Ecosystems and Communities Notes

Communities and Ecosystems

• Community: All the populations occupying the same area at the same time.
• Ecosystem: A community and its abiotic environment.

Community Diversity

• Defined as the diversity in a community.
• Factors:
  • Number of species (species richness).
  • Number of individuals in each species (species abundance).
• Example: Community 1 is more diverse because species are equally abundant, even with the same species richness.

Interspecific Interactions

• Interactions among species in a community.
• Types:
  • Interspecific competition.
  • Predation.
  • Symbiotic relationships.

Interspecific Competition

• Competition between species.
• Habitat: The place an organism lives in.
• Niche: Its way of life.
• Competitive Exclusion Principle: Two species can occupy the same habitat but not the same niche.

Predation

• Predator adaptations: Claws, teeth, fangs, stingers, speed, hunting strategies.
• Prey Adaptations:
  • Active defense strategies: Prey actively attack predator to drive it away (e.g., mobbing).
  • Passive defense strategies: Warning and cryptic coloration; mimicry.

Mimicry

• The resemblance of one organism to another for concealment or protection from predators (mimic and model).
• Types:
  • Batesian: Mimic is palatable, model is unpalatable. (Eastern Coral Snake (venomous) & Scarlet King Snake (non-venomous))
  • Mullerian: Both model and mimic are unpalatable and use the same coloration to reinforce the warning signal. (Monarch & Viceroy)

Herbivory (+/-)

• Interaction between two species which is beneficial to one (herbivore) and harmful to the other (plant).
• Examples: Opium poppy, tobacco plant, clove plant, cinnamon.

Symbiotic Relationships

• Interaction between two species where one organism (symbiont) lives in another organism (host).
• Types:
  • Mutualism (+/+): Both host and symbiont benefit. (Acacia and stinging ants, Bees and flowers, Birds and plants, Lichens - algae and fungi)
  • Commensalism (+/0): One benefits, the other is not affected. (Barnacles and whales, Remora fish and whale shark, Plants and animals)
  • Parasitism (+/-): One benefits (parasite), the other is harmed (host). (Tapeworm, Head louse, Mosquito)

Ecological Succession

• The process of biological community change resulting from a disturbance.
• Disturbances: Storms, floods, fires, volcanic activity, hurricanes, droughts, human activities (deforestation, pollution, overgrazing).
• No community is at equilibrium or is stable.
• Types:
  • Primary: Entire community wiped out; no soil is left behind. (Barren landscape after glacial retreat; Moss and lichen stage; Moss, grass, shrubs, and trees (alders and cottonwoods) covering newly formed soil; Spruce coming into the alder and cottonwood forest; Spruce and hemlock forest.)
  • Secondary: Entire community wiped out, but soil is left intact. (1st year remains of corn plants seen, 2nd year wild grasses colonize the area, 5th year, mature grasses. Sedges also colonize the area 10th year. Goldenrod plants, shrubs, small eastern juniper trees 20th year. juniper trees are mature; birch and maple trees also grow here.)

Ecosystem Dynamics

• Ecosystem: A community and its abiotic environment.
• Community: All populations occupying the same area at the same time.
• Population: A group of individuals belonging to the same species occupying the same area at the same time.

Trophic Relationships:

• Feeding or nutritional relationships among species in an ecosystem.
• Demonstrate energy flow through the ecosystem.
• Demonstrate how chemical elements are recycled in an ecosystem.

Trophic Levels

• Producers: Autotrophic organisms (self-nourishing). (Terrestrial: Green plants; Open ocean: Phytoplankton; Shallow waters: Algae; rooted green plants)
• Consumers: Heterotrophic organisms.
  • Primary consumers (herbivores): Eat the producers.
  • Secondary consumers (carnivores): Eat the primary consumers.
  • Tertiary consumers (carnivores): Eat the secondary consumers.
• Decomposers or detritivores: Organisms that decompose dead producers and consumers. (detritus- disintegrated matter)

Food Chain

• The succession of organisms in an ecological community that shows the flow of energy from one organism to another.

Food Web

• A complex of inter-related food chains.

Energy Flow in an Ecosystem

• Energy is not recycled.

Trophic Pyramid

• A diagrammatic representation of an ecosystem based on different trophic levels.
• Only 10% of the energy is transferred from one level to the next. 90% is lost as heat.

Ecosystem Survival Needs

• Energy flow and chemical cycling.
• Solar energy, inorganic nutrient pool, producers, consumers, decomposers.

Biogeochemical Cycles

• The transport of chemical elements through the earth and the biotic component of the ecosystem.

Carbon Cycle

• Reservoir of carbon: atmosphere
• Importance: Burning, CO_2 in atmosphere, Cellular respiration, Wood and fossil fuels, Decomposition, Photosynthesis, Higher-level consumers, Primary consumers, Plants, algae, cyanobacteria, Wastes; death, Plant litter; death, Decomposers (soil microbes), Detritus

Nitrogen Cycle

• Nitrogen-fixation: Conversion of atmospheric nitrogen into ammonium salts.
• Nitrification: Conversion of ammonium salts to nitrates.
• Denitrification: Conversion of soil nitrates to atmospheric nitrogen gas.
• Reservoir: atmosphere and soil. Bacteria play an important role
• Nitrogen fixing bacteria: Found in the soil; also found in the root nodules of legumes (peanuts, beans, peas, lentils).
• Nitrifying bacteria: Found in the soil.
• Denitrifying bacteria: Found in the soil.

Phosphorus Cycle

• Involves the cycling of phosphorus through rock, soil, water, and organisms.

Water Cycle

• Precipitation: Conversion of water vapor gas to liquid water.
• Evaporation: Conversion of liquid water to water vapor gas.
• Transpiration: Loss of water from the leaves to the atmosphere.
• Condensation: Conversion of water vapor gas into liquid water.
• Precipitation: Rain, sleet, hail, snow.
• Runoff: Flow of water above ground.
• Percolation: Sinking of water into the ground to form ground water.
• Aquifer: Cracks in rock underground that hold water.

Human Impact on the Environment

• Introducing non-native species.
• Impacting biogeochemical cycles.
• Releasing toxic chemicals into ecosystems.
• Impacting climate.

Introduced Species

• Species intentionally or accidentally introduced into a new geographic location.
• Examples: Northern snakehead fish, Kudzu plant, European starlings, Argentine ants, Zebra mussels.

Impact on Biogeochemical Cycles

• Carbon Cycle: Indiscriminate burning of fossil fuel leading to global warming. (The warming of Earth’s atmosphere by trapping heat radiated out to space.)
• Nitrogen Cycle: Drinking water supply contamination; Water bodies become hypoxic (low in oxygen); Algal blooms (excessive growth of algae).
• Phosphorus Cycle: Excessive use of fertilizers and pesticides leading to hypoxic water bodies.
• Water Cycle: Cutting of trees (no transpiration - no water vapor - no clouds - no rain); Depletion of ground water supply.

Release of Toxic Chemicals

• Biodegradable matter: Matter that can be broken down by bacteria.
• Non-biodegradable matter: Harms the environment. (Eg: DDT (dichloro diphenyl trichloro ethylene) used as a pesticide for mosquitoes. Eg: PCB (poly chlorinated biphenols) used in flame retardants)
• Biomagnification: The increase in the concentration of a substance in the tissues of organisms as it is passed up a food chain. ((10X1000) = 10,000 units in 1 bird; (10X100) = 1000 units in 1 big fish; (10X10) = 100 units in 1 small fish; (10X1) = 10 units in 1 zooplankton; 1 unit in 1 phytoplankton)

Impact on Climate

• Global warming: Increased evaporation - increased precipitation; Causes more erosion in deforested areas leading to desertification.
• Depletion of the ozone layer: CFC (Chlorofluro Carbons) used in refrigeration and as propellants in aerosol cans leading to Skin cancer, Cataracts, Immune system deficiencies, Reduced crop yield, Kills off bacteria.

Effects of UV Radiation

• Skin cancer
• Cataracts
• Immune system deficiencies
• Reduced crop yield
• Kills off bacteria

How is Ozone in the Ozone Layer Depleted?

• By CFCs (used as coolants in refrigeration and propellants in aerosol cans)
• Chlorofluro Carbons

CFC Usage

• Used as foaming agents in styrofoam packaging
• Used as sterilant to sterilize surgical instruments
• Used in solvents that clean electrical components
• Used for making semi conductors- the building block of the electronic industry

Human Impact on Biodiversity

• Why do we need biodiversity? For food, clothing, shelter, medicines, oxygen.
• How are we causing extinction of species? By destroying habitats; introducing foreign species; overexploitation.
• THE SINGLE GREATEST THREAT TO BIODIVERSITY IS HABITAT DESTRUCTION.

Causes for Loss of Biodiversity

• Habitat Loss
• Alien Species
• Pollution
• Overexploitation
• Disease

Effects of organisms death

• Genetic diversity decreases
• Causing populations to become genetically homogenous
• A genetically homogenous population is less able to evolve to a changing environment and can go extinct

Habitat Destruction

• Leads to fragmented populations (populations split into subpopulations)
• Source Habitat: High quality; Abundant food and space; Birth rate exceeds death rate; Species flourish.
• Sink Habitat: Low quality; Not abundant food and space; Death rate exceeds birth rate; Go extinct.
• More sink habitats than source habitats on Earth today

Edges and Corridors

• Edge: Region where one ecosystem ends and another begins. (Eg: cowbird)
• Corridors: Regions that connect isolated habitats

Conservation Biology

• The branch of biology that deals with the conservation of plants and animals
• Biodiversity “Hot spots”: Small areas that exhibit exceptionally high species diversity. Eg: Amazon rain forest, Chaparral
• Zoned reserve: is land that includes areas undisturbed by humans