ECOSYSTEMS

Question 1

Define population

Answer 1

All the organisms belonging to one species that live in the same area at the same time and can interbreed

Question 2

Define a community

Answer 2

Multiple organisms belonging to lots of species living in the same place, cannot interbreed

Question 3

Define a habitat

Answer 3

Place where organisms live

Question 4

Define niche

Answer 4

Role of an organism in the ecosystem including how it feeds, reproduces and finds shelter

Question 5

Define producer

Answer 5

e.g. plant

An organism that transfers energy from light to an inorganic compound to organic compounds

Question 6

Define a consumer

Answer 6

An organism that obtains energy from organic compounds which they digest and absorb
i.e. feed on other organisms

Question 7

Define a decomposer

Answer 7

Feed on dead organic matter releasing mineral ions and other matter into soil and air

Question 8

Define trophic level

Answer 8

Stage at which organism feeds in the food chain

Question 9

Define an ecosystem

Answer 9

Relatively self contained unit of living organisms interacting with each other and their abiotic environment
Community + habitat

Question 10

What are ecosystems

Answer 10

Dynamic- constantly changing

Question 11

What are biotic factors

Answer 11

Living factors- interact between living organisms (e.g. predator/prey)
Feeding- herbivores- plants
Competition- two organisms require something in short supply

Question 12

What are abiotic factors

Answer 12

Nonliving/physical factors (e.g. rainforest canopy effects temp and humidity)
Water availability
Oxygen conc

Question 13

What is the result of extreme abiotic factors

Answer 13

Often slow growth, may kill organisms

e.g. temp

Question 14

Ecological efficiency formula

Answer 14

Biomass/biomass x100

Question 15

What percentage of sunlight is converted into photosynthesis

Answer 15

Less than 3

Question 16

What are reasons for energy loss

Answer 16

light not hitting plant
Light being reflected from the leaf surface
Energy may be used to heat the plant or evaporate water

Question 17

Define gross primary productivity

Answer 17

The light energy converted into chemical energy by photosynthesis
Some GPP used for respiration and energy lost to the environment as heat and materials lost as CO2 and water
GPP= NPP+R

Question 18

Define NET primary productivity

Answer 18

Biomass and energy remaining in the plant after respiration

Question 19

NPP is available for primary consumers, less than 10% is passed on
Why?

Answer 19

Not all parts of the plant are eaten (e.g. roots, branches)
Primary consumers can not be digest all the plant (cellulose, passed out in faeces and available for decomposers)
Energy lost as heat in consumers digestive system

Question 20

Why is the efficiency of biomass transfer affected from consumer to consumer

Answer 20

Some animals are not eaten
Some parts of animals aren’t eaten (e.g. bones)
Energy is lost from the food chain as heat due to respiration

Question 21

Why is energy loss greater from mammals and birds compared to other organisms

Answer 21

They are endothermic (warm blooded) so will lose more energy as heat

Question 22

What does the primary productivity of an ecosystem vary due to

Answer 22

Climate- increased light intensity, rainfall, temp
Seasonal variation- organisms photosynthesise at diff times of year
Soil condition- mineral ion availability

Question 23

State and explain some methods of intensive agriculture to increase production

Answer 23

High crop density- close planting, light hitting photosynthesising plants not the ground
Fertilisers- increase mineral ions in soil, more nitrates= more amino acids
Herbicides- less crop loss, higher yield. Doesn’t c change NPP or GPP, decreases competition
GM- increase efficiency and growth of plants

Question 24

What is secondary productivity

Answer 24

Using primary consumer
Restrict movement- increase efficiency, decrease animal welfare
High energy foods
Use of antibiotics and steroids, increase resistance

Question 25

Roles and examples of decomposers

Answer 25

Bacteria and fungi

Recycle nutrients from dead organisms and waste materials back into the ecosystem

Question 26

How do decomposers feed

Answer 26

Saprotrophically

1. secrete enzymes onto dead or waste materials
2. digested/hydrolysed into smaller inorganic molecules
3. small molecules absorbed into organism
4. stored and respired

Question 27

Examples and roles of detritivores

Answer 27

Earthworms, maggots, woodlice
Speed up decay by feeding on dead material and breaking them into smaller pieces
Increases SA for decomposers to work on

Question 28

Why do living organisms need nitrogen

Answer 28

To make amino acids and nucleic acids

Question 29

How do plants get nitrogen

Answer 29

From fixed nitrogen (already reacted)

Ammonium + nitrate ions

Question 30

Where do animals get their nitrogen from

Answer 30

Food (amino acids)

Question 31

Nitrogen fixation

Answer 31

Nitrogen gas + other elements –> reactive nitrogen compound

Question 32

How does nitrogen fixation happen

Answer 32

Lightning strikes- 10%
Haber process
Nitrogen fixing bacteria (in the soil)- 90%

Question 33

Free living nitrogen fixing bacteria

Answer 33

In soil
Fix nitrogen gas from air spaces in the soil
Manufacturers amino acids for growth
Die, decompose + nitrates to soil

Question 34

Free living bacteria name

Answer 34

Azotobacter (italics, underline if writing)

Question 35

Nitrogen fixing bacteria in root nodules

Answer 35

Living in root nodules of leguminous plants such as peas, beans, alfalfa
Rhizobium (underline)
Bacteria have mutualistic relationship with plant- provide plant with fixed nitrogen in return for glucose
Leghaemoglobin in the nodules absorb oxygen oxygen and keeps condition anaerobic- nitrogen reductase to recur nitrogen gas and ammonium ins

Question 36

Ammonification

Answer 36

Decomposition of amino acids
Bacteria and fungi break down amino acids from dead organisms and nitrogenous waste for energy
-nitorgen compounds–> ammonia and ammonium ions

Question 37

Nitrification

Answer 37

Ammonium compounds are oxidised by bacteria in the soil into compounds that plants can use
Nitrifying bacteria are chemoautrophic (gain energy from reaction)

Question 38

Stages of nitrification

Answer 38

Ammonium ions oxidised to form nitrates (Nitrosomonas)
Nitrates are oxidised to nitrates (Nitrobacter)
Need oxygen from air bubbles

Question 39

Dentrificiation

Answer 39

Some bacteria convert nitrates back into nitrogen gas
These bacteria are present in water logged soils: grow in anaerobic conditions
In this situation they will use nitrates as a source of oxygen for respiration and produce nitrogen gas and nitrous oxide