chapter 21- populations and communities

Chapter 21

Populations and CommunitiesWeek 1

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?

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?

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.

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.

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

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

Limiting Factors

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

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.

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.

Predation

Symbiosis

• Mutualism- Relationship where both species benefit

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

• Parasitism- Host is harmed, parasite benefits

• https://www.youtube.com/watch?v=OMFiI2at1p4

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.