CHAPTER
4
Population Ecology
Lesson 4.1 Studying Ecology
Ernst Haeckel defined ecology in 1866 as “the
body of knowledge concerning the economy of
nature—the total relations of the animal to both its
inorganic and organic environment.”
Lesson 4.1 Studying Ecology
Levels of Ecological Organization
• The study of how organisms interact with each other and
with their environments
• Scientists study ecology at various levels of organization.
Lesson 4.1 Studying Ecology
Species
• Species: A group of organisms that interbreed and create
fertile offspring
• This definition does not work well for species that do not
reproduce sexually
• For example: Bacteria
• Today, most biologists assign species on the basis of
genetic similarity
• Community Ecology: The study of interactions among
species
• How a bee pollinates a flower
• How herds of animals interact as they migrate across Africa
Lesson 4.1 Studying Ecology
Biotic and Abiotic Factors
• Biotic factors: Parts of an
ecosystem that are living or
used to be living
• Abiotic factors: Parts of an
ecosystem that have never
been living
Did You Know? Decaying organisms
are biotic factors as long as their
structure remains cellular.
Stop and Jot: Think of some
abiotic and biotic factors for your chart
in your study guide.
Lesson 4.1 Studying Ecology
Habitat
• The specific environment in which an organism lives
• Habitats provide an organism with resources—anything an
organism needs to survive and reproduce, including food,
shelter, and mates.
Ecosystem vs. Habitat
• An ecosystem and habitat both include the
environment surrounding an organism
• A habitat’s boundary, however, depends on the
particular organism and the resources it needs
• It may be a subset of an ecosystem or more than
one ecosystem
• For example, compare the habitat of a tiny soil mite
to that of a vulture who soars through the air
• An organism depends on having a suitable habitat
where it can live as well as the availability of resources
within that habitat. It can not live without either.
Finding Gold in a Costa Rican
Cloud Forest
• Golden toads lived in Costa Rica’s Monteverde cloud
forest.
• Forest’s soil, rocks, leaf litter, humidity, plant life,
and seasonal pools of water were all parts of the
toad’s habitat
• Golden toads were first described in 1964. They
were extinct by 1989.
Learn more about the
Golden Toad on
Thursday!
Talk About It Why is the extinction of the golden
toad a global concern?