Ecology of Populations

Scope of Ecology

• Ecology - Study of the interactions of organisms with other organisms and the physical environment.– Habitat - Place where an organism lives.– Population - All the organisms within an

area belonging to the same species.– Community - All various populations

interacting at same locale.– Ecosystem - Community of populations.

Ecological Levels

Density and Distribution of Populations

• Population Density - Number of individuals per unit area or volume.

• Population Distribution - Pattern of dispersal of individuals within the area of interest.

Population Growth Models

• Exponential Growth– Number of individuals added each

generation increases as the total number of females increases.

Biotic Potential - Maximum population growth that can possibly occur under ideal circumstances.

Environmental Resistance - All environmental conditions that prevent populations from achieving biotic potential.

Logistic Growth

Carrying Capacity

• Carrying Capacity is the maximum number of individuals of a given species the environment can support.– The closer the population to the carrying

capacity, the greater the environmental resistance.

Biotic potential is having full effect and birthrate is a maximum during exponential growth.

Regulation of Population Size

• Density - Dependent Factors– Number of organisms present influences

the effect of the factor.CompetitionPredation

• Density - Independent Factors– Number of organisms present does not

influence the effect of the factor.Natural Disasters

Life History Patterns

• r - Strategists (Opportunistic)– Produce large numbers of offspring.– Small body size.– Early maturity– No parental care.– Density independent controls.– Good dispersers and colonizers.

Life History Patterns

• k - Strategists (Equilibrium)– Produce small numbers of offspring.– Large body size.– Late maturity– Significant parental care.– Density dependent controls.– Specialists

Environmental Impact

• Environmental impact of a population is measured in terms of:– Population Size– Resource Consumption Per Capita – Resultant Pollution

Community Ecology

Community Concept

• A community is an assemblage of populations interacting with one another within the same environment.– Composition is a listing of various species

in the community.– Diversity includes both species richness

and species diversity.

Habitat and Ecological Niche

• Habitat is the area an organism lives and reproduces in.

• Ecological niche is the role an organism plays in its community, including its habitat and its interactions with other organisms.– Fundamental niche - All conditions under

which the organism can survive.– Realized niche - Set of conditions under

which it exists in nature.

Predator-Prey Interactions

• Predation occurs when one living organism, the predator, feeds on another, the prey.– Presence of predators can decrease prey

densities, and vice-versa.

Prey Defenses

• Prey defenses are mechanisms that thwart the possibility of being eaten by a predator.– Spines– Tough Epidermis– Poisonous Chemicals– Camouflage– Bright Coloration– Flocking Behavior

Symbiotic Relationships

• Symbiosis refers to interactions in which there is a close relationship between members of two populations.– Parasitism

Parasite derives nourishment from a host, and may use host as habitat and mode of transmission.

Endoparasites Ectoparasites

Symbiotic Relationships

• Symbiosis refers to interactions in which there is a close relationship between members of two populations.– Parasitism

Parasite derives nourishment from a host, and may use host as habitat and mode of transmission.

Endoparasites Ectoparasites

Commensalism

• Commensalism is a symbiotic relationship in which one species is benefited and the other is neither benefited nor harmed.

Ex: Remoras and SharksMany examples may turn out to be

mutualism or parasitism.Amount of harm or benefit two species

do to one another is partially determined by the investigator.

Mutualism

• Mutualism is a symbiotic relationship in which both members of the association benefit.– Often help organisms obtain food or avoid

predation.Bacteria in human intestinal tact.

– Need not be equally beneficial to both species.

Predation, Competition, and Biodiversity

• In certain communities, predation by a particular species reduces competition and increases diversity.– Predators that regulate competition and

maintain community diversity are referred to as keystone predators.

• Introduction of exotic species into a new area may lead to unbridled competition and resultant reduction in biodiversity.

Ecosystems

Nature of Ecosystems

• Biosphere is part of the atmosphere, hydrosphere, and lithosphere that contains living organisms.– An ecosystem where organisms interact.

Ecosystems characterized by: One-Way flow of energy. Cycle of materials from abiotic

environment through biotic community.

Energy Balances

Ecological Pyramids

• A trophic level is composed of all the organisms that feed at a particular link in a food chain.– In general, only about 10% of the energy

of one trophic level is available to the next trophic level.

Explains why few carnivores can be supported in a food web.

Hydrologic Cycle

Carbon Cycle

The Nitrogen Cycle

Phosphorus Cycle

Sources of Water Pollution

The Biosphere

Biome Distribution

Climate and Biomes

Zones of a Lake

Conservation Biology

Conservation Biology and Biodiversity

• Conservation biology studies all aspects of biodiversity with the goal of conserving natural resources for this generation and future generations.– Primary goal is the management of

biodiversity for sustainable use by humans.

Value of Biodiversity

• Direct Value– Medicinal Value– Agricultural Value

CropsBiological Pest ControlsPollinators

– Consumptive Use ValueWoodSkins

Causes of Extinction

• Habitat Loss– Occurred in all ecosystems, but recent

concern focused on tropical rain forests and coral reefs.

Habitat Fragmentation

Pollution

• Pollution can be defined as any environmental change that adversely affects the lives and health of living things.– Acid Deposition– Eutrophication– Ozone Depletion– Organic Chemicals– Global Warming

• Sources:

Mader: Biology 8th Ed.

Raven & Johnson: Biology 8th Ed.

Mader: Biology 8th Ed.

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assisted program or activity.

Mader: Biology 8th Ed.

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