Module 6 Ecosystems

Question 1

What is an ecosystem?

Answer 1

It is the interaction of all living things and non-living things in an area.

Question 2

What is meant by a dynamic ecosystem

Answer 2

An ecosystem that changes all the time

Question 3

State some abiotic factors

Answer 3

• Water: affects photosynthesis
• Light: affects photosynthesis
• Oxygen levels: affects respiration
• Temperature : enzyme activity
• Edaphic soil factors: type of soil and ph of the soil

Question 4

State some biotic features

Answer 4

• Competition
• predation
• new diseases

Question 5

What are the biotic and abiotic factors in a rock pool

Answer 5

Biotic
-competition

Abiotic 
salinity 
ph
water
light
oxygen levels

Question 6

biotic and abiotic factors for a large tree

Answer 6

biotic
predators, disease, competition

abiotic
ph, soil, water, oxygen, light

Question 7

What are the biotic and abiotic features in a playing field

Answer 7

Biotic competition, humans

Abiotic
light, water, oxygen, soil

Question 8

What is a food chain

Answer 8

they show how energy is transferred through an ecosystem

Question 9

What is biomass

Answer 9

Mass of living material in the area

Question 10

How do we measure biomass

Answer 10

• use a calorimeter
• collect the sample
• kill the organisms
• place into an oven at 80 degrees (to ensure we remove the water by evaporation)
• check the mass throughout
• then when the mass stays the same that is the biomass

Question 11

What is biomass in animals measured in

Answer 11

gm-2

Question 12

What is biomass in marine animals measured in

Answer 12

gm-3

Question 13

What is the equation to work out net productivity

Answer 13

net productivity= gross productivity- respiratory loss

Question 14

what is the equation to work out %efficiency of energy transfer

Answer 14

% = net productivity of trophic level/net proudcity of previous trophic level x 100

Question 15

How do we lose energy down a food chain?

Answer 15

• some energy is the wrong wavelength, is reflected or just passes through
• some parts of the plant like bark can’t photosynthesise
• some parts of the animal-like bones may not be eaten by consumers
• some parts can’t be digested

Question 16

What is net productivity

Answer 16

it is the amount of energy available for the next trophic level

Question 17

How do we control energy flow through ecosystems

Answer 17

Using herbicides- this reduces competition

Fungicides- kill fungus so more need can be used for growth than fighting of disease

using insecticides- means less biomass is lost, so they can grow

Natural predators- can eat pest species, so crops lose less energy

Rearing livestock intensively- for example animals are kept warm, movement is restricted, may be given feed that is higher energy (so more good food), slaughtered before they reach adulthood , young animals use loads of energy for growth

Question 18

What are the stages of the carbon cycle

BTW explain each one

Answer 18

Photosynthesis

Decomposition: break down carbon by secreting enzymes, they then absorb products of digestion by feeding on dead matter (saprobiotic nutrition)

Respiration

Combustion: fossil fuels

Volcanoes

Weathering: can cause carbonates from rock to be released into solution like groundwater

Absorption from sea

Question 19

What are the stages of the nitrogen cycle

BTW explain each one

Answer 19

Nitrogen fixation: nitrogen from the atmosphere is converted into ammonia by azotobacter (free living) or rhizobium (in legumes) they have a mutualistic environment. Can also be made by the haber proces or lightning.

Ammonification: nitrogen compounds from dead organism turned into ammonia by decomposers. This forms ammonium ions (done with decomposers)

Nitrification: Nitrosomonas changes ammonium ion into nitrites. Then nitrobacter changes it from nitrites to nitrates .

Denitrification: nitrates from soil are converted into nitrogen gas by denitrifying bacteria. Happens in anaerobic conditions water logged soils

Question 20

What is succession

Answer 20

Process in which ecosystem changes over time

Question 21

What happens during primary succession

Answer 21

Start with bare rock
pioneer species seeds are blown in the wind
the harsh conditions (limited water, few minerals, no soil, high light intensity, flucating temperatures) mean that only pioneer species can grow (marram grass, lichens, shrubs of calligonum

The lichens die, decompose and form thin soil. Species like mosses can now grow because they have outcompeted the lichen

Larger plants that need more water grow start to grow. These out compete the mosses. These plants will die then decompose making the soil more nutrient rich.

Shrubs, ferns and new trees grow which outcompete grass. At this point diversity increases

The soil is deep and rich enough so it can support large trees. This is the dominant species and a climax community is formed

Question 22

What happens during secondary succession

Answer 22

Happens on land that has been cleared of plants but soil remains
Due to a forest fire or human activity
Pioneer species are larger

Question 23

How do we know what climax community will form

Answer 23

It depends on the temperature