Transcript (natural selection).

ENVIRONMENTAL SCIENCE 13e
CHAPTER 4:
Biodiversity and
Evolution
Core Case Study p. 59
• What is the problem with amphibians since
1980?
• ____ % of all known amphibian species
are threatened with extinction
• More than ____ % in the Caribbean
• Populations of another ____ % are
declining
Core Case Study: Why Are
Amphibians Vanishing? (1)
•
•
•
•
•
Habitat loss and fragmentation
Prolonged drought
Increased ultraviolet radiation
Parasites
Viral and fungal diseases
Core Case Study: Why Are
Amphibians Vanishing? (2)
•
•
•
•
•
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
• Species=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- the variety of genetic material
within a species or a population
• Ecosystem diversity- the variety of terrestrial
aquatic ecosystems found in an area or on the earth
– Biomes: Large regions with distinct climate and certain
species especially vegetation
• Functional diversity- the biological and
chemical processes such as energy flow and matter recycling
needed for the survival of species, communities, and
ecosystems
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
Major biomes
Average annual precipitation
found in 39th parallel across the US
Differences reflect changes in climate,
Mainly average precipitation and temp
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
• Most of what we know of the history of life on
earth comes from fossils
• 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
• P. 64
Population Changes over Time
• Populations (not individuals) 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.
Natural Selection
An example
• In face of snow and cold
a few gray wolves in a
population that have
thicker fur might live
longer and produce more
offspring. Genes for
thicker fur spread
throughout the population
and individuals with those
genes increase in number
and pass this helpful trait
on to more offspring.
Evolution by natural selection
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
•
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.
2.
3.
“Survival of the fittest” does not mean “survival of the
strongest”
Organisms don’t develop traits just because they
would be useful: giraffes and long necks
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 allow us to grip and use tools
– Walk upright which freed out hands for many uses
– Complex brains
• Transmit ideas to others
• Develop technologies to alter environment
We have developed powerful technology and
taken over much of the earth’s net primary
productivity for our own use
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
225 million years ago
135 million years ago
65 million years ago
Present
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
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
• Geographic isolation-occurs when different
groups of the same population of a
species become physically isolated from
one another for a long period of time
• Reproductive isolation- the inability of a
species to breed successfully due to
geographical, behavioral, physiological, or
genetic barriers or differences
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
Extinction (1)
• Biological extinction: entire species gone
• Local extinction: All members of a species in a
specific area gone
• Endemic species (species found only in one
area) vulnerable to extinction
• Background extinction- normal low rate of
species disappearance
• Speciation generally more rapid than extinction
• Extinction is normal process but humans
have become major source of premature
extinction of growing number of species
(Ch 8)
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
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: number of different species
combined with the relative abundance of
individuals within each of those species
• Species richness-the number of different species
contained in a community
• Species evenness-relative abundance of individuals
within each of the species in a community
• Fig 4-9 Coral Reef: high species richness, low
evenness. Grove of Aspen trees low richness, high
evenness.
• Varies with geographic location
• Species richness highest in the tropics, 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)
• Generalist species-broad niches, can live in
many different places, eat a variety of different foods, can
tolerate a wide variety of different environmental conditions
• Specialist species- narrow niches, may be able
to live only in one type of habitat, use one or a few types of
food, or tolerate a narrow range of climatic or environmental
conditions
• Native species
• Nonnative species
– Spread in new, suitable niches
Specialized feeding niches of various bird species in a coastal wetland.
What benefit does specialization provide?
Fig. 4-10, p. 72
Case Study: Cockroaches
Generalists or Specialists?
• Existed for 350 million years – 3,500
known species
• Highly adapted, rapidly producing
– Consume almost anything
– Endure food shortage
– Survive everywhere except polar regions
– Avoid predation
• Carry human diseases
Fig. 4-11, p. 72
Niches
• Niches can be occupied by native and
nonnative species
– Native species: those species that normally
thrive in a particular ecosystem
– Nonnative species: invasive, alien, exotic
• Migrate into or are deliberately or accidently
introduced into an ecosystem
Indicator Species
• Species that provide early warning of
damage to a community or
ecosystem
• Ex. presence or absence of trout species is
indicator of water quality because trout need
clean water with high levels of dissolved oxygen
• Birds
• Butterflies
• Amphibians
Fig. 4-12, p. 74
Keystone
• Keystone is a wedge
shaped stone placed at
the top of a stone
archway. Remove this
stone and the arch
collapses.
• In some communities and
ecosystems, ecologists
hypothesize that certain
species play a similar role
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 ex. American
alligator
• Pollinators ex. Bees, butterflies,
hummingbirds, bats
• Top predators ex. Alligator, wolf, leopard,
lion, shark
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).
Core Case Study p. 59
• What is the problem with amphibians since
1980? Hundreds of species vanishing
• __33__ % of all known amphibian species
are threatened with extinction
• More than __80__ % in the Caribbean
• Populations of another _43___ % are
declining