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?