Transcript Modern Evolutionary Classification

Modern
Evolutionary
Classification
NotesCh. 18.2
Evolutionary Classification
• Modern classification is
based on evolutionary
theory
• Phylogeny – study of
how orgs are related to
each other (their evo
relationships)
• Evolutionary
Classification –
grouping organisms
based on their
evolutionary history
Homologous Structures
•
•
•
One way to discover relationships is by comparing anatomical
structures (body organs and parts).
Parts that are alike in basic structure and origin in several
organisms but are not used for the same reason are called
homologous structures.
Ex. All above have the same bones and number, used differentlyevidence points to common ancestor.
Cladograms
• Certain features shared by
different group of
organisms are known as
“derived characters.”
• Derived characters –
characteristics that are in
recent parts of lineage but
not in older members
• Used to make cladograms
(aka phylogenetic tree)
• The more derived
characteristics two
organisms share, the
closer their evolutionary
relationship
Sample Evolutionary Tree
Common
Ancestor
Small
difference
Largest
difference
Moderate
difference
Smallest
difference
Relative Time
Section 18-2
Traditional
Classification Vs Cladogram
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Gastropod
Barnacle
Limpet
Molted
exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL
CLASSIFICATION
Go to
Section:
CLADOGRAM
Section 18-2
Traditional
Classification Vs Cladogram
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Gastropod
Barnacle
Limpet
Molted
exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL
CLASSIFICATION
Go to
Section:
CLADOGRAM
DNA & RNA
• All living things
have it
• Compare
organisms by
genes
• More similar =
more recent
common ancestor
Molecular Clocks
• Estimates amount
of time since
species diverged
• Uses mutations as
markers
• Compare
similarities and
differences in
genes
Quick Lab
Derived Characters in Organisms
Organism
Derived Characters
Backbone
Legs
Hair
Earthworm
Absent
Absent
Absent
Trout
Present
Absent
Absent
Lizard
Present
Present
Absent
Human
Present
Present
Present
1. Identify the organisms in the table that is the
least closely related to the others.
2. Construct a cladogram of these animals. Do
NOT copy the table.
3. Analysis questions on next slide.
3. Analysis Questions
a. What trait separates the least closely related organism from the other
animals?
b. List the animals in your cladogram in order of distance from the least closely
related organism.
c. Explain if your cladogram indicates that lizards and humans share a more
recent common ancestor than either does with an earthworm.
d. Where would you insert a frog if you added it to the cladogram? Explain your
answer.
Extra
Practice
Derived Characters in Organisms
Organism
Derived Characters
Backbone
Placenta
Foramen
Magnum
Forward
Tuna
Present
Absent
Absent
Horse
Present
Present
Absent
Human
Present
Present
Present
1. Construct a cladogram for the info above.
2. Three previously unknown vertebrates have been discovered in
a rainforest in South America.
a. “rat-like creature”
b. “iguana-like creature”
c. “goldfish-like creature”
Place these animals on your cladogram and justify your placement.