POPULATION DYNAMICS

LEVELS OF ORGANIZATIONsmallest unit of living thingsgroup of similar cells organized to work togethergroup of different kinds of tissues working togethergroup of organs working togetherone individual living thingall organisms of the same kind living in one areaall interacting populations in an ecosystem all living and nonliving things interacting within a certain area

large region with typical plants and animals that includes several ecosystems

cell

Population

Dynamics

Population DynamicsHow populations change in size due to birth rate/immigration and death rate/emigration and limiting factors ( abiotic and biotic)

Birth Rate:(number of live birth per 1000)

How does death rate affects

population size?

Death Rate ( number of

death per 1000)

How does death rate affects

population size?

Immigration: ( movement into

an area)

How does immigration

affects population size?

Emigration:(movement out

of an area)

How does emigration

affects population size?

Population Size

What goes up must come down

•Increases in population: through birth or immigration

•Decreases in population: through death or emigration.

Change in Population =

Birth Rate +

Immigration- Death Rate

+ Emigration

Change in Population =

Birth rate+

Immigration Rate

)( -Death Rate

+Emigration

Rate( )

• What Does a Negative change in population mean?• Birth rate & Immigration rate < Death rate and

Emigration rate• Decrease in Population

• What Does a Positive change in population mean?• Birth rate and Immigration rate > Death rate and

Emigration rate• Increase in population size

What’s happening to the population?

• 500 babies are born• 200 People move to the

area

400 people die100 people move out of the area

= +700

= -500

700 - 500 = +200

Is the population GROWING or DECREASING?

GROWING!!!

Logistic or Exponential Growth Curve?

“Boom and Bust” “Boom then stable”

Which graph is indicative of natural growth within a population?Can you think of an example of exponential growth? Logistic growth?

Exponential Growth (J-shaped Curve)

• Rate of growth speeds up at a doubling pace

• Y= x2

• Not realistic in nature indefinitely

Po

pu

lati

on

siz

e (N

)

Time (t)

Carrying capacity (K)

Environmentalresistance

Biotic potential

Exponential growth

• Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off

Logistic Growth (S-shaped curve)

Can you think of some resources that could limit population growth? Characterize these resources as abiotic or biotic?

Po

pu

lati

on

siz

e (N

)

Time (t)

Carrying capacity (K)

Environmentalresistance

Biotic potential

Exponential growth

• Carrying Capacity (K) is the maximum number of organism that an area can support

Logistic GrowthCan you think of some resources that could limit population growth? Characterize these resources as abiotic or biotic?

Exponential and Logistic Population Growth: J-Curves and S-Curves

• As a population levels off, it often fluctuates slightly above and below the carrying capacity.

Graphing Activity (complete on graphing paper)

• Review the Data and Construct a line graph to show the change in Deer Population over time– Make sure to TITLE your graph– Label your X and Y axes appropriately– Create an appropriate scale for the population– Use 2 different colors for the different populations; include a key

YEAR 1975 1980 1985 1990 1995 2000 2005 2010

Tahoma Deer Population size

300 450 650 750 825 850 850 825

Mt. Helen Deer Population Size

200 350 500 750 900 700 725 700

Exit Ticket-Analyze Data1. During which years did the deer populations

grow exponentially?

2. During which years did the deer populations reach carrying capacity?

3. What is the Carrying Capacity for the Tahoma Deer population?

4. What is the Carrying Capacity (K) for the Mt. Helen Deer population?

5. Which population grew the fastest?

Answer the following questions on the same paper as your graph.

Write the Questions and Answers

FACTORS THAT AFFECT POPULATION DYNAMICS

Limiting factors

Limiting Factors

• **A limiting factor (or limiting resource) is a factor that controls a process, such as organism growth or species population, size, or distribution

– Abiotic Limiting Population Factors (LPF)• Availability of space• Natural Disasters • Availability of water

– Biotic Limiting Population Factors (LPF)• Predation• Competition

Density***How compact, or crowded an area is

• **Population Density:– How many species occupying an area

• Population/unit area

• Density Independent Factors VS. Density Dependent Factors– Think what the difference is between

Independent and dependent

Density Dependent Factor

• limits the population depending on the the amount of organisms in a given area (Density!) – Predation– Competition– Human Activity– Disease

How many people live in your house?

What would happen is some one caught a contagious flu virus in your home?

Is it a good idea to invite lots of people over your house is some one in your house is very sick with a contagious flu?

Why or why not?

http://www.learner.org/courses/envsci/interactives/disease/

Think about this…

Density Independent Factor

• Does NOT matter how dense a population is

• Affects population size regardless of density– Seasonal Variations– Natural Disasters– Catastrophic Events

Think about this….

Tropical Plants like warm weather.

If it ever snowed In tropical regions, most likely ALL those plants would die, because it is just too cold for them to live

If there were 100 tropical plants where it snowed, what percent would die?

If there were 20 tropical plants where it snowed, what percent would die?

Does not matter how many people in an area

AKA- INDEPENDENT from DENSITY

Same Percent will still be affected

Human Population Growth

Question #1• A population of rabbits experience a decline in

population due to a parasitic bacteria that spread disease among the population, killing many of the rabbits.

– What is the limiting factor? Is it Density Independent or Density Dependent?

(2 points)

Question #2• A fire swept across the everglades. Many trees

were destroyed that were home to several species of birds. As a result, the bird populations experienced a large decline.

• Was the factor limiting bird population in this example density dependent or independent? What is the limiting factor for the bird population?

(2 points)

Question #3• A significant amount of a toxic chemical was

dumped into a small lake that served as a habitat for a population of catfish. As a result, the catfish in the lake became sick and died.

• Is the chemical a density independent or density dependent factor?

(1 point)

Question #4• A foreign species of carnivorous fish was

recently introduced into the bay area in Key Biscayne.

• What will most likely happen to the population of native fish in the area?

• (1 point)

Information-globalization revolution

Hum

an p

opul

ation

Industrial-medical revolution

Agricultural revolution

12,500 yrs ago

275 yrs ago 50 yrs ago Present

Time (not to scale)

Fig. 1-16, p. 19

Human Population Growth

Human Population Growth Rate Has Changed Throughout History

• Change has been a dramatic increase over time– Up until recently, only half of children born survived

into adulthood – Death rates were high due to disease, famine– Population growth rate was slow

• NOW: Advances in medicine, technology, and communication have increased human growth rate exponentially

Get thinkin’• How could have advances in medical

innovations affected population rate?

• How could have advances in technology and communication affect population rate?

How Do We Study Human Populations?

• Demography:The scientific study of human populations– Tries to explain how populations change over time

• Growth rates predicted based on:– Birth rates– Death rates– Age structure

• Compares the distribution of age groups in a population

Rapid Growth Slow Growth No Growth

Age Structure

• Age structure predicts population growth– Rapid growth

• More young people than older people

– Slow Growth• About even number of age groups

– No Growth• More older people than young people

Younger, juvenile ages more likely to reproduce than elderly people

Controversy with growing population

• The more people populating earth, the faster resources diminish (density dependent factor)

• Laws can be made to help slow this exponential growth state– China- only one child born per family un urban areas– Increase status of women– Increase education

Knowledge check

1. The number of individuals of a single species per unit are is known as:A. Carrying capacityB. Logistic growthC. Population densityD. Population growth

Knowledge Check

2. One example of a density-independent limiting factor is

A. PredationB. HurricanesC. CompetitionD. Parasitism

Knowledge Check3. The scientific study of human population growth is known as

A. ImmigrationB. EmigrationC. Demographic transitionD. Demography