#17 Community & Ecosystem Ecology

Question 1

Community ecology

Answer 1

Concerned with factors that

• influence species composition and distribution of communities
• affect community stability

Question 2

Biological community

Answer 2

all populations of organisms living close enough together for potential interaction
-described by its species composition

Question 3

Interspecific interactions

Answer 3

Relationships with individuals of other species in the community

• greatly affect population structure and dynamics
• can be categorized according to their effect on the interacting populations

Question 4

Interspecific competition

Answer 4

When populations of 2 different species compete for the same limited resources

• when niches of 2 populations overlap
• lowers carrying capacity of competing populations

Question 5

Mutualism

Answer 5

Both populations benefit

Win/win

Question 6

Predation

Answer 6

One species (predator) kills and eats another (prey)
-the prey then adapt

Question 7

Herbivory

Answer 7

Animal consumes plant parts or algae

-coevolution (series of reciprocal evolutionary adaptations in two species) will occur

Question 8

Parasitism

Answer 8

Host plants or animals are victimized by parasites or pathogens (disease-causing microscopic parasites)
-Non-native pathogens can have rapid and dramatic effects

Question 9

Ecological niche

Answer 9

The sum of an organism’s use of the biotic and abiotic resources in its environment

Question 10

Trophic structure

Answer 10

a pattern of feeding relationships consisting of several different levels

Question 11

Producers

Answer 11

Autotrophs

Support all other trophic life

Question 12

Consumers

Answer 12

Heterotrophs

• Primary (herbivores)
• Secondary (typically eat herbivores)
• Tertiary (eat secondary)
• Quaternary (eat tertiary)

Question 13

Detritivores

Answer 13

Derive their energy from detritus (dead material produced at all the trophic levels)

Question 14

Decomposers

Answer 14

• mainly prokaryotes and fungi

- secrete enzymes that digest molecules in organic materials and convert them into inorganic forms (decomposition)

Question 15

Food web

Answer 15

Network of interconnecting food chains

-length of food chain limited by energy supply

Question 16

Species diversity

Answer 16

1. Species richness (number of species in community)
2. Relative abundance (proportional representation of a species in a community)

Plant diversity affects species diversity

Question 17

Keystone species

Answer 17

Impact of species on community is larger than its biomass or abundance indicates
-occupies niche that holds rest of community in place

Question 18

Disturbances

Answer 18

Lead to diversity

Events that damage biological communities

• include storms, fire, floods, drought, overgrazing, human activity
• types, frequencies, and severity very from community to community

Question 19

Ecological succession

Answer 19

Result from colonization by a variety of species, which are replaced by a succession of other species.

Question 20

Primary succession

Answer 20

Begins in a virtually lifeless area with no soil (e.g., volcano)

Question 21

Secondary succession

Answer 21

Occurs when a disturbance destroys an existing community but leaves soil intact

Question 22

Invasive species

Answer 22

Organisms introduced into non-native habitats by human action

• establish selves at expense of native community (niche)
• absence of natural enemies often allows rapid population growth

Question 23

Ecosystem

Answer 23

All organisms in a community and the abiotic environment with which the organisms interact

Contains: energy flow and chemical cycling

Question 24

Energy flow

Answer 24

Moves through the components of an ecosystem (sun and Earth’s interior)

Question 25

Chemical cycling

Answer 25

Transfer of materials within the ecosystem (e.g., air, water, soil)

Question 26

Primary production

Answer 26

By producers (sun -> photosynthesis)
The amount of solar energy converted into chemical energy by an ecosystem's producers for a given area and during a given time period
Produces biomass (amount of living organic material in an ecosystem)

Flow of energy (producers -> primary consumers -> higher)
-only 10% of energy available to the next level (why chain is so short)

Question 27

Biomass

Answer 27

Amount of living organic material in an ecosystem

Question 28

Different ecosystems vary in their:

Answer 28

1. Primary production

2. Contribution to the total production of the biosphere

Question 29

Biochemical cycles

Answer 29

Include

• Biotic components
• Abiotic components
• Abiotic reservoirs (where a chemical accumulates or is stockpiled outside of living organisms)

Can be local or global

Question 30

Carbon cycle depends on

Answer 30

Photosynthesis and respiration

Question 31

Phosphorus cycle

Answer 31

Depends on: weathering of rock (only source)
-required for nucleic acids, phospholipids, and ATP

No atmospheric component
-returned to soil be decomposers

Question 32

Nitrogen

Answer 32

Ingredient of proteins and nucleic acids
Essential to the structure and functioning of an organism
Crucial and often limiting plant nutrient

Two abiotic reservoirs:

1. Atmosphere
2. Soil

Cycle dependent on bacteria

Question 33

Nitrogen fixation

Answer 33

Converts N2 to compounds of nitrogen that can be used by plants
Is carried out by some bacteria

Question 34

Rapid inflow of nutrients degrades aquatic ecosystems

Answer 34

Primary production limited by low nutrient levels of

• phosphorus
• nitrogen

Overtime, standing water ecosystems

• gradually accumulate nutrients from decamp. and influx from land
• primary production increases (eutrophication)

Question 35

Eutrophication of lakes, rivers, and costal waters

Answer 35

Depletes oxygen levels
Decreases species diversity

Phosphate pollution leading to, comes from

• agric. fertilizers
• pesticides
• sewage treatment facilities
• runoff of animal waste from feedlots

Results also possibly from increase of nitrogen from

• feedlots
• applications of large amounts of fertilizer