CHAPTER 5: POPULATIONS

How Populations Grow (5-1)

Limits to Population Growth (5-2)

Human Population Growth (5-3)

5-1: How Populations

Grow

POPULATION

A population is a group of organisms

that belong to the same species and live in a given area.

A. 3 Factors That Influence Population Size

1. Birth Rate

2.

3. Migration a. immigration =

b. emigration =

Death Rate

movement of organisms into an area

movement of organisms out of an area

4. Calculation of Population Growth

Population Growth Rate =

Zero population growth is when:

(Birth Rate+Immigration – Death Rate+Emigration)

Birth Rate+Immigration = Death Rate+Emigration

B. Population Dynamics

= Change in population size over time

Biotic Potential

+ Environmental Resistance

= Carrying Capacity

1. Biotic Potential= The at which a species can

increase if unchecked maximum rate

1. Biotic Potential

Considerations Include:

a.

b. frequency of reproduction during life

c.

d. survival rate of offspring to reproductive age

e.

age at which reproduction begins

# of offspring per reproductive event

length of reproductive ability

1. Biotic Potential

(logarithmic, J-shaped curve).

Many species, particularly herbivores, generally have

Creates a growth curve that is exponential

higher birth rates

2. Environmental Resistance= The sum of all the forces that cause death

or lowers reproduction

This includes: ( but is not limited to the following)StarvationClimatic factorsPredationDisease/parasitesNumerous human created elements

3. Carrying Capacity

= The number of organisms that can be supported in a given area at a given time

Carrying Capacity – The Kaibab If humans do not harvest part of the herd by

using licensed hunters, natural forces of disease and starvation will bring about the reduction with starvation and disease.

QUESTION:

Are human populations ultimately controlled by the same equation?

C. Change in Population Size Over Time Population increases for living things are

generally exponential

1. Exponential Growth (J-Shaped)a.

, followed by increasingly faster

rates of growth

b. , the exponential phase of growth may drop off sharply due to environmental constraints

c. Note: Happens to a population

Type of exponential growth that shows slow growth at first

Under natural conditions

only briefly

when encountering a new habitat.

J-Shaped Growth Curve

2. Logistic Growth (S-Shaped)a.

, but eventually the rate of growth slows and stabilizes at a certain level

A growth model that starts off like the J-shaped form

2. Logistic Growth (S-Shaped)

2. Logistic Growth (S-Shaped)b. Environmental resistance ultimately limits

growth in the S-shaped growth model.

c. Real-world populations vary in complex ways, and may show either a J- or an S-shaped growth form at different times in their history.

What factors limit population growth?

Environment

5-2: Limits to Population Growth

Objectives•Identify factors that limit population growth.•Differentiate between density-dependent and density-independent factors.

Density DEPENDENT Controls

Competition

Predation

Parasitism

Disease

POPULATION DENSITY

Remove higher % of individuals as population size increases

1. Density Dependent ControlsAs population size increases, competition for

resources also increases.

Density Dependent Controls:a. INTRASPECIFIC COMPETITION Intraspecific competition =

•Includes mate competition

Chuckwallas

Among same

species

Humans?

Density Dependent Controls:b. INTERSPECIFIC COMPETITION Interspecific Competition –

Does not include mate competition

Big Horn Sheep and Burros

Between species

Density Dependent Controls:c. PREDATION one organism feeding on another

C. PREDATION1. Types

a) Equilibrium –

b)

prey can avoid predator

Boom-Bust cycle – lynx and hare

c. PREDATION2. Plant Defenses

a)

b) Chemical –

Morphological (body forms) – thorns, spines

poisons

c. PREDATION3. Animal Defenses

a) Morphological

1. size –

2. coloration –

3.

hide, frightencamouflage, warning, mimicry

other - sting, bite, run

c. PREDATION3. Animal Defenses

b) Chemical – poison

c. PREDATION3. Animal Defenses

c) Vigilance (intelligence) – watch for

predators, learned behavior

Meerkats

c. PREDATION3. Animal Defenses

d) Parasitism -

Freshwater Leech

Predators feed on prey but

do not kill it immediately

c. PREDATION3. Animal Defenses

e) Crowding and Stress

c. PREDATION3. Animal Defenses

f)

Zebra and Wildebeest Migration

Migration

c. PREDATION3. Animal Defensesg) Broken wing display

2. Density Independent Controlsa) Remove a % of the population

b)

certainregardless of number of individuals in the population

Are typically random or extreme abiotic events (weather, natural disaster)

2. Density Independent Controls

Floods are an example of a density-independent factor. This is the aftermath of Katrina in New Orleans.

2. Density Independent Controls

c. After extreme abiotic events, new habitats are

opened for organisms to create new logistic

growth

POPULATION GROWTH

Density DependentFactors

Density IndependentFactors

Limited by

So let’s review!

The following statements will involve a situation that will affect the growth of a population. Classify each of the statements as:

DD Density Dependent

DI Density Independent

1. Fish A and Fish B attempt to occupy the same area. The more aggressive Fish A survives; Fish B does not.

DDCompetition between species only occurs at

certain densities

2. A severe flood brings a lot of sediment and silt into the lake. Turbidity (cloudiness) increases greatly.

DINatural disasters affect all populations

regardless of density

3. A drought decreases the water level in the lake. The carrying capacity of the lake decreases.

DINatural disasters affect all populations

regardless of density

4. Due to the introduction of Fish Z, the lake becomes crowded and some fish species do not survive.

DDCrowding only occurs at certain densities

5. Since sea otters prey on sea urchins, an increase in sea urchins causes an increase in the sea otter population.

DDPredation only occurs at certain densities.

6. Many fish die due to an increase in water temperature.

DITemperature affects all population densities.

7. Due to over-fishing, the number of Fish T in the lake decreases.

DIHuman activities affect all population densities.

8. A population is growing quickly when parasites cause disease to spread quickly.

DDParasitism only affects certain population

densities.

THE END

5-3: Human Population Growth

5-3 Human Population GrowthA. Human Populations

1. Growth rates were low for much of human history, but rates started

and became in the 1950’s, exhibiting a ever since.

increasing in the 1700’s exponential

J-shaped curve

Time Culture Strategy B D Graph

Pre-Industrial

Transitional

Industrial

Post Industrial

Agriculture

Moving into

cities

Living in cities

Technology

Large Family

Large Family

Smaller Families

and Labor Laws

College degree

to compete

Human Population Growth:Past History and Current ConditionsYEAR POPULATION

1804

1974

2005

End of 21st Century

1 billion

4 billion

6.2 billion

Estimated 8.5 – 11 billion

Human Population Growth:Past History and Current Conditions2. World population growth is fastest in

3. is a key in developing countries:

a) If educated to grade = 8 babies/female

b) Women with higher education/careers = delay childbirth and typically

developing countries

Education

2nd or 3rd

have fewer

children

Human Population Growth:Past History and Current Conditions

COUNTRY ANNUAL GROWTH RATE

Developed

Less-developed:

China, India, parts of Africa, and Latin America

0.4%

1.8 - 3%

B. Effects of Large Human Population 1. Food and agriculture

a) Only three plants provide of our food supply –

b) Crops are - not resistant to disease or weather, lose 70 to 80% of a crop

50%wheat, rice and corngenetically identical

Effects of a Large Human Population

2. Usable land

a)

b) is the fastest growing area of land being destroyed

c) removes circulating water and deserts are getting bigger

high percentage of potentially

usable land is being cultivated

agricultural land

removal of tropical forest

Deforestation in

the Tropics

Effects of a Large Human Population3. Other human impacts

a) Global warming – the increase in

during the last 150 years concerns ecologists because of its potential effect on global temperature

atmospheric CO2 concentrations

through the greenhouse effect.

Effects of a Large Human Populationb) Ozone depletion -

1979

2003

increased UV radiation hits

the earth

Effects of a Large Human Populationc) Acid rain/Water pollution

Statue of Queen Victoria - England

The Parthenon in Greece shows discoloration and

chemical weathering effects from air pollution and acid

rain

Effects of a Large Human Populationd) Habitat destruction/soil destruction

Effects of a Large Human Populatione) Biodiversity loss

Fragmentation of

habitat causes

species to go

extinct.

Effects of a Large Human Populationf) Waste build-up Example: Open Pit Mining

Effects of a Large Human Populationg) Non-native/exotic

species – would not be present without the direct or indirect help of humans

Walking catfish

Starlings