B4.1: Ecosystems

Question 1

How is an ecosystem organised?

Answer 1

• Organism
• Population
• Community
• Ecosystem

Question 2

What is biomass?

Answer 2

Biomass is the total quantity or weight of organisms in a given area/volume

Question 3

What are pyramids of biomass?

Answer 3

Used to show how the biomass changes

Question 4

What is biomass transfer?

Answer 4

Biomass is lost between each trophic level

Question 5

Importance of nitrogen

Answer 5

• used to make proteins
• have to get nitrogen in the form of nitrates from soil
• use nitrates to produce important proteins

Question 6

Nitrifying bacteria

Answer 6

Converts ammonia ions into nitrates in the soil

Question 7

What are biotic factors?

Answer 7

Biotic factors are due to the living organisms in a habitat

Question 8

Examples of biotic factors

Answer 8

• disease
• predation
• competition
• mates

Question 9

Why might gardeners add worms to their compost bins?

Answer 9

Worms are detritivores which means they eat large parts of dead material which increases the surface area for decomposers

Question 10

Food webs

Answer 10

Most animals eat more than one thing so a food web shows the different foods organisms eat

Question 11

What are abiotic factors?

Answer 11

Abiotic factors are non-living or physical factors in a habitat

Question 12

Examples of abiotic factors

Answer 12

• temperature
• moisture
• light intensity
• pH

Question 13

What is a pyramid of numbers?

Answer 13

Shows how many animals or organisms we are talking about

Question 14

What do the arrows in food chains show?

Answer 14

The arrows indicate where the energy is going

Question 15

What do food chains show?

Answer 15

They allow us to see feeding relationships and flow of energy through an ecosystem

Question 16

Detritivores

Answer 16

Eat large parts of dead material and they break down larger waste materials and excrete waste with a larger surface area

• woodlice, maggots, worms and flies

Question 17

Factors affecting the rate of decomposition

Answer 17

• Temperature: speed it up at the optimum temperature, exceeds -> denature as it is controlled by enzymes
• Water availability: Required but too much could drown, not enough dry up
• Aerobic conditions: more, faster (respiration)

Question 18

Producers

Answer 18

Organisms that make their own food by photosynthesis

• all plants

Question 19

Decomposing bacteria

Answer 19

Converts decomposed waste into ammonia -> ions

Question 20

Denitrifying bacteria

Answer 20

Converts nitrates in the soil to nitrogen in the air

Question 21

Key processes in the water cycle

Answer 21

• evaporation
• condensation
• transpiration
• precipitation
• surface run-off
• infiltration
• percolation

Question 22

Key terms in the nitrogen cycle

Answer 22

• nitrogen-fixing bacteria
• lightning
• nitrates in the soil
• decomposers
• decomposing bacteria
• nitrifying bacteria
• denitrifying bacteria
• ammonia (ions)

Question 23

Consumers

Answer 23

They can’t make their own food so they have to eat other organisms to gain energy

• all animals

Question 24

Decomposers

Answer 24

They chemically break down dead material - produce nitrogen based products

Question 25

What are decomposers?

Answer 25

Special group of consumers - they gain their energy by feeding on dead or decaying material

Question 26

Nitrogen-fixing bacteria

Answer 26

Convert nitrogen in the air to nitrates in the soil (in root nodules)

Question 27

Key processes in the carbon cycle

Answer 27

• respiration (both plants and animals)
• photosynthesis
• combustion
• eating

Question 28

Equation for rate of decay:

Answer 28

Rate of decay (g/day) = change in mass (g) / time (no. of days)