Ecology

Outline

• Regional Issues• Populations• Communities• Ecosystems• Organism Interactions• The Water Cycle• Nutrient Cycles• Succession• Global Concerns

Ecology:

Is the study of relationships of organisms (microorganisms, plants, and animals) to one another and their environment.

Regional Issues

• Acid Deposition Burning fossil fuels releases sulfur and

nitrogen compounds into the atmosphere.- Chemical reactions with sunlight and

rain convert the compounds into nitric acid (HNO3) and sulfuric acid (H2SO4).

Adversely affects living organisms. Tree loss

Accelerates weathering

Regional Issues

• Water Contamination Surface Water Contamination

- Runoff From Polluted Areas- Pesticide Spraying- Engine Exhaust

Ground-Water Supplies- Pesticides- Septic Tanks- Fertilizers

Regional Issues

• Wetlands Wetlands have historically been regarded

as wastelands and routinely drained and converted to agricultural land.

One hectare of a tidal wetland can perform the same recycling functions as approximately $150,000 of the latest wastewater treatment equipment.

- Also provide habitat for a wide variety of wildlife.

Regional Issues

• Hazardous Waste Earlier generations routinely disposed of

toxic industrial wastes in a casual fashion.- Even under strict modern rules, serious

accidents and spills occur. At most solid waste dumps, it is now

illegal to dispose of almost any form of hazardous material.

Global Concerns

• Many problems are global in scope and have long-lasting impacts. Stratospheric Ozone Depletion Climate Changes Loss of Biodiversity

Populations

• A population is defined as a group of individuals of the same species inhabiting the same area at the same time. Important characteristics:

- Population Size: biologists estimate population size by

counting total number of individuals or by estimating the # of individuals per unit

volume (density) or by estimating the total biomass (total mass of

individuals present) if the individuals have different sizes or unevenly distributed

- Population Density - Genetic Diversity

Communities

• Communities are composed of populations of many species living together in the same location at the same time. Similar communities occur under similar

environmental conditions.- Composition can vary considerably from

one location to another. Ecotones - Transitions between

communities.

Ecosystems

• Ecosystems are composed of all the communities and their associated physical environments, including the physical, chemical, and biological processes. Ecosystems may sustain themselves

entirely through photosynthetic activity, energy flow through food chains, and nutrient recycling.

Ecosystems

• Producers are capable of carrying out photosynthesis and storing the energy produced. Primary consumers feed on producers.

- Secondary consumers feed on primary consumers, and / or producers.

• Decomposers break down organic material to forms that are released back into the ecosystem for reassimilation by other organisms.

• A food chain consists of primary producers, primary consumers, secondary consumers, and finally decomposers. Energy flows through a food chain starting from primary producers all the way up to secondary consumers.

Ecosystems

• Interlocking food webs determine the flow of energy through the different ecosystem levels. Food web made up of interlinking food

chains.

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Ecosystems

• Only about 1% of the light energy falling on a temperate zone community is involved in the production of organic material. In general, only about 10% of the energy or

biomass from one level in a food chain, (trophic level) is transferred to the next level.

- Consequential sharp reduction in the number of individuals at each level of the food chain.

- A vegetarian diet makes more use of solar energy than diets containing meats.

Energy Pyramid

Organism Interactions- Secretion of chemical substances:• Some plants secrete herbicidal substances.

Roots of black walnut trees produce a substance that wilts tomatoes and potatoes and inhibits apple trees from growth.

• Many plants produce phytoalexins, an inhibitor for the growth of disease-causing fungi and bacteria, making them resistant to various diseases.

• Some bacteria and fungi produce various inhibitory chemicals that limit plant growth.

Organism Interactions- Parasitism:• The snapdragons lack chlorophyll and rely on their

flowering host for obtaining energy and food.

- Mutualism (exchange benefits):• Mycorrhizal Fungi associated with plant roots.

Fungi obtain energy from the plants and in return they increase the surface area of the roots and thus help plants absorb more nutrients.

• Acacia plants attract ants to live in their hollow thorn. Ants obtain sugars from the nectaries and in return attach any insect that come in contact with Acacia.

• Herbivores and plants involved in co-evolution.

Water Cycle

• Earth’s water is constantly being recycled. Amount remains relatively stable.

- Some percentage of rainfall percolates down through the soil to the water table, while other water is uptaken by plants, or evaporated back into the atmosphere.

- Water also evaporates from the soil surface, plants, animals, and the lower atmosphere.

The Water Cycle

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The Carbon Cycle• Carbon dioxide constitutes 0.037% of the

atmosphere. • Carbon dioxide needed for photosynthesis is

replaced by: - decomposers (decay bacteria and fungi replace 90% of carbon). Bacteria process carbon in a fashion that allows it to be recycled. Bacteria obtain energy from the molecules, and convert carbohydrates to carbon dioxide as a result of respiration.- Burning of fossil fuels has significantly increased the amount of carbon dioxide released into the atmosphere. May initially increase plant growth.

- Becomes limited by other growth factors.

The Carbon Cycle

The Nitrogen Cycle

• Most nitrogen in living organisms is in the protoplasmic proteins of their cells.

• Nitrogen gas constitutes 78% of the atmosphere. • Most of the nitrogen supply of plants is derived from

the soil in the form of inorganic compounds and ions taken in by the roots. Some nitrogen fixed by nitrogen-fixing bacteria.

Ammonia produced by the effect of decomposers is fixed by nitrogen fixing bacteria, either free in soil or in association with roots of legumes, to nitrite then nitrate (a form useful for plants).

The Nitrogen Cycle• Significant amounts of nitrogen continually lost from

our soils by harvesting crops, fires, leaching, or erosion of topsoil. Fire can cause serious loss of nitrogen.

• Farmers often add nitrogenous fertilizers to compensate for nitrogen loss, but organic matter must be added at the same time, otherwise a hardpan soil may eventually be created.

• In poorly aerated soils (flooded), denitrifying bacteria use nitrate instead of oxygen for their respiration and convert it to inert nitrogen adding to the depletion of soils from useful nitrate.

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Succession• During succession, plant species and other

organisms gradually alter their environment such that the changes begin to favor new, different species. New species eventually become the dominant

plant forms in the area.- Primary Succession – First time soil formation

on exposed rocks.- Secondary Succession - Disturbed areas

following fires, floods and landslides, start succession by establishing new vegetation. It is faster than primary succession. Grasses establish first followed by trees and shrubs.

Climax Vegetation - Stable plant associations

Succession

• Xerosere (terrestial)- Primary succession that begins with bare rocks and lava that have been exposed through glacial or volcanic activity, or through landslides.

Lichens Larger lichens Soil accumulates mosses establish ferns and seed plants.

• Hydrosere - Succession in wet habitats. May be accelerated by eutrophication.

- Enrichment from sediment or other runoff components.

Fertilizers, Detergents

Fire Ecology

• Natural fires, started primarily by lightning, have played a role in ecosystems for thousands of years. In the Western US, growth rings of

Ponderosa Pines show that in the past, forest burned on average of every 6-7 years.

- Trying to eliminate fires thus disrupts natural cycles, and resultant communities and ecosystems.

Fire Ecology

• Fires also play a role in forest composition. Many species repeatedly replace

themselves after fires.- Seeds of some species must be

exposed to fire in order to germinate.• Fires maintain grasslands by recycling dead

organic material, and by eliminating shrubs and woody species. Amount of biomass (energy allocation) in

above-ground structures.

Global Warming

• The Greenhouse Effect occurs because certain gases, greenhouse gases, allow sunlight to pass through the atmosphere, but trap the heat radiation given off after the ground absorbs the solar energy. Carbon Dioxide and Methane

- Act similar to the glass panels on a greenhouse.

Carbon Dioxide and Methane

• Burning of fossil fuels has two significant effects on the content of carbon dioxide in the atmosphere. Eliminates photosynthesizing organisms

that remove carbon dioxide from the atmosphere.

Releases carbon stored in the fossil fuels.• Swamps and wetlands release methane

produced by anaerobic bacteria.

Ozone Depletion

• Methane Gas and Chlorofluorocarbons (CFCs) are broken down in the atmosphere into active compounds. Destroy Ozone (O3) in the stratosphere.

- Helps block Ultraviolet (UV) radiation. Increased UV radiation linked to

increased skin cancers.• Halons (bromine-based cpmounds) are

reported to be 3-10 times more destructive than chlorofluorocarbons.

Loss of Biodiversity

• If natural habitats are destroyed at a rapid rate, many organisms may not be able to adapt quick enough to the changing conditions to survive. Extinction rates have greatly accelerated

over the past 50 years as humans have altered numerous ecosystems.

- Potential crop plants, and their as-yet -unknown benefits, are a serious casualty of the reduction in biodiversity.

Review

• Regional Issues• Populations• Communities• Ecosystems• Organism Interactions• The Water Cycle• Nutrient Cycles• Succession• Global Concerns

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