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Transcript
Evidence of Species Change
Evidence of Evolution

What is evolution?


Evolution is change over time
Scientific theory of evolution explains how living
things descended from earlier organisms
Evidence of Evolution

What evidence supports evolution?

Fossils



Fossils are preserved remains or traces of organisms
that lived in the past
Scientists can infer the structure of ancient organisms by
looking at fossils
Fossil evidence supports the idea that living things
evolved from earlier organisms
Evidence of Evolution
Evidence of Evolution

What evidence supports evolution?

Similarities in DNA and protein







Scientists infer that species inherited many of the same genes
from a common ancestor
Genes are segments of DNA that determine the
characteristics in an organism
The more similar the sequence of bases in a strand of DNA,
the more closely the organisms are related
Genes determine the types of protein produced
Proteins are made of amino acids
Scientists compare sequences of amino acids to determine
closeness
Evidence from DNA and protein structures has confirmed
conclusions based on fossils, embryos, and body
structure
Evidence of Evolution
Section of Cytochrome c Protein in Animals
The table shows the sequence of amino acids in one region of a
protein, cytochrome c, for five different animals. Each letter
corresponds to a different amino acid in the protein.
Evidence of Evolution

What evidence supports evolution?

Similarities in body structure


An organism’s body structure is its basic body plan
Similar structures that related species have inherited
from a common ancestor are called homologous
structures
Evidence of Evolution
Homologous Structures
The bones in a bird’s wing, a dolphin’s flipper,
and a dog’s leg have similar structures. Which
bones in the dog's leg match those in the
flipper and which match those in the wing?
Evidence of Evolution

What evidence supports evolution?

Similarities in early development

Scientists infer evolutionary relationships by
comparing the early development of different
organisms
Evidence of Evolution
Can you tell which of
these four embryos
is:
a.
pig
b.
chicken
c.
turtle
d.
fish
Evidence of Evolution
Similarities in
Development
These four organisms
all look similar during their
early development. What
are similarities and
differences among them?
Evidence of Evolution - Classwork
1.
2.
3.
Compare and contrast the bones of a bird’s wing and a seal’s
flipper.
What can scientists infer from the similarities between these two
structures?
Describe how DNA evidence might be used to confirm scientists’
conclusions about any
relationship between birds and seals
Darwin’s Theory

What was Darwin’s hypothesis?
In 1831, the HMS Beagle set sail from England on a
five year trip around the world
Naturalist Charles Darwin was on board. He
 Was amazed by the diversity of living organisms
(different from England)
 Saw fossils of animals (that resembled the bones
of then-living organisms) that had died long ago
 Compared species living on the Galapagos
Islands with those living on the mainland of South
America
Darwin’s Theory

What was Darwin’s hypothesis?



Compared species living on different Galapagos
Islands
Concluded that different finches he found on the
Galapagos Islands were descended from the
same finches he found on the mainland of South
America
Different finches developed different beak shapes
and sizes depending on the food they ate
Darwin’s Theory

What was Darwin’s hypothesis?



Beak shape is an example of an adaptation, a
trait that increases an organism’s ability to survive
and reproduce
Darwin’s hypothesis was that species change
over many generations and become better
adapted to new conditions
This hypothesis had become known as the
Scientific Theory of Evolution, because it is a
well-supported and widely accepted explanation
Darwin’s Theory
Galápagos
Finches
The structure of
each bird’s beak is
an adaptation to
the type of food
the bird eats.
Match each
finch to the
type of food
you think it
eats.
Darwin’s Theory

What was Darwin’s hypothesis?
Update
 Peter Raymond Grant and Barbara Rosemary
Grant, British evolutionary biologists have spent
six months of the year each year since 1973
capturing, tagging, and taking blood samples of
the finches on the island.
 They have demonstrated how very rapid changes
in body and beak size in response to changes in
the food supply are driven by natural selection. Darwin’s Theory

What was Darwin’s hypothesis?



Darwin studied domestic animals produced by
artificial selection (selective breeding)
In artificial selection, only organisms with
desired traits are bred
A trait is a specific characteristic that an organism
can pass to its offspring
Ideas about Evolution

What was Darwin’s hypothesis?

Species


Individuals of the same species can interbreed and have
fertile offspring
Individuals of the same genus, but not the same
species, may be able to interbreed, but their offspring
are not fertile
Ideas about Evolution

What was Darwin’s hypothesis?

Artificial selection




All dogs and wolves are Canis lupus
Wolves are Canis lupus lupus
Domestic dogs are Canis lupus familiaris
Since they are all the same species, wolves and dogs
they can interbreed and have fertile offspring
The wolf
Great Dane
Chihuahua
Breeds of domestic dogs
Darwin’s Theory - Classwork

How does artificial selection support Darwin’s
hypothesis?