Transcript A Closer Look at Natural Selection…

We’ve already learned that biodiversity is important. Let’s define
the various types of biodiversity, however, since there are many:
• Species Diversity
• Ecosystem diversity
• Functional diversity
• Genetic diversity
• Cultural diversity
• Supplies us with food, wood, fibers, medicines, and energy
• Preserves the quality of our water and air
• Maintains the fertility of the soils
• Helps in the disposal of wastes
• Helps control populations of pests
Kingdom Plantae, 250,000
We’ve already spent some time evaluating
the importance of
species
Protista…250,000
biodiversity.Kingdom
Let’s
remind ourselves exactly what biodiversity
species
Kingdom
is…
Animalia,
1,000,000
• The variety of the Earth’s species, the genes
they contain,
species
the ecosystems in which they live, and the ecosystem
processes such as energy flow and nutrient cycling that
sustain all life.
fly agarics
mushroom
Kingdoms Eubacteria, and
Kingdom
Archaebacteria…10,500 speciesFungi,
50,000
far, scientists
species
So
have identified 1.8
million of Earth’s
predicted 4-100
million species.
So…just where did all these
organisms come from, and how did
this biodiversity happen?
There are few things in science that are as controversial
as the origins of life, but the fact is that however it
started, it has persisted on Earth for nearly 3.8 billion
years! As scientists speculate that the first life on Earth was
Prokaryotic…just how did such diversification occur?
The work done in the 1800s by Charles Darwin, and Alfred Wallace helped to
explain how this all happened.
Fossil
Stromatolites
Current Stromatolites Complex Multicellular Heterotrophs
A Closer Look at Natural Selection…
Stromatolites: A record of the oldest life on Earth…
Teleoceras: Fossilized Rhino
Fossil Stromatolites
The fossil
record is
incomplete.
Why?
Some animals
don’t leave
fossils behind.
Still others
have been
destroyed by
the rock cycle.
The work of piecing together evidence of past life from fossils is done by the
Paleontologist
Which of life’s kingdoms contains the most
species?
What two people contributed most to our
understanding of evolutionary processes?
Describe the process of Natural Selection…in a
nutshell.
How do we know anything about prehistoric life
on Earth?
Why is the fossil record incomplete?
How do species evolve?
The environment in which an organism lives determines
what traits or variations are favorable
• Genetic Drift
Slight random changes in the genetic makeup of a
population over time
This genetic variability is created by chance mutations in genes of organisms, while
DNA is replicating.
• Natural Selection
• Somatic cells
• Germ cells
What characteristics have allowed humans to dominate Earth the
way they have?
 Opposable Thumb
 Walking Upright
 Complex Brain
Will humans escape
extinction?
NO!
What are agents of mutation called?
What is the difference between somatic cells and
germ cells?
Why are germ cells important to evolution?
What three adaptations are most important to
Homo sapiens’ success as a species?
Nature does not “create” advantageous traits…it will only select
advantageous traits that already exist in a population that have
been created by mutations.
 Even if that trait is present, reproductive capacity
may hold back the evolutionary tendency
K-Selected strategies
r-Selected strategies
Throughout Earth’s Geologic History, the environments have
changed greatly.
Gorgonopsid in Permian Desert
A high degree of genetic biodiversity allowed life to continue on
this planet that is constantly changing!
What type of reproductive strategies gives organisms
more of a chance to evolve rapidly?
How do r-selected species differ from K-selected
species? Give examples of each.
How do plate tectonics influence evolution?
How can earthquakes and volcanoes influence
evolutionary processes?
When natural selection leads to an entirely new species, a
process called “speciation” has occurred. Speciation can occur
in a number of ways:
 A species may become Geographically Isolated
 A Species is Reproductively Isolated
A natural process which affects the levels of biodiversity on Earth
is extinction. Extinction occurs when the last surviving individual
of a species is gone.
The most vulnerable species
are “endemics”, who are only
found in one area.
• Amphibians
Coqui
Blue Poison Dart Frog of Surinam
Takahe in New Zealand
Panamanian golden frog
137
species
The one plus that occurs during periods of mass extinction is that
it gives new species the opportunity to fill the habitats and niches
left by the now extinct organisms.
What two ways did we learn that speciation can occur?
Why are amphibians so sensitive to extinction?
What is an endemic and why are they especially
vulnerable to extinction?
In what ways are mass extinctions good for organisms?
What does it mean to be “endangered”?
Niche is not to be
confused with habitat,
which is where an
organism lives.
Niches are used to
help define species
as either
“generalists” or
“specialists”.
Roaches, the great generalists
The narrower the niche, the more prone to extinction a species is.
Giant Swallowtail Butterfly
American Elm in Fort Worth
Lichens
Tree of Heaven
North American Bison
Remove the keystone, and the arch tumbles
Black-Tailed Prairie Dogs
Bald and golden eagles, swift foxes, coyotes, ferruginous hawks, burrowing owls,
badgers and black-footed ferrets, countless insects and other invertebrates, as well as
plants also rely on Prairie Dogs and their activities.
What’s the difference between the niche of the generalist, and the niche of the
specialist?
Which are more susceptible to extinction, and why?
What are some other names that non-native species go by?
Why are non-native species especially dangerous to native species?
By what types of organisms do ecologists gauge the health of an ecosystem?
What types of organisms make good “indicator” species?
Give an example of a keystone species, and describe why they are considered
“keystone”.
Give an example of a foundation species…etc..
Each of you will produce at least a four-slide PowerPoint presentation…to be added
to a “class presentation”. Each person will become an expert on one extinct, and
one endangered organism, and be prepared to discuss and answer questions after
their presentations. Each person’s presentation must have a cover slide (slide one)
with name, and species identification, as well as three other slides with imported
graphics/pictures/animation, and:
Slide Two: Highlight one species that has become extinct on Earth (with
picture)
 When? Why…what were the circumstances?
What niche did they fill in their ecosystem? (generalist or specialist?)
What was their habitat like? Were they keystone species, or
foundation? Etc…
 Tell how the extinction of that species impacted/affected/ caused a
cascade effect in their ecosystem, or impacted at least two other
organisms (with pictures)
Slide Three: Choose an endangered species, (with picture) and tell about why
they’re endangered (niche? Habitat? Keystone? Endemic? Etc…) Predict what
would happen in their ecosystem if they were to become extinct.
 Slide Four: Citations page
You will have two days in class to work on this project…