chapter 21- populations and communities

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Chapter 21 Populations and Communities Week 1

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Page 1: Chapter 21- Populations and Communities

Chapter 21

Populations and CommunitiesWeek 1

Page 2: Chapter 21- Populations and Communities

Habitats

• Organisms obtain food, water, shelter, and other things to live, grow and reproduce from the environment, also known as a habitat.

• One area may contain many habitats.

• What are some examples of habitats?

Page 3: Chapter 21- Populations and Communities
Page 4: Chapter 21- Populations and Communities

Biotic Factors

• An organism interacts with both the living and nonliving parts of its habitat.

• The living parts of a habitat are the Biotic Factors.

• What are examples of Biotic Factors in various habitats?

Page 5: Chapter 21- Populations and Communities

Abiotic Factors

• Abiotic factors are nonliving parts of a habitat– This includes water, sunlight, oxygen,

temperature, and soil– Water is required for various processes– Sunlight is needed for photosynthesis– Oxygen is needed for respiration– Animals are adapted to survive in specific Temp.– Soil is a mixture of rocks, nutrients, air, water and

decaying matter.

Page 6: Chapter 21- Populations and Communities
Page 7: Chapter 21- Populations and Communities

Levels of Organization

• Populations- all members of one species in a particular area are called a population.

• Communities- all different populations that live together in an area make up a community

• Ecosystems- the community of organisms along with the nonliving surroundings make up an ecosystem.

Page 8: Chapter 21- Populations and Communities
Page 9: Chapter 21- Populations and Communities

Determining Population Size

• Direct Observation- count all members• Indirect Observation- observe signs of

organisms rather than actual organisms themselves

• Sampling- estimate based on smaller area• Mark-and-Recapture Studies

Page 10: Chapter 21- Populations and Communities

Changes in Populations Size

• Birth and Death Rate– When does popul. Increase, decrease?

• Immigration and Emigration– Population change when individuals move into or

out of the population.• Population Density

= number individuals/ unit area

Page 11: Chapter 21- Populations and Communities

Limiting Factors

• A limiting factors is anything that keeps a population from growing too large– Food and Water– Space–Weather

Page 12: Chapter 21- Populations and Communities
Page 13: Chapter 21- Populations and Communities

Adapting to the Environment

• Natural Selection- a process during which a characteristic that makes an individual better suited to its environment eventually becomes common. Characteristics get passed down from parents to children and result in adaptations.

• Niche- adaptations that are suited to an organism’s specific living conditions. Aka- role in the environment.

Page 14: Chapter 21- Populations and Communities

Competition

• Competition is a relationship between organisms that strive for the same resources in the same place.

• Intraspecific competition occurs between members of the same species. It improves the species’ adaptations.

• Interspecific competition occurs between members of different species. It may lead to one species going extinct or both becoming more specialized.

Page 15: Chapter 21- Populations and Communities
Page 16: Chapter 21- Populations and Communities

Predation

Page 17: Chapter 21- Populations and Communities

Symbiosis

• Mutualism- Relationship where both species benefit

• Commensalism- One species benefit, the other is not affected

• Parasitism- Host is harmed, parasite benefits

Page 19: Chapter 21- Populations and Communities

Changes in Communities

• Primary Succession- changes that occur in an area where no soil or organisms exist.

• Secondary Succession- changes that occur in an area where ecosystem has been disturbed, but soil and organisms exist.