Ecosystem

Question 1

Ecosystem

Answer 1

• made up of all living organisms that interact with one another in a defined area

Question 2

Abiotic factors

Answer 2

• non-living
• e.g light, temperature, water availability, 02 availability, soil factors

Question 3

Biotic factors

Answer 3

• living
• e.g competitor for space, food, breeding partners

Question 4

Biomass transfer between trophic levels

Answer 4

• starts with producers = converts light energy into chemical energy by photosynthesis
• the consumers = organism that obtains energy by feeding on other organisms
• decomposers = break down the dead organisms releasing nutrients into the ecosystem

Question 5

measuring biomass

Answer 5

• biomass present in each organism x total number of organism in trophic level
• doesn’t take into account seasonal differences

Question 6

measuring mass of dry material

Answer 6

• gm-2 (land) or gm-3 (water)

Question 7

efficiency of biomass and energy transfer

Answer 7

• measure in KJm-2yr-1
• allows changes in photosynthesis production and consumer patterns throughout the year

Question 8

efficiency at producer level

Answer 8

• convert 1-3% of light into chemical energy
• not all the solar energy available is used for photosynthesis (wavelength)

Question 9

net production

Answer 9

= gross production - respiratory losses

Question 10

efficiency at consumer level

Answer 10

• convert 10% of the biomass of their food
• not all the biomass of an organism is eaten (e.g bones)
• some of their energy is transferred into the environment as metabolic heat
• some parts of the organism is indigestible

Question 11

ecological efficiency

Answer 11

= energy or biomass available after the transfer / energy of biomass available before the transfer x100

Question 12

Human activities (agriculturre)

Answer 12

• manipulating the environment to favour the plant species to grow
• removal of competition fro mother species and threat of predators
• ensures that as much energy as possible is transferred into biomass to be eaten by humans

Question 13

Nitrogen cycle

Answer 13

• N2 = NH3 = NO2 = NO3 = N2

Question 14

Nitrogen fixing

Answer 14

• by living organisms
• rhizobium = fixes n2 to NH3 in bacteria
• azotobacter = free living soil bacteria, fixes N2 to NH3

Question 15

Nitrification

Answer 15

• turning ammonia into nitrogen containing molecules
• oxidation reaction
• Nitrosomonas = ammonium into nitrites
• Nitrobacter = nitrites into nitrates

Question 16

Denitrification

Answer 16

• denitrifying bacteria convert nitrates into the soil back into nitrogen gas
• occurs in anaerobic conditions
• Pseudomonas

Question 17

Decomposition

Answer 17

• chemical process where compounds are broken down into smaller molecules

Question 18

Decomposer

Answer 18

• organism that feeds on and breaks down dead plant or animal matter

Question 19

carbon cycle

Answer 19

• main source is the atmosphere
• constantly recycled
• Co2 levels fluctuate throughout the day and seasonally
• global levels increased compared to 200 years ago

Question 20

processes in the carbon cycle

Answer 20

• combustion
• photosynthesis
• respiration
• feeding
• decomposition

Question 21

succession

Answer 21

• progressive replacement of one dominant type of species or community by another in an ecosystem
• until a stable climax community is established

Question 22

primary succession

Answer 22

• occurs in an area that has been newly formed or exposed
• no soil or organic matter

Question 23

secondary succession

Answer 23

• occurs on an area that soil is present but contains no animal species or plants

Question 24

stages of succession

Answer 24

• pioneer community = intermediate community = climax community

Question 25

pioneer community

Answer 25

• species arrive as spores or seed carried by the wind
• ability to produce large quantities of seeds and germinate rapidly
• can tolerate extreme condition

Question 26

intermediate community

Answer 26

• over time soil forms and is able to support the growth of ew species of plant (secondary colonisers)
• pioneer species also provide a food source for consumers so some animal species colonise the area
• multiple stages occur over time until the climax community is reached
• become more adapted to the current conditions

Question 27

climax community

Answer 27

• final stages
• stable state = little change over time
• few dominant species which are specific to the climate
• not always the most diverse (peaks in mid succession)

Question 28

deflected succession

Answer 28

• human activities can halt the natural flow of succession
• when stopped artificially = PLAGIOCLIAMX
• e.g agriculture

Question 29

distribution of species

Answer 29

• where individual organisms are found within an ecosystem
• usually uneven
• measured by a belt/line transect

Question 30

abundance of species

Answer 30

• number of individuals of a species present in an area at any given time
• fluctuate daily (immigration and emigration)
• measured by population number (quadrats)