C21L3
• What defines a community?
• How do the populations in a
community interact?
A community is made up of all the
species that live in the same ecosystem
at the same time.
 The place within an ecosystem where an
organism lives is its habitat.
 A habitat provides all the resources an
organism needs, including food and shelter.
A habitat has the right temperature, water,
and other conditions the organism needs to
survive.
• A niche is what a species does in its habitat to
survive.
• Different species have different niches in the
same environment.
• All living things use energy to
carry out life processes such as growth and
reproduction.
• How an organism obtains energy is an important part
of its niche.
• Almost all the energy available to life on Earth
originally came from the sun.
Producers are organisms that get energy
from the environment, such as sunlight, and
make their own food.
Consumers are organisms that get energy by
eating other organisms.
 Herbivores get their energy by eating
plants.
• Carnivores get their energy by
eating other consumers.
• Omnivores, such as most humans, get their
energy by eating producers and consumers.
• Detritivores get their energy by eating dead
organisms or parts of dead organisms.
A food chain
is a way of
showing how
energy moves
through a
community.
A food web
shows many
food chains
within a
community
and how they
overlap.
• The populations that make up a community
interact with each other in a variety of ways.
• Some species have feeding relationships,
meaning they either eat or are eaten by another
species.
• Predators help prevent prey populations from
growing too large for the carrying capacity of
the ecosystem.
• The members of some populations, like
meerkats, work together in cooperative
relationships for their survival.
A close relationship between two or more
organisms of different species that live in
direct contact is called symbiosis.
A symbiotic
relationship
in which both
partners
benefit is
called
mutualism.
A symbiotic
relationship that
benefits one
species but does
not harm or
benefit the other
is
commensalism.
•A symbiotic relationship that benefits one
species and harms the other is parasitism.
•In parasitism, the species that benefits is the
parasite, and the species that is harmed is the
host.