Biodiversity and Evolution
Core Case Study: Why Should We Care about
the American Alligator?
 Largest reptile in North
America
 Importance of gator
holes and nesting
mounds
• Gator holes hold
freshwater during dry
spells and serve as
habitats for many
aquatic species
Core Case Study: Why Should We Care about
the American Alligator?
 1930s: Hunters and
poachers
 1967: endangered
species; protected from
poaching
 1977: comeback,
threatened species
Types of Diversity
 Species diversity
 Genetic diversity
 Ecosystem diversity
 Functional diversity –
variety of processes
such as matter cycling
and energy flow
Natural Capital: Major Components of
the Earth’s Biodiversity
What is classification?
 Classification
• a systematic
arrangement of
organisms into groups
or categories
 Taxonomy
• science of classifying
organisms
Why Classify?
 Set up an organized
system so scientists can
communicate
 Study similarities and
propose relationships
between organisms
 Show evolutionary
linkages between
organisms
Why Classify?
 Prevents misnomers
such as starfish and
jellyfish
 Prevents duplicated
names
• International Naming
Congress
Common Names
 One species can have many different names
• Example:
Mountain lion, puma, cougar, or panther?
•Vary among languages and regions
Keys to Binomial Nomenclature
Felis domesticus
 Must be in Latin
 Must be in italics or underlined
 Genus (1st word) must be capitalized
 Species (2nd word) must be lowercase
Correct or Incorrect?
 Triticum Aestivum - wheat
 Felis domesticus - cat
 canis lupus - wolf
 Canis familiaris - dog
 Populus deltoides - cottonwood
DICHOTOMOUS KEY
 Identification tool
 Uses paired statements to assist a person in learning
the identity of an object.
• Characteristics such as structure and behavior
 Think of a dichotomous key as a type of scavenger
hunt!
DICHOTOMOUS KEY EXAMPLE
1. a. tail fins are horizontal—whale………………….go to 2
b. tail fins are vertical—fish……………………….go to 3
2. a. has teeth or tusk—toothed whale………………..go to 4
b. has no teeth………………………...BALEEN WHALE
3. a. has gill slits behind mouth—shark…….………...go to 4
b. has no gill slits……………………..NONSHARK FISH
4. a. black with white underside………….KILLER WHALE
b. tusk, gray with dark spots………………....NARWHAL
5. a. head is hammershaped……..HAMMERHEAD SHARK
b. tail is half the body length……….THRESHER SHARK
Hierarchy of Classification
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Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Dear
King
Philip
Came
Over
For
Good
Soup
Inclusive: broad or
general in scope
Inclusive: broad or
general in scope
Exclusive: limited and
restricted; specific
Your Turn!
 Leaf and Seed Identification Kits
Biodiversity and Evolution
Chapter 4
Part 2: Natural Selection
Six Major Kingdoms of Species as
a Result of Natural Selection
Evolution by Natural Selection
 The Struggle for
Existence
• Darwin realized that
high birth rates and a
shortage of life's basic
needs would force
organisms to compete
for resources.
Evolution by Natural Selection
 Fitness
• Ability of an
individual to survive
and reproduce in its
specific environment
• Result of
adaptations.
Individuals in Populations with Beneficial Genetic
Traits Can Leave More Offspring
 Natural selection: acts
on individuals
 Differential
reproduction –
individuals with a
certain desirable trait
leave more offspring
than other members
The Genetic Makeup of a Population
Can Change
 Populations (not individuals) evolve by becoming
genetically different
 Genetic variations
• First step in biological evolution
• Occurs through mutations in reproductive cells
Individuals in Populations with Beneficial Genetic
Traits Can Leave More Offspring
 When environmental conditions change,
populations
• Adapt
• Migrate
• Become extinct
 Genetic resistance – ability of one or more
organisms in a population to tolerate a chemical
designed to kill it
• Malaria
A group of bacteria,
including genetically
resistant ones, are
exposed to an antibiotic
Normal
bacterium
Resistant
bacterium
Most of the normal
bacteria die
The genetically
resistant bacteria
start multiplying
Eventually the
resistant strain
replaces the strain
affected by
the antibiotic
What do you think…
 Will human adaptations allow our
skin to become more resistant to
the harmful effects of UV
radiation, our lungs to cope with
air pollutants, and our livers to
better detoxify pollutants?
Adaptation through Natural Selection Has
Limits
 Genetic change must
precede change in the
environmental conditions
• If the genes aren’t there, the
change won’t take place!
 Reproductive capacity –
species that reproduce in
greater numbers at a
higher frequency adapt
more quickly
Things to remember:
 “Survival of the fittest” is not “survival of the
strongest”
 Organisms do not develop traits out of need or want
Classification Systems
 Taxonomy – science of classifying organisms
• Assigns each organism a universally accepted
name that has biological significance
Classification Systems
 Taxonomic classification may change with
expanding knowledge about new and known
organisms
How do scientists classify new
organisms?
 They study their
characteristics.
 They try to see if they are
similar to other already
known organisms.
 They group a new
organism with others that
have similar
characteristics.
The Fossil Record Tells Much of the Story of
Evolution
 Fossils
• Physical evidence of ancient organisms
• Reveal what their internal structures looked like
• Represents only 1% of all species that have ever
lived
 Fossil record is incomplete: why?
Fossilized Skeleton of an Herbivore that Lived
during the Cenozoic Era
Scientists need to study organisms
COMPLETELY
Whale’s closest relative?
Whale’s closest living relative!
What characteristics are important?
 Similarities in DNA and RNA
• Genes show similarities at the
molecular level
• More similar the DNA, the more
recently they shared a common
ancestor
• Myosin: Humans and Yeast?
Your Turn!
 Lords of the Wild
• Panda Bears
• 29:30 – 33:00
 Computer Lab
 Phylogenetic Analysis
Using Molecular Data
Sets
• PART A ONLY
Biodiversity and Evolution
Chapter 4
Part 3: Species Richness vs.
Evenness
Species Diversity: Variety, Abundance of
Species in a Particular Place
 Species diversity
• Species richness –
number of different
species in a community
• Species evenness –
abundance of organisms
within each type of
species
Species Diversity: Variety, Abundance of
Species in a Particular Place
 Most species-rich
communities
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Tropical rain forests
Coral reefs
Ocean bottom zone
Large tropical lakes
Species Diversity: Variety, Abundance of
Species in a Particular Place
 1,700 different species
of beetles in a SINGLE
tree
• Tropical Rainforest –
Panama
• Species Richness?
• Species Evenness?
Worldwide Richness?
 Diversity varies with geographical location
• Richness is highest at tropics
• Lowest at the poles
Science Focus: Species Richness
on Islands (Ease of Study)
 Species equilibrium
model, theory of
island biogeography
• Rate of new species
immigrating should
balance with the rate of
species extinction
 Island size and distance
from the mainland
need to be considered
Species-Rich Ecosystems Tend to Be
Productive and Sustainable
 Species richness seems
to increase productivity
and stability
 Organisms more
resilient; greater
genetic diversity
Species-Rich Ecosystems Tend to Be
Productive and Sustainable
 Research suggests
annual net primary
productivity reaches its
peak with 10-40
primary producer
species
Your Turn!
 Species Diversity Index
Biodiversity and Evolution
Chapter 4
Part 4: Speciation
Geologic Processes Affect Natural Selection
 Tectonic plates affect evolution and the location of
life on earth
• Location of continents and oceans
• Species physically move, or adapt, or form new
species through natural selection
 Earthquakes
 Volcanic eruptions
225 million years ago
65 million years ago
135 million years ago
Present
Changes in Ice Coverage in the Northern
Hemisphere During the last 18,000 Years
Speciation
 Speciation is the
formation of new
species.
• Group of organisms that
breed with one another
and produce fertile
offspring.
What factors are involved in the
formation of new species?
 The gene pools of two populations must become
separated for them to become new species.
 As new species evolve, populations become
reproductively isolated from each other.
Geographic Isolation
 Geographic isolation
occurs when two
populations are
separated by
geographic barriers
such as rivers,
mountains, bodies of
water.
Geographic Isolation
 Does not guarantee
the formation of
new species
• May separate certain
types of organisms
(small rodents) but
not others (birds).
Genetic Drift
 Individuals may carry alleles in different relative
frequencies than did the larger population from
which they came.
The Founder Effect
 Situation in which allele frequencies change as a
result of the migration of a small subgroup
Reproductive Isolation
 When the members of two populations cannot
interbreed and produce fertile offspring,
reproductive isolation has occurred.
Reproductive Isolation
 Each population will respond to natural
selection as separate units
Geographic Isolation Can Lead to
Reproductive Isolation
Extinction is Forever
 Extinction
 Endemic species
• Species found only in
one area
• Particularly vulnerable
• Golden Toad (Costa
Rica) died out when
habitat dried up
Extinction Can Affect One Species or Many
Species at a Time
 Background extinction – throughout most of
history species have disappeared at a low rate
• Average annual extinction = 1 to 5 species for every
million on earth
 Mass extinction
• Significant rise in extinction rates
• Scientists estimate between 3 and 5 mass extinctions
during the history of the Earth
Video Clip
 Endangered Animals
• Echo 25:44 – 31:30
Science Focus: We Have Two Ways to Change
the Genetic Traits of Populations
 Artificial selection
 Genetic engineering, gene splicing
 Consider
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Ethics
Morals
Privacy issues
Harmful effects
Natural Selection on Polygenic Traits
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How does natural selection affect polygenic traits?
1. Directional Selection
2. Stabilizing Selection
3. Disruptive Selection
Directional Selection
 When individuals at one
end of the curve have
higher fitness than
others
 Range of phenotypes
shifts as some
individuals survive and
reproduce while others
fail
Stabilizing Selection
 When individuals near
the center of the curve
have higher fitness than
at either end
• Keeps the center of the
curve at its current
position
• Narrows the overall
graph
Stabilizing Selection
 Example
• Human babies born at
an average mass are
more likely to survive
than babies born either
much smaller or much
larger than average
Disruptive Selection
 When individuals at the
upper and lower ends of
the curve have higher
fitness than individuals near
the middle
 If the pressure of natural
selection is strong enough
and long enough, the curve
will split, creating two
distinct phenotypes
Disruptive Selection
 Example
• If average-sized seeds
become scarce, a bird
population will split into
two groups:
• One that eats small
seeds and one that eats
large seeds
Your Turn…Seed Lab!
 Step 1 – Sort your pile
of sunflower seeds
according to number of
stripes
• Only count ONE side
 Step 2 – Place your
seeds in appropriate
tubes
 Step 3 – Create a
paragraph describing a
situation which lead to
EACH of the following
types of selection
• Directional
• Stabilizing
• Disruptive
Biodiversity and Evolution
Chapter 4
Part 5: Ecological Roles
Each Species Plays a Unique Role
in Its Ecosystem
 Ecological niche
• Role a species plays in
an ecosystem
• Pattern of living
(reproduction, amount
of sunlight, space,
temperature, etc.)
 Habitat
• Location organism lives
Keystone, Foundation Species Determine
Structure, Function of Their Ecosystems
 Keystone species –
have a large effect on
the types and
abundances of other
species in an ecosystem
• Pollinators
• Top predator
Keystone, Foundation Species Determine
Structure, Function of Their Ecosystems
 Foundation species
• Create or enhance their
habitats, which benefit
others
• Elephants
• Beavers
Case Study: Why Should We
Protect Sharks?
 Keystone species
• Eat dead and dying fish
in the ocean
• Strong immune systems
• Wounds do not get
infected
• Almost never get cancer
• Could help humans if we
understood their immune
system
Each Species Plays a Unique Role
in Its Ecosystem
 Generalist species
• Broad niche
• Live in different places, eat
different food, high range of
tolerance
• Examples?
 Specialist species
• Narrow niche
• More prone to extinction
• Examples?
Specialist Species and Generalist Species
Niches
Niches Can Be Occupied by Native and
Nonnative Species
 Native species –
organisms that
normally live and thrive
in a particular
ecosystem
 Nonnative species invasive, alien, or exotic
species
• May spread rapidly
• Not all are villains
Indicator Species Serve as Biological Smoke
Alarms
 Indicator species – species that provide early
warnings of damage to a community or ecosystem
• Can monitor environmental quality
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Trout
Birds
Butterflies
Frogs
Coal Canaries: 1800s – 1900s
 Coal miners took caged
canaries into mines to
act as early warning
sentinels
 If birds stopped singing
and appeared to be
distressed miners knew
there were poisons
being released
Case Study: Why Are Amphibians Vanishing?
 Sensitive biological
indicators of
environmental changes
 Adult amphibians
• Eat more mosquitoes
than birds
 Genetic storehouse of
pharmaceutical
products
Case Study: Why Are Amphibians Vanishing?
 Habitat loss and fragmentation
 Prolonged drought
 Pollution
 Increase in UV radiation (no protection for eggs)
 Parasites, viral and fungal diseases
 Climate change
 Nonnative predators and competitors
Strange Days on Planet Earth Video Clip
 Troubled Waters: Frogs and
Atrazine