Evolution: Evidence
SC.912.L.15.1 Explain how the scientific
theory of evolution is supported by the
fossil record, comparative anatomy,
comparative embryology, biogeography,
molecular biology, and observed
evolutionary change
Types of Evidence we will be covering
• Fossil Records
– Transitional fossils
• Comparative Anatomy
– Homologous Structures
– Analogous Structures
• Vestigial Structures
• Biogeography
Fossil Records
• Fossils support the idea
of evolutionary
progression.
• By looking at fossils
Paleontologists/zoologists
can:
– Identify extinct animal
species
– Follow the path of
evolution through different
stages of development
Evolution of the Whale
Key Points of the Fossil Record
• Provides evidence of
evolution from one
species to another
– Shows ancestral
intermediates
• Only hard tissue is
preserves
• Fossil Formation
Transitional Fossils
• FLASH CARD ALERT:
•
TRANSITIONAL FOSSIL: fossils
that show transitions in
evolution.
• Transitional fossils are
RARE findings
– Small proportion of
organisms become
fossils
– Many fossils represent
dead evolutionary
branches
Support: Comparative Anatomy
• Homologous Structures:
Similar features found in
different species that are
derived (come from) a
common ancestor
– Ex. Tetrapod limbs, fur,
lungs
• Bone formation:
developmental and
evolutionary similarities
• Evidence of intermediates
Analogous Structures
• FLASH CARD ALERT:
• Analogous Structures: a trait or an organ that
appears similar in two unrelated organisms
• Happens because of convergent evolution:
– FLASHCARD ALERT: CONVERGENT EVOLUTION: Species
evolve in similar environments and have similar
environmental stressors/survival factors
Analogous Structures
Vestigial Structures
• Vestigial Structures: characteristics found in
existing species that have no known function
• Provide evidence of common ancestry
• As species evolve their structures change
– Two things will happen
• Species will adapt the organ/structure to a new use
– penguin
• The organ or structure will no longer have a use
– Whale pelvis/snake feet.
Useless for Flying but excellent for
swimming
Vestigial Structures
• Stubs on pythons, boas,
and other snakes
– Ancestral legs
• No known
function
• Useless Vestigial
structures are
BETTER sources
of evidence for
evolution
Amphiuma
Flightless Wings
Plica semilunaris
CFU:
• What is the major difference between
analogous and homologous structures?
• What structure is the best evidence of
evolution: analogous, homologous or vestigial
• What kind of tissue/part of an animal is
preserved in fossils?
• What type of fossils are paleontologists most
interested in?
– Why are they hard to find?
Comparative Embryology
• Incredible similarities in
embryos of different
species provides
evidence of common
ancestor
– Patterns of embryo
development are also
important.
Biogeography
• Zoologists seek to
understand how very
closely related species
ended up in completely
different parts of the
world
Support for Pangaea
Key Point of Biogeography
• Seeks to answer the question: how/why different but
similar species exist in similar yet separate parts of
the world
• Can be explained by geological changes, migrations,
convergent evolution
• Support ideas of common ancestor and Pangaea
EVOLUTION CFU
• What are the five steps of evolution?
• How does the environment affect the process of
evolution?
• Adaptations help the organism:
• The three types of structures that support evolution
are:
• Paleontologists are excited to find what kind of
fossil and why?