Chapter 23- Ecosystems

Question 1

Define an ecosytem

Answer 1

Is made up of all the living organisms that interact with one another in a defined area, and also the physical factors present in that region.

Question 2

Biotic factors that affect an echo stem

Answer 2

The living factors. For example, in a forest ecosystem, the presence of shrews and hedgehogs are biotic factors, as is the size of their populations- the competition between these two animal populations for a food source is also a biotic factor

Question 3

Abiotic factors affecting ecosystem

Answer 3

The non living factors.

Question 4

Abiotic factors

Answer 4

Light
Temperature 
Water availability
Oxygen availability 
Edaphic soil factors

Question 5

Biotic factors

Answer 5

Food
Space
Breeding partners

Question 6

How to calculate efficiency

Answer 6

Biomass transferred/biomass intake x100

Question 7

Trophic levels

Answer 7

Produce

Consumers

Question 8

Define biomass

Answer 8

Is the mass of living material present in a particular place or in particular organisms

Question 9

How to measure biomass

Answer 9

Measure mass of fresh material present
Organisms killed
Then heated to 80 degrees until all water has been evaporated- this point is indicated by two identical mass readings

Question 10

How to calculate net production

Answer 10

Gross production- respiratory losses

Question 11

Human activities that can affect biomass

Answer 11

Shorten the food changing meaning minimum energy is lost since there are fewer tropic levels present.

Question 12

Role of decomposers

Answer 12

Is an organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic ones available to photosynthetic produces in the ecosystem

Question 13

What are decomposers an example of

Answer 13

Saprotrophs because they obtain their energy from dead or waste organic material.

Question 14

Nitrogen fixation

Answer 14

Bacteria such as rhizobium and azotobacter contain the enzyme nitrogenase, which combines with atmospheric nitrogen with hydrogen to produce ammonia. A form of nitrogen that can be absorbed and used by the plants

Question 15

Where do the nitrogen fixing bacteria live

Answer 15

Inside root nodules

Question 16

Mutualistic relationship between plant and bacteria

Answer 16

Plant gains amino acids

Bacteria gains carbohydrates

Question 17

Nitrification

Answer 17

Process by which ammonium compounds in the soil are converted into nitrogen containing molecules that can be used by plants

Question 18

Two steps of nitrification

Answer 18

1. Nitrifying bacteria (such as nitrosomonas) oxidise ammonium compounds to NO2-
2. Nitrobacter oxidise nitrites to NO3- nitrates

Question 19

Denitrification

Answer 19

In the absence of oxygen, denitrifying bacteria converts nitrates in the soil back to nitrogen gas. Only happens under anaerobic conditions
NO3- to N2
Bacteria use the nitrates as a source of energy for respiration

Question 20

Ammonifcation

Answer 20

Is the name given to the process by which decomposers convert nitrogen containing molecules in dead organisms into ammonium compounding

Question 21

Fluctuations of CO2 levels

Answer 21

Photosynthesis only occurs during day

Whereas respiration always occurs therefore atmospheric CO2 leves are higher at night

Question 22

Why have CO2 levels increased significantly

Answer 22

Combustion of fossil fuels

Deforestation

Question 23

Define succession

Answer 23

One proccess by which ecosystems change over time is called succession

Question 24

Define primary succession

Answer 24

Occurs on a area of land that has been newly formed or exposed such as bare rock. There is no soil or organic materials present to begin with

Question 25

Define secondary succession

Answer 25

This occurs on areas of land where soil is present, but it contains no plant or animal species

Question 26

Where does primary succession occur

Answer 26

Volcanoes erupt Sand is blown by the wind Slit and mud are deposited at river estuaries Glaciers retreat

Question 27

What is each stage in succession known as

Answer 27

Seral stage

Question 28

Main seral stages

Answer 28

1. Barren land 2. Pioneer community 3. Intermediate community 4. Climax community

Question 29

Pioneer community

Answer 29

The first species to arrive usually carried by the wind from nearly by land masses

Question 30

How are pioneer species adapted

Answer 30

Able to produce large amounts of seeds or spires Seeds that germinate fast Ability to photosynthesise Tolerance to extreme environments

Question 31

Explain environment in climax community

Answer 31

In a stable state Will show very little change over time Often not the most biodiversity often mid succession is most diverse

Question 32

Explain deflected succession

Answer 32

Human activities can halt the natural flow of succession and prevent the ecosystem from reaching a climax community. When succession is stopped the final stage is known as phagioclimax

Question 33

Why does deflected succession occur

Answer 33

Grazing and trampling of vegetation Removing existing vegetation Burning

Question 34

Measuring distribution

Answer 34

A line or belt transfer is used A line transect involves laying a line or surveyors tape along the ground and taking samples at regular intervals. A belt transfer provides more info- two parallel lines are marked, and samples are taken of the area between specified points They are both forms of systematic sampling

Question 35

Definition of abundance of organisms

Answer 35

Refers to the number of individuals of a species present in an area at any given time

Question 36

Measuring plant abundance

Answer 36

Use quadrants | Estimated population= number of individuals in sample / area of sample

Question 37

Measuring animal abundance

Answer 37

1. Capture as many individuals in a given area as possible 2. Mark or tag each individual 3. Release the marked animals back into area 4. Recapture as many individuals as possible 5. Record the number of marked and unmarked individuals caught 6. Use Lincoln’s index first sample x second sample / number of recaptured individuals

Question 38

Define a producer

Answer 38

Convert light energy to chemical energy

Question 39

Define a consumer

Answer 39

Which lives and feeds of other animals

Question 40

Define a trophic level

Answer 40

A stage in a food web

Question 41

Difference between conservation and preservation

Answer 41

Maintains ecosystems with active management | Whereas preservation leaves the ecosystems I disturbed