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Artificial Selection aka Selective Breeding
 Darwin noted that plant and animal breeders would breed
only the largest hogs, the fastest horses, or the cows that
produced the most milk.
 Darwin termed this process artificial selection or selective
breeding.
Copyright Pearson Prentice Hall
Evidence of Evolution
Darwin argued that living things have
been evolving on Earth for millions
of years. Evidence for this process
include:
1. Fossils
2. Comparative anatomy
3. Biochemistry of different life forms
Fossil Evidence
 Paleontology: Study of the
fossil record.
 Fossils: Remains or traces of
organisms that lived in past
ages, to understand past life
forms.
Fossil Evidence
 By comparing fossils from
older rock layers with fossils
from younger layers, scientists
could document that life on
Earth has changed over time.
Copyright Pearson Prentice Hall
Fossil Evidence in sedimentary rock
Fossil Evidence
 Some scientists have found
transitional fossils.
 Transitional fossils: Show a
transition from one species to
another.
 For example: Whales
Transitional Fossils of Whales
• Older whales were hoofed
mammals that lived on land.
• These animals were able to
walk on land and swim.
• Later, fossils suggest that over
time, the hind limbs of the
whales’ ancestors shrank.
• Their forelimbs became
flippers.
• Their hind limbs became a tail
called a fluke.
Comparative Anatomy/Physical Features:
Homologous Structures
Body parts of different
organisms that have a
similar structure but may
have different functions.
Copyright Pearson Prentice Hall
Comparative Anatomy: Homologous
Structures
Composed of similar bones. Must mean they all shared an
ancestor that had a similar structure.
Comparative Anatomy: Analogous
Structures
Analogous Structures
 Body parts that have a similar
function but not a similar
structure.
 They do not indicate shared
ancestry.
Copyright Pearson Prentice Hall
Comparative Anatomy: Analogous
Structures
Bird wing and butterfly wing
Comparative Anatomy: Vestigial Structures
Vestigial Structure:
A body part that does not
seem to play a major role in
an organism’s life functions
but was more important in
the organism’s ancestors.
Rats also have an appendix
suggesting we share a
common ancestor.
Copyright Pearson Prentice Hall
Comparative Anatomy: Embryology
Embryology: Study of embryos.
Embryo: Early stage of development in an organism.
Embryos of related organisms develop in similar ways.
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Copyright Pearson Prentice Hall
Human embryo
Biochemical Evidence of Evolution
 Recall that all organisms contain the nucleic acid:
DNA.
 DNA directs the production of proteins which are
made of amino acids.
 The more similar an amino acid sequence is, the
more closely related organisms are and most likely
shared an ancestor.
 We can compare hemoglobin: a protein found in
RBC’s to determine this.
Biochemical Evidence
Biochemical Evidence
 In addition to hemoglobin,
Cytochrome C is another
protein that determines
how closely related species
are to one another.