Transcript Forces of Change

The process of change in a
species over a long period of
time
 Organisms with the traits
that help them survive best in
their environment, will survive
longer and pass on their genes
to more offspring.
 This will cause these traits or adaptations to be
found in higher frequencies in future
populations.

Overproduction
 Finite Resouces
 Natural Selection
 Genetic Variation

Every generation
produces more offspring
than can possibly survive.
 If all of these organisms
survived they would
overrun the Earth.
 These organisms compete
for the finite resources to
determine which
organisms survive and
which die.

Overproduction lead to
competition for resources.
 Most resources, such as food, water,
shelter, mates, and sunlight, will run out.
 These are finite
resources because there
is not enough to support
every organism born.

The organisms
with adaptations
that help them
outcompete
other organisms
for the finite
resources are the
ones who will survive to pass on their genes.
 These organisms typically have traits that help
them evade predators, deal with harsh
conditions of the environment, and find or
hunt food.

New traits usually start from
normal variations that
already exist within a
population.
 Some of these variations
give an organism an
advantage .
 For example, the whiter a
arctic hare is, the more it will
blend in with its surrounding
to hide from predators. This is
a high adaptive value.
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Genetic variation is cause by:
› Sexual reproduction
› Crossing over during meiosis
› Mutations

Changes in genes can lead to:
› Structural changes (ex: skin color,
limb structure, etc)
› Functional Changes (ex: eels using
the electrical output created by
muscles to electrocute prey)
› Behavioral Changes (ex: blinking
of fireflies that allows them to
communicate)
Variation in a
population is important
because the
environment changes.
 If all organisms of a
species were exactly the
same, a small
environmental change
could wipe out an entire species.
 Once diversity is lost it is nearly impossible to get
back.
 That is why scientists try to protect endangered
species.
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Changes in a species is often related to
environmental changes
› So, a rapidly changing environment will lead
evolution to occur more rapidly.
Species with short reproductive cycles
producing more offspring tend to evolve
more quickly.
 Failure to adapt to a change in the
environment may lead to extinction.

The disappearance of an
entire species.
 Extinction is possible when the
death rate is higher than the
birth rate.
 Extinction is usually caused by
big environmental changes
 Sometimes these big
environmental changes are
the fault of humans.
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Phylogenetic trees show
us when a species
divided to become two
separate species.
We can also see which
species were poorly
adapted and became
extinct.
We can determine
which organisms are
most closely related, by
looking at which
organisms have the
most recent common
ancestor.

What everyday things do we categorize or
group?
 Example: You group your own friends into
categories like jock, smart, popular, etc . . .

How do we determine these groups?
 Example: Those groups are determined by how
people dress, talk, who their friends are, their
hobbies, and their grades.
I’m not saying it’s good that we group people that
way, just using it as an example. Now think of your
own ‘non-people’ examples.
Must be meaningful and easy to
understand.
 Must be standard (the same) at different
times and in different places.
 Taxonomy – the science of classifying
and naming organisms.

Aristotle
 A Greek philosopher and
scientist
 Created two kingdoms:
Plant and Animal
 Grouped the animal
kingdom based on where
they lived: creatures of the
air, water, and land.
 Too many animals didn’t
fit into those categories.
Linnaeus
 A doctor and scientist who created a system
to classify animals based on similarities
 These similarities included body structure,
body systems, size, color, and means of
obtaining food.
Looks at the traits Linnaeus used
(size, body shape, etc) and traits
that are not so easy to observe
(chemicals in the body, DNA, etc)
 Modern classification has seven
levels.
Kingdom
King

Phylum
Class
Order
Family
Genus
Species
Phillip
Came
Over
For
Good
Spaghetti
Since Darwin came up
with the theory of common
descent, we have been trying to make
connections between species and figure
out how the diversity of life progressed
 We use trees to show these connections
 Any branch point on a tree indicates when a
common ancestor changed to become two or
more separate species.
 The organisms that share a more recent
common ancestor are more closely related

What we created with the shoes.
 Uses yes or no questions to create
groups.
 Gives a visual of the groupings.

An organized way
for other scientists
to find out which
group(s) a new
organism might
belong to.
 Puts the tree into
chart form.
 To use it you just
follow the steps . . .
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