Ecosystems ✅

Question 1

What are biotic factors affecting ecosystems

Answer 1

Competition and consumption, Eg Living organisms

Question 2

What are abiotic factors affecting ecosystems

Answer 2

Temperature: Enzyme activity, thermoregulation, leaf-fall and flowering (in plants)

Photosynthetic rate (in plant) eg light

Question 3

What is a trophic level

Answer 3

A stage in a food chain

Question 4

List the names of a food chain with 5 stages

Answer 4

Producer-primary consumer-secondary consumer-tertiary consumer-quaternary consumer

Question 5

What is a producer

Answer 5

An organism (eg a plant) that converts light energy to chemical energy (ie autotrophic nutrition)

Question 6

What is a consumer

Answer 6

An organism that gains energy by feeding in other organisms (ie heterotrophic nutrition)

Question 7

What is procedure, adv and disadv of measure of fresh (wet) biomass

Answer 7

Procedure: living organisms measured
Adv: no organisms are killed
Disadv: presence of water reduces accuracy

Question 8

What is procedure, adv, disadv of measure of dry biomass

Answer 8

Procedure: organisms are killed and heated at 80^C until all water removed
Adv: estimates of mass are more accurate
Disadv: organisms must be removed from ecosystem and killed

Question 9

When might a pyramid of biomass not be a pyramid

Answer 9

When the consumer is usually large but in small number Eg trees may be few in number within an ecosystem, but their total biomass will still be greater then that of primary consumers

Question 10

What transfer occurs at producer level and consumer level

Answer 10

Producer: light energy conveyed to chemical energy in producers

Consumer: stored energy in biomass of one trophic level is transferred to next trophic level by consumption

Question 11

What is some energy not transferred at producer and consumer level

Answer 11

Producer: most light energy (90%) cannot be absorbed by plants. Some energy used in reactions of respiration and bud not converted to chemical energy in biomass

Consumer: some parts of organism (eg bones, roots, feathers) are inedible or indigestible. Some energy lost from food chain as heat, through movement or urine

Question 12

What is the calculation formula for producer and consumer levels

Answer 12

Producer: net production=gross production - respiratory losses

Consumer: ecological efficiency= (energy available after transfer/ energy available before transfer) X100

Question 13

How can humans manipulate factors in the production of plants

Answer 13

Light: plants grown in greenhouses under optimal light intensity and duration, seed sowing times to maximize leaf area present for photosynthesis during brightest months of year

Temperature: greenhouses provide regulates optimal temps

Water: irrigation, genetically engineered to drought resistant crops

Nutrient levels: fertilizer

Pests: pesticides

Question 14

How do humans manipulate the efficiency of energy transfers to primary consumers

Answer 14

Movement: movement of farm animals limited. More energy channeled into growth

Disease: antibiotic use reduces energy expenditure in immune systems

Question 15

What is decomposition

Answer 15

Process of large organic molecules (in dead animals and plants) being broken down into smaller inorganic molecules

Question 16

What can decomposes be classed as

Answer 16

Bacteria
Fungi
Or can be referred to as saprotrophs

Question 17

What is decomposition in the nitrogen cycle called

Answer 17

Ammonification- breakdown of proteins, nucleic acids, vitamins in dead organisms, faeces, iron to form ammonia and ammonium compounds

Question 18

What are the 3 processes to re enter nitrogen into food chain

Answer 18

Nitrification
Nitrogen fixation
Denitrification

Question 19

What is the reaction of nitrification and name of bacteria

Answer 19

NH3/NH4+ ions to NO2- (nitrosomonas)
NO2- to NO3- (nitrobacter)

Question 20

What is the reaction for nitrogen fixation and what bacteria is used

Answer 20

N2 (in atmosphere) converted to NH4+ions/NH3
rhizobium (which lives in roots of some plants)
Azotobacter (free living in soil)

Question 21

What is the reaction for denitrification and what bacteria is used

Answer 21

NO3- to N2 gas
Denitrifying bacteria (required anaerobic conditions)

Question 22

Describe nitrogen cycle

Answer 22

Ammoinium ions—>nitrite ions—> nitrate ions (all by nitrification)
Nitrate ions to N2 in atmosphere (denitrification) or nitrogen containing molecules in producers (absorption)
Nitrogen containing molecules in producers to consumers by feeding and digestion
Both nitrogen containing molecules go to ammoinium containing molecules in decomposes which go to ammonium ions by ammonification

Question 23

Describe carbon cycle

Answer 23

Photosynthesis converts CO2 to organic molecules in organisms
Respiration, decomposition, combustion return CO2 to atmosphere

Question 24

What is succession

Answer 24

Composition of an ecosystem gradually alters as abiotic factors in environmental changes, progression from bare ground to stable complex community of organism

Question 25

Describe the process of primary succession from bare rock to stable community

Answer 25

Only pioneer species can colonise bare rock eg lichen and algae which can fix nitrogen from atmosphere. Pioneer species represent the fist seral stage Erosion of rock produces basic soil Death and decomposition of pioneer organism adds nutrients to soil Soil development enables secondary colonizers eg mosses Improved environmental conditions enable more species to colonise Climax community forms which is stable and relatively biodiverse

Question 26

What is deflected succession

Answer 26

Human activities can prevent climax community from forming

Question 27

What is the result of deflected succession and give examples

Answer 27

Plagioclimax Found on agricultural land and in managed forests

Question 28

Describe the stages from barren land to climatic climax

Answer 28

Barren land Primary colonizers (lichen) Secondary colonizers (mosses) Tertiary colonizers (grasses) Scrubland (shrubs) Climatic climax (woodland) Last 3 can go to plagioclimax Eg farmland

Question 29

What is used to analyze how distribution of organisms varies in an ecosystem, what type of sampling is this

Answer 29

Transect, systematic

Question 30

What can be uses to estimate abundance of plant species per area

Answer 30

Quadrats

Question 31

What technique is used to estimate animal abundance

Answer 31

Capture-mark-release-recapture

Question 32

describe the factors that reduce the efficiency of energy transfer between trophic levels (3 marks)

Answer 32

inedible/ indigestible parts energy used in respiration/ to produce heat energy used for movement some energy lost in excretion

Question 33

explain how farmers can increase the proportion of consumed energy that is used for growth in cattle (3 marks)

Answer 33

restrict movement use antibiotics to reduce amount of energy used by the immune system maintain optimal environmental temperature more energy is converted to biomass

Question 34

explain how human activity has upset the natural balance of the carbon cycle (3 marks)

Answer 34

deforestation reduces photosynthesis more combustion in industry/vehicles/as fuel higher CO2 concentrations in the atmosphere

Question 35

suggest why farmers may try to prevent their soils becoming waterlogged (3 marks)

Answer 35

anaerobic conditions increased denitrification reduced nitrification lower concentrations of nitrates for crop plants to absorb

Question 36

explain what is meant by a plagioclimax, and identify one example resulting from land management (2 marks)

Answer 36

a community resulting from deflected succession, where human influence gas prevented succession from producing s climax community (examples include) managed forests, grazing grassland, arable crop fields

Question 37

describe 3 important characteristics of a pioneer species (3 marks)

Answer 37

tolerance of extreme conditions/ environments ability to fix nitrogen from the atmosphere ability to photosynthesise production of many seeds/ spores that can be carried by the wind rapid germination of seeds

Question 38

describe the difference between primary succession and deflected succession, and explain why primary succession is likely to result in greater biodiversity (3 marks)

Answer 38

primary succession is the natural development of an ecosystem to form a climax community deflected succession is when human activity interrupts succession, producing a plagioclimax primary succession tends to produce greater biodiversity because deflected succession reduces the number of ecological niches available

Question 39

explain why the measurement of distribution should be systematic (2 marks)

Answer 39

different areas within an ecosystem are identified