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Populations and Communities

Chapter 1

Section 1: Living Things and the Environment

Ecology

� The study of the interactions between organisms and the living and non-living components of their environment.

Things to know:

� An organism obtains the things it needs to live from its environment (habitat)

� One area may contain many habitats

� A species is a group of organisms that can mate and produce offspring that can reproduce

Factors in the Environment

� Biotic factors- all the living things in an ecosystem

� Abiotic factors- all the non-living things in an ecosystem

� Water

� Sunlight

� Oxygen

� Temperature

� Soil

Levels of Organization

� The smallest level of organization is a single organism, which belongs to a population that includes all other members of its species in the area

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Levels of Organization

� The population belongs to a community of different species.

Living Thingsand the Environment

Levels of Organization

� The community and abiotic factors together form an ecosystem.

Living Thingsand the Environment

Levels of Organization in Ecology

Ecosystem

Community

Population

Organism

Section 2: Studying Populations

Main Idea

Detail Detail Detail Detail

Graphic Organizer

Direct observation

Indirect observation

Sampling Mark-and-recapture studies

There are four main ways to determine the size of a population.

How do you determine population size?

� Direct observation- count all

� Indirect observation- count signs of organisms (nests)

� Sampling –an estimate; count organisms in a small area and multiply to find the number in a large area

� Mark & Recapture – mark so many then recapture and use a formula to estimate

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Factors that determine population growth rate

� Death rate

� Birth rate

� Immigration (movement in)

� Emigration (movement out)

Changes in Population Size

� Populations change in size if new members join the population or if members leave the population.

� If BR > DR then population increases

� If BR < DR then population decreases

Population density

� The size of a population that occupies a limited area

� Measures how crowded a population is

Formula:

D = number of individuals

unit of area

Limitations of Growth

� Only occurs for a short period of time

� Due to environmental limitations

� Limiting factor – a factor that restrains the growth of a population

EX: resources (food and water), habitat size (space), competition, weather

An important limiting factor:

� Carrying capacity (K) – the number of individuals the environment can support over a long period of time

� Capacity is greater when prey is abundant and smaller when prey is scarce

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http://www.emc.maricopa.edu/faculty/farabee/biobk/expgrowth.gif

Section 3: Interactions Among Living Things

Natural Selection

� The “fittest” survive and pass on traits to offspring

� Result: Adaptations- the physical and behavioral characteristics that allow organisms to survive in their environment

� Ecological niche- the role each organism plays in the community.

*Example: the producer

the consumer

Interactions Among Organisms

1. Competition

2. Predation

3. Symbiosis

1. Competition

� Occurs when 2 species occupy the same niche

� 2 organisms struggle to survive using the same limited resource

� Eventually one will die off

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2. Predation

� One organism kills another for food

� Predator does the killing

� Prey gets eaten

� Can affect population size

a. Predator adaptations

� Help them catch prey

� Examples

� Jellyfish tentacles

� Speed (cheetah)

� Sticky bulbs on plants

� Seeing at night

b. Prey adaptations

� Help them avoid being killed

� Examples:

� Mimicry- looking like another animal or plant

� Protective covering

� False coloring

� Camouflage- looks like environment

� Warning coloration- bright colors often mean poisonous

Predator/Prey Relationship

As hare increase-more food for lynx which also increasesMore hare get killed and population drops offThey keep each other in balance

3. Symbiosis

� Close relationship between species that benefits at least one of the species

� 3 types:

� Mutualism- both benefit

� Commensalism – one benefits, other is neither helped or harmed

� Parasitism – one lives off of and harms another

� Host: organism affected

� Parasite: organism that benefits

Section 4: Changes in Communities

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Succession

� Two types:

1. Primary

2. Secondary

1. Primary Succession

� Changes in a community where no soil or organisms exist such as volcanic island or glacial rock

a. Pioneer species move in (moss, lichens)

b. Soil formed by rocks breaking up and organisms decaying

c. Plants grow

2. Secondary Succession

� Series of changes in a community where soil and plants have existed but were destroyed

a. Grasses and wildflowers

b. Shrubs and small trees

c. Forest trees crowd out plants and grass

d. Mature forest develops (pine, oak hickory)—takes about 100 years