitrogen gas.

Fungi: help to convert dead plants and animals and their wastes into ammonia in the soil

Plants: absorb nitrates from the soil to make proteins.

Animals: consume plants and use it to form animal protein

Humans: contribute by adding nitrogen rich fertilisers to the soil and by using manure

Question 33

Define ecosystem.

Answer 33

The interaction between a community of living organisms and their environment

Question 34

Define environment.

Answer 34

Consists all the conditions that surround any living organism - both the other living things and the non-living things or physical surroundings

Question 35

Define population

Answer 35

All the organisms of the same or closely-related species in an area

Question 36

Define ecosystem

Answer 36

two or more populations of organisms in their environment

Question 37

Define habitat

Answer 37

The place where an organism lives

Question 38

Define community

Answer 38

Two or more populations or organisms. The rate of growth of a population

Question 39

What are the factors affecting the rate of population growth.

Answer 39

Food supply - abundant food, means organisms breed successfully (vice versa)

Predation

Disease - a problem in large populations because disease can spread easily from one individual to another

Question 40

What are abiotic factors?

Answer 40

non-living factors (limiting factors )

e.g. temperature, rainfall, light intensity

Question 41

What are biotic factors?

Answer 41

Living limiting factors

e.g. predation, food supply, disease

Question 42

Draw a population growth curve.

Answer 42

Question 43

What happens in the lag phase?

Answer 43

The population is small since its in its early stages of growth.

Numbers double at each generation but is not a large increase as there are only few individuals.

Question 44

What happens in the Exponential phase?

Answer 44

Steepest part of the growth curve.

Continued doubling of the population - each generation produces a logarithmic growth rate

Considerable competition for food and space.

Growth rate starts to slow down.

Question 45

What happens in the stationary phase?

Answer 45

Resources don’t support a growing population

The food supply may limit further expansion of the population, diseases may start to spread due to overcrowding.

Reproduction and mortality rate is the same.

Question 46

What happens in the death phase?

Answer 46

The mortality rate is greater than the reproduction rate.

Population numbers begin to decline

Fewer offspring live long enough to reproduce

Food supply is insufficient, waste products contaminate the habitat or disease spreads through the population

Question 47

What happens to the population growth if there were no limiting factors?

Answer 47

There will be no stationary or death phase.

The log phase will continue upwards instead of levelling off.

This has happened to the human population growth due to improvements in food supply and development of medicine to control diseases.

Infant mortality has decreased while life expectancy has increased.

Question 48

What implications does a rapid increase in population size have?

Answer 48

1. increase demand for basic resources
2. Increase pressure on environment
3. Larger population of young people
4. More old people

Question 49

What does abundant food supplies lead to?

Answer 49

More people becoming obese, so increased healthcare demands.
In the long term, this reduces life expectancy