Lecture 23

Question 1

Requirements for life supporting system

Answer 1

1. Energy
   - source
   - sink for degraded energy (heat)
2. Chemical elements

Question 2

Energy

Answer 2

• needed to produce organic matter
• photosynthesis by autotrophs requires energy and produced glucose
• called primary production

Question 3

Primary producers (autotrophs)

Answer 3

1. Produce organic matter via photosynthesis
2. Use organic matter as fuel for metabolism and respiration (releases energy)
3. Store some of the organic matter for future use (net production)

Question 4

Heterotrophs build body mass by eating

Answer 4

Other organisms (autotrophs or other heterotrophs)

Called secondary production

Question 5

Food chains

Answer 5

• arrange species in a community into trophic levels

- the trophic level indicates how many feeding steps the species is away from the autotroph level (level 1)

Question 6

Energy flow

Answer 6

• energy is lost at each step of a food chain
• e.g. respiration converts energy into heat
• represents increase in entropy (2nd law of thermodynamics)

Question 7

Can a circular food chain work

Answer 7

No

Question 8

Energy flow #2

Answer 8

At each level of a food chain, energy is used-it cannot be recycled or recovered

• limits number of trophic levels
• biomass decreases from bottom to top of food chain (trophic pyramid)

Question 9

Food web

Answer 9

More complex ecosystems that have multiple food chains woven into a food web

Question 10

Macronutrients

Answer 10

Required by all living things in large amounts

C H N O S P

Question 11

Micronutrients

Answer 11

Required in small amounts by all life, or in moderate amounts by some forms of life

Question 12

Toxins

Answer 12

Detrimental to living organisms

Question 13

Nutrients must be available

Answer 13

• at the right time
• right amount
• appropriate relative concentration to each other
• correct chemical structure

If not elements can become a LIMITING factor, preventing growth of organism, population or species

Question 14

Bioconcentration

Answer 14

Happens when an organism takes in a substance faster than it can use or excrete it

Question 15

Bioconcentration mechanisms

Answer 15

Bioaccumulation: substance taken in, not excreted at comparable rate, becomes more concentrated in organism with age

Biomagnification: substance is passed from consumer to consumer up the food chain

Question 16

Biogeochemical cycle

Answer 16

Describes the movement of a chemical element or compound through the biosphere and the rest of the earth system

Cycles may include the biosphere, geosphere, hydrosphere, and atmosphere

Question 17

Nitrogen cycle

Answer 17

• large component of atmosphere at unreactive N2
• also occurs as oxidized N2O, (NO3)2- and as reduced NH3 and NH4+

Essential to life (proteins and DNA)

Question 18

Nitrogen fixation

Answer 18

Atmospheric N2 is unreactive and must be converted into biologically useful forms, NH3 and (NO3)2-

• 90%done by nitrogen fixing bacteria
• once converted it is taken up by plants and algae and consumed by animals

Denitrification: bacteria convert dead nitrogen computer dd back into N2 and return it to the atmosphere

Question 19

Phosphorous cycle

Answer 19

Essential to the biosphere

• forms part of helical framework of DNA
• facilitates life energy transactions
• often a limiting nutrient

Occurs as phosphates in rocks in soils (low concentrations)

Liberated by weathering

Taken up by plants, bacteria, plankton from surface and sea water

Question 20

Phosphorous cycle (2)

Answer 20

Heterotrophs concentrate phosphorous (important for vertebrate bones)

Fish eating birds excrete phosphorous as guano deposits in arid climates (guano deposits are mined for phosphorous)

Question 21

Carbon cycle: RESERVOIRS

Answer 21

Atmosphere (CO2 and CH4)

Hydrosphere (carbonic acid, bicarbonate, organic carbon)

Biosphere (land and marine plants and animals, soil microbes)

Geosphere (carbonate rocks, soils, fossil fuels, crustal organic matter, graphite, diamond, other forms in earth’s mantle)

Question 22

Carbon cycle

Answer 22

• Enters atmosphere via volcanoes, respiration, fires, decay, ocean diffusion
• removed by photosynthesis and dissolution into water
• dissolved carbon (as carbonic acid) is converted to bicarbonate which is used by organisms and buried and stored in sediment
• photosynthesis produces organic carbon compounds in living organisms
• preserved as dead organic matter
• can be transformed into coal, Kerogen, natural gas, oil, graphite or diamond
• can be subducted and recycled into mantle