Download Chapter 21

Objectives:
1. Complete activity on reading from last night.
2. Evolution Game finally???
3. Notes on Evolution
HW: Flashcards 21-40 – Quiz Tmo.
Chapter 21
The Evidence for Evolution
Natural Selection can
Produce Evolution
Fossil Record
Direct Evidence!
Embryology
Evolution
Molecular Biology
Anatomy
Biogeography
Fossil Record
• Shows change has occurred.
• Detailed information on course of evolution
through time.
How to Create a Fossil
1.
2.
3.
Organism must immediately be buried in sediment.
Calcium in hard tissue and bone must mineralize.
Surrounding sediment must harden to rock.
Only a fraction of extinct animals known from fossils because they may be
inaccessible, destroyed or may not fossilize.
Article on dino fossils
Fossil Dating
• Date the rocks where fossils occur.
• Relative Dating (umm ew)
– Deeper rocks = older
• More accurate if you know the erosion rate of sedimentary
rock and find a relative age.
• Absolute Dating – radioactive isotopes decay at constant
rate. Can express date in millions of years.
When arranged oldest to youngest you can se progression of
life through time.
See worksheet on radioactive dating
Simple Evidence
• Genus: Hyracotherium (horse)
55 mya
30 mya
Present
Small, short legs, broad feet
Getting bigger
Large
4 toes on front feet, 3 toes on
back with fleshy pads
Increased length of central
toe, bony hoof, loss of toes,
longer limbs and skeletal
structure
Single toe enclosed by hoof
Small simple teeth
Tooth Change
Increased length with molar
ridge patterns for grazing and
stronger skull
Fossils
• Clear record of major evo transition through
time.
• There are gaps that paleontologists are
continually trying to fill.
• Why are there gaps?
• Fossils found to link all major vertebrate
groups.
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–
–
–
Land hoofed orgs  whales and dolphins
Lizards  snakes
Curved oysters  rounded oysters
Archaeopteryx – transition between birds and
dinosaurs.
• Shows strongest evidence that evo has
occurred.
Not always simple
• Horse evidence simple.
• Evo is NOT uniform/constant over time. Rates
vary and non-uniform branches exist. Not
going toward “perfect”
Natural Selection
• Most agree that this is responsible for
evolutionary change.
• Modern day evidence confirms through
– Field research
– Lab
– Natural selection
– Human altered
Since D’s Finches
• More finch testing has been conducted to
prove adaptive radiation of finches is genetic,
not environmental.
Modern Day Evolution
• Biston betularia = peppered moth in 19th
Century.
• Industrial Melanism Rule
Moth activity/bunny demo/mark and
recapture
Artificial Selection Mimics Natural
Selection
• Favors phenotypes and if they are genetic – allowed to pass on and
lead to evo change. Strong proof that selection is an effective evo.
Process.
• Traits WE have selected for
– Fruit fly body size, eye color, growth rate, lifespan, exploratory
behavior.
– Cattle
– Pigs
– Strawberries – much different today
– Corn – selected for oil content in 1986. 10yrs later inc. of 450%
Unintentional Selection
• Breeding for specific traits may allow other traits to
come forward
• Foxes – genes for docile had other effects
(pleiotropy)
– Floppy ears, curled tails, etc.
• Because Art.Sel has worked, most scientists believe
Nat.Sel caused evo in fossil record.
• Some changes may seem minor (fruitflies) but look
at others (dog breeds) to see massive evo. Change.
Fox Article
Evidence
• Homology – same bones put to different
uses. Forelimbs of vertebrates are
homologous. Different appearances and
functions but common ancestor.
• Embryology – embryos exhibit
characteristics of early ancestors. As if
new instructions are layered on old
ones.
– Gill slits
– Long bony tail
– Fine fur (Lanugo)
Evidence
• Vestigial Structures – no apparent function for
structure but resembles structure presumed
ancestors had.
– Wiggling ears
– Tail
– Appendix
– Wisdom teeth
– Hip bones in snakes
– Finger nails on manatee flippers.
Evidence
• Molecular Record – when ancestors give rise to 2+
descendents the descendents will initially have
increased similarity in DNA. More closely related
means more similar DNA.
• When degree of genetic similarity is compared
with fossil relationships = close match.
– Human hemoglobin polypeptide compared with
chimps, gorillas, orangutans, macaques. Fewer diff
from humans in the 146 aa chain than dogs and
distantly related mammals.
– Non mammals are more different and non
vertebrates are most different.
• DNA codes for physical appearance so it makes
sense that DNA is similar in similar appearing
organisms.
• Junk (non-coding DNA) is similar too = direct
evidence for evolution.
Objectives
•
•
•
•
Quiz on 21-40
Open Ended Question on Evolution
Complete Evolution Notes
Review Important Flashcard Information.
H.W.
www.Khanacademy.org
Hardy-weinberg principle
Watch and take notes. WILL be on AP test!
Types
of
Evolution
Convergent evolution – same forms, different lineage.
•
• Divergent evo – two organisms don’t resemble each other anymore but
began with a similar ancestor. Clearly related but different features.
– Tortoise went moist dome shell vs. dry saddle shell
– Finch beak types x13!
– Divergent because different in only a few traits and similar in so many.
• Parallel Evo – when different organisms are placed under similar env.
Pressures and adapt similarly.
• Homologous is most like…
• Analogous is most like…
• Australia split 50 mya after marsupials but before placentals but they
resemble placentals because of similar selective pressures in similar env.
Critics of Darwin
• Evolution is just a theory…
• Fossils jump – no intermediates
• Complex structures are too complex for random
processes
• Evo violates the second law of thermodynamics
“things become more disorganized due to
random events, not more organized”
• Proteins are too improbable.
• Natural selection doesn’t imply evo.
• Irreducible complexity argument.