Transcript Evolution

Define the following:
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Micro
Macro
Gradual
Barrier
Reproductive Isolation
Diversity and Speciation
What is a species?
• A population or group of populations
whose members:
– have the ability to breed with one another IN
NATURE
– Produce fertile offspring
Macroevolution
• Dramatic biological changes including:
– Origin of new species (speciation)
– Extinction
– Evolution of major new features
Reproductive Isolation
• Reproductive barriers keep two very
similar species from interbreeding.
Reproductive Barriers Between Species
• Timing
– Different breeding seasons.
– Breed at different times of the day.
Reproductive Barriers Between Species
• Behavior
Reproductive Barriers Between Species
• Habitat
– Wolves and domestic dogs
Reproductive Barriers Between Species
• Reproductive structures are incompatible.
Reproductive Barriers Between Species
• Hybrid offspring may be infertile.
Geographic Isolation
• Separation of
populations as a result of
geographic change or
dispersal to isolated
places.
Geographic Isolation
• Small “splinter” populations can break off
from a larger population and evolve into a
new species.
• Speciation only occurs if one population
can no longer breed with the other
population.
Adaptive Radiation
• Evolution from a common ancestor of
many species adapted to diverse
environments.
Rates of Speciation
Do Now
Identify three
homologous
structures that all
of these
organisms share.
Do you think these
structures arose
independently of
one another or did
they arise from a
common
structure?
Evolution:
A remodeling Process
Section 15.2
Refining Existing Adaptations
• In some cases complex structures evolve
from simpler structures.
• Example: Eyes of different mollusks
Limpet
• The cells can only
detect light or dark. It
can’t detect the
direction of the light.
Slit Shell Mollusk
• Detects light and the
direction of light,
allowing the animal to
move towards or
away from the light.
• Can not form an
image.
• Pinehole Eye:
– Dim image – little light
enters the eye
• Eye is fragile as it is
exposed to the
outside environment.
Marine Snail
• Allows more light in than the
pinehole does.
• Image is brighter but still
fuzzy.
• Cornea protects the eye.
Squid
• Camera type eye which
makes a sharp image.
• The shape of the lens
changes to sharpen the
image.
Simple vs. Complex
• Simple eyes are enough to meet the
needs of certain organisms.
• Complex eyes probably evolved from
small steps of adaptation.
Adapting Existing Structures to
New Functions
• How has the shell of a
lobster adapted?
• Think about the
environments where
these animals live.
Adapting Existing Structures to
New Functions
• How has the penguin
adapted?
The fossil record
How fossils form
• Hard parts such as shells, bones, or teeth,
are long-lasting and may become
preserved as fossils.
• Under the right conditions, minerals
dissolved in groundwater seep into the
tissues of a dead organism and replace its
organic material. The remains become
petrified—they turn to stone.
What we can learn
Some fossils consist of footprints, animal
burrows, or other impressions left in
sediments. These tracks provide clues
about whether the animal walked or ran
and about its size and speed.
Dating fossils: Relative Ages
Because younger sediments are usually
layered over older ones, you can tell which
layers formed before others. The relative
ages of fossils reflect the order in which
groups of species existed compared to one
another.
Dating fossils: Absolute Ages
• Radiometric dating - method most often
used to determine the absolute ages of
rocks and fossils.
• Based on the measurement of certain
radioactive isotopes in objects.
How is radiometric dating done?
• Every radioactive isotope has a fixed rate
of decay.
• half-life - the number of years it takes for
50 percent of the original sample to decay.
How is radiometric dating done?
Uranium-238 has a half-life of 4.5 billion years.
Uranium-238 is not present in living organisms.
It occurs in molten lava and volcanic rock that
forms as lava cools. After volcanic rock forms,
no more uranium-238 is incorporated. As the
isotope decays it becomes lead-206.
By measuring the ratio of uranium-238 to lead206, researchers can find the absolute age of
volcanic rocks.
Direct determination
• Fossils contain isotopes of elements
that accumulated in the organisms
when they were alive—i.e. carbon-12
and radioactive carbon-14.
• When an organism dies radioactive
decay continues. Changes in the ratio
of carbon-14 to carbon-12 can be
measured to calculate how long the
organism has been dead.
• What was the mass before nuclear decay
if two half lives occurred and the mass
after nuclear decay was 8g?
• The uranium-238 to lead-206 ratio in a
rock is found to be equal. How old is the
fossil if the half life of uranium is 4.5 billion
years?
• 32
• 4.5 billion years old.
Taxonomy
What is Taxonomy??
• The identification, naming, and
classification of species.
• Why bother with taxonomy?
Linnaean System
• 2 part Latin name
– 1st part was the genus name
– 2nd part was the species name
• Example: Panthera pardus (lepard)
Phylogenetic Tree
• A diagram that reflects a
how evolutionary
relationships are thought
to develop.
• Homologous structures
are used to determine
how closely related
organisms are.
PROBLEMS!
• Not all similar structures are inherited from
a common ancestor!
• Unrelated species who share a similar
environment may have developed similar
adaptations (analogous structures) for that
environment. This process is known as
convergent evolution.
Cladograms
• Phylogenetic tree
constructed from a
series of two-way
branch points.
• The cladogram to the
right shows that
lepards and cats are
more closely related
than wolves and cats.
Cladograms
• Each evolutionary
branch is called a
clade.
• A clade consists of an
ancestral species and
all its decedents.
• How many do you
see here?
Make this cladogram