Download Other Evidence for Evolution

Many types of evidence
support evolution.
Chapter 6 Section 4
The Fossil Record
• Preserved remains or traces of an
organism that lived in the past
What Is
A
Fossil?
How Do MOST Fossils Form?
• An
organism
dies and
becomes
buried in
sediment
How Most Fossils Form
Then People Find Them!
What Do Fossils Reveal?
• Fossil record: millions of fossils that scientists
have collected
• Most of what we know about extinct species
• Provides clues about how and when new
groups of organisms evolved
• Extinct: no members of the species are alive
Fossils and Evolution
Fossils!
Elephant Evolution
Elephant Evolution!
Common Ancestor
Evidence for Evolution
Biological evidence
supports evolution.
• State evidence from modern-day
organisms that scientists use to show
evolutionary relationships among groups.
• Describe how scientists classify organisms
and place them on branching trees.
Vestigial
Structures
Similarities in Body Structure
• homologous structures: similar structures
that related species have inherited from a
common ancestor
• Example: fish, amphibians, reptiles, birds
& mammals all have an internal skeleton
with a backbone
Homologous Structures
Similarities in Early Development
• embryos suggest common ancestor
• Similar organisms go through similar
stages in early development
• Who is a closer relative: chickens and rats
or chickens and turtles?????
Which Embryo Is Human?
Guess The Embryo!
Try Your Luck!
Genetic Evidence:
Similarities in DNA
• Related Species have many of the same
nitrogen bases in common
• Compare order of amino acids in similar
proteins
• Elephant shrews – rodent or elephant????
Golden-rumped sengi
Rhynchocyon chrysopygus
Weight = 550 g.
Gedi Ruins, Kenya
• The new species, named the gray-faced sengi (Rhynchocyon
udzungwensis), weighs about 1.5 pounds, 25 percent larger
than any other member of the elephant-shrew family. It is
known to exist in only two groups in a 115-square-mile area
of this largely unexplored forest.
• Scientists report that its relatives include elephants,
manatees, and the aardvark. In recent years, a number of
other new species have been discovered here, including the
Udzungwa partridge, a monkey known as the kipunji, and
several amphibians and reptiles.
African Elephant
ORDER: Proboscidea
FAMILY: Elephantidae
GENUS: Loxodonta
SPECIES: africana
The Clock Gene – Circadian Rhythms
Our Family Tree
Our Family Tree
How Fast Does Evolution Occur?
• Fossil record is incomplete
• Fossils don’t always tell when something
evolved
• Some scientists think it occurs slow and
steady
• Some think it occurs in occasional rapid
bursts
Horses!
How Fast Does Evolution Occur?
• Usually find fossils unchanged for long
periods of time
• Fossils appear that are very different
Explanation for lack of intermediate forms
• Fossil record incomplete
• Assume that more forms will eventually be
discovered
How Fast Does Evolution Occur?
Gradualism
• Slowly but steadily
• Tiny changes gradually add up to major
changes over very long periods of time
• This is what Darwin thought
• If correct, many intermediate forms for all
species should exist
How Fast Does Evolution Occur?
Punctuated Equilibria
• Evolution occurs during short periods of rapid
•
•
•
•
•
change
Most new species form when small populations
become isolated
Small, isolated populations can evolve quickly
and adapt to new environment
Maybe as quick as a few hundred years
Not many intermediate fossil forms would exist
Both seemed to have occurred