Food Webs and Trophic Cascades

Question 1

matter

Answer 1

is conserved, there is a set amount

Question 2

biotic

Answer 2

biosphere

Question 3

abiotic

Answer 3

atmosphere, hydrosphere and lithosphere

Question 4

water cycle

Answer 4

evaporation, transpiration, precipitation, run off

Question 5

carbon cycle

Answer 5

PS, CR, burial, extraction, combustion

Question 6

sulfur cycle

Answer 6

oceans, volcanoes, factories, rain, assimilation, decomposition, fossil fuels

Question 7

phosphorous cycle

Answer 7

weathering, erosion, fertiliser, assimilation, excretion, decay, sediments and rock
limiting nutrients: essential to life but too much leads to eutriphication (algal blooms)

Question 8

nitrogen cycle

Answer 8

nitrogen fixation - N2 - NH3 assimilation, ammonification, nitrification, leaching and denitrification

limiting nutrient so can lead to eutrophication

Question 9

community

Answer 9

set of all populations found in a given place

Question 10

primary producer

Answer 10

an organism that takes up inorganic CNP and converse it to organic compounds which provide food for other organisms

• plants, photosynthetic bacteria
• first reservoir of carbon once it is taken from the environment

Question 11

consumer

Answer 11

obtains carbon by eating and respiting it for energy

• primary consumer: herbivores (2nd carbon reservoir)
• secondary consumer: predators or scavengers that feed on primary consumers

return some carbon by respiration

Question 12

decomposer

Answer 12

break down dead tissues, feed on dead cells or bodies

carbon returned by respiration of fungi, bacteria etc,

Question 13

the carbon cycle has changed dramatically

Answer 13

increased O2 has changed organisms

Question 14

ecosystems

Answer 14

a community of organisms and the physical environment they occupy - physical and biological components are linked by processes that cycle nutrients and energy

Question 15

food chain

Answer 15

linear transformation of carbon from one organism to another

Question 16

trophic level

Answer 16

an organisms typical place in the food web (producers etc.)

Question 17

species interactions that transfer energy

Answer 17

• energy does not cycle, it must be continuously harvested (unidirectional)
• sunlight or chemicals
• energy stored in bonds of carbohydrates (rest lost as heat) - energy harvested by other trophic levels

Question 18

trophic pyramid

Answer 18

a diagram that traces the flow of energy showing available energy at each level to feed the next
shape results because biomass and the energy it represents generally decrease from one trophic level to the next
waste, heat (10% of energy and biomass from one level moves to next)
pyramid inverted for marine communities (plankton are small and reproduce rapidly)

Question 19

Liebig’s law of the minimum

Answer 19

primary production is limited by the nutrient that is least available

• greater primary production = greater variety of plants and animals
• greater biodiversity also increases production - no species carries out all functions and uses all resources

Question 20

carbon cycle

Answer 20

natural process: just a bit more carbon taken in than out (buried etc.) - 3gT per year decrease
humans add 8gT to the atmosphere a year (more than volcanoes etc.) - less trees, more output

Question 21

atmospheric carbon

Answer 21

carbon (from Vostok glacier - history over 400 000 years) shown to be between 180 and 285 ppm
ratio of O18: O16 decreases as temperature decreases - water that carriers O18 is heavier and requires more heat to evaporate so is less common in snow flakes
temp and CO2 are linked

Question 22

trophic cascades

Answer 22

ecological process that starts at the top of the food chain and tumbles down to the bottom
- wolves