53 Ecology & Global Ecology

Question 1

Primary producer

Answer 1

i.e. autotroph; any organism that creates its own food by photosynthesis or from reduced inorganic compounds and that is a food source for other species in its ecosystem; only transfers energy

Question 2

Primary consumer

Answer 2

a herbivore; an organism that eats plants, algae, or other primary producers

Question 3

Secondary consumer

Answer 3

a carnivore; an organism that eats herbivores

Question 4

Tertiary consumer

Answer 4

a carnivore; in a food chain or web, organisms that feed on secondary consumers

Question 5

Decomposers or detritivores

Answer 5

an organism whose diet consists mainly of dead organic matter (detritus) e.g. various bacteria, fungi, protists, and animals

Question 6

Detritus

Answer 6

a layer of dead organic matter that accumulates at ground level or on seafloors and lake bottoms

Question 7

Trophic (“feeding”) level

Answer 7

a feeding level in an ecosystem occupied by organisms that obtain energy from the same type of source

Question 8

Food chain

Answer 8

simple pathway of energy flow through a few species, each at a different trophic level, in an ecosystem

Question 9

Grazing food chain

Answer 9

ecological network of primary producers, herbivores, and the predators and parasites that consume them

Question 10

Decomposer food chain

Answer 10

ecological network of detritus, decomposers that eat detritus, and predators and parasites of the decomposers

Question 11

Primary decomposer

Answer 11

a decomposer that consumes detritus from plants; at the second trophic level of the decomposer food chain

Question 12

Food web

Answer 12

complex network of interactions among species in an ecosystem formed by the transfer of energy and nutrients among trophic levels; consists of many food chains

Question 13

Biomagnification

Answer 13

in animal tissues, an increase in the concentration of particular molecules that may occur as those molecules are passed up a food chain

Question 14

Biogeochemical (“life Earth chemical”) cycle

Answer 14

the pattern of circulation of an element or molecule among living organisms and the environment

Question 15

Soil organic matter

Answer 15

organic (carbon-containing) compounds of food in soil; a mixture of partially and completely decomposed detritus

Question 16

Humus

Answer 16

decayed organic matter or detritus in soils

Question 17

What are the 3 factors that affect the decomposition rate of detritus?

Answer 17

(1) abiotic conditions like oxygen availability, temp, and precipitation (2) quality of the detritus as a nutrient source for fungi, bacteria, and archaea that accomplish decomposition (3) abundance and diversity of detritivores

Question 18

Global nitrogen cycle

Answer 18

the movement of nitrogen among terrestrial ecosystems, the oceans, and the atmosphere

Question 19

Atmospheric nitrogen (N2)

Answer 19

biologically inert molecule that comprises ~78% of the air we breathe; usable by organisms only when it is reduced or fixed

Question 20

How does nitrogen fixation naturally occur?

Answer 20

through lighting-driven reactions in the atmosphere and enzyme-catalyzed reactions in bacteria that live in the soil and oceans

Question 21

What human activities alter the nitrogen cycle?

Answer 21

(1) cultivation of crops that harbor nitrogen-fixing bacteria (2) industrially produced fertilizers (3) burning of fossil fuels, which releases nitric oxide

Question 22

Global carbon cycle

Answer 22

the movement of carbon among terrestrial ecosystems, aquatic ecosystems, and the atmosphere

Question 23

Gross primary productivity (GPP)

Answer 23

total amount of carbon fixed by photosynthesis, including that used for cellular respiration, over a given time period

Question 24

What two ways do primary producers use chemical energy?

Answer 24

cellular respiration and growth and reproduction

Question 25

Net primary productivity (NPP)

Answer 25

total amount of biomass generated by the fixation of carbon through photosynthesis per year minus the amount oxidized during cellular respiration; energy used for growth and reproduction

Question 26

Biomass

Answer 26

total mass of all organisms in a given population or geographical area; usually expressed as total dry weight

Question 27

Ecosystem

Answer 27

a community of organisms that live in a specific area and the non-living surroundings

Question 28

Omnivores

Answer 28

organisms that move between consumer trophic levels

Question 29

Mutualists

Answer 29

two organisms that mutually transfer energy to each other

Question 30

Dead zone

Answer 30

where dissolved oxygen is too low to support most life

Question 31

Limiting nutrient

Answer 31

addition into the ecosystem enables more growth of the producers, which will allow transfer of biomass to more of the community e.g. nitrogen (cannot be assimilated by most organisms)