Transcript Evolution - Cobb Learning

Evolution
Chapter 15
What is Evolution?
Evolution, or change over time, is
the process by which modern
organisms have descended from
ancient organisms.
Who is Charles Darwin?
Charles Darwin – born in England
 Joined the crew of the
H.M.S. Beagle
 Sailed around the world
 Made numerous observations
and collected evidence that
led him to propose his
hypothesis.

What did Darwin Observe during his voyage?
Patterns of Diversity:
•
Puzzled by where different species lived and did not live
•
He Asked:
* Why were there no rabbits in Australia, despite the
presence of habitats that seemed perfect for them?
* Why were there no kangaroos in England?
* Why do they look so similar?
What did Darwin observe during his voyage?
Living Organisms & Fossils
•
Darwin collected and preserved fossils
•
Fossils resembled organisms that were still alive –
other looked completely unlike any creature he had
ever seen.
He Asked:
Why had so many of these species
disappeared?
Looks nothing like any living
species
Looks LIKE a Kangaroo
What did Darwin Observe?
The Galapagos Islands
•
Most influential place Darwin visited
•
Although islands were so close together, the islands had very
different climates.
•
Fascinated by the land tortoises, marine iguanas, & finches.
Clicker Question:
Where are the Galapagos Islands?
D
A
C
B
What did Darwin observe on the
Galapagos Islands?
Click to zoom into Galapagos Islands
What did Darwin observe on the Galapagos Islands?
Galapagos Tortoises
* Domed shell w/ short neck
* Live on wetter islands
* Have short necks that
can reach grasses and
vegetation on the ground
What did Darwin observe on the Galapagos Islands?
* Flatter shell compared to
domed
* Live on slightly drier
islands
* Have longer necks than
domed to reach short
bushes and trees
What did Darwin observe on the Galapagos Islands?
* “Saddle” w/ VERY long necks
* Live on dry islands
* Dry climates have less
vegetation on the ground
* Long neck used to reach
vegetation up in bushes & trees
growing off the ground
What did Darwin observe on the Galapagos Islands?
•
All tortoises resemble a species living in South America
•
Saw that giant tortoises varied in predictable ways from
one island to another.
•
The shape of a tortoise’s shell could be used to identify
which island a particular tortoise lived.
http://www.anapsid.org/chaco4.html
Natural Selection Questions
(Bill Nye)
1.
2.
3.
4.
5.
6.
7.
A young man that walked out was __ ___.
He quit medical school to become a ___.
How long did the Beagle stay in the Galapagos
Islands? __ days
Finches had different shaped ___: varied by
the environment they inhabited.
What was the mechanism that made evolution
occur? ___ ____
When did he publish his book?
Now, every where we look at today, we see
something that came from ___.
Natural Selection Clip
(Bill Nye)
Who influenced Darwin’s ideas?
James Hutton and Charles Lyell

Recognized that Earth is many millions of years old.

And the processes that changed Earth in the past are
the same processes that operate in the present.
Hutton and Lyell
said…

Volcanoes release hot lava and gases now, just
as they did on an ancient Earth.

Erosion continues to carve out canyons, just as
it did in the past.

Also said that awesome geological features
could be built up or torn down over long periods
of time. (examples: earthquakes and volcanoes)
Wild/Crazy Idea: Earth changes over time
Hutton and Lyell
So……Because of Hutton & Lyell’s work…..
Darwin then asked:
If the Earth could change over time,
might life change as well?
Who else influenced Darwin’s Ideas?

Malthus (an economist) – Studied population
growth - observed that babies were being born
faster than people were dying.
He reasoned that if the human population
continued to grow unchecked, sooner or
later there would be insufficient living space
and food for everyone.

What is Carrying Capacity?
A VERY brief look:
The largest number of individuals
of a population that a given
environment can support.
Carrying capacity & darwin
Who else was thinking about evolution?
Lamarck’s Theory of Evolution
Proposed that by selective use or disuse of
organs, organisms acquired or lost certain
traits during their lifetime.
Was he “right”?
These traits could then be passed on to their
offspring.
Lets break it down….
Over time, this process led to change in a species
How did Lamark think organisms changed?
Fiddler Crabs: An Example
1. The male crab uses its small front
claw to attract mates and ward off
predators
2. Because the front claw has been
used repeatedly, it becomes
larger (acquired).
3. A larger claw, is then passed on to
the crab’s offspring.
He was WRONG! He did not realize
that the large claw traits were
inherited
Lamark’s Theory
Another Example:
According to Lamarck's
theory, a given giraffe could,
over a lifetime of straining to
reach high branches,
develop an elongated neck.
The long neck is ACQUIRED
Darwin’s Book
The Origin of Species

The actual title of his book is:
The Origin of Species by Means of Natural Selection
•
The book proposed a mechanism for
evolution that he called natural selection.
•
He presented evidence that demonstrates
the process of evolution has been taking
place for millions of year. Darwin was 50 when it was
published!
What were Darwin’s arguments in his book?
Natural Variation and Artificial Selection
•
Argued that species were NOT perfect and
unchanging.
•
Natural Variation: There are differences
among individuals of a species.
What is Natural Variation?
White Version/Morph
Peppered moths
come in two
versions
Black Version/Morph
If trees in an area have dark bark, the
black version blends in better and is
less likely to be eaten by predators.
If trees in an area have white bark, the
white version blends in better and is
less likely to be eaten by predators.
What is Natural Variation?
Bessie
Elsie
* Elsie’s natural variation is to produce more milk than Bessie
* Which cow would the farmer use to reproduce offspring? Why?
What were Darwin’s
arguments in his book?
Artificial Selection: Nature provided the
variation among different organisms, and
humans selected those variations that they
found useful.
* Only the largest hogs, fastest horses, and the
cows that gave the most milk were selected to
breed and produce offspring.
Darwin’s Evolution by Natural Selection

The Struggle for Existence: Means that
members of each species compete regularly to
obtain food, living space, and other necessities
of life.

A predator that is the fastest or has a particular
way of catching prey can catch more prey.

Prey that are faster, better
camouflaged, or better protected
avoid being caught.
Darwin’s Evolution by Natural Selection

Survival of the Fittest: Process by which
individuals that are better suited to their
environment survive and reproduce most
successfully; also called Natural Selection.

Darwin called the ability of an individual to
survive AND reproduce in its specific
environment fitness.

An adaptation is any inherited characteristic
that increases an organism’s chance of
survival.
Darwin’s Discoveries Video Clip
Survival of the Fittest

The concept of fitness, Darwin argued, was
central to the process of evolution by natural
selection.
Example:
Baby birds compete for food in the nest. The
stronger bird may take food from the weaker
siblings.
Evolution by Natural Selection
Descent with Modification: Principle that each
living species has descended, with changes,
from other species over time.
•
Implies that all living organisms are related to
one another.
Common Descent: The principle that says all
species – living and extinct – were derived from
common ancestors.
What are some evidence of Evolution?
Fossil Record
Fossils that had formed in
the different layers of rock
were evidence of gradual
change over time.
One could view how a
species had changed and
produced different species
over time.
What are some evidence of Evolution?
Geographic Distribution of Living Species
• Species now living on different
continents had each descended from
different ancestors.
• However, because some animals on
each continent were living under similar
ecological conditions, they were
exposed to similar pressures of natural
selection.
• They ended up evolving certain
striking features in common.
• This is called Convergent Evolution
What are some evidence of Evolution?
Sugar Gliders & Flying Squirrels
Convergent evolution
What are some evidence of Evolution?
Homologous Structures: Structures that have
different mature forms in different organisms
but develop from the same embryonic tissues.
What are some evidence of Evolution?
Similarities in Early Development
In their early stages of development, chickens,
turtles, and rats look similar, providing evidence
that they shared a common ancestry.
Evolution
What are some evidence of Evolution?
•
Analogous structures can be superficially
similar in construction, but are NOT inherited
from a common ancestor.
•
Example: The wing of an eagle & the wing of a
insect have the same function (both enable the
organism to fly) – but are constructed in
different ways & from different materials.
What are some evidence of Evolution?
* While analogous structures do not indicate
close evolutionary relationships, they do show
that functionally similar features can evolve
independently in similar environments.
Vestigial Structures
•
Vestigial Structures are structures that are the
reduced forms of functional structures in
different species.
Examples:
1. Snake Pelvis: The pelvis is the attachment
point for legs and is therefore nonfunctional in
an animal without legs
Vestigial Structures
2. Kiwi Wing: The wings of kiwis are too small to
be of any use in flight
3. Human Appendix: Important for digestion in
many mammals, but of limited use in humans &
some apes
Adaptations:
A body part, body covering, or
behavior that helps an organism
survive its environment.
Adaptations:

Mimicry: Adaptation in which one species
evolves to resemble another species for
protection or other advantages.
Adaptations:

Camouflage: Adaptation
that allows organisms to blend
into their surrounds.
Plants:
Tropisms (Responses):
1) Phototropism: Responds to light
Plants:
Tropisms (Responses):
2) Thigmotropism: Responds to touch
Plants:
Tropisms (Responses):
3) Gravitropism: Responds to gravity
Video Here/Turn volume off!
Cactus
Waxy Covering:
Prevent water loss
Ridges:
Expand to store more water
when it rains
Thorns:
Protect against being eaten
No Leaves:
Prevent water loss
Polar Bear
Short/small Ears:
Thick Blubber:
Save Heat
Keep warm
Large Paws:
Walking on snow
White/clear Fur:
Blend in with snow
Long Claws:
Catching prey/digging
Adaptation Poster
1.) Animal must be drawn, in color, & neat
2.) Must include background environment
3.) Must have at least 5 adaptations w/ explanation
Not adaptations:
* How long they live
* Where they live
* How many babies the have
* What they eat
Adaptations:
* Large paws, thick beak, bright colored feathers,
skinny legs, large ears, sharp teeth, fur thickness….