Ch.22 Populations and Communities

Ch.22 Populations and
Section 1: Living Things
and the Environment
 Ecosystem- All the living and nonliving things that
interact in an area.
 Why would this
be an ecosystem?
• What are some
other ecosystems?
Section 1: Living Things
and the Environment
 Habitat- a place where an organism lives and that
provides the things that the organism needs.
 A needs of an organism: food, water, shelter, and
other things it needs to live, grow and reproduce from
its surroundings.
Abiotic vs. Biotic Factors
 Biotic Factors- living parts of an ecosystem.
 Grass, fungi, animals, etc.
 Abiotic Factors- the nonliving parts of an ecosystem
 Water, sunlight, oxygen, temperature, and soil.
Abiotic Factors
Water- your body is about 65 percent water.
 Water is needed for chemical reactions, dissolving substances,
keeping cell shape and size, keeping body temperature
Plants need water for photosynthesis.
Sunlight- energy needed from the sun for photosynthesis.
Oxygen- most living things require oxygen (respiration).
 Atmosphere is 20 percent oxygen and 78 percent nitrogen.
 Aquatic animals receive dissolved oxygen in water from
Abiotic Factors
4 Temperature- the temperature of an area
determines the types of organisms that can live
 Plants and animals have adaptations to help them
survive in different temperatures
5 Soil- mixture of rock fragments, nutrients, air,
water, and the decaying remains of living things.
 The type of soil influences the type of plants.
 Population- all the members of one species in a
particular area.
 Oak trees, ladybugs, prairie dogs.
 Why would trees in a forest not be a population?
 Community- all the different populations that live
together in an area.
 Levels of organization in an ecosystem (smallest to
 Ecology- the study of how living things interact
with one another and with their environment.
 Ecologists- are scientists who study ecology, look at
how the biotic and abiotic factors in an ecosystem
are related.
Section 2: Studying
 Population Density- the number of individuals in a
specific area.
 The equation for figuring out population density is:
Population density= Number of individuals
Unit area
 Example: 50 butterflies
10 square meters
 Equals five butterflies per square meter
Determining Population
 Direct observation- counting all the members.
 Indirect observation- may be too small or too hard
to find exact population number, so evidence is
used (tracks, nests, or other signs) to estimate the
 Sampling- the population may be too large or
spread out over a large area, so an estimate – or an
approximation of a number, based on reasonable
assumptions (count a small area and then multiply
the number in a large area).
Determining A Population
 Mark-and-recapture- animals are first captured,
marked, and released, then another group of
animals is captured. The marked animals determine
the population size.
 Hunters: what are some signs that you look for to
determine how many bucks are in an area?
Changes in Population Size
 Populations change in size when new members
enter the population or when members leave the
 Birth rate- the number of births in a certain amount
of time
 Death rate- the number of deaths in a certain
amount of time.
If birth rate > death rate, population size increases
If death rate > birth rate, population size decreases
Changes in Population Size
 Immigration- moving in to a population
 Emigration- moving out of a population.
 Refer to page 698 graph.
Limiting Factors
 Limiting factor- an environmental factor that
prevents a population from increasing.
 Food, space, and weather conditions.
 Through human activity, how are we a limiting
 Carrying capacity- the largest population that an
environment can support.
How does the predator/prey relationship affecting
carrying capacity?

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