B4 Ecosystems

Question 1

Ecosystem

Answer 1

All living organisms and physical conditions in the area

Question 2

Community

Answer 2

All the organisms in the ecosystem

Question 3

Habitat

Answer 3

Area where an organism lives

Question 4

Consumers

Answer 4

Organisms that eat others to gain energy

Question 5

Decomposers

Answer 5

Special group of consumers that feed on dead or decaying material

Question 6

Population

Answer 6

Total number of organisms of each species

Question 7

Producers

Answer 7

Organisms that make their own food by photosynthesis

Green plants
Algae
Phytoplankton

Question 8

Interdependence

Answer 8

Organisms that rely upon each other to survive

Question 9

Abiotic factors that affect communities

Answer 9

Moisture levels – water is required by all living things
Temperature – affects the rate of chemical reactions in organisms
Light intensity – necessary for photosynthesis - change in light over seasons can affect flowering of certain plants too
Soil type – level of nutrients and ability to hold water, pH
Gas levels – humidity and temperature can affect the amount of oxygen in the air
Fire – can be devastating for some organisms, but necessary for others (e.g. Australian plants/Scotish gorse/Heathland control)

Question 10

Biotic factors that affect communities

Answer 10

Number of predators
Food availability
Disease
Human activity

Question 11

Types of interdependence

Answer 11

Predation
Mutualism
Parasitism

Question 12

Commensalism

Answer 12

When one organism benefits from another organism, which is unaffected

Question 13

Competition

Answer 13

Two or more organisms fight over a resource
Can occur between different species, or within same species or family

Question 14

Parasitism

Answer 14

When one organism lives on or in another organism and takes nutrients from (feeds off) the other organism
Benficial to parasite but detrimental to host

Question 15

Mutualism

Answer 15

When 2 organisms living closely together both benefit from each other
Both depend on each other

Question 16

4 things animals compete for

Answer 16

Water
Space
Mates
Food

Question 17

4 things plants compete for

Answer 17

Water
Space
Light
Minerals

Question 18

Primary consumer

Answer 18

Organism that feeds on producers

Question 19

Secondary consumer

Answer 19

Organism that feeds on primary consumers

Question 20

Biomass

Answer 20

DRY mass of all living organisms in an area

Question 21

Why dry mass is used for biomass

Answer 21

Wet mass varies because volume of water in organism varies

Question 22

Efficiency of biomass transfer

Answer 22

Efficiency = (energy transferred / total energy available) x 100

(As a percentage)

Question 23

Why biomass transfers are not 100% efficient

Answer 23

Energy is lost through:
Egestion (removal of faeces)
Excretion (removal of urine)
Respiration
Inedible bones / hair / shells / teeth / spines

If there was no wastage, all of the energy that entered a trophic level would be used for growth

Question 24

How efficiency of biomas transfers affect number of levels in a biomass pyramid

Answer 24

The less efficient the transfers,
lower the number of trophic levels and fewer organisms in higher trophic levels

Question 25

3 molecules which are cycle through ecosystems

Answer 25

Oxygen Carbon dioxide Water

Question 26

How water is cycled through an ecosystem

Answer 26

Water evaporates from rivers and lakes and from transpiration Water condenses as clouds Water is returned through precipitation

Question 27

How carbon is cycled through an ecosystem

Answer 27

Carbon dioxide is taken in by plants through photosynthesis Respiration releases carbon dioxide Decomposition releases carbon dioxide Combustion releases carbon dioxide

Question 28

How nitrogen is cycled through an ecosystem

Answer 28

Nitrogen is fixed by lightening and nitrogen-fixing bacteria Denitrifying bacteria release nitrites in soil into nirtogen in the air Denitrifying bacteria covert nitrates in soil into nitrites, and nitrites to ammonia Nitrifying bacteria convert ammonia in soil into nitrites, and nitrites to nitrates Nitrates in soil taken up by plants and combined with carbohydrates to make plant proteins Plant proteins either eaten by other animals to form animal protien or die and decompose to release ammonia into soil Animals excrete ammonia and die and decompose to release ammonia into soil

Question 29

Why recycling in ecosystems is necessary

Answer 29

To create a continuous flow of nutrients To provide fresh water

Question 30

How a descrease in oxygen availabilty would affect rate of decomposition

Answer 30

Lack of oxygen causes micro-organisms to respire anaerobically Anaerobic decay is slower that aerobic decay

Question 31

How would a descrease in water availabilty affect the rate of decomposition

Answer 31

Decomposing microorganisms need water for chemical processes The less water available, slower the rate of these processes

Question 32

How a change in temperature would affect the rate of decomposition

Answer 32

Decrease in temperature slows rate of decomposition reactions Large increase in temperature would denature enzymes, slowing or even stopping decomposition

Question 33

Difference between a detritivore and a decomposer

Answer 33

Detritivores are small animals that speed up decomposition by shredding DOM into very small pieces creating a larger surface area for decomposers to work upon Detritivores use external digestion to break DOM down Decomposers are microorganisms that breakdown dead organic matter and organic waste upon a microscopic level Decomposers use external digestion

Question 34

Nitrogen cycle - bacteria

Answer 34

Bacteria are essential for nitrogen cycle Decomposers - break down organic matter contain nitrogen, back into nitrogen accessible in soil Denitrifying bacteria - break down nitrates into nitrogen gas, remove nitrates from soil Nitrifying bacteria - break down ammonia into nitrates, add nitrates to soil Nitrogen-fixing bacteria in root nodules - convert nitrogen gas into nitrates

Question 35

Nitrogen cycle diagram

Answer 35

According to this diagram, plants absorb nitrates ————————> Primary consumers feed ———————> Death and excretion———————— | v Nitrogen fixing by root nodule bacteria <— Nitrogen gas in the air Proteins and urea ^ | ^ v Absorption by roots v | Decomposers (soil bacteria) | Nitrogen fixing bacteria or lightning Breakdown by denitrifying bacteria | ^ | ^ | | v | v L_________________________________________ Nitrates in the soil < Oxidation by nitrifying bacteria < Ammonia

Question 36

How much of the atmosphere is composed of nitrogen gas

Answer 36

78%

Question 37

Main difference between denitrification and other three steps of nitrogen cycle

Answer 37

Denitrification changes nitrogen into a gaseous form