Transcript Inquiry into Life, Eleventh Edition

Honors Biology
Chapter 34
Nature of Ecosystems
John Regan
Wendy Vermillion
34-1
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
34.1 The biotic components of
ecosystems
• Populations of an ecosystem
– Autotrophs- primary producers
• Require an energy source and inorganic nutrients to produce
organic food molecules
• Manufacture organic nutrients for all organisms
• Green plants and algae-photosynthesis
• Bacteria-chemoautotrophs
– Heterotrophs- consumers
• Consume organic nutrients
– Herbivores, carnivores, omnivores
• Decomposers- fungi, bacteria
– Break down decaying matter releasing nutrients
– Detritus- partially decomposed matter
– Detritivore-eats detritus
34-2
Biotic components
• Fig. 34.1
34-3
The biotic components of ecosystems
cont’d.
• Energy flow and chemical cycling
– Energy enters ecosystem in the form of sunlight absorbed by
producers
– Chemicals enter when producers absorb inorganic nutrients
– Producers then make organic nutrients for themselves and all
other organisms in the ecosystem
• Consumers (herbivores and omnivores) gain nutrients and energy
from eating producers
• Higher level consumers (carnivores) then gain nutrients and energy
from eating herbivores and omnivores
– Some energy is released at each level to the environment in the
form of heat and waste products
34-4
Energy flow and chemical cycling
• Fig. 34.2
34-5
Energy balances
• Fig. 34.3
34-6
The biotic components of ecosystems
cont’d.
• The following two slides illustrate food webs
– Food webs illustrate the interrelationships between organisms in
the food chain
– Identify the producers, primary consumers, and secondary
consumers
• Laws of thermodynamics
– First law- energy is neither created nor destroyed
• Ecosystems depend on continual outside source of energy
– Second law- with every transformation, some energy is given off
as heat
• The amount of available energy at each successive trophic level is
less than the one below it
34-7
Grazing food webs
• Fig. 34.4
34-8
Detritis food web
• Fig. 34.5
34-9
34.2 Energy flow
• Trophic levels
– Trophic level is composed of all organisms that feed at a
particular link in the food chain
• Primary producers- first trophic level
• Primary consumers- second trophic level
• Secondary consumers- third trophic level
• Ecological pyramids- diagrams of the community
– Represent amount of available energy in each trophic level
– Producers are at the base- the most available energy
• Energy is given off in less usable forms as producers are eaten by
primary consumers, etc.
– Numbers, biomass, or energy
– Biomass- the number of organisms at each level multiplied by
their weight
34-10
Ecological pyramid
• Fig. 34.6
34-11
34.3 Global biogeochemical cycles
• Biogeochemical cycles
– Pathways involve both biotic and abiotic components
• Reservoir-source unavailable to producers
• Exchange pool-source from which organisms take chemicals
• Biotic community-chemicals move through community along food
chains
– 2 main types of cycles
• Gaseous cycle-drawn from and returns to the atmosphere
• Sedimentary cycle-element is drawn from soil by plant roots, eaten
by consumers, returned to soil by decomposers
34-12
Model for chemical cycling
• Fig. 34.7
34-13
Global biogeochemical cycles cont’d.
• The water cycle
–
–
–
–
Freshwater evaporates from bodies of water
Precipitation over land enters ground, surface waters, aquifers
Eventually returns to oceans over time
Hydrologic cycle is illustrated on the following slide
• Note that size of arrow is proportional to rate of transfer
– Human impact
• In arid southwest and southern Florida, water mining is occurring
– Aquifers are being drained faster than they can be
naturally replenished
34-14
The hydrologic cycle
• Fig. 34.8
34-15
Global biogeochemical cycles cont’d.
• The phosphorus cycle
– Phosphate enters soil as rocks undergo weathering process
– Picked up by producers and cycles through consumers and
finally decomposers
– Human impact
• Accelerated transfer rate due to phosphate mining, supplementation
on farm fields, detergents
– Cultural eutrophication- over-enrichment
» Can lead to increased algal bloom
» As algae die off, decomposers consume high levels of
oxygen in the water
» Results in massive fish kills
– Phosphorus cycle is illustrated on the following slide
34-16
The phosphorus cycle
• Fig. 34.9
34-17
Global biogeochemical cycles cont’d.
• The nitrogen cycle
– Nitrogen fixation-conversion of nitrogen gas N2 to ammonium
NH4+ by bacteria
– 78% of atmosphere is nitrogen gas, but unusable by
plants
– Root nodules of legumes house nitrogen-fixing bacteria
– Nitrification-production of nitrates which plants can also use
• Nitrogen gas converted to nitrate in atmosphere by lightning
• Ammonium in soil converted to nitrate by nitrifying bacteria
– Nitrite bacteria ammonia →nitrite (NO2-)
– Nitrate bacteria nitrite → nitrate (NO3-)
– Denitrification-conversion of nitrate back to nitrogen gas by
denitrifying bacteria
– Human activities- N2 from fertilizers increases transfer rates
34-18
The nitrogen cycle
• Fig. 34.10
34-19
Global biogeochemical cycles cont’d.
• The carbon cycle
– Photosynthesis takes up carbon dioxide from the atmosphere
– Cell respiration returns it to the atmosphere
– Reservoirs of carbon
• Dead organisms- fossil fuels
• Forests
– Human activities
• More carbon dioxide is being deposited in atmosphere than is being
removed
– Due to deforestation and burning of fossil fuels
• Increased carbon dioxide in atmosphere contributes to global
warming
34-20
The carbon cycle
• Fig. 34.11
34-21
Ozone
• O2 → O 3
•
•
•
•
Oxygen is converted into ozone in atmosphere by UV rays
Also by lightning and industry
Ozone in lower atmosphere –air pollutant
In stratosphere- blocks UV rays
•
•
UV rays cause sunburn, skin cancer, cataracts, slows growth of plants
Ozone has been depleted
– 10% ↓ ozone, 26% ↑ cataracts, skin cancer
– Cause of ozone depletion- Chlorofluorocarbons (CFCs)
– CFCs banned 2000
34-22