Ecology and
species
interaction
Ecology
•Ecology: is he study of how
organisms interact with each
other and with their
environments
•Ecologists: scientists who study
Ecology
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•Ecologists study life at many
different levels, from individual
organism to the entire biosphere
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Levels of Ecological
organization
Levels of Ecological organization
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Level 1 (Individual/ organism)
individual is one organism and is
also one type of organism.
Examples: human, cat, moose,
palm tree, gray whale,
tapeworm, or cow
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Level 2 (Population)
A population is a group of organisms
belonging to the same species that
live in the same area and interact
with one another. A species is a group
of individuals that are genetically
related.
Example: Population of deer in
Africa, Population of oaks(trees) in
North America, Etc......
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Level 3 (Community)
• A community is all of the
populations of different
species that live in the same
area and interact with one
another.
• A community is composed
of all of the biotic factors of
an area.
Example:
The community in the picture in Botswana (a country in Africa)
You can see different populations live together in the same area.
Think! What are the populations in the picture?
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Level 4 (Ecosystem)
An ecosystem includes the living
organisms (all the populations) in an area
and the non-living aspects of the
environment.
Ecosystem is made of the biotic and
abiotic factors in an area.
Example of biotic factors:
Animals, Fish, plants, bacteria, and even
dead plants or animals
Examples of abiotic factors:
Light, water, temperature, pH, oxygen,
minerals in the soil, rocks and soil, etc....
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Species interactions
There are three
major types of
interactions among
organisms
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A Niche is the role of an organism in its habitat, or how
it makes its living.
Every species has a role that it plays in nature. That role is defined by a
combination of the organism's behaviors, habitat, and interaction with
other species.
For example,
A garden spider is a predator that hunts for prey among plants.
An oak tree grows to dominate a forest canopy, turning sunlight into
food. The role that a species plays is called its ecological niche.
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Species interactions
Predation
Predation
An interaction in which one
organism kills another for food
Competition
The struggle between organisms
to survive as they attempt to use
the same limited resources
Symbiosis
A close relationship between two
species that benefits at least one
of the species
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Competition
Symbiosis
Interspecies
interactions
Commensalism
Intraspecies
interactions
Mutualism
Parasitism
Predation
An interaction in which one organism kills another for
food
Predator
The organism that does the killing
Prey
The organism that is killed
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Competition
• Intraspecific competition: competition among members of the same
species
• Interspecific competition: competition among members of two or
more different species
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To reduce competition, species often partition resources.
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Symbiosis
A close relationship between two species that benefits at least one
of the species is called There are three types of symbiotic
relationships:
Mutualism: A relationship in which BOTH species benefit.
Commensalism: A relationship in which ONE species benefits and
the other species is neither helped nor harmed.
Parasitism: A relationship in which one organism lives ON or IN
another organism and HARMING it.
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Population
Growth
Exponential Growth
Population increases by
a fixed percentage
every year.
Normally occurs only when
small populations are
introduced to an
area with ideal
environmental conditions
Rarely lasts long
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What do you think
will happen if it lasts
long?
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Population growth limiting factors
Growth almost always slows and stops due to limiting
factors
• limiting factors: Are abiotic or biotic factors that restrict
the number, distribution, or reproduction of a population
of organisms
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Population growth limiting factors
1. Density - Independent
Factors
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2. DensityDependent Factors
3.Carrying Capacity
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1. Density - Independent Factors:
Any factor in an organisms’
environment that does not
depend on the number of
individuals in the population
Usually abiotic and include
natural phenomena such as
weather events
Ex: rain, drought, tornado, fire,
etc.
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2. Density-Dependent Factors
Any factor in the
environment that depend on
the number of individuals in
a population
Often biotic factors
Ex: predation, disease,
parasites, and competition
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3.Carrying Capacity
The maximum number of individuals an environment can support
long term
The carrying capacity of organisms is limited by the amount of
resources available to the population
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