Topic 29 -Energy and Nutrient Cycling

Question 1

ecosystems are considered to be ____systems

Answer 1

open

Question 2

inputs

Answer 2

exchanges from the surrounding environment into the ecosystem

Question 3

outputs

Answer 3

exchanges from the inside of the ecosystem out to the surrounding environment

Question 4

nutrients are typically

Answer 4

recycled through ecosystems

Question 5

energy comes from the

Answer 5

sun (input) and leaves the ecosystem as heat (output)

Question 6

energy in ecosystems exist as two forms

Answer 6

Potential energy -stored energy (available for performing work, stored in biomass of organisms)

kinetic energy -expended energy (used to perform work)

Question 7

1st Law of thermodynamics

Answer 7

the amount of energy is constant (in a closed system)
energy can not be created nor destroyed
energy can change form

although energy can not be created or destroyed, often much potential energy degrades into an unusable form

Question 8

2nd law of thermodynamics

Answer 8

whenever energy is transformed, some energy becomes unavailable for further use

Question 9

1st law of thermodynamics and ecology

Answer 9

energy can not be created or destroyed in an ecosystem
energy from the sun is harvested by primary producers and used to form chemical bonds in carbon based compounds
potential energy stored in these chemical bonds is transferred to consumers when they eat plants

Question 10

2nd law of thermodynamics and ecology

Answer 10

energy becomes unavailable when transferred among trophic levels through feeding relationships

as energy is transferred from one organism to another -a portion is used (stored as energy in living tissues as the organism grows) but a large part dissipates as heat

Question 11

Primary production

Answer 11

refers to the rate at which plant tissue (organic matter) is created during photosynthesis

Question 12

photosynthetic rates will be influenced by

Answer 12

leaf morphology (surface area)

modified photosynthetic pathways to increase water use efficiency (C4 vs CAM plants)

Adaptations to low light or high light

Question 13

secondary production

Answer 13

refers to the efficiency of consumers to transform energy consumed into growth and offspring

Question 14

the total energy consumed/ingested in the form of plant material flows through each individual consumer:

Answer 14

a portion is assimilated through the gut wall

remainder is expelled from the body as waste

Question 15

Assimilated energy (A)

Answer 15

portion is used in respiration
remainder is used for maintenance

some dissipates as heat during capture or harvest of food, muscular work, repair wear and tear on the animals body

Question 16

secondary production (P)

Answer 16

left over energy is used in growth and reproduction

Question 17

Production efficiency

Answer 17

the efficiency of consumer species to transform energy consumed into secondary production

=P/A (production/assimilation)

Question 18

general patterns for P/A

Answer 18

invertebrates»>vertebrates

ectotherms»»endotherms -higher allocation of energy to maintain constant body temp

carnivores»»herbivores -harder to assimilate plant tissue

Question 19

P/A of all species at each trophic level will determine the

Answer 19

energy available for the next level

Question 20

trophic efficiency general pattern

Answer 20

quantity of energy available for use by a trophic level decreases with each successive trophic level in the food chain due to production efficiencies (2nd law)

Question 21

ecological rule

Answer 21

only 10% of the energy stored as biomass within a given trophic level is converted to biomass at the next higher trophic level (10% rule)

Question 22

Nutrients (Ca, N, P) source is

Answer 22

atmosphere or weathering of rocks and minerals

taken up by plants -> move through the food chain via feeding relationships

a significant portion of the nutrients in an ecosystem are stored in organic form within living tissue of plants and animals

Question 23

most of the essential nutrients are recycled within the ecosystem by decomposers=

Answer 23

internal cycling (essential for ecosystem function)

once living tissue dies it falls to the soil or aquatic sediments in the form of dead organic matter

decomposers breakdown the chemical bonds formed during construction of plant and animal tissue, converts organic back to inorganic compounds (mineralization)

Question 24

Detritovores

Answer 24

animals that feed on dead organic material and waste products (primarily invertebrates)
aid decomposition by fragmenting larger pieces

Question 25

Microbial decomposers

Answer 25

bacteria and fungi

secrete enzymes into plant and animal tissues to breakdown the complex organic compounds -some products absorbed as food

Question 26

the rates of internal cycling of nutrients depend directly on the rates of two processes:

Answer 26

primary production determines the rate of nutrient transfer from inorganic to organic form (nutrient uptake)

decomposition determines the rate of transformation of organic to inorganic form (mineralization)

Question 27

Abiotic factors have a direct influence on decomposition rates

Answer 27

temperature and moisture effect microbial activity

cool, dry conditions reduce or inhibit activity

warm moist conditions are optimal