Download Divergent Evolution creates Homologous structures

Warm-Up: page 32
How is the evolution of earth’s surface related to the
evolution of living organisms? Be very specific in your
answer and use vocabulary
5pts
Date
1/13-14
1/15-16
Session #
Activity
Page #
Principles of Evolution Stations Review
30
Evidence of Evolution
31
Evidence of Evolution Notes
32
Genotype vs Phenotype
Quick Write
33
h/w: complete on p33 of your notebook
Complete phenotype and genotype compare and contrast activity
8.L.4 Understand the evolution of organisms and
landforms based on evidence, theories and
processes that impact the earth over time.
8.L.4.1 Summarize the use of evidence drawn
from geology, fossils, and comparative anatomy to
form the basis for biological classification systems
and the theory of evolution
TLW identify the evolutionary relationship
between organisms by comparing and
contrasting structures, DNA and embryology
then summarize how evidence is used to
support evolution in a quick write.
Contents, Covers and the stories they tell
Part 1
Carefully examine the bone structures on Lab Sheet 1.
(Note: bones are not drawn to scale.)
All are forelimbs of mammals. Look for key structural features that give
tell-tale clues about which mammal the bones are from.
Bone Set
Key Structural Features
Proposed Animal Source
Five separate digits or fingers; hand-like structure;
long, thin upper and lower arm segments
Human
A
B
C
D
E
1 MOLE
2 SEAL
3 ELEPHANT
4 OPOSSUM
5 WOLF
7 BAT
Evidence of Evolution p.32
• Comparative Anatomy
– Homologous structures (divergent evolution)
– Analogous structures (convergent evolution)
– Vestigial Structures
• Embryological Similarities
• Cellular/Molecular Similarities
– Similar DNA
– Similar Biochemistry
• Fossils
Homologous Structures
Traits inherited by two different organisms from
a common ancestor
Similar anatomy, different function
Example of Homology:
the tetrapod limb
The tetrapod limb
In an evolutionary tree, traits are passed from
ancestor to decendent
The wing of a dragon fly and the wing of a butterfly
are homologous – they were both inherited from
an ancient flying insect
Not all homologous structures are obvious if they
have been adapted for different roles. For example,
the chomping front teeth of a beaver look quite
different than the tusks of an elephant. Each is a
modification of the basic incisor tooth structure
Homologous structures show that
Divergent Evolution takes place
Divergent Evolution creates Homologous
structures: A common ancestor evolves into
new species, which continue to evolve and
become less and less alike over time due to
differences in their environments
Brown bears and polar bears illustrate divergent evolution.
Scientists think that a long time ago a group of brown bears
became geographically separated from the rest. This isolated
group acquired new characteristics, such as the ability to eat
meat, blubber to keep warm in snowy weather, and a white coat
for camouflage. They slowly evolved into polar bears.
So what about ANALOGOUS STRUCTURES??
Consider the following example…..
Thylacosmilus
Smilodon
Both are extinct animals and both of them have
saber-teeth…but are they homologous structures?
(Consider that Australia had separated from the
Supercontinent a loooooong time ago)
They are Analogous structures!
Similarity due to convergent evolution (evolved
to the same environment)
Not common ancestry
CONVERGENT Evolution creates Analogous
Structures: When two separate groups of
animals evolve to have similar structures because
they have evolved in a similar environment
Similar function, different anatomy
How do analogous structures evolve?
Often, two species face a similar selection
pressure. Natural selection may then shape
both of them in similar ways – resulting in
analogous structures…...like the saber teeth.
So there you have it…..
HOMOLOGY
Similar due to inheritance
vs
ANALOGY
Similar due to other factors
Apply your knowledge p32
For each of the 4 example3, write:
Organisms’ names and structure we are comparing
Are they homologous or analogous structures?
In one sentence, explain your answer
1. Sugar Glider & Flying Squirrel “cape”
Squirrel
Glider
Placental
reproduction
Marsupial
reproduction
Large eyes
Large eyes
Fur
Fur
While sugar gliders (marsupials) superficially
resemble the placental flying squirrels of North
America, the ability to glide through the air evolved
independently in these mammals.
2. Shark and Dolphin body shape
Streamlined body
Streamlined body
Triangular Dorsal Fin
Triangular Dorsal Fin
Skeleton made of cartilage
Skeleton made of bone
Use gills to get oxygen from the
water in which they swim
Go to the surface and breathe
atmospheric air through their blowholes
Don’t nurse their young
Do nurse their young
Don’t have hair
Do have hair –they are born with hair
around their “noses”
Propels through water in side-to-side
motion
Propels through water in up and down
movement
They have ANALAGOUS structures
Sharks are closely related to rays, and dolphins
are closely related to other mammals.
Streamlined bodies and fins are traits that
dolphins and sharks evolved separately, both as
adaptations from swimming.
3. Leaves of oak trees and the leaves of gingko trees
Oak Leaves
Ginko Leaves
Photosynthesis
Photosynthesis
Cell walls
Cell walls
Multi lobed shape leaf
Single lobed shape leaf
Large leaf surface area
Large leaf surface area
4. Pointed Snout and Sharp Claws
Anteater
Echidna
Fur
Fur
Placental Mammal
Egg Laying Mammal
Eats from Anthills
Eats from Anthills
Latin & South America
Australia
Long, Sticky Tongue
Long, Sticky Tongue
Vestigial structures/organs
Structures or organs that seem to serve no useful function.
Vestigial organs are often homologous to organs that are useful
in other species
For example: snakes have tiny pelvic bones and limb bones
eyes on cave salamanders (blind)
leg bones in whales
Organisms having vestigial structures probably share a
common ancestry with organisms in which organisms in which
the homologous structure is functional.
Hind limbs in Whales
Pelvis & Hind limbs in Snakes
Embryology
Similar early development
Developmental similarities can be see in
comparing the early embryos of many species
Embriological Evidence
Similar early development
Embryos are very similar
Early in development
Cellular/Molecular Evidence
Related organisms have similar chemical processes,
chemicals and proteins.
Examples:
– photosynthesis,
– hemoglobin in mammals vs hemocyanin in mollusks
– DNA (gene codes)
Related organisms share large % of similar DNA
sequences (lots of genes in common)
Fossil Evidence
Preserved remains of ancient organisms….these allow
us to compare anatomies and trace change….how?
Fossils provide evidence of:
• Other organisms that lived at the same time
• Progression of life
• Geological Events that changed the
environment and changed selective pressures
Tape onto page 33
30-30-30
Turn and talk to your partner for 30
seconds…you will summarize the evidence of
evolution and how we use it
Quick Write page 33
• Summarize 2 types of evidence we have
learned and how it is used to classify
organisms and support the theory of
evolution