Download Evidence of Evolution

Evidence of Evolution
Section 16.4
Opening Question
Pretend you are an evolutionary
scientist studying a species of eels that
have been around for millions of years.
How could you show this eel is related
to some common fish? What would you
compare?
Answers
• Compare fossils for similarities in structure
• Compare the areas where the eels and fish
live
• Compare the anatomy or structure of the eels
and fish
• Compare the development of the eels & fish
• Compare DNA sequences
Fossils
Fossils - preserved remains or markings
left by an organism that lived in the past
• Older fossils are found in deeper layers
of rock. Younger fossils are found in
superficial layers of rock.
• Carbon dating can
be used to determine
the age of a fossil.
Geographic Distribution
• Two organisms living in the same area
are more likely to be ancestors than two
organisms living in different areas.
Ex. Tropical birds on an island will more
likely have evolved from mainland birds
than from birds on another tropical island
on the other side of the world.
Similarities in Structure
Homologous Structures – a similar
structure in two or more organisms that
share a common ancestor; do not
necessarily have the same function
Ex. human’s arm, cat’s front leg, bird’s
wing
Similarities in Structure
Vestigial Structures – remnants of
structures that may have had an
important function in ancestors but has
no clear function now
Ex. appendix of humans
hip bones of whales
Hip bones of Whales
http://taxonomy.zoology.gla.ac.uk/~rdmp1c/teaching/L1/Evolution/l1/unity.html
Similarities in Development
• Embryos of closely related species have
similar stages of development.
• As development proceeds organisms
look less like the embryos of other
organisms and more like the adult
organism.
Similarities in Development
Human Embryo
Mouse Embryo
Molecular Biology
• The DNA sequences of related
organisms are similar.
• The more similarities in DNA sequences
the more closely related two organisms
are.
Ex. Human hemoglobin is 1 amino acid different
than gorilla hemoglobin. Frog hemoglobin is
67 amino acids different than human
hemoglobin.
Comparison of hemoglobin
amino acid sequence