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

Types of changes in ecosystems

Answer 10

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 11

Components of an ecosystem

Answer 11

Habitat
Population
Community

Question 12

Community

Answer 12

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

Question 13

How is biomass lost

Answer 13

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 14

Loss of biomass in endotherms vs ectotherms

Answer 14

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

Question 15

Why is the producer efficiency v. low

Answer 15

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

Question 16

Succession

Answer 16

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 17

Pioneer species

Answer 17

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

Question 18

Use of transects

Answer 18

Look for changes in vegetation across a habitat

Question 19

Line transect

Answer 19

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

Question 20

Belt transect

Answer 20

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 21

Estimating pop. size

Answer 21

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

Question 22

How did cane toads rapidly increase in population?

Answer 22

• 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 23

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

Answer 23

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