Ch.22 Populations and Communities
Section 1: Living Things and the Environment
Ecosystem- All the living and nonliving things that interact in an area.
Why would thisbe an ecosystem?• What are someother 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
1 Water- your body is about 65 percent water. Water is needed for chemical reactions, dissolving
substances, keeping cell shape and size, keeping body temperature constant.
Plants need water for photosynthesis.
2 Sunlight- energy needed from the sun for photosynthesis.3 Oxygen- most living things require oxygen (respiration). Atmosphere is 20 percent oxygen and 78 percent
nitrogen. Aquatic animals receive dissolved oxygen in water from
plants.
Abiotic Factors
4 Temperature- the temperature of an area determines the types of organisms that can live there.
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.
Populations
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?
Communities
Community- all the different populations that live together in an area.
Levels of organization in an ecosystem (smallest to largest): Organism Population Community Ecosystem
Ecology
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 Populations
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 Size
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 population
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 Size
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 population.
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 increasesIf death rate > birth rate, population size decreases
Changes in Population Size
Immigration- moving in to a populationEmigration- 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
factor?Carrying capacity- the largest population that
an environment can support.How does the predator/prey relationship
affecting carrying capacity?