Chapter 35Population

and Community

Ecology

• What is a population?

• A. Consists of all individuals of a species that live together in one place at a time.

• What are some examples of a population that live in an ocean?

• What is population density?

• A. Number of individuals of a particular specie that live in a given area.

• How could we find the population density of Oxford?

• About how many people live in Oxford?

• A. 5,000

• B. 8,000

• C. 10,000

• D. IDK

A. 5,000

• What other information do we need to find out the population density of Oxford?

• What is the area of Oxford?

• A. 1 square mile

• B. 2 square miles

• C. 6 square miles

• D. IDK

• A. 2 square miles.

• 5,000 people

-----------------------

2.00 square miles

= About 2,500 people per square mile in Oxford.

• Population in West Chester is 23,214.

• Area is 1.84 square miles.

• Will the population density in West Chester be bigger or small than Oxford?

• Bigger

• About 12,616 people per square mile in West Chester.

• Which city will have the highest population density? Oxford, West Chester, or Philadelphia?

• How many people live in Philadelphia?

• A. 500,000

• B. 1,500,000

• C. 2,000,000

• D. 4,000,000

• B. 1,528,074 people live in Philadelphia

• Philadelphia is 135.1 square miles.

• 1,528,074 people / 135.1 square miles = 11,312 people per square mile.

• Oxford= 2,500 people per square mile

• Philadelphia= 11,312 people per square mile

• West Chester= 12,616 people per square mile

• Why is Philadelphia’s population density smaller than West Chester when it is so much bigger?

1. Certain areas may be uninhabitable.

2. Philadelphia has more stadiums, airports, restaurants, roads, etc than West Chester.

3. More people move in and out of Philadelphia.

4. West Chester could be more desirable.

5. West Chester is awesome!

35.1 Population

How do scientists monitor plant populations?

• Use a method called quadrat sampling.

• Quadrats, or rectangular frames, are randomly placed on a study site.

• Scientists count the number of plants within each randomly selected plot. The total number is plugged into a mathematical formula to determine the entire site.

Sampling Technique

• Indirect counting are used for species that are difficult to track. Scientists search INDIRECTLY for other signs of its presence, such as feces, nests, tracks, or a recent kill.

Mark-Recapture

• Use mark-recapture which is a method used by scientists to estimate the populations size of mobile organisms.

• Ie. Scientists capture and mark prairie dogs with ear tags and release them back into the wild.

• Scientists capture prairie dogs and calculate the ratio of marked to unmarked animals to estimate the population.

35.2 Population Growth

• Exponential Growth:

• Population multiplies by a constant factor at a constant time interval.

• J shape curve:

Carrying Capacity

• Carrying capacity:

• Is the maximum number of individuals of a particular species that the environment can normally and consistently support.

• Population of deer. We put a small amount of deer on a remote island. The island was lush for green grass. What happened to the deer population over time?

• S shape curve:

Limiting Factor

• Limiting factor:

• A condition that can restrict a population’s growth.

• Ex.

• Disease

• Limited food

• Space

Factors Affecting Population Growth

• Density- Dependent Factors:

• A factor that limits a population more as population increases.

• Ex.

• Disease that spreads more easily among organisms in a dense population than in a less dense population.

• Density- Independent Factors:

• Factors that limit populations but are unrelated to population density.

• Ex.

• Weather events- hurricane, blizzard, droughts

Boom or Bust Cycle

• Increase rapidly for a period of time then decrease rapidly for a period of time.

• Ex. Hares and Lynx

35.3 Human Population Growth

• Most of history, human population growth was very slow.

• 10,000 years ago saw a huge spike!

Why?

• Changes in human culture

• Wide scale farming provided more food

• Death rates decline because medicine

Predicting Future Population

• Age Structure:

• Population is the proportion of people in different age groups.

35.4 Species Interactions

What kind of people do you interact with? • Friends

• Parents

• Teammates

• Teachers

• Coaches

• Boyfriend/Girlfriend

What kind of relationships do you

have with them?

Story

• In terms of Arnold and I, what kind of relationship did we have?

• +,--

• In terms of Nicole and I, what kind of relationship do we have?

• +,+

What kind of relationship do these

organisms have? • Human

• ___

• Mosquito

• +

What kind of relationship do these

organisms have? • Black billed Magpie

•+• American Bison

•+

Why does the tortoise have a neutral

relationship while the rodent and frog are

positive? • Gopher Tortoise

• 0

• Rodent

• +

• Frog

• +

• Interspecific Competition:

• When two or more species rely on same limited source.

•Ex.

• Africa Savanna

• When drought occurs all species rely on the limited amounts of grass.

• Competitive exclusion:

• If two species are similar in their requirements that the same resource limits both species growth, one species may succeed over the other.

Competitive Exclusion

Niche

• Niche:

• An organisms role in the environment (its job)

• What is a plants niche?

• Photosynthesis and give us oxygen.

• Predation:

• In interaction in which one organisms eats another.

Symbiotic Relationships

• Parasitism:

• One organisms benefits, other is harmed.

• Mutualism:

• Both organisms benefit

• Commensalism:

• One organisms benefits, the other is neither harmed or benefited

Parasitism

Commensalism

Mutualism

35.5 Disturbances in Communities

• Ecological Succession:

• Communities that change drastically as a result of a disturbance such as fire, flood, storms, drought.

• Primary succession:

• Community arises in a lifeless area that has no soil.

• Secondary succession:

• When disturbances damages an existing community but leaves soil intact.

Primary Succession

• Introduced Species:

• Organisms that humans move from species native land to new areas.

• Ex.

• Kudzu plant from Japan to stop erosion.

Succession

Secondary Succession 1 Year

Secondary Succession 5 years

Secondary Succession 10 years

Secondary Succession 25 years

Secondary Succession 30 years