LIVING IN THE ENVIRONMENT 17THMILLER/SPOOLMAN

CHAPTER 4Biodiversity and Evolution

Core Case Study: Why Should We Protect Sharks?

• 400 known species• 6 deaths per year from shark attacks• 79-97 million sharks killed every year• Fins, organs, meat, hides• Out of fear • 32% shark species threatened with extinction

• Keystone species – species that play roles affecting many other organisms in an ecosystem…they are needed!

• Cancer resistant, highly effective immune system• Why should we protect them? They have a right to exist; we

(and other species) need them

Biodiversity Is a Crucial Part of the Earth’s Natural Capital

• Species: set of individuals who can mate and produce fertile offspring

• Species diversity – Number of different species combined with the relative abundance of individuals within each of those species in a given area.

• Genetic diversity – Variability in the genetic makeup within a single species

• Ecosystem diversity – the Earth’s variety of regions

• Biomes: regions with distinct climates/species• Functional diversity – Biological and chemical processes or

functions such as energy flow and matter cycling needed for the survival of the species and biological communities

Fig. 4-2, p. 82

Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems.

Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth.

Solar energyChemical

nutrients (carbon dioxide, oxygen, nitrogen, minerals)

Heat

Heat Heat

Decomposers (bacteria, fungi)

Producers (plants)

Consumers (plant eaters, meat eaters)Heat Heat

Genetic Diversity The variety of genetic material within a species or a population.

Species Diversity The number and abundance of species present in different communities.

Biological Evolution by Natural Selection Explains How Life Changes over Time (1)• Fossils• Physical evidence of ancient organisms• Reveal what their external structures looked like

• Fossil record: entire body of fossil evidence, uneven and incomplete

• Only have fossils of 1% of all species that lived on earth

Biological Evolution by Natural Selection Explains How Life Changes over Time (2)• Biological evolution: how earth’s life changes over time

through changes in the genetic characteristics of populations• Darwin: Origin of Species

• Natural selection: individuals with certain traits are more likely to survive and reproduce under a certain set of environmental conditions

• Huge body of evidence has supported biological evolution through natural selection

Evolution by Natural Selection Works through Mutations and Adaptations (1)• Populations evolve by becoming genetically different

• Genetic variations• First step in biological evolution• Occurs through mutations in reproductive cells• Mutations: random changes in DNA molecules

Evolution by Natural Selection Works through Mutations and Adaptations (2)• Natural selection: acts on individuals• Second step in biological evolution

• Adaptation may lead to differential reproduction

• Genetic resistance: ability of one or more members of a population to resist a chemical designed to kill it

Fig. 4-7, p. 87

(a) A group of bacteria, including genetically resistant ones, are exposed to an antibiotic

(b) Most of the normal bacteria die

(c) The genetically resistant bacteria start multiplying

(d) Eventually the resistant strain replaces all or most of the strain affected by the antibiotic

Normal bacterium Resistant bacterium

Adaptation through Natural Selection Has Limits

• Adaptive genetic traits must precede change in the environmental conditions

• Reproductive capacity• Species that reproduce rapidly and in large numbers

are better able to adapt

Geologic Processes Affect Natural Selection

• Tectonic plates affect evolution and the location of life on earth• Locations of continents and oceans have shifted• Species physically move, or adapt, or form new

species through natural selection

• Earthquakes

• Volcanic eruptions

225 million years ago 135 million years ago

65 million years ago Present

Stepped ArtFig. 4-8, p. 89

How Do New Species Evolve?

• Speciation: one species splits into two or more species

• Geographic isolation: happens first; physical isolation of populations for a long period

• Reproductive isolation: mutations and natural selection in geographically isolated populations lead to inability to produce viable offspring when members of two different populations mate

Extinction is Forever

• Extinction• Biological extinction• Local extinction

• Endemic species • Found only in one area• Particularly vulnerable

• Background extinction: typical low rate of extinction• Mass extinction: 3-5 over 500 million years

LIVING IN THE ENVIRONMENT 17THMILLER/SPOOLMAN

Chapter 5Biodiversity, Species Interactions, and Population Control

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?• Habitat – giant kelp fields in shallow waters

• Hunted: early 1900s for their fur and competition with fishermen

• Partial recovery - declared endangered in 1977

• Why care about sea otters?• Ethics• Tourism dollars• Keystone species for the kelp forest system. They help control

the population of sea urchins and other kelp eating organisms.

Southern Sea Otter

Fig. 5-1a, p. 104

Species Interact in Five Major Ways• Interspecific Competition

• 2 or more species interact to gain access to limited resources (food, water, space)

• Predation• One species feeding on another

• Parasitism• One organism feeds on another by living on or in the other

• Mutualism• Interaction benefitting both species

• Commensalism• Benefits one species but has little or no effect on the other

Most Species Compete with One Another for Resources

• Limited resources – competition among species involves one becoming more efficient than the other in getting the resource.

• Ecological niche is the role of a species in an ecosystem and can be general or narrow.

• Some niches overlap and competition increases.

Some Species Evolve Ways to Share Resources and Survive

• Resource partitioning involves:• Using only parts of resource• Using at different times• Using in different ways• Evolving new species, through natural selection, with

specialized parts• Prey species evolve ways to avoid predators• Highly developed senses• Protective shells• Camouflage• Poisons

Resource Partitioning Among Warblers

Fig. 5-2, p. 106

Specialist Species of Honeycreepers

Fig. 5-3, p. 107

Some Ways Prey Species Avoid Their Predators

Fig. 5-5, p. 109

Populations Can Grow, Shrink, or Remain Stable

• Population size governed by• Births• Deaths• Immigration• Emigration

• Population change = (births + immigration) – (deaths + emigration)

Some Factors Can Limit Population Size• Range of tolerance• Variations in physical and chemical environment

• Limiting factor principle• Too much or too little of any physical or chemical

factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance

• Precipitation• Nutrients • Sunlight, etc

Trout Tolerance of Temperature

Fig. 5-13, p. 113

No Population Can Grow Indefinitely: J-Curves and S-Curves (1)

• Size of populations controlled by limiting factors:• Light• Water• Space• Nutrients• Exposure to too many competitors, predators or

infectious diseases

No Population Can Grow Indefinitely: J-Curves and S-Curves (2)

• Environmental resistance • All factors that act to limit the growth of a population

• Carrying capacity (K)• Maximum population a given habitat can sustain

Humans Are Not Exempt from Nature’s Population Controls

• Ireland• Potato crop in 1845

• Bubonic plague• Fourteenth century

• AIDS• Global epidemic

Some Ecosystems Start from Scratch: Primary Succession

• No soil in a terrestrial system

• No bottom sediment in an aquatic system

• Takes hundreds to thousands of years

• Need to build up soils/sediments to provide necessary nutrients

Primary Ecological Succession

Fig. 5-19, p. 119

Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (1)

• Some soil remains in a terrestrial system

• Some bottom sediment remains in an aquatic system

• Ecosystem has been• Disturbed• Removed• Destroyed

Natural Ecological Restoration of Disturbed Land

Fig. 5-20, p. 120

What is the ecosystem approach to sustaining biodiversity?

• Wilderness is an amount of land legally set aside to prevent/minimize harm from human activities - where human beings may visit but not remain.

• Wilderness areas are important for: • their natural beauty, • their natural biological diversity, • their enhancement of mental and physical health of

visitors, • their contributions to biodiversity and to evolutionary

possibilities.

What is the ecosystem approach to sustaining biodiversity?

• Ecological restoration is the process of repairing damage caused by humans to the biodiversity and dynamics of natural ecosystems.

• Initiatives that would help to sustain the earth’s biodiversity include:• Immediately preserving the world’s biological hot spots• Protecting the remaining old-growth forests • Mapping the world’s terrestrial and aquatic biodiversity• Identifying and taking action for the world’s marine hot spots,

just as for the terrestrial hot spots • Protecting and restoring the world’s lakes and river systems• Developing a global conservation strategy that protects the

earth’s terrestrial and aquatic ecosystems• Making conservation profitable• Initiating ecological restoration projects worldwide

LIVING IN THE ENVIRONMENT 17THMILLER/SPOOLMAN

Chapter 6The Human Population and Its Impact

Core Case Study: Slowing Population Growth in China: A Success Story

• 1.3 billion people – worlds most populous country• Promotes one-child families• Offer contraception, abortion and sterilization

information and help for married couples• Fast-growing economy – people working their way

from poverty to middle class.• Serious resource and environmental problems –

more middle class equals more consumption of resources per person.

• Increasing the ecological footprint of China has an impact on the whole world.

Human Population Growth Continues but It Is Unevenly Distributed (1)

• Reasons for human population increase• Movement into new habitats and climate zones• Early and modern agriculture methods• Control of infectious diseases through• Sanitation systems• Antibiotics• Vaccines• Health care

• Most population growth over last 100 years due to drop in death rates

Human Population Growth Continues but It Is Unevenly Distributed (2)

• Population growth in developing countries is increasing 9 times faster than developed countries

• 2050• 95% of growth will be in developing countries• 7.8-10.8 billion people

• What is cultural carrying capacity? The maximum number of people who can live in reasonable freedom and comfort indefinitely, without decreasing the ability of the Earth to sustain future generations.

Human Population Growth

Fig. 1-18, p. 21

Five Most Populous Countries, 2010 and 2050

Fig. 6-4, p. 127

Science Focus: Projecting Population Change

• Why range of 7.8-10.8 billion for 2050?

• Demographers must:1. Determine reliability of current estimates2. Make assumptions about fertility trends3. Deal with different databases and sets of

assumptions

The Human Population Can Grow, Decline, or Remain Fairly Stable

• Population change• Births: fertility• Deaths: mortality• Migration

• Population change = (births + immigration) – (deaths + emigration)

• Crude birth rate: # live births/1000/year

• Crude death rate: # deaths/1000/year

Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population• Fertility rate• number of children born to a woman during her

lifetime• Replacement-level fertility rate• Average number of children a couple must have to

replace themselves• 2.1 in developed countries• Up to 2.5 in developing countries

• Total fertility rate (TFR)• Average number of children born to women in a

population

Fig. 6-5, p. 130

8

7 Less-developed countries

6

5World

Tota

l fer

tility

rate

(c

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ren

per w

oman

)

3

More-developed countries

4

2

1955 1970 1990 2010 2030 20501

Year

Case Study: The U.S. Population Is Growing Rapidly

• Population still growing and not leveling off• 76 million in 1900• 310 million in 2010• 439 million by 2050

• Drop in TFR in U.S.• Rate of population growth has slowed to at or below

replacement rate since 1972• Changes in lifestyle in the U.S. during the 20th

century. Ex: women having opportunities of employment and to attend college.

Fig. 6-7, p. 132

20th Century Lifestyle Changes in the U.S.

Several Factors Affect Birth Rates and Fertility Rates

• Children as part of the labor force• Cost of raising and educating children• Availability of private and public pension• Urbanization• Educational and employment opportunities for women• Average age of a woman at birth of first child• Availability of legal abortions• Availability of reliable birth control methods• Religious beliefs, traditions, and cultural norms

Several Factors Affect Death Rates • Life expectancy• Infant mortality rate - Number of live births that die in first

year• Why are people living longer?

• Increased food supply and distribution• Better nutrition• Medical advances• Improved sanitation

• U.S. is 54th in world for infant mortality rate• U.S. infant mortality rate high due to

• Inadequate health care for poor women during pregnancy and their infants

• Drug addiction among pregnant women• High birth rate among teenagers

Fig. 6-10, p. 134

200

150 Less-developed countries

100

World

Infa

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rate

(d

eath

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00 li

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irths

)

50 More-developed countries

01960 1970 1980 1990 2000 2010 2020 2030 2040 2050

Year

Migration Affects an Area’s Population Size

• Reasons to migrate:• Economic improvement• Religious freedom• Political freedom• Wars• Environmental refugees

Case Study: The United States: A Nation of Immigrants

• Historical role of immigration in the U.S. – since 1820 the U.S. has admitted almost 2 times the number of immigrants as all other countries combined.

• Legal immigration – can help the economy by paying taxes, doing menial and low paying jobs.

• Illegal immigration – 2009 about 11 million illegal immigrants in the U.S.

• Controversy over immigration policy – currently 36% of the U.S. population growth.

Fig. 6-11, p. 135

Legal Immigration to the U.S. between 1820 and 2006

A Population’s Age Structure Helps Us Make Projections

• Age structure categories• Prereproductive ages (0-14)• Reproductive ages (15-44)• Postreproductive ages (45 and older)

• Seniors are the fastest-growing age group

Fig. 6-12, p. 136

Generalized Population Age-Structure Diagrams

Fig. 6-13, p. 136

Population Structure by Age and Sex in Developing and Developed Countries

Populations Made Up of Mostly Older People Can Decline Rapidly

• Slow decline• Economically and socially manageable

• Rapid decline• Severe economic problems• How pay for services for elderly• Proportionally fewer young people working• Labor shortages

• Severe social problems

Fig. 6-15, p. 138

Some Problems with Rapid Population Decline

As Countries Develop, Their Populations Tend to Grow More Slowly

• Demographic transition – as countries become industrialized and economically developed:• First death rates decline, then birth rates decline

• Four stages1. Preindustrial – slow pop. growth – high birth rate/high

death rate2.Transitional – rapid pop. growth – high birth

rate/lowering death rate3. Industrial – slowing pop. growth – birth/death rates drop4.Postindustrial – pop. growth levels then declines – birth

rates start to fall below death rate.

Fig. 6-17, p. 140

Four Stages of the Demographic Transition

Empowering Women Can Slow Population Growth

• Factors that decrease total fertility rates:• Education• Paying jobs• Ability to control fertility

• Women• Do most of the domestic work and child care• Provide unpaid health care• 2/3 of all work for 10% of world’s income• Discriminated against legally and culturally

Promote Family Planning• Family planning in less-developed countries• Responsible for a 55% drop in TFRs• Financial benefits: money spent on family planning

saves far more in health, education costs

• Two problems1.42% pregnancies unplanned, 26% end with abortion2.Many couples do not have access to family planning

Case Study: Slowing Population Growth in India

• 1.2 billion people, most populous country in 2015• Problems• Poverty – 1 out of 4 people is poor• Malnutrition – 40% of the population• Environmental degradation

• Bias toward having male children• Poor couples want many children• Only 48% of couples use family planning• 4th largest economy• Nearly 50% unemployed or underemployed