Transcript Document
Theory of Evolution
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.
How do you think Darwin came
up with his theory?
Voyage of the Beagle
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.
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?
Fossils
The Galapagos Island
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.
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
Land Tortoises
Darwin Finches
Blue-Footed Booby
Marine Iguanas
Animals
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
To understand how radical Darwin’s thoughts
appeared, you must understand a few things
about the world in which he lived
Most Europeans belived the world was only a
few thousand years old
Nothing had changed since creation
Rocks and major geological features were
thought to have been produced suddenly by
catastrophic events that humans rarely ever
witnessed
Slowly after studying many scientific theories
of his time, Darwin began to change his
thinking dramatically
Hutton and Lyell
Geological forces that have shaped Earth
form very slowly, often over millions of
years
Hutton and Geological Change
Geological
forces that have shaped
Earth form very slowly, often over
millions of years
Therefore Earth had to be much
more than a few thousand years old
Lyell’s Principles of Geology
Lyell – author “Principles of
Geology”
Process that shaped the Earth millions
of years earlier continue in the present
Darwin Thought: If the earth could
change over time, could life be
changing as well?
Charles
Lamarck
Lamarck’s Theory of Evolution
Tendency toward Perfection(Giraffe
necks)
Use and Disuse (bird’s using forearms)
Inheritance of Acquired Traits
Lamarck’s Evolution Hypothesis
Jean – Baptiste Lamarck
French naturalist
One of the first scientists to recognize that
living things have changed over time, and that
all species were descended from other species
Also realized, that organisms were somehow
adapted to their environments
Lamarks theory had 3 aspects to it
Tendency toward perfection
Organsims continually change
and acquire features that help
them live more successfully
Ex.) Birds wanted to fly, so their
wings grew and became suited to
flying
1.
2. Use and Disuse
Body parts that were used developed, and
those that were not went away
Ex.) Reptiles stopped using their legs and
evolved into snakes
3. Evolution of Acquired Traits
Organsims that changed a characteristic
in their lifetime, would pass that change
on to its offspring
This
theory is WRONG!
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
Natural Selection
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.
Adaptation
when an organism becomes better fitted to survive and
multiply in its environment.
Evolution by Natural Selection
The Struggle for Existence-members of
each species have to compete for food,
shelter, other life necessities
Survival of the Fittest-Some individuals
better suited for the environment
Struggle For Existence &
Survival of The Fittest
Natural Selection
Over time, natural
selection results in
changes in inherited
characteristics of a
population. These
changes increase a
species fitness in its
environment
Extinct Species
a species that no longer exists anywhere on
earth
Classification/Taxonomy
biological classification is a system which is
used to organize and codify all life on Earth.
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
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
The Fossil RecordLayer show change
Geographic
Distribution of Living
Things
Homologous Body
Structures
Similarities in Early
Development
Evidence of Evolution
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
Evidence for Evolution
Vestigial
organs-organs that serve
no useful function in an organism
i.e.) appendix, miniature legs, arms
Similarities in Early
Development
DNA
deoxyribonucleic acid: an extremely long macromolecule
that is the main component of chromosomes and is the
material that transfers genetic characteristics in all life
forms
Genetic Diversity
- the level of biodiversity, refers to the total number of
genetic characteristics in the genetic makeup of a species.
Phenotype
is an organisms observable characteristics which are
influenced both by its genotype and by the environment.
Genotype
is the set of genes that an organism carries.
Similarities in Embryology
Many
embryos look especially similar
during early stages of development
All vertebrates go through a stage in
which they have gill pouches
Similarities suggest an evolutionary
relationship among all vertebrate
species
Nature at Work Intro
Mendel’s Work
Gene
A segment of DNA that codes for a particular protein.
Gene Pool
All the genes of all the members in a population.
Nature at Work Intro
Mendel’s Work
Vocab:
Allele
Dominant
Recessive
Pure bred
Hybrid
Genotype
phenotype
Mutation
- A mutation occurs when a DNA gene is damaged or
changed in such a way as to alter the genetic message
carried by that gene.
Selective Pressure
Any environmental factor that favors one trait over
another.
Genetics – working (non-technical) definitions
Allele
The variations a trait comes in
Tall, short (inherit 1 allele from each parent)
Dominant The allele that will show if it is present
T
Recessive Only shows when both alleles are recessive tt
Present but not showing when dominant is
present Tt
Pure bred Both inherited alleles are the same TT or tt
Hybrid
Inherits 1 dominant & 1 recessive allele from
parents Tt
Genotype The gene type
TT, Tt, tt
Phenotype The visible trait
Evidence of Evolution
DNA
How does DNA support the Theory
of Evolution?
DNA has double helix structure
All animal DNA very similar
(except human)
Plant DNA similar but with less
chromosome pairs
All DNA has similar nucleic acids
Summary of Darwin’s Theory
1.
2.
3.
4.
Individual organisms in nature differ from one
another. Some of this variation is inherited
Organisms in nature produce more offspring than
can survive, and many of those that survive do not
reproduce.
Because more organisms are produced than can
survive, members of each species must compete for
resources.
Because each organism is unique, each has different
advantages and disadvantages in the struggle for
existence.