Transcript Mutations - "The Biosphere": Biology at PHA

Friday: 5.1.09
Title: Homologous Structures
DO NOW:
What are the three types of
homologies?
HOMEWORK:
Finish Anatomical Tree from
Part B
EVIDENCE FOR EVOLUTION:
What is the evidence that all species on earth are
related to each other and share common
ancestors?
1. Homologous Structures
a) Anatomical homologies and vestigial
structures
b) Embryos
c) Molecular/Genetic
2. Fossils
3. Geographic Distribution of Species
1. HOMOLOGOUS STRUCTURES –
similar structures due to sharing a
common ancestor that had those
structures
Three Types of Homologies:
1. Anatomical (including vestigial)
2. Embryological/ Developmental
3. Molecular/ Genetic
1a. Anatomical Homology –
similar body parts or bone structures
(They 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
* Don’t confuse homologous
structures with 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
Bird wing
Insect wing
bio.miami.edu
Homologous structures can be
vestigial - don’t have a function now, but
suggest that they descended from an ancestor
that did use them.
Ex: human tailbone, human goose bumps, ostrich
wings
Ex: human tail bone, human goose
bumps,
animal.nationalgeographic.com
www.toptenz.net
1b. Embryological/Developmental
Homology
Ex: fish, reptile, bird, and human emrbyos all have gill
slits and a tail (but some lose these features before
birth
1c.Molecular/Genetic Homology –
similar DNA or amino acid sequences
Complete Question 4 from All in the
Family

Finish Question 4 for “All in the Family”
Phylogenetic Tree for All Living Things
Time -------------------------------------------------------------------->present
Nodes indicate most recent common ancestor of two branches
Evolution Dry Lab PART B:
Comparing Anatomical and Genetic Evidence
Monday: 5.4.09
DO NOW:
Which is more reliable, Molecular
Evidence or Anatomical Evidence?
Why?
HOMEWORK:
No Homework.. Get ready for
Exhibition Night 
Complete Evolution Dry Lab PART
B:
Comparing Anatomical and Genetic Evidence
Tuesday: 5.5.09
Title: Evidence for Evolution (cont.)
DO NOW:
We have discussed Homologous Structures,
what are the other two TYPES of evidence
used to suggest common ancestry among
species?
HOMEWORK:
Type Analysis Questions for
Part B by Friday…
EVIDENCE FOR EVOLUTION:
1. Homologous Structures
a) Anatomical homologies and vestigial structures
b) Embryos
c) Molecular/Genetic
2. Fossils
3. Geographic Distribution of
Species
2. Fossils:
- show species that are now extinct
- show transitions to new body forms
Example A: Tiktaalik (lived 375 million years ago)
– fish with legs and (maybe) primitive lungs…
earliest amphibian?
Fossil evidence, continued:
Example B: Archaeopteryx (lived 150 million years ago)
– earliest bird… but has many dinosaur features
www.ansp.org
Interpreting Fossil Evidence



Fossils form in layers of
rock (older = lower layer)
Fossils in the same layer
lived at the same time
Radiometric dating:
determine the age of a fossil
based on how much
radioactive carbon it
contains
What lived at the same time as
the fossil fish?
3. Geographic Distribution of Species
Species that live on the same continents are often
closely related to each other (based on DNA and
embryos), even though they look more similar to
species elsewhere.
Example: North vs. South
American rodents
Example: Placental Mammals vs.
Australian Marsupial Mammals

Australia has been
separated from other
continents for a long
time – its marsupials
evolved
independently

Marsupial traits are
analogous, NOT
homologous, to
placental mammals
Recap: Analogy vs. Homology

Analogous Structures – similar due to natural
selection in similar environments (common
ancestor did not have it, but descendents
evolve it independently)

Homologous Structures – similar due to
shared ancestry (common ancestor had this
feature, so all descendents have it)

Results from divergent (branching) evolution
Wednesday: 5.6.09
Title: No Title in Notes
DO NOW:
Actively Read PBS Evolution
Library: Whale Evolution
HOMEWORK (both due Fri.):
1.
2.
Complete up to Task 4 on Part C
Type Analysis Questions for
Part B
DIVERGENT (branching) EVOLUTION
Evolution Dry Lab PART C: Whale
Evolution Day 1

Complete Tasks 1-4 before watching the video

You may also have the reading to go along with this video
Friday: 5.8.09
Title: No Title Today
DO NOW:
Take out the Part C of Evolution
Dry Lab. Check Answers…
HOMEWORK:
Type Analysis Questions for Part C
Ambulocetus natans in action
A reconstruction of an early close cousin of whales
Shown here with the kind permission of artist Carl Buell. http://www.indiana.edu/~ensiweb/lessons/whale.ev.html
Check the Answers…
Check the Answers…
Check the Answers…
Modern Whales…
Evolution Dry Lab PART C: Whale
Evolution Day 2

PBS Evolution Library: Whale Evolution


http://www.pbs.org/wgbh/evolution/library/03/4/l_034
_05.html
Create your Phylogenetic Trees for Whale
Evolution (Task 5)
Class Discussion:
Compare Timelines from Task 4
Where Did Whales Evolve From?
Zooming in on Whale Evolution
EVOLUTION SUMMARY



Populations of living things change over time.
Due to change over time, a species can
evolve into one or more new species. This
results in the branching view of the tree of
life.
All living things are related because we all
evolved from a common ancestor.
Phylogenetic Tree for All Living Things
Time -------------------------------------------------------------------->present
“There is grandeur in this view of life…” – Charles Darwin