19 organisms and their environment

Question 1

What is the principle source of energy to biological systems?

Answer 1

The sun is the principle source of energy input to biological systems

Question 2

Describe the flow of energy through living organisms, including light energy from the Sun and chemical energy in organisms, and its eventual transfer to the environment

Answer 2

• Energy flows from the sun to the first trophic level (producers) in the form of light
• Producers convert light energy into chemical energy and it flows in this form from one consumer to the next
• Eventually all energy is transferred to the environment
  – Energy is passed on from one level to the next with some being used and lost at each stage

Question 3

food chain

Answer 3

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

Question 4

food web

Answer 4

a network of interconnected food chains

Question 5

producer

Answer 5

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

Question 6

consumer

Answer 6

an organism that gets its energy by feeding on other organisms

Question 7

herbivore

Answer 7

an animal that gets its energy by eating plants

Question 8

carnivore

Answer 8

an animal that gets its energy by eating other animals

Question 9

decomposer

Answer 9

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

Question 10

Advantages of using a biomass pyramid rather than a number of species pyramid

Answer 10

more accurate as it takes the organisms size/mass into account

Question 11

trophic level

Answer 11

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

Question 12

How is energy lost from one trophic level to the next?

Answer 12

Energy is lost as metabolic heat. It is used for: muscle contractions, maintaining body temperatures, movement, excretion, egestion.

Question 13

Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels

Answer 13

Only 10% of energy is transferred from one trophic level to the next. The loss of energy at each step is so great that very little usuable remains after four or five levels.

Question 14

Explain why it is more energy efficient for
humans to eat crop plants than to eat livestock
that have been fed on crop plants

Answer 14

1) Crops is at a lower trophic level than animals
2) energy is lost between trophic levels
3) 10% of energy is lost
4) lost by respiration/metabolic
5) lost by movement/muscle contraction
6) material that is inedible/not digested
7) energy lost by excretion
8) less fuel required to farm seaweed

Question 15

population

Answer 15

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

Question 16

community

Answer 16

all of the populations of different species in an ecosystem

Question 17

ecosystem

Answer 17

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

Question 18

factors that affect the rate of population growth

Answer 18

food supply, competition, predation and disease

Question 19

4 phases of sigmoid growth curve

Answer 19

lag phase, log phase, stationary phase and the death phase

Question 20

lag phase

Answer 20

organisms are adapting to the environment before they are able to reproduce
- few organisms and so reproduction is not producing larger numbers of offspring

Question 21

log phase (exponential phase)

Answer 21

food supply is abundant, birth rate is rapid and death rate is low; growth is exponential and only limited by the number of new individuals that can be produced

Question 22

stationary phase

Answer 22

population levels out due to a factor in the environment, such as nutrient, becoming limited as it is not being replenished.
- birth rate and death rate are equal until either the nutrient is replenished or becomes severly limited

Question 23

death phase

Answer 23

population decreases as death rate is now greater than birth rate; usually because food supply is short or metabolic wastes produced by the population have built up to toxic levels

Question 24

Why are organisms in natural environments unlikely to show population growth like a sigmoid growth curve

Answer 24

Because they are affected by many other factors, including:
- changing temperature or light
- predators
- disease
- immigration (individuals moving into the area)
- emigration (individuals moving out of the area)

Question 25

nitrification

Answer 25

Converts ammonia ions to nitrate ions.(Occurs in the soil with nitrifying bacteria)

Question 26

denitrification

Answer 26

Converts nitrate ions to nitrogen gas
(Occurs in the soil with denitrifying bacteria)

Question 27

nitrogen fixation

Answer 27

Converts nitrogen gas to ammonia ions.
(Occurs in the soil or in root nodules of legumious plants wtih nitrogen-fixing bacteria)

Question 28

deamination

Answer 28

the removal of the nitrogen part of excess amino acids to produce ammonia. Which is then converted to urea.

Question 29

negative impacts of chemicals to the natural environment, other than fertilisers

Answer 29

Pesticides/insecticides/herbicides;
kill/harm non target species;
loss of biodiversity/disrupt food chains;
bioaccumulation;
pollute area;
antibiotic resistance;

Question 30

Treatment of sewage

Answer 30

1. screening/removal of, large pieces of waste;
2. flocculation/coagulation/clump suspended particles
3. settling of insoluble particles
4. digestion/decomposition by bacteria
5. with aeration tank/activated sludge
6. slugde should be treated with anaerobic decomposers
7. water treated with chlorine/UV
8. distillation/collection of water from evapourater

Question 31

Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants.

Answer 31

Plants are at a lower trophic level than livestock;
Energy transfer along food chain is inefficient;
Energy is lost in metabolic processes;
More material that is lost of faeces;
Energy lost in excretion/urine;