Ecosystems

Question 1

What is an ecosystem?

Answer 1

The sum of all the organisms living in a given area and the abiotic factors with with they interact

Question 2

Tell me about this desert spring ecosystem.

Answer 2

Most plants rely on little water

Question 3

Tell me about this island ecosystem.

Answer 3

Large amount of available water– a lot of plant growth

Question 4

What do we mean by energy flow?

Answer 4

Energy enters most ecosystems as sunlight, converted to chemical energy by autotrophs, passed to heterotrophs in the organic compounds of food, and dissipated as heat

Question 5

What do we mean by chemical cycling?

Answer 5

Chemical elements such as carbon and nitrogen are cycled among abiotic and biotic components of the ecosystem

Question 6

Why do we say energy flow and not energy cycling?

Answer 6

Energy cannot be recycled

Question 7

What is the first law of thermodynamics, and how does it apply to ecosystems?

Answer 7

Energy cannot be created or destroyed but only transferred or transformed- plants and photosynthetic organisms converts solar energy to chemical energy but the total amount of energy does not change- amount of energy stored in organic molecules must equal the total solar energy intercepted by plant minus amount dissipated as heat

Question 8

What is the second law of thermodynamics, and how does it apply to ecosystems?

Answer 8

Every exchange of energy increases the entropy (disorder) of the universe- some energy is always lost as heat

Question 9

What is the law of conservation of mass?

Answer 9

Matter cannot be created or destroyed

Question 10

How does the conservation of mass differ from the conservation of energy, and how does it apply to ecosystems?

Answer 10

Because mass is conserved, we can determine how much of a chemical element cycles within an ecosystem or is gained or lost by that ecosystem over time

Question 11

What do we mean by trophic levels?

Answer 11

Species are grouped into these levels based on their main source of nutrition and energy

Question 12

What are primary producers?

Answer 12

Trophic level that supports all others (autotrophs)

Most are photosynthetic organisms that use light energy to synthesize sugars and other organic compounds

Question 13

What are primary consumers?

Answer 13

Herbivores which eat plants and other primary producers

Question 14

What are secondary consumers?

Answer 14

Carnivores that eat herbivores

Question 15

What are tertiary consumers?

Answer 15

Carnivores that eat other carnivores

Question 16

What are detritivores (decomposers)?

Answer 16

consumers that get their energy from detritus (nonliving organic material, such as the remains of dead organisms, feces, fallen leaves, and wood

Question 17

What is primary production?

Answer 17

The amount of light energy converted to chemical energy (in the form of organic compounds) by autotrophs during a given period

Question 18

What sets the global energy budget?

Answer 18

The total amount of photosynthetic production

Question 19

What is gross primary production?

Answer 19

The amount of energy from light converted to the chemical energy of organic molecules per unit time

Question 20

What is net primary production?

Answer 20

Equal to gross primary production minus the energy used by the primary producers for their “autotrophic respiration”

Question 21

How is net primary production expressed in terms of energy?

Answer 21

Expressed as energy per unit area per unit time

Question 22

How is net primary production expressed in terms of biomass?

Answer 22

or as biomass added per unit area per unit time

Question 23

What do the next two slides tell you about global net primary production?

Answer 23

Tropic land areas have the highest rates of production

Question 24

What is net ecosystem production?

Answer 24

Measure of the total biomass accumulation during that time

Question 25

How can net ecosystem production be measured in terms of the net flow of CO2 or O2 entering or leaving the ecosystem?

Answer 25

If more CO2 enters than leaves, the system is storing carbon. Because O2 release is directly coupled to photosynthesis and respiration, a system that is giving off O2 is also storing carbon.

Question 26

Energy transfer between trophic levels is typically only __ efficient.

Answer 26

10%

Question 27

What is secondary production?

Answer 27

The amount of chemical energy in consumers’ food that is converted to their own new biomass during a given period

Question 28

What is assimilation of primary production?

Answer 28

Energy assimilated for cellular respiration??

Question 29

What is net secondary production?

Answer 29

Energy stored in biomass represented by growth and reproduction

Question 30

What is production efficiency?

Answer 30

Percentage of energy stored in assimilated food that is not used for respiration

Question 31

Why do endotherms have lower production efficiency than ectotherms?

Answer 31

Because they use so much energy in maintaining a constant high body temperature

Question 32

What is trophic efficiency?

Answer 32

Percentage of production transferred from one trophic level to the next

Question 33

How much energy is typically transferred from one trophic level to the next?

Answer 33

10%

Question 34

How does this limit the number of trophic levels in a food web?

Answer 34

Progressive loss of energy limits the abundance of top-level carnivores that an ecosystem can support because only about .1% of chemical energy fixed by plants can flow all the way through a food web

Question 35

What does this mean for secondary and tertiary consumers?

Answer 35

Limits the abundance of top-level carnivores that an ecosystem can support

Question 36

This is a biomass pyramid. What do you see here?

Answer 36

Each tier represents the standing crop (the total dry mass of all organisms) in one trophic level

Question 37

This is an aquatic biomass pyramid. What do you see here?

Answer 37

These are inverted because the producers (phytoplankton) grow, reproduce, and are consumed so quickly by the zooplankton that they never develop a large population size, or standing crop (short turnover time)

Question 38

What is the water cycle?

Answer 38

Evaporation of liquid water by solar energy, condensation of water vapor into clouds, and precipitation. Transpiration by terrestrial plants also moves large volumes of water into the atmosphere. Surface and groundwater flow returns water to the oceans, completing water cycle

Question 39

What is the Carbon cycle?

Answer 39

Photosynthesis by plants and phytoplankton removes substantial amounts of atmospheric CO2 each year. This Quantity is approx. equaled by CO2 added to the atmosphere through cellular respiration by producers and consumers. The burning fossil fuels and wood is adding amounts of additional CO2 to atmosphere and so are volcanou

Question 40

What is the phosphorus cycle?

Answer 40

Weathering of rocks gradually adds phosphorus to soil; some leaches into groundwater and surface water and may eventually reach sea. Phosphate taken up by producers and incorporated into biological molecules may be eaten by consumers. Phosphate is returned to soil or water by decomposition of biomass or excretion by consumers. Only small amounts move through atmosphere usually in the forms of dust or sea spray

Question 41

What is the Nitrogen cycle?

Answer 41

Major pathway for nitrogen to enter ecosystem is through nitrogen fixation- conversion of N2 to forms that can be used to synthesize organic nitrogen compounds. Certain bacteria, lightning, and volcanic activity fix nitrogen naturally. Nitrogen inputs by humans outweigh the natural fixation. Industrially produced fertilizers and legume crops that fix nitrogen and other bacteria in soil