Organisms and Their
Relationships
Chapter 2
Section 1
Learning Targets
1. I can define and give examples of each
level of ecological organization
2. I can contrast biotic and abiotic factors
3. I can explain the types of symbiosis
4. I can describe the effects of competition
and predation
Ecology
• Scientists can gain valuable insight about
the interactions between organisms and
their environment.
– Each organism, regardless of where it lives,
depends on nonliving factors found in its
environment and on other organisms living in
the same environment, for survival
Ecology
• Ecology – the scientific discipline in which
the relationships among living organisms
as well as the interactions the organisms
have with their environment are studied
– Individuals who study ecology are known as
Ecologists
The Biosphere
• Because ecologists study organisms and
their environments, their studies take
place in the biosphere
– Biosphere: the portion of Earth that supports
life
– Bio means “life” and sphere means “ball”
The Biosphere
• Biotic Factors – living factors in an
organism’s environment
– Interactions of organisms are important for
the health of all species in the same
geographic location.
The Biosphere
• Abiotic Factors – nonliving factors in an
organism's environment
– Factors might include: temperature, air or
water currents, sunlight, soil type, rainfall, or
available nutrients
– Organisms are adapted to surviving in the
abiotic factors that are present in their natural
environment.
• If placed in a different environment, they might
die if they cannot adjust quickly
Levels of Organization
• The biosphere is too large and complex for most
ecological studies. So, scientists have broken
down the biosphere to make it easier to study.
• Levels of Organization:
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–
–
–
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Organism
Population
Biological Community
Ecosystem
Biome
Biosphere
Levels of Organization
1. Organism: individual organisms
themselves
2. Population: individual organism of a
single species that share the same
geographic location at the same time
3. Biological Community: a group of
interacting populations that occupy the
same geographic area at the same time
Levels of Organization
4. Ecosystem: a biological community and
all of the abiotic factors that affect it
5. Biome: a large group of ecosystems that
share the same climate and have similar
types of communities
6. Biosphere: all of the biomes on earth
combined
Ecosystem Interactions
• Interactions between organisms are
important in an ecosystem.
– Chances for survival of any one species
increases by using available resources in
different ways
– Habitat – an area where an organism lives
• Might be a single tree or a whole forest
– Niche – the role or position that an organism
has in its environment
Community Interactions
• Organisms that live together
in a biological community
constantly interact.
– These interactions shape an
ecosystem
• Competition: occurs when
more than one organism
uses a resource at the same
time
– Ex: during a drought, water is
scarce and the strong
organisms will compete with
the weak organisms for water
Predation
• Some species get their food by eating
other organisms
– Predation: the act of one organism consuming
another organism for food
• Ex: Lion (predator) stalks
Zebra (prey)
• Not all predators are
animals
Ex: Venus Fly Trap
Symbiotic Relationships
• Some species survive because of the
relationships they have developed with
other species.
• Symbiosis: The close relationship that
exists when two or more species live
together
– There are 3 types: mutualism, commensalism,
and parasitism
Symbiotic Relationships
• Mutualism: relationship between two or
more organisms that live closely together
and benefit from each other
– Ex: Lichen
• Commensalism: a relationship in which
one organism benefits and the other
organism is neither helped nor harmed
• Parasitism: one organism benefits at the
expense of another organism
Symbiotic Relationships