It Sustains Itself Through Energy Flow and Nutrients

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

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

• Environmental threats: Human colonization, wood harvest for timber & paper, building materials, wood pulp

• About less that ¼ of the original forests remains

•

Coniferous ForrestTaiga – 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

BioSphereDiverse EcosystemsCh 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