Ch. 19.1: Populations

Chapter 19.1: Populations

1. What defines a population?

2. What factors affect the size of a population?

Focus Questions

1. What defines a population?

• Ecology: study of all ecosystems on Earth

1. What defines a population?

What defines a population?

A species is a group of organisms that have similar traits and are able to produce fertile offspring.

Biosphere

Ecosystems

Communities

Populations

Organism

•The biosphere is the part of Earth where life exists. It extends from the deepest parts of the ocean to high in the air where plant spores drift.

• An ecosystem is made up of a community of organisms and the abiotic factors of the community.

• A community consists of all of the populations of species that live and interact in an area.

• Each animal is a part of a population, or a group of individuals of the same species that live together.

5 levels of Environmental Organization

•Each animal is a part of a population, or a group of individuals of the same species that live together.

•A community consists of all of the populations of species that live and interact in an area.

•An ecosystem is made up of a community of organisms and the abioticfactors of the community.

•The biosphere is the part of Earth where life exists. It extends from the deepest parts of the ocean to high in the air where plant spores drift.

On what level in the environment would your neighborhood be? (including:

you, your pets, houses, streets, yards, etc.)

A. Organism

B. Population

C. Community

D. Ecosystem

E. Biosphere

Organism

Populatio

n

Comm

unity

Ecosy

stem

Biosp

here

0 0 000

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Factors that affect the size of a population:

• Competition is the demand for resources that are in short supply in a community.

– food, water, shelter, mates, space

• When there are not enough resources available to survive, there is more competition.

2. What factors affect the size of a population?

• Populations change as environmental factors change

Limiting factors:

A. Sunlight availability is a limiting factor for most organisms.

• Without sunlight, green plants cannot make food, which effects animals that eat plants.

2. What factors affect the size of a population?

B. Temperature is a limiting factor for some organisms.

– When the temperature drops below freezing, many organisms die because it is too cold to carry out their life functions.

C. Diseases

D. Predators

E. Natural disasters

– fires

– Floods

F. Food, Water,

Shelter, & Mates

Which of these refers to anything that restricts the size of a population?

A. population density

B. limiting factor

C. carrying capacity

D. biosphere

populatio

n densit

y

limiti

ng fact

or

carry

ing ca

pacity

biosp

here

0 000

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Which of the following is NOT an example of a limiting factor?

A. Sunlight

B. Natural disasters

C. Temperature

D. Population

E. Predators

F. Diseases

G. FoodSunlig

ht

Natura

l disa

sters

Tempera

ture

Populatio

n

Predato

rs

Disease

s

Food

0 0 0 0000

45

2. What factors affect the size of a population?

• Population density is the population count in a specific area.

• One way of estimating population density is by sample count.

2. What factors affect the size of a population?

• Biotic potential – the potential growth of a population if it had no limiting factors (if it had perfect conditions).

• No population on Earth ever reaches its biotic potential because no ecosystem has an unlimited supply of natural resources.

2. What factors affect the size of a population?

• Carrying Capacity (K): largest population that an environment can support

• A population grows until it reaches the carrying capacity of an environment.

2. What factors affect the size of a population?

Carrying capacity is determined in part by limiting factors.

Starting to increase

Carrying capacity (stabilizes)Rapid

increase

2. What factors affect the size of a population?

• Carrying capacity of an environment is not constant –it increases and decreases as the amount of available resources increases and decreases.

• When the size of a population becomes larger than the carrying capacity of its ecosystem, overpopulation occurs.

• When one population

(meerkats) overpopulates,

often it results in another

population decreasing

(spiders).

The graph below shows the growth over 18 days of a population of paramecia (single-celled organisms) in a test tube. The test tube

contained food. Use this graph to answer the questions that follow.

What is the carrying capacity of the test tube when food is provided?

A. 0 Paramecium/mL

B. 6 Paramecium/mL

C. 65 Paramecium/mL

D. 6 Days

E. 18 Days

0 Pa

ram

eciu

m/m

L

6 Pa

ram

eciu

m/m

L

65 P

aram

eciu

m/m

L

6 Day

s

18 D

ays

0 0 000

45

The graph below shows the growth over 18 days of a population of paramecia (single-celled organisms) in a test tube. The test

tube contained food. Use this graph to answer the questions that follow.

Predict what will happen if no additional food is provided.

A. The carrying capacity will stay the same

B. The carrying capacity will increase

C. The carrying capacity will decrease, then stabilize at a lower number.

D. The carrying capacity will decrease and eventually all the organisms will die.

The carry

ing ca

pacity

will

...

The carry

ing ca

pacity

will

...

The carry

ing ca

pacity

wil.

..

The carry

ing ca

pacity

wil.

..

0 000

45

Which of these increases when there are not enough resources available in a community for all its organisms to

survive?

A. B. C. D.

0 000

A. Competition

B. Population

C. Organism

D. Food

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Which term refers to all the populations of different species that live together in the same area at the

same time?

A. B. C. D.

0 000

A. Population

B. Biosphere

C. Community

D. Ecosystem

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