Download Evidence for Evolution

EVIDENCE FOR EVOLUTION
Biology 9
EVIDENCE FOR EVOLUTION
What is the evidence that all species on earth are related
to each other and share common ancestors?
Overview:
4 Major Types of Evidence:
1.
Homologous Structures
2.
Embryos
3.
Gene Sequences
4.
Fossils
1. HOMOLOGOUS STRUCTURES –
Similar body parts or bone structures due to sharing a
common ancestor that had those structures
 Don’t necessarily have the same function now, but did
in the common ancestor
 Ex: human arm, cat leg, whale flipper, bat wing all
have same bones
Homologous Structures, continued:
Vestigial Traits  Don’t
have a function now, but
suggest that they descended from an
ancestor that did use them.

Examples:

www.toptenz.net
human tailbone, human goose bumps,
ostrich wings
Ex: human tail bone, human goose
animal.nationalgeographic.com
Don’t confuse Homologous Structures
with Analogous Structures
Analogous Structures structures that have the same function but NOT the same skeletal
structure
 This suggests these organisms did NOT descend from a
common ancestor with that trait
Ex: insect wing and bird wing
Insect wing
bio.miami.edu
Bird wing
2. Embryos
Similar characteristics appearing during specific embryonic/
developmental stages of development
 Example: Fish, reptile, bird, and human embryos all have gill slits
and a tail (but some lose these features before birth)
3. Gene Sequences
Similarities between DNA or amino acid sequences for
different organisms

Closer the similarities = Closer relationships
4. FOSSILS
Fossils show…



show species that are now extinct
show transitions to new body forms
Example: Tiktaalik (lived 375 million years ago)
 fish with legs and (maybe) primitive lungs…
 earliest amphibian?
Fossil
Artist Rendering
Objectives for Class:
• Describe how fossils are used as evidence for evolution and give one example that illustrates this.
FOSSILS, cont.

Example: Archaeopteryx (lived 150 million years ago)
 earliest
bird… but has many dinosaur features
www.ansp.org
Objectives for Class:
• Describe how fossils are used as evidence for evolution and give one example that illustrates this.