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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.
 Competition
 Predation
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 Sharks
 Many 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
 Crops
 Biological Pest Controls
 Pollinators
– Consumptive Use Value
 Wood
 Skins
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.
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assisted program or activity.
Mader: Biology 8th Ed.
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•
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Mader: Biology 8th Ed.