23 - Ecosystems

Question 1

What is an ecosystem?

Answer 1

-All the interacting living organisms and the non-living conditions in an area
-Dynamic
-Range in size

Question 2

What is a biotic factor?

Answer 2

Living components of an ecosystem

Question 3

What is an abiotic factor?

Answer 3

Non-living components in an ecosystem

Question 4

What are the biotic factors that affect ecosystems?

Answer 4

Interactions between organisms
-Competition (intraspecific/interspecific) for food, territory, breeding partners, etc

Question 5

What are the abiotic factors that affect ecosystems?

Answer 5

-Light: Affects photosynthesis, greater success of a plant species where light availability is greater
-Temperature: Affects enzyme controlled metabolic reactions, both plants and ectotherms develop faster in warmer temps
-Water availability: lack of water leads to water stress, causing wilting as water is required to maintain turgidity of cells, also needed for photosynthesis
-Oxygen availability: necessary for respiration (fast flowing cold water, but not water logged soils)
-Edaphic (soil) factors: CLAY - fine particles, easily waterlogged, clumps when wet / LOAM - particle size varies, retains water, not waterlogged / SANDY - coarse and separated particles, water drains, does not retain water, erodes easily

Question 6

What is a trophic level?

Answer 6

Stage in a food chain

Question 7

What is a food chain?

Answer 7

Diagram showing direction of energy flow

Question 8

What is a food web?

Answer 8

Series of interlinked food chains

Question 9

What is a producer?

Answer 9

Organism that coverts light energy into chemical energy

Question 10

What is a consumer?

Answer 10

Organism that obtains its energy by feeding off another organism

Question 11

What is biomass?

Answer 11

Mass of living material

Question 12

List the trophic levels/

Answer 12

Producer - organism that converts light energy to chemical energy
Primary consumer - animal that eats a producer
Secondary consumer - animal that eats a primary consumer
Tertiary consumer - animal that eats a secondary consumer
Quaternary consumer- animal that eats a tertiary consumer

Question 13

Why don’t food chains usually have more than five trophic levels?

Answer 13

There is not usually sufficient biomass and energy stored left to support any further organisms

Question 14

What is a decomposer?

Question 15

What are the 3 types of ‘pyramids’ that represent food chains

Answer 15

Pyramid of energy
Pyramid of biomass
Pyramid of numbers

Question 16

How do you calculate biomass at each trophic level

Answer 16

Multiply biomass of each organism by the total number of organisms in that area
BUT water content must be discounted (dry mass) and must be killed to be dried

Question 17

What is biomass measured in?

Answer 17

g/m^2
OR
g/m^3

Question 18

Why does biomass always decrease between successive trophic levels?

Answer 18

Only a small proportion of food ingested is converted into new tissue

Question 19

What are the units for energy at each trophic level

Answer 19

kJ/m^2/yr

Question 20

What is ecological efficiency?

Answer 20

Efficiency with which energy or biomass is transferred from one trophic level to the next

Question 21

What is the efficiency of a producer

Answer 21

Convert 1-3% of light energy into chemical energy and hence biomass

Question 22

Explain the efficiency of a producer

Answer 22

-Not all light energy available is used for photosynthesis (90% is reflected)
-Other factors may limit photosynthesis
-Some energy is lost as it is used for photosynthetic reactions

Question 23

What is gross production?

Answer 23

The total light energy that plants convert into organic matter