Ecosystems 2

Question 1

Components of an ecosystem

Answer 1

Habitat
Population

Community

Question 2

Habitat

Answer 2

Where an organism lives

Question 3

Population

Answer 3

Where all the members of a species living in same place at a given time

Question 4

Community

Answer 4

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

Question 5

Why are there fewer consumers at higher levels

Answer 5

Energy (biomass) is lost at each trophic level so unavailable to organism at next trophic level, therefore there’s less energy available to sustain living tissue

Question 6

How is biomass lost

Answer 6

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 7

Loss of biomass in endotherms vs ectotherms

Answer 7

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

Question 8

Saprotrophs

Answer 8

Secrete extracellular enzymes onto dead/waste materials

Digest the materials into small molecules which are then absorbed and stored/respired

Question 9

Why is the producer efficiency v. low

Answer 9

Approx 90% of light is reflected, unusable wavelength and transmitted through leaf
Limiting factors

Energy used for photosynthetic reactions

Question 10

Succession

Answer 10

Progressive change in a community of organisms over time

Affects vegetation first but then brings about corresponding changes in bacteria, fungi, insects, birds and mammals

Question 11

Climax community

Answer 11

Final, stable community that exists after the process of succession has occurred
Usually woodland communities

Question 12

Deflected succession

Answer 12

Happens when succession is stopped/interfered w/ e.g. grazing so a plagioclimax develops as the species are stuck in that one stage of succession

Question 13

Pioneer species

Answer 13

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

Question 14

Primary succession

Answer 14

If a community is developed from bare ground e.g. volcanic eruptions
Pioneer communities start succession —> conditions change (build up or organic material /nutrients) and other species succeed them

Larger plants continuously succeed small plants until a climax community is formed

Question 15

Secondary succession

Answer 15

Does not start from bare ground

Takes place on a previously colonised but damaged/disturbed habitat

Question 16

Why are sand dunes helpful in terms of succession

Answer 16

Shows us the stages of succession in order of occurrence whereas usually we only see the current stage

Question 17

How does succession affect species diversity

Answer 17

Increases it however dominant species may outcompete the smaller species killing whole species off

Question 18

Weathering

Answer 18

Breakdown or decomposition of rock in situ

Question 19

How does water availability affect ecosystems?

Answer 19

lack of water leads to water stress
-lack of water causes plants to wilt (water is needed to keep cells turgid and plant upright) except xerophytes

-needed for photosynthesis

Question 20

How does oxygen availability affect ecosystems?

Answer 20

• in aquatic ecosystems fast-flowing cold water is beneficial as it contains a high O2 conc
• in water logged soil, air spaces are filled with water instead of oxygen

-needed for aerobic respiration

Question 21

How do edaphic (soil) factors affect ecosystems?

Answer 21

different soil types have different particle sizes (which effects which organisms can survive there)
-clay - fine particles, easily waterlogged, clumps when wet

• loam - diff particle sizes, retains water, not easily waterlogged
• sandy - coarse/well separated particles, free draining, water not retained, easily eroded