ECOSYSTEM
Ch 29 – 30
BIO 100
•
•
•
What is an Ecosystem?
Ecosystem is a self-sustaining, self-regulating community of plants and animals within a defined
area along with their nonliving environment (sunlight, air, water, land).
Habitats in the ecosystem interact with one another and the physical environment in which they
are dependent.
It sustains itself through energy flow and nutrients.
Ecosytems
• There are 3 Major classes of ecosystems
• Freshwater Ecosystems
• Terrestrial Ecosystems
• Marine Ecosystems
Fresh Water Ecosystems
There are three basic types of freshwater ecosystems:
• Lentic: slow-moving water, including pools, ponds & lakes.
• Lotic: rapidly-moving water, like streams & rivers
• Wetlands: areas where the soil is saturated for at least part of the time (swaps)
•
Lentic lakes are classified by nutrient content
– Oligotrophic lakes – low in nutrients, clear, with extensive light penetration; fed by mountain
streams that carry little sediment nutrients.
– Eutrophic lakes – receives large amts. of sediments, organic & inorganic nutrients from its
surroundings to support a dense community (like murky waters with poor light penetration)
– Envn, threats: eutrophication by human activity
• Water becomes rich in nutrients from fertilizers or sewage, and encourage the growth and
decomposition of oxygen-depleting plant life, results in harm to other organisms
•
•
•
•
Lotic lakes are fast moving, turbulent water
Contains greater concentrations of dissolved oxygen
Food base of streams derive from the trees and fishes
Environmental threats to rivers: loss of water, dams, chemical pollution and introduced species
•
•
•
•
Wetlands are the most productive natural ecosystems because of the proximity of water and soil
Dominated by vascular plants that have adapted to water-saturated soil
Used for agricultural purposes – drained & dyked to convert into dry lands
Environmental threats: human development & settlement
Life Zones of a lake
Shallow waters rooted with plants where algae, bacteria, insects
larvae, crustaceans, snails, worms, frogs, minows turtles & snakes.
Photosynthesis supported, no plants, nonphotosynthetic protist
Deep waters, insufficient photosynthesis support, oganisms nourish
by detritus falling from the zones above – decomposers, detritus
feeders bacteria, snails, scavengers
Terrestrial Ecosystems: Biomes
• Earth is divided into different geographic areas called biomes
• A biome is a terrestrial ecosystem that occupies an extensive geographical area,
characterized by a specific type of community (desert)
• Biomes have similar climate conditions and ecosystems
• The location of the 8 major types of biomes depends on the latitude of the area,
and amount of precipitation
Tropical Rain Forrest
• Precipitation - 250cm – 400 cm/yr.
• Little temp.variation, evenly warm, abundant moisture, no dry seasons, near equator
• Contains more species than other biomes
• Amazon, Peru, Hawaii, Southeast Asia
Environmental threats:
• Deforestation caused by lumbering, ranching & farming
• As rain forest disappears, rainfall is reduced causing the region to become drier, stressed &
susceptible to fire.
• Threat to medicinal commercialism
Deciduous Forrest
•Further from equator; Rainfall not as constant; has both Wet & dry seasons
• Predominance of trees that shed their leaves at dry season
•woodEnvironmental
threats: Human colonization, wood harvest for timber & paper, building materials,
pulp
• About less that ¼ of the original forests remains
Coniferous Forrest
Taiga – known as the northern coniferous forest
• Coming from the cones• Precipitation: 50-200 cm/hr.
• Consist of trees that produce cones: Pines, Spruces & Cedars • Important biome for the
habitat of prized Christmas Trees
• Animal hibernate or migrate cold seasons
• Pacific Northwest, Sequoia Redwoods, Oregon, New Zealand, Colorado Rockies
Environmental threats:
• Storms & fires
• Deforestation, logging & lumber construction
• Human activities: recreation, camping
Savannas
•
•
•
•
Precipitation 90-150cm/yr.
Open, grassland, scattered trees, seasonal rainfall
Found to the north & south of tropical rainforest biomes
Parts of Africa, South America, Australia, Southern Appalachian
Environmental threats:
• Expanding human population threatening the wildlife
• Land used for cattle grazing
• Poaching (African elephant, black rhinoceros)
• Built fences disrupt the wildlife herd migration
Desert
•Dry lands
•Precipitation: 25-50cm/yr.
• Drought-resistant
• Environmental threats: fragile ecosystem, destroyed by off-road vehicles – soil
erosion, desertification – the spread of dessert by overgrazing & human activities
•Defined by lack of water rather than temp.
•Land appears devoid of life
• Widely spaced vegetation with large areas of bare ground – cacti & succulents
• Annual wild flowers after a rainfall
Environmental threats: fragile ecosystem, destroyed by off-road vehicles – soil
erosion, desertification – the spread of dessert by overgrazing & human activities
Chaparral
•
•
•
•
Precipitation: 75 cm/yr.
Coastal regions that border on desert; Wet winters, dry summers; Hardy shrubs, small trees or
large bushes
So. Cal., (Like San Diego area), Mediterranean regions
Envn. threats: summer fires started by lightning
Grasslands (Prairie)
•
•
•
Precipitation: 25-75 cm/yr.
Continuous grass cover with no trees
Two types of grasslands:
– Tall-grass, (humid & very wet)
– Short-grass (dry – summers; cold – winters).
• Grasses survive fires because the root systems survive, they grow from the bottom
instead of the top
Environmental threats:
• Land plowing, • Agriculture • Cattle overgrazing • Grasses replaced by cool desert plants
•
•
•
•
•
•
Tundra
Open; wind swept; dry; ground always frozen
Polar ice cap and the vast treeless region bordering the Artic Ocean
Severe living conditions: - 40 °F or below
30-60 mi/hr. howling winds
Precipitation: 25cm or less “frozen dessert”
Envn. threats: human activitiss that scar the land for centuries, drilling sites,
pipelines, mines, & military bases
• Tundra is the most fragile biome – slow to recover damage or disturbances
• Far northern Asia; Northern North America
Marine Ecosystem
Costal waters- ocean habitat
• Intertidal zone
• Nearshore zone – submerged area
• Plants & seaweed grow in the nearshore zone
• jelly fish, sea urchins, sea stars, snails, mussels, sea otters, annelid worms
• open ocean: bays & salt marshes for breeding grounds for crabs, shrimp, fish, kelp
• Environmental threats: Human activities, water recreation, mineral & oil fuel extraction from
organisms living in the ocean
• Coast development & increase population
Coral Reefs
•
•
•
•
•
Exist in warm tropical waters
Require wave actions & adequate ocean depth, light for photosynthesis, thrive on photic zone
Corals build reefs from their own calcium carbonate skeletons
Pacific & Indian Ocean, Carribean & Gulf of Mexico
Threats: Diminish photosynthesis – hinders coral growth, sewage, agricultural runoff, coastline
development6, land erosion (silt), overfishing – disrupts ecology, coral harvesting, bleaching,
human disturbances & global warming
Sustaining Ecosystems
•Ecosystems contain energy•Sunlight is the energy that powers life activities
•Solar energy is captured in the ecosystems
– transformed into chemical reactions
– converted into heat energy
– radiated back into the atmosphere
•Energy flows consistently through ecosystems: replenished from an outside source
•
•
•
•
•
Ecosystems contains nutrients
Elements that build and maintain life within that ecosystem
Nutrients are not replenished, they are re-cycled within the ecosystem
Photosynthesis – stores energy (sugar)
Autotrophs = (the produces of food) use nonliving nutrients & sunlight to produce food for
themselves and for other organisms. (plants, microorganisms)
• Heterotrophs = (consumers) cannot photosynthesize and acquire energy from the bodies of other
organisms (animals)
Grazing Food Webs - the food chain
Illustrates interelationships between organisms in the food chain
Identify the producers, primary consumers, and secondary consumers
Trophic levels
(Category of Organisms)
• Herbivores – (plant eaters) are the primary consumers (grasshoppers, giraffes)
• Carnivores – (meat eaters) are the predators that feed on primary consumers. (spiders, eagles, wolfs)
• Omnivores – (racoons, bears, rats, humans) are primary consumers. Can be secondary and tertiary
consumers at times.
Energy flow and chemical cycling
The Organization of Life: Ecosystems of the
Terrestrial and Marine
Biotic components of ecosystems
•
•
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 level is less than the one below it
Energy flow and chemical cycling
– Energy enters ecosystem in the form of sunlight, absorbed by producers
– Chemicals enter when producers absorb inorganic nutrients
– Produces then make organic nutrients for themselves and all other organisms in the ecosystem
– Some energy is released at each level to the environment in the form of heat and waste products
Detritus Feeders
•
•
•
•
•
The decomposers
Small, unnoticed animals (protists) that live on the refuse of live
Feed on leaves, dead organic matter, waste, molted exoskeleton – stored energy is extracted
Worms, centipedes, insects, pillbugs, nematodes, vultures – scavengers
Fungi & bacteria
•
•
•
Inorganic Nutrients
Macronutrients: carbon, nitrogen, phosphorus, sulfur &calcium
Micronutrients: zinc, iron, iodine, molybdenum, selenium
Nutrients move from its reservoir (usually a nonliving portion of the ecosystem) through the living
portion of the ecosystem and back to the reservoir.
Resources (required by Humans and habitats of ecsystems
BioSphere
Diverse Ecosystems
Ch 30 - BIO 100
•
Human use of resources
– Resource- biotic or abiotic factor that helps meet basic needs
• Nonrenewable resource- limited in supply
– Amount of land; Fossil fuels
• Renewable resource- not limited, but must not be wasted
– Water; Solar energy; Plants and animals for food
– Pollution- side effect of resource use
– Human impact is proportional to size of population
Human use of resources
– Beaches - human habitation effects
• Leads to erosion and loss of habitat for marine organisms
• Erosion
– 70% of world’s beaches are eroding
– Often result of human factors, construction --- causes also due to Global warming
• Coastal pollution
– Toxic substances travel downstream to sea
Human use of resources
•
•
•
•
•
•
•
•
•
Land
– Semi-arid lands and human habitation
• Desertification- degrading a once-fertile land
– From overgrazing by livestock
– Tropical rainforest and human habitation
• Deforestation- causes loss of soil nutrients and fertility
– Danger of desertification
• Loss of biodiversity
Human use of Water Resources
Most water worldwide is used in agriculture and industry, and not for drinking
– Irrigation-intensive agriculture 40% of world’s food crops
– Dams - 45,000 dams worldwide trap 14% of all precipitation runoff
• Disrupt flow of rivers- many barely reach sea
• Disadvantages to dams
– Evaporation and seepage into ground rock
– Increases concentration of salt from evaporation can make downstream water unusable
– Silt buildup decreases reservoir size
Aquifers (rock layer that contains water)
– Hold 1000 times as much water
– People are tapping into aquifers as a source of water
Environmental consequences
– Sinkholes - settling of soil as it dries out from lack of groundwater
– Saltwater intrusion- as water table lowers, sea water can back up into streams and rivers
– Reduces supply of freshwater along the coasts
Conservation of water
– Planting drought-resistant and salt-tolerant crops
– Drip irrigation
• Saves 50% over traditional methods
• Used on < 1% of irrigated land
– Governments subsidize irrigation so farmers have little incentive to use drip irrigation
By using conservation methods and reusing water, we can help the world’s industries cut water
demands by MORE THAN HALF
Human use of Food Resources
6 billion people on Earth - only enough food to provide 2,500 calories per person per day
Food comes from growing crops, raising animals, and fishing
Biggest increase in food production comes from modern farming methods- (include some harmful
practices)
• Heavy use of fertilizers, herbicides, pesticides- kills desirable species and causes pollution
• Generous irrigation- consumes water
• Excessive fuel consumption
Human use of Food Resources (continue)
•
•
•
•
•
•
•
•
– Soil loss and degradation
• Loss of topsoil
• Single row crop planting
• Salinization
Genetic engineering - produces transgenic herbicide & drought resistant plants
Domestic livestock – 2/3 of cropland is used to grow feed
Fisheries - impacts biodiversity as “undesirable” because other marine organisms are caught in
fishing nets
– Annual world’s shrimp fishery yields 1.8 million tons of fish; 9.5 million tons
of other animals are caught in the nets and destroyed
Energy - nonrenewable sources
– 6% of world’s energy comes from nuclear power
• Concerns: possible meltdown, disposal radioactive waste on our land
• Fossil fuels and global climate change
– Greenhouse gases- CO2, methane
– Do not allow infrared heat to escape back into space
– Global warming effect
Recycling of Nutrients Within the Ecosystem
How do Nutrients move within the ecosystem?
– Macronutients (C, H, O2, N, P, Ca, S)
– Micronutrients (Zn, Fe, I, Se, Mo)
• Recycling – Biochemical Cycles
Pathway of substances moving through communities to nonliving portions of the ecosystems
Accumulate in reservoirs and then return to the communities
Global biogeochemical cycles
• Reservoir - source unavailable to producers
• Biotic community- chemicals move through community along food chains
• Gaseous cycle - drawn from and returns to the atmosphere (evaporation)
• Sedimentary cycle - element is drawn from soil by plant roots, eaten by consumers, returned
to soil by decomposers
The water cycle (like a hydrologic cycle)
– Freshwater evaporates from bodies of water
– Re-enters the ground, surface waters, aquifers through precipitation
– Eventually returns to oceans over time
•
•
•
– Human impact
• water mining causes aquifers to drained faster than they can be naturally replenished
The phosphorus cycle
– Phosphate enters soil as rocks undergo weathering process
– Picked up by producers and cycles through consumers and finally decomposers
– Human impact – eutrophication - over-enrichment
• Can lead to increased algal bloom
• As algae dies, decomposers consume high levels of oxygen in the water
• Results in massive fish kills (Salton Sea)
The nitrogen cycle
– Nitrogen fixation-conversion of nitrogen gas (N2) to ammonium NH4+ by bacteria
• 78% of atmosphere is nitrogen; but unusable by plants
• Root nodules house nitrogen-fixing bacteria
– Nitrification-production of nitrates which plants can also use
– Denitrification-conversion of nitrate back to nitrogen gas by denitrifying bacteria
– Human activities- N2 from fertilizers increases transfer rates
The carbon cycle
– Photosynthesis takes up CO2 from the atmosphere
– Cell respiration returns it to the atmosphere
– Reservoirs of carbon include dead organisms (fossil fuels); Forests
– Human activities
• More CO2 atmosphere than is being removed
– Due to deforestation and burning of fossil fuels
• Increased CO2 in atmosphere contributes to global warming
•
•
Disruption of Carbon-Cycle Contributes to Global Warming
Atmospheric CO2 acts like glass in a green house by trapping heat
It allows solar energy to pass through to the earth’s surface but it’s absorbed & heated by
wavelength energy that radiates it back to the atmosphere
Greenhouse effect traps some of the sun’s energy as heat and keeps the Earth’s atmosphere warm
Greenhouse gases: methane, chlorofluorocarbons, nitrous oxide, water vapors
•
•
•
•
•
Global Warming Consequences
Melting of the polar ice cap/glaciers
Cause different weather patterns
Effect agriculture weather: (rainfall, dry or wet)
Forest growth will increase, but species distribution will change: disappearnce of the sugar maples
Migrating animals are changing thier migration ranges
•
•
•
Acid Rain & Global Warming
Disruption of the ecosystems caused by:
– Agriculture producing more waste nutrients
– Industrial processes that release toxic substances into the environment: lead, mercury, uranium,
•
oil, arsenic.
– Our use of fossil fuels used to supply heat, light, transportation and manufacturing.
These have disrupted the natural cycles of carbon, sulfur & nitrogen causing acid rain & global
warming.
Working toward a Sustainable Society
Today’s society is not sustainable because:
– Considerable portion of land is used for human purposes
– Agriculture requires large amts of nonrenewable resources
– ½ of the agricultural yields (U.S.) goes toward feeding animals
• Takes 10 lbs. of grain to make 1 lb. of meat
– We are running out of available fresh water
– We are using more nonrenewable fossil fuels
• Global warming, acid precipitation, smog
– Use of nonrenewable minerals for manufacturing products are causing pollution
•
•
•
•
•
Human use of resources
Minerals – are depleting at a rapid rate
– No recycling done at any step in the production process
– Strip mining
• Leaves land void of vegetation and top soil
• Toxic wastes washes into streams and rivers
• Law now requires reclamation of land
• Heavy metals- dangerous to human health
– Lead, arsenic, cadmium, tin, chromium, zinc, copper
– Found in batteries, paints
Example: Modern mining capabilities
Synthetic organic compounds
– Halogenated hydrocarbons- halogens (chlorine, bromine, fluorine) have replaced hydrogen in
chemical structure
• Thins the ozone shield, increases solar radiation
– The use of many pesticides - DDT
Wastes - Sewage
– Raw sewage depletes oxygen levels in lakes and rivers
– Feces can contain human pathogens- cholera, typhoid fever, dysentery
Treatment plants use bacteria to break down raw sewage
– Breaks down to inorganic nutrients- nitrates, phosphates
– Releases it into surface waters
Industrial wastes
• Biological/biohazard waste
• Humans are final consumers (chemicals in Human milk in some areas contains DDT, PCBs)
– Pollution control measures are the
best way to address the problem.
Impact on biodiversity
•
Habitat loss
– Most frequent cause of extinction
– Has occurred all over biosphere
– Big concerns are focused on tropical rain forests and coral reefs
• Alien species - Nonnative to the ecosystem
– Introduced by
• Colonization by Horticulture and agriculture
• Accidental transport
Impact on biodiversity
• Pollution is causing Ozone depletion
• Release of CFCs causes ozone shield to break down
• Impairs growth of crops and trees growth
•Disease
–Wildlife exposed to new diseases and to human encroachment
–Zoo animals
Alien species
Impact of Global Warming on Coral Reefs
What Can You Do?
• Use fuel-efficient vehicles, car pool
• Conserve electricity – power plants emit CO2, Sulfur dioxide, nitrogen oxides
• Use efficient appliances, solar energy features added to homes, insulation & weatherproofing,
planting trees, reduce heat & A/C, turn off unused lights, computer – line dry clothes
• Recycle – 95% energy used to produce an aluminum can from raw materials
•
•
Human use of resources
2 types of Energy commonly used - renewable energy sources
– Hydropower - small dams vs. large dams
– Geothermal power - from radioactive decay of elements
Other types may be used more in the future
– Wind-generated
– Solar power