Download 3.2 Origins of Biodiversity

Topic 3
Biodiversity & Conservation
3.2 Origins of
Biodiversity
Evolution by Natural Selection
• Darwin proposed his theory in The Origin of
Species by Means of Natural Selection (1859)
“Survival of the Fittest”
Main idea:
More favorable genes
increase in frequency in
successive generations, and
fewer unfavorable genes
survive.
Darwin’s Voyage
Evolution by Natural Selection
• 4 observations about nature:
1. Overproduction
• More offspring produced
than will survive to maturity.
2. Competition
• Environment can’t support everyone…
• competition for resources
• disease
3. Variation
• Individuals have unique
combinations of traits that
make them more/less “fit”
for their environment.
4. Differential reproductive success
•Those individuals with the
most “fit” traits for their
environment are more likely
to survive, reproduce, and
pass their traits on to the
next generation!
Natural Selection Summary
• Overproduction  Competition
• Variation  Differential Reproductive Success
• Comp + Diff Repro Succ  Natural Selection
Types of
Natural Selection
Directional
Selection
• One extreme of a
specific trait is more
advantageous than both
the other extreme and
the average trait.
• It pays to be different!!
• Examples:
– Peppered Moth
– Bacteria that are
genetically resistant to
some antibiotics.
Stabilizing
Selection
• Tends to eliminate
individuals on both ends
of the genetic spectrum.
• It pays to be average!!
• Occurs when the
environment changes
little and most species
are well-adapted.
• Often mistaken for no
selection
• Example: birth weight
Diversifying
(Disruptive) Selection
• Individuals at both
extremes are selected for,
average is selected against.
• It pays to be either
extreme!!
• Examples:
– Green vs.
Brown Anole
– Darwin’s Finches
Darwin’s Finches
Each finch species is specialized
for a particular lifestyle (structure
of their beaks)
An adaptation to their specific
diets seed eaters, cactus eaters,
insect eaters, fruit eaters) and
different from finches on the
South American mainland.
14 species of Galapagos finches
decended from a single ancestorone or a small population of
finches that originally colonized
the Galapagos.
Types of
Species Evolution
Convergent Evolution
• Two different species who live in the same
type of habitat evolve to have similar traits.
• Example: Sharks and dolphins
– Dolphins are mammals, Sharks are fish.
– So how did they convergently evolve?
• They look the same and act in similar manners
because they both live in the ocean, so they’ll need
similar traits!
CONVERGENT
EVOLUTION
Convergent Evolution
Divergent Evolution
• Two populations of the same species who
live in different places evolve to become
different…
• Example: Birds
– Now we have penguins & puffins!!
– So how do they divergently evolve?
• Penguins live where it’s cold and where there’s lots
of water. There’s more food for them in the water, so
they evolved to “fly” underwater.
• Puffins live where it’s slightly warmer. There’s lots
of food sources outside of the water, so they
continued to fly normally.
Again… Darwin and the birdies
Adaptive
Radiation
process by which
ancestral species
evolve into a
number of diff
species
**special type of divergent evolution**
Divergent Evolution
Divergent Evolution
Coevolution
• Two species that interact closely
may change in a similar fashion
He is fast!
I have to
run faster!!
Yummy….
Rabbit for
dinner!
• Example: a wolf and a rabbit
Why
does he
want to
eat me?
I am
sooo
cute!
I will run
faster
then…
– How are they related in an ecosystem?
– So how do they co-evolve?
• If the rabbit evolves to be faster, the wolf will have to
keep up, so it must also evolve to be faster.
Animal/Plant Coevolution
The gracefully
curved bill of the
‘I’iwi enables it to
sip nectar from
flowers of the
lobelia. The ‘I’iwi
bill fits perfectly
into the long tubular
lobelia flowers.
Coevolution in Plants
Acacia Tree & Ant
* Tree has large hollow thorns that provide a
protected nesting site for stinging ants.
Ants attack any animal and clear away
vegetation surrounding the tree which helps
the tree get the sunlight it needs.
Caterpillars & Plants
•Plants may have poisonous
chemicals that prevent insects from eating
them.
•Some caterpillars have the ability to resist
these poisons.
•They can feed on plants that other insects
can’t
•As the plant adapted by producing poisonous
chemicals, the caterpillar adapted by
resisting them.
Coevolution
Natural Selection
&
Species Evolution
THERE IS A BIG DIFFERENCE!!!
What is it???
Nat Select  Evolution  Speciation
• Remember from earlier:
– Overproduction  Competition
– Variation  Differential Reproductive Success
– Comp + Diff Repro Succ  Natural Selection
• So……..
• NAT SEL + GENERATIONS  EVOLUTION
• SPECIATION: Evolution that causes a species
to change enough to not be able to interbreed
anymore
Speciation occurs from:
• Physical Barriers
– Gene pool no longer mixes, so two populations develop in
different directions
– New mountain range, river flow change, etc
• Land Bridges
– Allow species to invade new areas
– Sea level falling, continental drift, etc.
• Continental Drift
– Cause climates to shift & food supplies to change
– Ex: Antarctica was tropical, has now lost its forested area
PHYSICAL BARRIERS
cause
GEOGRAPHIC ISOLATION
leading to
World
Grand
SPECIATION
Isolation
Canyon
Group Discussion
How can Plate Tectonics act as a speciation force?
What type of Natural Selection would this be?
What type of Species Evolution would this be?
Continental Drift
Continental Drift- The continents have moved.
They were together in Pangaea. Began to separate ~200 MYA.
Proposed by German scientist Alfred Wegner (1912)
SUPPORTING EVIDENCE:
- Puzzle-like continental shape
Hi! I'm Alfred!
- Rock correlations
- Fossil correlations
- Climatic data
EVIDENCE FOR CONTINENTAL DRIFT
1. “Puzzle” - like fit to
the continents
CLICK HERE
FOR
ANIMATION
2. Fossil Evidence
- Animal and plant fossils have been found on
distant continents
3. Rock Evidence
Appalachian Mountains
share the same rock
features as mountains in
Greenland & Europe
4. Climatic evidences: Coal in Antarctica
There's coal in Antarctica!!!
What's the big deal? Isn't coal just a rock?
1. Coal is made from swamp plants that live in
rainy, temperate climates
2. These plants could NEVER have lived in a
climate like Antarctica's!!
3. CONCLUSION: It must have been nearer to the
Equator once
4. Climatic Evidence: Glacial Deposits
- Found in Africa, India, Australia & South America
- CONCLUSION: must have been nearer to the
South Pole once!
Continental Drift VS Plate Tectonics
• Continental Drift: the continents used to be
together in Pangaea, but have slowly drifted apart.
• Why was Alfred Wegener not believed?
• He couldn’t explain WHY! He died in 1930. 
• WHY do the continents drift?
• …PLATE TECTONICS!!!
Earth's Structure
Three main sections: crust, mantle, core
Demo:
Plasticity
PLATE TECTONICS
Movement of lithospheric plates carrying the continents.
Plate Boundary:
Where two plates meet and interact.
Intense geologic activity occurs here!
Plates are made of lithosphere and float on
asthenosphere (magma)
Plate motion is due to convection currents
in the asthenosphere.
Three types of Plate Boundaries:
(1) DIVERGENT BOUNDARY
-plates move apart
-creates a rift valley
-magma is exposed at the boundary
-constructive or destructive margin?
Divergent (oceanic)
Divergent (continental)
(2) Convergent Boundary: plates come together
3 types:
a. Continental-Continental:
-creates mountains
(Appalachian & Himalayas)
b. Continental-Oceanic:
-oceanic subducts (> density)
to create a trench & land
volcanoes (West Coast US)
c. Oceanic-Oceanic:
-older plate subducts (>density)
to create a trench & volcanic
islands (Japan, Philippines)
SUSUBDUCTION ZONE:
One plate is forced below another.
Constructive or destructive margin?
Convergent Continental-Continental
Convergent Oceanic-Continental
Convergent Oceanic-Oceanic
(3) Transform Boundary:
plates slide past one another
-creates a fault line
Transform
Where are the Constructive and Destructive Margins?
Click for
ANIMATION!
What kind of boundary is this...
convergent, divergent, or transform?
Is it constructive or destructive?
The arrows represent what process?
Geologic Time Scale
• Earth is 4.6 BY old
• First life: bacteria, 4 BYA
• Dinosaur Extinction 65 MYA
• Humans: 200,000 years ago
• Currently in:
–Phanerozoic Eon
–Cenozoic Era
–Quaternary Period
–Holocene Epoch
Background vs Mass Extinctions
• Background Extinction: natural species extinction.
• Expected to be about
1 species per million species per year
(that’s about 10-100 species per year)
• Contrast with Mass Extinction: many species go
extinct at the same time.
•  Our current extinction rate is significantly higher
than 1species/million species/year… Mass Extinction!!!!
Past Mass Extinctions
• Many species die at the same time. They cannot
withstand significant changes in conditions from:
– Rapid climate changes
– Some natural disaster (volcanic eruption, meteor impact)
• There have been 5 major mass extinctions.
• Most recent historical mass extinction was 65 MYA
when the dinosaurs went extinct. Due to:
– Meteor impact off the Yucatan Peninsula
– Series of long-term volcanic eruptions in India
– Both ejected dust into atmosphere
• (↓photosynthesis, breaking down food webs)
Current Mass Extinction
• We may now be in a sixth mass extinction…
• The Holocene Extinction Event.
– Anthropogenic
– Began ~10,000 years ago with large mammal extinction
(mammoth, etc) from hunting
– Accelerated greatly in last century due to modern humans
•
•
•
•
Transform environment (cities, roads, industry, agriculture)
Overexploit other species (fishing, hunting, harvesting)
Introduce invasive species (may have no predators)
Pollute the environment (may kill species directly or indirectly)
Extinction Rebounds
• After each past mass extinction, there was a rebound
of species.
The rebounds take
5-10 million years.
• Humans have made such a significant impact in such
a short time. Would you expect this same type of
rebound to occur? If so, would it be faster, slower, or
the same?