Download Evidence for Evolution Note Guide

Evidence for Evolution Note Guide
Remember… individuals cannot evolve… only populations over time!
Evidence for Evolution:
1. FOSSIL EVIDENCE
Fossils = the remains of organisms that lived in the past, usually
preserved in sedimentary rock; frequently formed from petrified
bone structures
Fossil Record = represents all of the identified fossil specimens
and the sequence in which fossils appear within layers (strata) of
sedimentary rock
2. BIOCHEMICAL EVIDENCE
See diagram of molecular evidence on page 15 of your textbook.
Different species have the same genes, with similar DNA sequences, which encode for the
similar stretches of amino acids.
Things to note…
1. All species use the same DNA letters (A, T, G, and C).
2. All species have the same genetic code (i.e. the DNA sequence TAC codes for the same
amino acid in all organisms!).
3. Biochemical compounds are common across species (ATP carries energy)
4. Proteins across species have highly similar amino acid sequences (i.e. hemoglobin… which
carries oxygen in your blood).
3. ANATOMICAL STRUCTURES
Anatomy = the study of the structure of
living organisms
a. Homologous Structures
A homologous structure is one that is shared
between species because it was inherited
from a common ancestor. Each species
has the same structure, but it performs a
different function for each organism.
In the diagram, each organism has the same bones, but they are all used for different things!
b. Analogous Structures
An analogous structure is a characteristic that is similar between two different species, but
has evolved from very different origins.
This is an example of divergent evolution.
Each species has a different structure that
performs the same function.
 In the diagram, each organism has
developed a wing for flying, but the moth
on the left has little relation to the feathered
bird in the middle.
c. Vestigial Structures
Vestigial structures are any structures or organs that no longer serve a purpose for the
organism, but are present due to its function in an ancestral species.
Examples:
1. Wings on an ostrich
2. Eyes on a naked mole rat
3. Whale hip bone
4. EMBRYOLOGICAL EVIDENCE
Take a look at the first row… all of the
embryos look the same in early stages
regardless of whether it is a turtle or a
human!
Main Take-Away: The longer two
organisms look the same in embryological
development, the closer related they are.
Ex: Fish and salamanders are more closely related
then fish and rabbits based on their embryo
development.
PHYLOGENETIC TREE (aka evolutionary tree)
A phylogenetic tree is a branching diagram or “tree” showing the inferred evolutionary
relationships among various species based upon similarities and differences in their physical
and/or genetic characteristics.
The degree of “relatedness” is reflected in the total length of the branches connecting two
species and how far back in time (how far down the tree) the two species split (or diverged)
from one another.
For example, from the
evolutionary tree shown to the
right, we can determine that
Halophiles of domain Archaea
are the most closely related to
Methanosarcina, and more
distantly related to
Pyrodicticum.
Note: If you see a “tree” in which are
the lines are fairly symmetrical, they
do not relate to time.
Identifying a COMMON ANCESTOR using an evolutionary tree…
Understanding an evolutionary tree is a lot like reading a family tree. The root of the tree
represents the ancestral lineage, and the tips of the branches represent the descendents of
that ancestor. As you move from the root to the tips, you are moving forward in time.
 When a lineage splits to form two distinct species (an
event known as “speciation”), this event is represented
as branching on an evolutionary tree. When a
speciation event occurs, a single ancestral lineage
gives rise to two or more daughter species.
Thus, evolutionary trees trace patterns of shared ancestry between lineages. Each lineage
has a part of its history that is unique to it alone and parts that are shared with other lineages.
Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are
shared with other lineages—COMMON ANCESTORS.