Unit 6 - Ecosystems

Question 1

Open ecosystem

Answer 1

When living things can move between ecosystems

Question 2

Closed ecosystems

Answer 2

When living things cannot easily move between ecosystems e.g. islands

Question 3

Biotic factors affecting ecosystems

Answer 3

Predators
Food supply (prey)
Disease
Cooperation between species
Competition between species

Question 4

Abiotic factors affecting ecosystems

Answer 4

pH
Conc of pollutants
Temp (climatic)
Moisture/ rainfall/ relative humidity
O2 level
Soil type (edaphic)
Light intensities

Question 5

How does low light intensity affect the ecosystem

Answer 5

Plants develop photosynthetic pigments that require less light
Grow larger leaves
Reproductive systems that only work in optimum light intensities

Question 6

How does temp affect the ecosystem

Answer 6

Temp has the biggest effect on enzymes in the organisms that live in the ecosystem
May trigger migration/ hibernation
Dormancy/ leaf fall/ flowering in plants

Question 7

How are ecosystems organised

Answer 7

In trophic levels

Question 8

Producers in an ecosystem

Answer 8

Lowest trophic level
Involves autotrophs, chemotrophs and photoautotrophs

Question 9

Autotrophs

Answer 9

Convert energy from environment into complex organic matter, then are used as respiratory substrates or for growth

Question 10

Consumers

Answer 10

Higher/est trophic levels
Feed on complex organic matter made by autotrophs and other organisms and use the products of digestion as respiratory substrates or for growth
1’<2’<3’

Question 11

Decomposers

Answer 11

Feed on waste or dead organsims to gain energy by digesting and respiring organic matter
Recycling - returns inorganic ions to the air/soil

Question 12

Types of changes in ecosystems

Answer 12

Cyclical - repeated change e.g. seasons, day/night
Directional - in one direction e.g.global warming, erosion
Unpredictable/ erratic - no rhythm or constant direction e.g. volcanic eruption

Question 13

Components of an ecosystem

Answer 13

Habitat
Population
Community

Question 14

Community

Answer 14

All the populations of diff species who live in some place at a given time, who can interact w/ each other

Question 15

How is biomass lost

Answer 15

Cellular respiration - conversion to inorganic molecules such as CO2 and H2O
Excretory materials
Indigestible matter
Not everything is fit for consumption e.g. bones
Transferred at metabolic heat (movement)

Question 16

Loss of biomass in endotherms vs ectotherms

Answer 16

Ectotherms use less energy in maintaing body heat so there is more biomass availabe

Question 17

Why is the producer efficiency v. low

Answer 17

Approx 90% of light is reflected, unusable wavelength and transmitted through leaf
Limiting factors
Energy used for photosynthetic reactions

Question 18

Succession

Answer 18

Progressive change in the structure and species composition in a community
Affects vegetation first but then brings about corresponding changes in bacteria, fungi, insects, birds and mammals

Question 19

Pioneer species

Answer 19

Species that begin the process of succession, often colonising an area as the first living thing there

Question 20

Use of transects

Answer 20

Look for changes in vegetation across a habitat

Question 21

Line transect

Answer 21

At reg. intervals
Note of which species are touching the tape

Question 22

Belt transect

Answer 22

At reg. intervals
Place a quadrat next to the line (interrupted belt transect) or move the quadrat along the line (continuous)
Used to sample succession

Question 23

Estimating pop. size

Answer 23

Mean number of a species in a quadrat/ fraction of the total habitat area covered by a single quadrat

Question 24

How did cane toads rapidly increase in population?

Answer 24

• Fast moving -> rapidly disperse to find new sources of food in areas with reduced competition and less predators (these are selection pressures) -> interbreed and produce fast, long-legged offspring -> move faster into new territory

Question 25

How did the prickly pear change in population in Australia (increase/decrease)?

Answer 25

Increase:
- Conditions in Australia similar to native environment
- Predator free environment
- Fast growing
Decrease:
- Introduction of moth that controlled it