chapter 53 - ecosystems and global ecology

Question 1

define ecosystem

Answer 1

one or more communities in an area + abiotic components

Question 2

what are ecosystems tied together by?

Answer 2

flow of nutrients

Question 3

define primary producer/autotroph

Answer 3

plants!
can synthesize its own food from inorganic sources
total energy captured = gross primary productivity

Question 4

gross primary productivity (GPP)

Answer 4

total energy produced by autotrophs

used in 2 ways:
1) to stay alive through cellular respiration
2) growth and reproduction (net primary productivity)

Question 5

Net Primary Productivity can be calculated as

Answer 5

NPP = GPP – R
R = energy used is cellular respiration
basically total energy minus energy used to stay alive

Question 6

net primary productivity (NPP)

Answer 6

total energy used for growth and reproduction
builds biomass

Question 7

why can so little solar energy be captured?

Answer 7

mostly due to light and temperature changes

• visible light only a fraction of the wave length
  spectrum
  – low or zero during winter
  – stalled if too dry (stomata will close, plant can’t take in nutrients)
  – enzyme efficiency varies with temperature

Question 8

proportions of solar energy used

Answer 8

GPP uses 0.8% of total available solar energy
Cellular respiration (heat loss, waste) 55%
NPP 45%

Question 9

nutrients cycle

Answer 9

sunlight -> primary producer
primary producer -> primary consumer
primary consumer -> secondary consumer
secondary consumer -> tertiary consumer
tertiary consumer -> decomposer
decomposer -> primary producer

energy dissipates as it flows through system
all produce heat

Question 10

grazing vs decomposer food chain

Answer 10

difference in primary producer

Grazing: live plants
Decomposing: dead plants

Question 11

10% rule

Answer 11

generally 10% of energy is transferred among trophic levels

Question 12

biogeochemical cycle

Answer 12

paths that an element takes as it moves from abiotic systems through organisms and back again
- decomposition of detritus may limit how fast nutrients cycle through an ecosystem

Question 13

detritus decomposition rate depends on…

Answer 13

3 factors

1. ABIOTIC CONDITIONS (O2, temperature, precipitation)
2. QUALITY OF DETRITUS (as a nutrient source for fungi that accomplish decomposition)
3. ABUNDANCE + DIVERSITY of detritivores PRESENT

Question 14

abiotic factors effecting nutrient cycling

Answer 14

temperature + climate

• nutrients cycle faster in tropical wet forests (smaller organic matter layer)
• slower in cooler climates (larger organic matter layer)

Question 15

why is there more live biomass consumed alive in the ocean than on land?

Answer 15

?

Question 16

in what places on earth is NPP highest? lowest? why?

Answer 16

highest on land near the equator because there’s more light available to photosynthesize

lowest in the ocean because water absorbs light, less photosynthesis

Question 17

detritus

Answer 17

region in soil that contains waste and dead organisms

Question 18

sources of local nutrient import and export

Answer 18

1) rocks weather - ions released and at as nutrients
2) nutrients blow in on soil particles or as solutes in streams
3) carbon added when primary producers fix carbon
4) nitrogen added when nitrogen fixing bacteria N2 in atmosphere to usable N

Question 19

what is local nutrient import and export

Answer 19

nutrients constantly cycled within an ecosystem and can be exported to another
for an ecosystem to function normally, nutrients must be replaced

Question 20

major nutrient import/export agents and 4 major ways they can be replaces

Answer 20

export: farming, logging, burning, soil erosion

1) ions released as rocks weather
2) nutrients arrive on soil particles in wind or solutes in streams
3) carbon added when primary producers fix carbon via photosynthesis
4) nitrogen added when nitrogen fixing bacteria convert N2 into usable nitrogen

Question 21

explain the global water cycle and human’s impact on it

Answer 21

1. Ocean evaporation + precipitation
   - more evaporating, net gain of water into atmosphere
2. Vapour moves over continents
   - joined by evaporation/precip cycles from lakes and water lost from plants
   - more precipitation than evaporation
3. Water moves back to oceans via streams and groundwater

*no net gains or losses of water *

HUMAN IMPACT: groundwater depletion, pavement reduces water percolation, agriculture lowers water holding capacity

Question 22

name global biogeochemical cycles

Answer 22

water, nitrogen, phosphorus and carbon cycles

Question 23

water numbers

Answer 23

97.5% water in ocean
2.5% freshwater in icecaps and glaciers
0.5% freshwater in lakes, rivers and groundwater

Question 24

different types of aquifers

Answer 24

layers of rock, sand or gravel saturated with water underground

closed: nonporous rock above
open: can be recharged with water from above

Question 25

explain global nitrogen cycle and how human’s impact it

Answer 25

slow process that can stall primary productivity in terrestrial and aquatic ecosystems. N makes up over 70% of atmosphere.

1. Nitrogen fixation
   - atmospheric N converted to usable N via N-fixing bacteria and lighting
2. Biologically active reservoirs: aquatic and terrestrial organisms
   - plants and water cycle nitrogen back into soil
3. bacteria metabolize N and convert it back to atmospheric N

HUMAN IMPACT: crops that harbour N-fixing bacteria, fertilizers (causing eutrophication and O2 dead zones, reduces biodiversity), burning fossil fuels that release nitric oxide

Question 26

explain global phosphorus cycle and human’s impact on it

Answer 26

• main source of P in earth’s crust, slowly metabolized by rock weathering
• mining and fertilizing increase amount of P, often causing eutrophication

Question 27

explain the global carbon cycle and human’s impact on it

Answer 27

Photosynthesis and cellular respiration cycle with atmospheric carbon (small amount) in oceans and on land (2 natural reservoirs)

HUMAN IMPACT: deforestation and burning fossil fuels releases stored carbon

Question 28

define global warming vs global climate change

Answer 28

warming: avg temp increasing
climate change: sum of all changes in local temperature and weather patterns caused by global warming

Question 29

define the greenhouse effect, greenhouse gas

Answer 29

greenhouse gas: atmospheric gas that absorbs and reflects infrared radiation. heat radiated from earth retained instead of going out to space.
- CO2, methane, water vapour, nitrous oxides

greenhouse effect: selective energy absorption by greenhouse gases, letting short wave light out but keeping long waves infrared energy in and heating earth

Question 30

explain connection between solar energy cycles and climate change

Answer 30

• solar energy cycles show no net increase, so they can not explain global warming
• carbon dioxide and temperature levels are increasing steadily, showing that C02 and greenhouse effect contributing to global warming, not solar energy

Question 31

why is Co2 rising so rapidly?

Answer 31

population size and resource use (fossil fuels)

Question 32

effects of average temperature increase on climate

Answer 32

• polar regions warming more than tropics
• different latitudes experience different degrees of climate changes

in short, A MESS

Question 33

climate change and impacts on water cycle

Answer 33

• higher temps change when, where and how water falls
• major oceanic currents and upwelling change
• some soils gain moisture, others drier (more fires, floods, erosion)

Question 34

positive and negative feedback loops

Answer 34

positive increases climate change, negative reverses

examples of positive:

FOREST: warmer and drier -> fires -> release carbon -> more warming

TUNDRA: warming -> increased decomposition rates (when usually low) -> release carbon -> more warming

OCEAN: polar caps melt -> more open water -> less reflection of solar radiation -> more warming

release of more potent greenhouse gasses

Question 35

biological effects of climate change

Answer 35

• geographic regions shift
• phenology shifts (change in timing of seasonal events such as migration)
• evolutionary adaptation (allele frequency shifts)
• extinctions
• ocean acidification (more C02 dissolving in oceans means more carbonic acid)

Question 36

effect of climate change on NPP

Answer 36

LAND: warming and drying areas in Southern Hemisphere lose NPP, cancel out gains in NPP in northern hemisphere

OCEAN: currents not string enough to move dense water to top of ocean through increased density gradient (water stratification), limiting nutrients available

Question 37

explain water stratification and effects from climate change

Answer 37

currents cycle nutrients in the water, bringing them up from the bottom.

when surface water is warmer there is a steep density gradient and currents can’t move nutrients past it