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ENVIRONMENTAL SCIENCE 13e
CHAPTER 4:
Biodiversity and
Evolution
Core Case Study: Why Are
Amphibians Vanishing? (1)
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Habitat loss and fragmentation
Prolonged drought
Increased ultraviolet radiation
Parasites
Viral and fungal diseases
Core Case Study: Why Are
Amphibians Vanishing? (2)
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Pollution
Climate change
Overhunting
Nonnative predators and competitors
33% of all amphibian species face
extinction
Fig. 4-1, p. 61
4-1 What Is Biodiversity and
Why Is It Important?
• Concept 4-1 The biodiversity found in
genes, species, ecosystems, and
ecosystem processes is vital to
sustaining life on earth.
Biodiversity (1)
• Species diversity
• A set of individuals that can mate and
produce fertile offspring
• 8-100 million species total; likely 1014 million
• 2 million species identified
• ~50% in endangered tropical
rainforests
Biodiversity (2)
• Genetic diversity
• Ecosystem diversity
– Biomes
• Distinct climate
• Certain species, especially vegetation
• Functional diversity
Fig. 4-2, p. 61
Functional Diversity
The biological and chemical processes such as energy
flow and matter recycling needed for the survival of species,
communities, and ecosystems.
Genetic Diversity
The variety of genetic material
within a species or a population.
Ecological Diversity
The variety of terrestrial and
aquatic ecosystems found in
an area or on the earth.
Species Diversity
The number and abundance of species
present in different communities
Fig. 4-2, p. 61
Fig. 4-3, p. 61
Fig. 4-4, p. 63
Average annual precipitation
100-125 cm (40-50 in.)
75-100 cm (30-40 in.)
50-75 cm (20-30 in.)
25-50 cm (10-20 in.)
below-25 cm (0-10 in.)
Denver
Baltimore
San Francisco
St. Louis
Las Vegas
Coastal
mountain
ranges
Sierra
Nevada
Great
American
Desert
Coastal chaparral Coniferous
and scrub
forest
Rocky
Mountains
Desert
Great
Plains
Coniferous
forest
Mississippi Appalachian
River Valley Mountains
Prairie
grassland
Deciduous
forest
Fig. 4-4, p. 63
Science Focus: Insects
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Around for ~400 million years
Bad reputation
Useful to humans and ecosystems
Vital roles in sustaining life
– Pollinators
– Natural pest control
– Renewing soils
Fig. 4-A, p. 62
Fig. 4-A, p. 62
4-2 How Does the Earth’s Life
Change over Time?
• Concept 4-2A The scientific theory of
evolution explains how life on earth
changes over time through changes in the
genes of populations.
• Concept 4-2B Populations evolve when
genes mutate and give some individuals
genetic traits that enhance their abilities to
survive and to produce offspring with
these traits (natural selection).
Theory of Evolution
• Fossils
– Mineralized and petrified remains
– Skeletons, bones, and shells
– Leaves and seeds
– Impressions in rocks
– Fossil record incomplete: ~1% of all
species
• Charles Darwin, On the Origin of
Species, 1859
Population Changes over Time
• Populations evolve by becoming
genetically different over time
• Genetic variability – mutations
– Random changes in DNA molecules in
genes
– Can occur spontaneously
– External agents: radiation
– Can create a heritable trait
Natural Selection
• Adaptive traits - genetically favorable
traits that increase the probability to
survive and reproduce
• Trait – heritable and lead to differential
reproduction
• Faced with environmental change
– Adapt through evolution
– Migrate
– Become extinct
Evolution through Natural
Selection Summarized
• Genes mutate, individuals are
selected, and populations evolve
such that they are better adapted to
survive and reproduce under existing
environmental conditions.
Fig. 4-5, p. 65
(a)
(b)
(c)
(d)
A group of bacteria,
including genetically
resistant ones, are
exposed to an
antibiotic
Most of the normal
bacteria die
The genetically resistant
bacteria start multiplying
Eventually the
resistant strain
replaces all or most of
the strain affected by
the antibiotic
Normal bacterium Resistant bacterium
Fig. 4-5, p. 65
A group of bacteria,
including genetically
resistant ones, are
exposed to an
antibiotic
Normal
bacterium
Most of the normal
bacteria die
The genetically
resistant bacteria
start multiplying
Eventually the
resistant strain
replaces the strain
affected by
the antibiotic
Resistant
bacterium
Stepped Art
Fig. 4-5, p. 83
Adaptation through Natural
Selection Has Limits
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Humans unlikely to evolve and have skin
that’s not harmed by UV radiation
1. Desired trait must already be in the gene
pool.
2. Must have high reproductive capacity so
adaptive traits can be spread rapidly
Three Myths about Evolution
through Natural Selection Refuted
1. “Survival of the fittest” does not mean
“survival of the strongest”
2. Organisms don’t develop traits just
because they would be useful: giraffes
and long necks
3. There is no grand plan of nature to
create more perfectly adapted species –
no trend toward genetic perfection
Science Focus: How Did We
Become Such a Powerful Species?
• Key adaptations – also enabled us to
modify environment
– Opposable thumbs
– Walk upright
– Complex brains
• Transmit ideas to others
• Develop technologies to alter environment
Technology dominates earth’s life support
systems and NPP
4-3 How Do Geological Processes and
Climate Changes Affect Evolution?
• Concept 4-3 Tectonic plate
movements, volcanic eruptions,
earthquakes, and climate change
have shifted wildlife habitats, wiped
out large numbers of species, and
created opportunities for the evolution
of new species.
Plate Tectonics
• Locations of continents and oceans
determine earth’s climate
• Movement of continents allow species to
move and adapt
• Earthquakes and volcanoes affect
biological evolution by separating
populations of a species and allowing new
species to develop
Fig. 4-6, p. 66
225 million years ago
135 million years ago
65 million years ago
Present
Fig. 4-6, p. 66
225
million
years
ago
65
135
million
years
ago
Present
Stepped Art
Fig. 4-6, p. 66
Earth’s Long-Term Climate
Changes
• Cooling and warming periods – affect
evolution and extinction of species
– Change ocean levels and area
– Glaciers expanding and contracting
– Climate changes
• Opportunities for the evolution of new
species
• Many species go extinct
Fig. 4-7, p. 67
18,000
years before
present
Northern Hemisphere
Ice coverage
Modern day
(August)
Legend
Continental ice
Sea ice
Land above sea level
Fig. 4-7, p. 67
Science Focus: Earth is Just
Right for Life to Thrive
• Life needs a temperature range that
results in liquid water
• Earth’s orbit: right distance from sun
• Earth’s optimal gravity: keeps atmosphere
• Favorable temperature range over earth
history has promoted evolution and
biodiversity
• Favorable oxygen level in atmosphere
4-4 How Do Speciation, Extinction, and
Human Activities Affect Biodiversity?
• Concept 4-4 Human activities
decrease the earth’s biodiversity by
causing the premature extinction of
species and by destroying or
degrading habitats needed for the
development of new species.
Speciation
• Speciation
– One species splits into two or more
species that can no longer breed and
produce fertile offspring
• Geographic isolation
• Reproductive isolation
Fig. 4-8, p. 68
Arctic Fox
Northern
population
Early fox
population
Spreads
northward
and southward
and separates
Adapted to cold
through heavier
fur, short ears,
short legs, and
short nose.
White fur
matches snow
for camouflage.
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Gray Fox
Southern
population
Adapted to
heat through
lightweight
fur and long
ears, legs, and
nose, which
give off more
heat.
Fig. 4-8, p. 68
Science Focus: Changing
Genetic Traits
• Artificial selection
– Selective breeding: crossbreeding varieties
within same species to enhance desired traits
– Grains, fruits, vegetables, dogs, other animals
• Genetic engineering
– Add, delete, or alter DNA segments
– Add desirable genes from other species
– New drugs, pest-resistant plants
– Controversial
Extinction (1)
• Biological extinction
– Entire species gone
• Local extinction
– All members of a species in a specific area
gone
• Endemic species vulnerable to extinction
• Background extinction
• Speciation generally more rapid than
extinction
Extinction (2)
• Mass extinction
– Earth took millions of years to recover
from previous mass extinctions
• Balance between speciation and
extinction determines biodiversity of
earth
• Humans cause premature extinction
of species
Human Activities and Extinction
• Cause premature extinction of species
4-5 What Is Species Diversity
and Why Is It Important?
• Concept 4-5 Species diversity is a
major component of biodiversity and
tends to increase the sustainability of
some ecosystems.
Species Diversity
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Species richness
Species evenness
Varies with geographic location
Species richness declines towards
poles
Richness and Sustainability
• Hypothesis
– Does a community with high species
richness have greater sustainability and
productivity?
• Research suggests “yes”
4-6 What Roles Do Species
Play in an Ecosystem?
• Concept 4-6 Each species plays a
specific ecological role called its
niche.
Ecological Niche (1)
• Species occupy unique niches and play
specific roles in an ecosystem
• Includes everything required for survival
and reproduction
– Water
– Sunlight
– Space
– Temperatures
– Food requirements
Ecological Niche (2)
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Generalist species
Specialist species
Native species
Nonnative species
– Spread in new, suitable niches
Fig. 4-10, p. 72
Herring gull
is a tireless
scavenger
Black skimmer
seizes small fish
at water surface
Flamingo feeds on
minute organisms
in mud
Brown pelican
dives for fish,
which it locates
from the air
Avocet sweeps bill
through mud and
surface water in
search of small
crustaceans, insects,
and seeds
Louisiana heron
wades into water
to seize small fish
Scaup and other diving
ducks feed on mollusks,
crustaceans, and aquatic
vegetation
Ruddy
turnstone
searches
under shells
and pebbles
for small
invertebrates
Dowitcher probes
deeply into mud in
search of snails,
marine worms, and
small crustaceans
Oystercatcher feeds on
clams, mussels, and other
shellfish into which it
pries its narrow beak
Piping plover
feeds on insects
and tiny
crustaceans on
sandy beaches
Knot (sandpiper)
picks up worms
and small crustaceans
left by receding tide
Fig. 4-10, p. 72
Science Focus: Cockroaches
• Existed for 350 million years – 3,500
known species
• Highly adapted, rapidly producing
generalists
– Consume almost anything
– Endure food shortage
– Survive everywhere except polar regions
– Avoid predation
• Carry human diseases
Fig. 4-11, p. 72
Indicator Species
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Early warning system
Fish
Birds
Butterflies
Amphibians
Fig. 4-12, p. 74
Adult frog
(3 years)
Young frog
Tadpole
develops
into frog
Sperm
Sexual
reproduction
Eggs
Fertilized egg
development
Tadpole
Egg hatches
Organ formation
Fig. 4-12, p. 74
Keystone Species
• Significant role in their food web:
large affect on types and abundances
of other species in an ecosystem
• Elimination may alter structure and/or
function of ecosystem
• Pollinators
• Top predators
Foundation Species
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Create habitats and ecosystems
Beavers
Elephants
Seed dispersers
Science Focus: American
Alligator
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Highly adaptable
Only natural predator is humans
1967 – endangered species list
Successful environmental comeback
Keystone species
Case Study: Why Should We
Protect Sharks?
• Remove injured, sick animals
• Many are gentle giants
• Provide potential insight into cures for
human diseases such as cancer
• Keystone species
• Hunted and killed by humans
Three Big Ideas from This
Chapter - #1
• Populations evolve when genes
mutate and give some individuals
genetic traits that enhance their
abilities to survive and to produce
offspring with these traits (natural
selection).
Three Big Ideas from This
Chapter - #2
• Human activities are decreasing the
earth’s vital biodiversity by causing
the premature extinction of species
and by disrupting habitats needed for
the development of new species.
Three Big Ideas from This
Chapter - #3
• Each species plays a specific
ecological role in the ecosystem
where it is found (ecological niche).
Animation: Carbon Bonds
Animation: Stanley Miller’s
Experiment
Animation: Evolutionary Tree of
Life
Animation: Stabilizing Selection
Animation: Disruptive Selection
Animation: Moth Populations
Animation: Adaptive Trait
Animation: Speciation on an
Archipelago
Animation: Evolutionary Tree
Diagrams
Animation: Gause’s Competition
Experiment
Animation: Species Diversity By
Latitude
Animation: Humans Affect
Biodiversity
Animation: Habitat Loss and
Fragmentation
Animation: Transferring Genes
into Plants
Video: Ancient Human Skull
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Video: Asteroid Menace
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Video: Bachelor Pad at the Zoo
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Video: Cloned Pooch
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Video: Creation vs. Evolution
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Video: Dinosaur Discovery
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Video: Glow-in-the-Dark Pigs
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Video: Hsing Hsing Dies
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Video: Mule Clones
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Video: New Species Found
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Video: Penguin Rescue
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