Content Outline for Teaching - Potosi School District - Home

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Section 2
Content Outline
for Teaching
Ecology
Relationships Among Living Things
Underlined words and
phrases are to be filled
in by students on the
Note-taking Worksheet.
A. Ecologists organize living things into groups to make it easier to study ecosystems.
1. A population is a group of the same type of organisms living in the same place at the
same time.
2. All of the populations that live in an area make up a community.
3. Ecologists want to know the size of a population, where its members live, and how it
is able to stay alive.
4. Ecologists determine population density by comparing the size of a population with
its area.
5. Ecologists use tags to study populations of animals that travel long distances.
B. Populations do not have enough resources to grow larger and larger forever.
1. Things that limit the size of a population are called limiting factors.
2. Limiting factors include food, water, living space, and other resources.
C. The most common interactions in a community are feeding interactions.
1. Organisms will compete for any resource that is in limited supply.
a. The greater the population size of an area, the greater the competition for resources.
2. Predation is the act of one organism feeding on another.
a. A bird of prey, such as a falcon, is an example of a predator.
b. A facon’s prey is the organism it eats.
3. When the African tickbird eats insects off a zebra’s skin, both organisms in the relationship
benefit.
4. A bird that builds its nest in a tree benefits but the tree is neither harmed nor helped.
5. Insects biting a zebra’s skin harm the zebra but benefit themselves.
D. Each type of organism has a different role to play in an ecosystem.
1. The role of an organism in an ecosystem is called its niche.
2. The place where an organism lives out its life is called its habitat.
Discussion Question
What factors might prevent a population of dandelions from overtaking a lawn? Answers
will vary. Student responses should include competition for soil nutrients, availability of
water, competition from other plant populations for space.
Ecology 70