Download Adaptations Over Time

Standard
S7L5
Students will examine how organisms have
changed because of inherited
characteristics that promote the survival of
the organism and future generations of
offspring.
Learning Target
I can explain the process of natural
selection.
Adaptations Over Time
Many organisms on the Earth today
existed millions of years ago. Do you
think they stayed exactly the same or
have changed over time?
Characteristics within the next
generation are sometimes altered.
One change over time involves the
camel.
Let’s look at some of the changes that
have occurred in camels.
The characteristics of a species
are passed from parent to
offspring.
• Characteristics of a species may
evolve or change.
• This is simply saying organisms
change over time.
• This is a theory.
A Theory is…
an explanation of things or
events based on scientific
knowledge that is the result
of many observations
and/or experiments.
Species
• A species is a group of organisms that share
similar characteristics and can produce fertile
offspring.
• A species is the smallest of the classification
system.
• There are 34 species of deer.
• Related species would be in a genus.
• There may be many species within a genus.
• Note the next slides to help explain this.
Levels of Classification
Clues about Changes
•
•
•
•
Vestigial Structures
Homologous Structures
Fossil Record
Natural Selection
Vestigial Structures
Features which
serve no useful
function any longer
in the organism.
An example of such features is
the pelvis bone in the whale or
the “wisdom” teeth in humans.
Homologous
Structures
Those which share a
common origin, but
serve different
functions in today’s
species.
Clues in Fossils
• There were fossil clues left behind in the
rocks!
• This is called the fossil record.
The Fossil Record
• Fossil remains have been found in rocks of all
ages.
• Fossils of the simplest organisms are found in
the oldest rocks on the bottom of layered rock
• Fossils of more complex organisms in the
newest rocks, or rock layers stacked on top
• The fossil record supports the theory that simple
life forms gradually evolved into more complex
ones.
Rocks and Fossils
• Sedimentary rocks are made up of
deposits of organic (once living) and
other material, laid down over
hundreds of thousands of years.
• Organisms are buried in between the
layers and their remains may
eventually be preserved as fossils.
History of the Horse
• The history of the horse has
been preserved in fossil
form.
• Over 60 million years the
horse evolved from a dogsized rainforest-dwelling
creature, into an animal
adapted to plains-dwelling
and standing up to two
meters high.
Relative Dating
• This does not tell the exact age of a fossil
It is an approximation or estimation of age.
• The estimation is made by looking at the
rock layers below and above the layer in
which the fossil is found.
• The older rocks are usually below the
younger rocks.
• So, fossils found in lower layers are
usually older than those found in upper
rocks.
Note the Timeline…..
Index Fossils
• INDEX FOSSILS are unique or found in
only certain time periods.
• Index fossils are used to date rock layers.
Radioactive Dating
• This is a more accurate picture of the age
of a fossil.
• Radioactive elements are used for this.
• While organisms are alive, they take in
small amounts of radioactive elements.
This stops when they die. By comparing
the amount of radioactive element in a
sample to the amount of element into
which it decays, scientists can calculate
the age of a fossil.
The Dog
Fossil evidence shows
that all dogs (scientific
name: Canis familiaris)
have a common
ancestor - the wild grey
wolf (Canis lupus).
Over 14,000 years
humans have 'designed'
some 400 breeds of
domestic dog,
artificially selecting the
looks and behavior of
each breed.
• Neither Precise NOR
Accurate
• This is a random-like
pattern, neither
precise nor accurate.
The darts are not
clustered together
and are not near the
bull’s eye.
• Precise, Not Accurate
• This is a precise
pattern, but not
accurate. The darts
are clustered together
but did not hit the
intended mark.
• Accurate, Not Precise • Precise and Accurate
• This is an accurate
• This pattern is both
pattern, but not
precise and accurate.
precise. The darts
The darts are tightly
are not clustered, but
clustered and their
their “average”
average position is
position is the bull’s
the center of the bull’s
eye.
eye.
Who realized things evolved?
• In 1831,
Charles
Darwin, a
naturalist,
sailed on the
HMS Beagle
from England
to the
Galapagos
Islands off the
coast of South
America (near
Ecquador).
Just so you know …
• Darwin made his journey on the HMS
Beagle during his twenties.
• His book was published in his fifties.
On his journey he
observed 13 species of
small birds called finches.
He noticed they were all
the same except for body
size, beak shape, and what
they ate. He then made a
startling discovery----- the
shape of the beak
influenced what the
finches ate.
Many times more offspring are
produced than can survive.
• Galapagos finches lay eggs every few
months. Darwin realized that in several
years two parent finches could produce a
huge population!
• A population is all the individuals of a
species that live in the same area at the
same time!
• Members of a large population compete
for food, space, and other resources.
• Darwin realized that the finches must have had
to compete for food!
• Those finches that can best survive are more
likely to reproduce and pass on their
characteristics to the next generation.
• Finches which had beak shapes that allowed
them to eat available food survived and were
able to pass on their DNA.
• After many generations, these groups of finches
became separate species with genetic
variations of their beaks to the kinds of foods
they ate!
What did Darwin do with his
discoveries?
1. He shared his findings.
2. He wrote a book known as The Origin of
Species.
Darwin suggested…
1. An organism’s fitness depends on the
traits it inherits from its parents.
2. Any inherited trait that increases an
organisms’ fitness is called an
adaptation. (The beaks were
adaptations.)
3. The fittest survive, or those best adapted
to their environment.
For Example:
• Early giraffes may have had short necks and
legs.
• When their population grew, they competed for
food.
• As they ate all the ground vegetation, they
started competing for low-hanging leaves.
• Some were born with mutations that resulted in
longer necks and legs. These were more
successful at getting food.
• These were the survivors that were left to pass
on their DNA.
Natural selection in brief..
• Natural selection is the natural process
where the best-adapted individuals
survive, reproduce, and pass on their
DNA.
• DNA controls the traits of an organism.
• Natural selection is also called “survival of
the fittest.”
Example of Natural Selection in
Action
• Before the industrial revolution most peppered
moths were pale.
• This allowed them to be camouflaged against
the pale tree trunks.
• Moths with the black colored mutation were
easily seen and eaten.
• The industrial revolution in the 19th century
brought airborne pollution. This put soot
everywhere. It also allowed the black moths to
blend-in better against the darkened tree bark.
• Over time, the mutated black peppered moths
were naturally selected to survive and pass on
their DNA.
Which moth is camouflaged?
Black Peppered Moths
before the Industrial
Revolution
Black Peppered Moths
after the Industrial
Revolution
Simulation
• After completing this section of the notes,
you will participate in a simulation.
• Who will survive?
• http://peppermoths.weebly.com
Variations
• The theory of natural selection
emphasizes differences among individuals
of a species.
• These differences are called variations.
• A variation is an inherited trait that makes
an individual different from other members
of its species.
• Variations result from mutations in an
organism’s genes.
Variations
• Beneficial variations are what allow an
organism to adapt to its environment.
• Variations that are involved in adaptations
can be color, shape, behavior, or chemical
makeup.
Darwin’s Theory
1. Every species is fertile enough that if all
offspring survived there would be too many.
Yet, populations remain roughly the same size.
2. Resources are limited and a struggle for
survival takes place.
3. In species that reproduce sexually, no two
individuals are identical.
4. There are inherited variations.
5. Those that are less suited to the environment
will not survive to pass on DNA.
6. Those individuals that do survive pass on their
DNA.
These occurrences
• slowly produced populations adapted to
the environment.
• created new varieties and new species
after many generations.
The Speed of Change
• There are two major hypotheses on how
change takes place.
• Gradualism—Organisms evolve through
a process of slow and constant change.
(Examples: Camel, Horse-many millions
of years)
• Punctuated Equilibrium—Species
change very rapidly. (Example:
Bacteria—decades, thousands, or a few
millions of years)
Those organisms that can’t adapt or
change may become extinct. How do we
know that extinct organisms have existed
or organisms have changed?-----Clues are
there.
Extinction
• Sometimes species
die out or become
extinct.
• There are many
endangered species
threatened with
extinction now.
Reasons
for Extinction
• Increase in the Number
of predators
• Failure to compete with
other species in the
same habitat
• Natural catastrophes
• Impact of New
Diseases
• Impact of Man
• Rapid Climatic or Other
Environmental Change
Changes Over
Time!
Evolution – changes of
species over time due
to adaptation to their
environment
• https://www.youtube.com/watch?v=wrTXvr
KBlbc