© 2014 Pearson Education, Inc.

Lecture Presentation

Anne Gasc

Hawaii Pacific University and

University of Hawaii–Honolulu Community College

BIOLOGY OF HUMANSConcepts, Applications, and Issues

Fifth Edition

Judith Goodenough Betty McGuire

24Human Population,

Limited Resources,

and Pollution

© 2014 Pearson Education, Inc.

Human Population, Limited Resources, and

Pollution

OUTLINE:

Population Changes

Patterns of Population Growth

Environmental Factors and Population Size

Earth’s Carrying Capacity

Human Impacts on Earth’s Carrying Capacity

Global Climate Change

Looking to the Future

© 2014 Pearson Education, Inc.

Population Changes

Population size

Births increase population size

Deaths decrease population size

Birth rate

Number of births per a specified number of individuals in the

population during a specific time

Example: 20 births per 1000 individuals per year

The age at which a female has her first offspring has a

dramatic impact on the rate at which a population grows

This is the most important factor in determining a female’s

reproductive potential

© 2014 Pearson Education, Inc.

Population Growth Rate

Death rate

Number of deaths per a specified number of individuals

in the population during a specific time

Example: eight deaths per 1000 individuals per year

Growth rate

Difference between the birth rates and death rates of a

population

Example: (Births Deaths)/1000 (20 8)/1000 1.2%

© 2014 Pearson Education, Inc.

Population Growth Rate

Size of the starting population affects how quickly

new individuals will be added

At the same growth rate, the larger the size of the

starting population, the more individuals produced

Age structure

Relative number of individuals of each age

Important because only individuals within a certain

age range can reproduce

© 2014 Pearson Education, Inc.

Figure 24.2 Age structures of Afghanistan, the United States,

and Canada.

© 2014 Pearson Education, Inc.

Immigration and Emigration

Individuals also can be added to a population by

immigration

Arrival of individuals from other populations

Individuals also can be lost from a population by

emigration

Exodus of individuals from a population

© 2014 Pearson Education, Inc.

Immigration and Emigration

Web Activity: Age Structure and Population Growth

© 2014 Pearson Education, Inc.

Patterns of Population Growth

Exponential growth

Unrestricted growth at a constant rate

Occurs in environments with plenty of resources and

adequate waste removal

J-shaped growth curve

© 2014 Pearson Education, Inc.

Patterns of Population Growth

Carrying capacity

Number of individuals of a given species that a

particular environment can support for a prolonged

period

Determined by many factors:

Availability of resources (food, water, space)

Ability to remove wastes

Predation pressure

© 2014 Pearson Education, Inc.

Patterns of Population Growth

Logistic growth

Growth slows as population approaches carrying

capacity and eventually levels off

S-shaped growth curve

© 2014 Pearson Education, Inc.

Patterns of Population Growth

Web Activity: Human Population Growth

© 2014 Pearson Education, Inc.

Figure 24.3 Population growth is often restrained by environmental

factors.

© 2014 Pearson Education, Inc.

Figure 24.4 The human population has grown steadily throughout

most of human history.

© 2014 Pearson Education, Inc.

Environmental Factors and Population Size

Environmental factors regulate population size

Density-independent regulating factors

Events that cause death that are not related to

population density

Natural disasters such as hurricanes, earthquakes, and

fires

Density-dependent regulating factors

Events that have a greater impact on the population as

conditions become more crowded

Food scarcity

Disease

© 2014 Pearson Education, Inc.

Earth’s Carrying Capacity

Earth’s carrying capacity for humans depends on

Natural constraints such as resource availability

Human activities and choices

Estimates range from 5 to 20 billion people

In mid 2010, there were 6.8 billion people on Earth

© 2014 Pearson Education, Inc.

Human Impacts on Earth’s Carrying Capacity

Ecological footprint

A measure of the amount of productive land and

water required to support a person or population

based on consumption levels

Calculation of an ecological footprint includes

everything that is consumed and the corresponding

waste removal

More affluent people or populations typically have

larger ecological footprints

© 2014 Pearson Education, Inc.

Figure 24.6 Ecological footprint.

© 2014 Pearson Education, Inc.

Agricultural Advances

The green revolution

Development of high-yield varieties of crops and use

of modern cultivation methods

Benefit: increased crop production

Costs: requires more energy and causes more

environmental damage

© 2014 Pearson Education, Inc.

Figure 24.7 Desertification.

© 2014 Pearson Education, Inc.

Depletion of Resources

Depletion of resources

Desertification

Overfarming and overgrazing transform marginal farmland

into desert

Soil erosion

Deforestation

Removal of trees without replacing them

Tropical forests most affected

Results in decline in soil fertility

Overfishing

Leading to depleted fish populations

Worldwide, 70% of fisheries are overexploited

© 2014 Pearson Education, Inc.

Figure 24.8 Deforestation.

© 2014 Pearson Education, Inc.

Water Shortage

Water shortages

97% of Earth’s water is in the oceans

Freshwater scarcity is an emerging crisis

Water footprint

Indicator of direct and indirect water use by a person,

locality, or nation

Direct use

Water use at home

Indirect use

Water used to produce goods and services

© 2014 Pearson Education, Inc.

Water Shortage

Irrigation

Benefit: allows crops to grow in areas that would

otherwise be barren

Cost: salinization

Irrigation water contains dissolved minerals that stay in

the soil

When water evaporates from the soil, salts accumulate

Worldwide, salinization destroys the fertility of 5000 km2

(1930 mi2) of irrigated land each year

© 2014 Pearson Education, Inc.

Water Shortage

Steps to reduce water shortages

Reduce water use

Raise the price of water

© 2014 Pearson Education, Inc.

Pollution

Water pollution

Surface water: mercury, PCBs, fertilizers

Groundwater: leaks from underground tanks and septic

systems

© 2014 Pearson Education, Inc.

Ozone Pollution and Ozone Depletion

Ozone: gas, O3

Can be an air pollutant at Earth’s surface (component of

photochemical smog)

Naturally produced ozone is an essential part of the

stratosphere: shields Earth from excessive UV radiation

Ozone depletion: chlorofluorocarbons (CFCs) are the

primary culprit responsible for the destruction of the ozone

layer in the stratosphere

© 2014 Pearson Education, Inc.

Figure 24.9 The thinning of the ozone layer.

© 2014 Pearson Education, Inc.

Global Climate Change

Climate describes a region’s average temperature,

precipitation, humidity, solar radiation, etc.

Global climate change

Changes in Earth’s climate patterns

Two key conclusions of Intergovernmental Panel on

Climate Change (IPCC)

Global climate is getting warmer

Most of the increase in global temperature is due to

human activity that releases greenhouse gases into

the atmosphere

© 2014 Pearson Education, Inc.

Global Warming and Greenhouse Gases

Greenhouse gases include

Carbon dioxide

Methane

Nitrous oxides

CFCs

Trap heat in the atmosphere

© 2014 Pearson Education, Inc.

Figure 24.10 Greenhouse gases promote global warming.

© 2014 Pearson Education, Inc.

Figure 24.11 The concentration of CO2 in the atmosphere has

been increasing for many years.

© 2014 Pearson Education, Inc.

Global Warming and Greenhouse Gases

Possible consequences of global warming

Melting polar ice caps cause rising sea levels

Flooding of coastal cities

Warmer oceans

Changing weather patterns

Warmer oceans may fuel more hurricanes

Altered distribution of climax communities

Negative impacts on human health

© 2014 Pearson Education, Inc.

Carbon Footprint

Carbon footprint is a measure of the amount of CO2

entering the atmosphere due to a person’s or a

nation’s daily activities

Important to reduce your individual (direct) carbon

footprint and for nations to reduce the global carbon

footprint

Reducing reliance on fossil fuels is key

© 2014 Pearson Education, Inc.

Figure 24.12 Possible causes of global climate change.

© 2014 Pearson Education, Inc.

Looking to the Future

Our future depends on the decisions we make today

Humans must realize that Earth’s resources are

limited and must be shared with all living things

Requires changes in the way governments and

businesses operate and the ways in which individuals

think

© 2014 Pearson Education, Inc.

Looking to the Future

Humans are a small part of a large ecosystem

We must find ways to work within natural laws to

preserve ecosystem Earth and its biodiversity

Jane Goodall’s optimism about our future is

based on

Human brain

Resilience of nature

Energy and enthusiasm of young people

Indomitable human spirit

© 2014 Pearson Education, Inc.

You Should Now Be Able To:

Understand population changes

Know the patterns of population growth

List environmental factors and population size

Define Earth’s carrying capacity

Understand human impacts on Earth’s carrying

capacity

Explain global climate change

Look to the future!