Transcript Document

Change Over Time
Are living things
related to other
living things?
Why do living
things change?
How do living
things change?
In your own words, describe
what YOU think the theory of
evolution means…
Charles Darwin
Darwin’s Theory of Evolution

Evolution, or change over time, is the
process by which modern organisms have
descended from ancient organisms.

A scientific theory is a well-supported
testable explanation of phenomena that have
occurred in the natural world.
Voyage of Beagle
Dates: February 12th, 1831
 Captain: Charles Darwin
 Ship: H.M.S. Beagle
 Destination: Voyage around the world.
 Findings: evidence to propose a
revolutionary hypothesis about how life
changes over time

Patterns of Diversity

Darwin visited Argentina and Australia which had
similar grassland ecosystems.

those grasslands were inhabited by very different
animals.

neither Argentina nor Australia was home to the sorts
of animals that lived in European grasslands.
What shaped Darwin’s theory?
Darwin studied the many different species
he saw on his voyage.
 He was curious and wanted to explain why
some species greatly resembled others
found elsewhere. He thought that they must
have had a common ancestor.

What shaped Darwin’s theory?

He noticed that most plants and animals that
inhabit a specific area are well suited to
their environment, but yet there are
different species all over the world even in
similar habitats.
 Example: Argentina, Australia, and
England have similar grassland
ecosystems, yet the animals living in
the areas were different.
What shaped Darwin’s theory?

•
Darwin collected and analyzed fossils.
Some of the fossils resembled organisms
that were still alive and others looked
completely unlike any creature he had ever
seen.
What shaped Darwin’s theory?

The Galapagos Islands
 Darwin observed that the characteristics
of many animals and plants varied
noticeably among the different
Galapagos Islands.
What shaped Darwin’s theory?
The finches on each island were different
 Beak type seemed to match the food available
on each island

What shaped Darwin’s theory?

Selective Breeding Experiments or
Artificial Selection
 Artificial selection is where plants or
animals with a desired trait are
specifically bred with the hopes of
increasing the chances that the trait will
appear in the offspring.
 Examples include dog breeding and
cultivating hybrid plants.
Patterns of Diversity

Darwin posed challenging questions.
 Why were there no rabbits in Australia, despite the
presence of habitats that seemed perfect for them?

Why were there no kangaroos in England?
Living Organisms and Fossils

Darwin collected the preserved remains of
ancient organisms, called fossils.

Some of those fossils resembled organisms that
were still alive today.
Living Organisms and Fossils
Others looked completely unlike any creature he had
ever seen.

As Darwin studied fossils, new questions arose.
 Why had so many of these species disappeared?

How were they related to living species?
The Galapagos Islands
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The smallest, lowest islands were hot, dry,
and nearly barren-Hood Island-sparse
vegetation

The higher islands had greater rainfall and
a different assortment of plants and
animals-Isabela- Island had rich
vegetation.
The Galapagos Island

Darwin was fascinated in particular by the land
tortoises and marine iguanas in the Galápagos.

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
inhabited.
If the only available food is located high on a bush,
which turtle is better adapted to eat?

Galapagos Island tortoises
• The tortoises’ shell shape and neck corresponded
to different habitats.
The Isabela Island tortoise has a
dome-shaped shell and a shorter
neck. The vegetation is more
abundant and closer to the ground
here.
The Hood Island tortoise has a long
neck and a shell that is curved and
open around the neck and legs,
allowing the tortoise to reach the
sparse vegetation on Hood Island.
There are finches on the mainland and on all the islands
The finches are very similar except for their beaks
The beaks differ from island to island
The beaks are always a match to the food source.
Darwin reasoned
the finches began as a single species in Equator
As competition for space & food increases, some finches fly to
one of the islands.
The food source on that island is slightly different, finches
lucky enough to have the ‘right’ beak for the new food – eat,
grow, develop, reproduce & pass on that “beak” trait.
Over time, more & more of the finches have the ‘new’ beak
A new species of finch begins.
Repeat to other islands
What did Darwin find out? How did Darwin interpret his observations?
Observation
Inference
Very similar birds
All finches
Lots of variation
Lots of competition
Environment can only support a limited
number of birds
By chance, some birds inherit beaks
that enable them to eat different
foods
Eat – survive -- reproduce –
Pass on “good” trait
Group 1
Group 2
Original beak
New beak
The birds share common ancestry
Similar birds
Different beaks
Different food sources
More birds can share same
environment because they are
not eating the same food
Natural Selection
-Species change, morph toward better balance with environment
-One species splits into 2 species
Animals found in the Galapagos
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Land Tortoises

Darwin Finches
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Blue-Footed Booby
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Marine Iguanas
The Journey Home
 Darwin
Observed that characteristics of
many plants and animals vary greatly
among the islands
 Hypothesis:
Separate species may have
arose from an original ancestor
What shaped Darwin’s theory?

Charles Lyell (geologist)
 Proposed the idea of uniformitarianism
 Proposed the idea that the age of the
Earth was much older than commonly
thought at that time (Like billions of
years old instead of thousands)
Lamarck’s Theory of Evolution
•
Jean-Baptiste Lamarck (Was TOTALLY WRONG!)
 Thought organisms could change their traits in
response to environmental changes. Then these
changes would be passed on to their offspring.
 Example: Thought that a giraffe could stretch its
neck to reach higher food and then pass its long
neck on to its kids.
 Lamarck was WRONG, but he was the first to
figure out that organisms adapt to their
environments.
What shaped Darwin’s theory?

Thomas Malthus (Economist)


Said that there were too many organisms and
not enough natural resources so organisms
were in competition with each other.
Darwin realized Lyell’s idea of an older
earth allowed for the time needed for
changes to occur in populations. Malthus’
idea on competition provided the force that
caused changes in a population.
The Science Theory of Evolution
• Species* change over time and space – staying a
good match to their environment
• All organisms share common ancestors with
other organisms.
explains the similarities of organisms & the inheritance of traits
The primary mechanism of change over time is natural
selection.
species - populations of interbreeding organisms
Essential Question
Why do some
organisms survive
and others do not?
Moth Story
There is naturally variation in the color in
moth offspring - light to dark gray. In the
original forest, moths live near tree trunks
that are light in color. In this environment
the light gray color moths have advantage.
(matching the tree color helps them not get
eaten, so they can eat and survive.)
However, when a new factory is built nearby
soot and smoke accumulates in the air
causing the tree trunks to darken.
In terms of Natural Selection - what will
happen to the moth population?
Let’s explain how that will happen
Natural selection (12:44): http://www.youtube.com/watch?v=aTftyFboC_M&safe=active
Darwin’s Theory of Natural
Selection:
1.
In nature, organisms produce more offspring than can
survive.
2.
Individuals have variations that make them different
from others of their own kind.
3.
Individuals in the same population compete to survive.
4.
Individuals with favorable variations survive and pass
their genes on to offspring.
5.
Over time, offspring with certain variations make up
most of a population and can look and act very
different from their ancestors.
What is the “good” variation(s) ?
How does that “good trait” give advantage ?
What is the ‘good” variation ?
How does that “good trait” give advantage ?
What is the ‘good” variation ?
How does that “good trait” give advantage ?
What is the “good” variation ?
How does that “good trait” give advantage ?
What is the ‘good” variation ?
How does that “good trait” give advantage ?
Who has the answer?
Natural Selection & Artificial
Selection

Natural variation--differences among
individuals of a species

Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
useful.
Evolution by Natural Selection

The Struggle for Existence-members of
each species have to compete for food,
shelter, other life necessities
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Survival of the Fittest-Some individuals
better suited for the environment
Natural Selection

Over time, natural
selection results in
changes in inherited
characteristics of a
population. These
changes increase a
species fitness in its
environment
Natural Selection
Adaptation: any inherited characteristic that
increases an organism’s chance of survival.
 Explains how evolution occurs: the gradual
change in species over time
 Evolution occurs in species if the variation
helps the organism to survive. This variation
must then be passed on to offspring.


Evolution applies to a whole population
NOT an individual!
Adaptations

Structural Adaptations:
1. Mimicry: one species mimics the appearance
of another.
Viceroy
Bee
(Non-Toxic)

Monarch
Bumble Bee Moth
(Toxic)
How would looking like a dangerous species be a survival
advantage?
Adaptations

Structural Adaptations:
2. Camouflage: species blend in with
surroundings.
Walking stick
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Leopard
Ground squirrel
How would blending in be a survival advantage?
http://www.pbs.org/wgbh/nova/evolution/evolution-action-salamanders.html
Adaptations

Physiological Adaptations:
 Adaptations in the jobs that body parts
perform
 Antibiotic Resistance (MRSA)
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http://www.popsci.com/article/science/fda-aims-reduce-use-antibioticsfattening-farm-animals
http://www.popsci.com/science/article/2012-02/how-antibiotics-yourmeat-are-making-superbugs-stronger
Pesticide Resistance

http://www.nytimes.com/2010/05/04/business/energyenvironment/04weed.html?pagewanted=all&_r=0
2 ways the present day
chicken is better adapted to
today’s environment than its
ancestor would have been
1. smaller size – needs less food for survival,
2. has feathers rather than fur – lighter and water
resistant – can fly?
Descent
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Descent with Modification-Each living organism has
descended, with changes from other species over time
Common Descent- were derived from common
ancestors
Evidence of Evolution

The Fossil Record

Geographic Distribution of Living Things

Homologous Body Structures

Similarities in Early Development
Evidence for Evolution
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The Fossil RecordLayer show change
Geographic
Distribution of Living
Things
Homologous Body
Structures
Similarities in Early
Development
Evidence of Evolution
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The Fossil Record
Geographic
Distribution of
Living Things-similar
environments have
similar types of
organisms
Homologous Body
Structures
Similarities in Early
Development
Homologous Structures
 Homologous
Structures-structures that
have different mature forms in different
organisms, but develop from the same
embryonic tissue
Comparative Anatomy
In what specific ways are these ‘forearms’ alike?
Comparative Anatomy
How does anatomy support the
Theory of Evolution?
 Common prototypes
o backbone, legs, eyes
•Internal organs – heart,
digestive, nervous
 Same structure modified
for different purposes
Well adapted animals have advantage
in their environment
Let’s activate our thinking with this
brainstorm:
Limbs
help an animal
move - but there are
lots of variations.
Record 3 different types of limbs &
how they help animals move
Evidence for Evolution
 Vestigial
organs- any structure that is
so reduced in function or size that they
are just vestiges or traces of the original
structure.
 The structure may have been used in
an ancestor, and may still be used in
another animal alive today.
 i.e.)
appendix, miniature legs
Example #1:
Appendix in
humans
Example #3:
Pelvic bone in
whales
Example #2:
Small leg bones in
pythons
Evidence for Changes Over Time

SIMILARITIES IN
EMBRYOS: similar embryos
suggest that similar genes are
at work in early development.
 Groups of embryonic cells
develop in the same order
and in similar patterns. The
same set of genes control
this development. Suggest a
common ancestor. Show
strong evolutionary
relationships
Evidence for Changes Over Time

DNA/amino acid comparisons:
 The more similar the DNA the more
closely related organisms are.
What’s an embryo?
Embryology = the study of embryos
How does embryology
support the Theory of
Evolution?
Similar developmental
pattern
Supports common
ancestry
Evidence of Evolution
Embryology
How does embryology
support the Theory of
Evolution?
Evidence of Evolution
Embryology
How does embryology
support the Theory of
Evolution?
Similar developmental
pattern
Evidence of Evolution
Embryology
How does embryology
support the Theory of
Evolution?
Similar developmental
pattern
Supports common
ancestry
Embryos and DNA (3:43) :
http://www.dnatube.com/video/420
7/What-Can-Embryos-Tell-UsAbout-Evolution
4 Key Points that support the Theory of Evolution
#1
• in any population, lots of offspring are born
• many die
• There is a struggle to survive
4 Key Points that support the Theory of Evolution
#2
•There are variations within a population
• Some variations make it easier to survive
4 Key Points that support the Theory of Evolution
#3
• Well adapted adults survive (eat & don’t get
eaten)
• grow & develop
• reproduce
• pass on traits
• resulting in well adapted offspring
4 Key Points that support the Theory of Evolution
#4
•As the environment changes, different
variation in traits help an organism survive.
• Individuals with these variations survive
Adaptation & Evolution is always about the ones who
survive!!
Summary of Darwin’s Theory

Individuals in nature differ from one
another

Organisms in nature produce more offspring
than can survive, and many of those who do
not survive do not reproduce.
Summary of Darwin’s Theory

Because more organisms are produced than
can survive, each species must struggle for
resources

Each organism is unique, each has
advantages and disadvantages in the
struggle for existence
Summary (cont.)

Individuals best suited for the environment
survive and reproduce most successful

Species change over time
Summary (cont.)

Species alive today descended with modification
from species that lived in the past

All organisms on earth are united into a single
family tree of life by common descent
Meerkat Adaptations (45sec): http://video.nationalgeographic.com/video/education-videos/education-general/edu-meerkatadaptations/
Zebra Stripes: http://animal.discovery.com/tv-shows/other/videos/fooled-by-nature-zebras-stripes.htm
Extinction
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Adaptations allow organisms to survive in their
environment.
However, organisms that are too well-adapted (or
specialized) to their environment have trouble
adjusting if the environment changes suddenly.
Extinctions occur when species disappear from earth
forever.
Mass extinctions occur when a lot of different species
become extinct in a short period of time.
Extinction rate is the speed at which species are
disappearing.
Mass Extinction
The first mass extinction, the Permian extinction,
occurred 248 mya and wiped out 90% of the
species on earth.
 Possibly caused by an Ice Age and/or a massive
volcano.
 The second major mass extinction, the
Cretaceous-Tertiary extinction, occurred 65 mya
and wiped out 50% of species including
dinosaurs.

Human-Caused Extinctions

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Human activities are rapidly changing natural habitats.
Extinction rate is skyrocketing right now. This is
known as the “biodiversity crisis”
Biodiversity refers to the wide variety of different
types of organisms that live on Earth.
Biodiversity is important for a healthy ecosystem.
It is easier for bio-diverse ecosystems to recover from
natural disasters and other sudden changes.
 Different species are all connected in the ecosystem so the
extinction of one might lead to the extinction of lots more.

Why Is Biodiversity Important? Who Cares?
Endangered Species
In order to protect biodiversity many
governments and non-profit organizations
are committed to protecting endangered
species.
 An endangered species is one whose
numbers are so low that it is in danger of
going extinct.
