EVOLUTION
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Transcript of EVOLUTION
EVOLUTIONEVOLUTIONEvidence of Change
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Evolution:Evolution:
The process by which modern organisms have descended from ancient organisms
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Charles DarwinCharles DarwinFirst published his book “Origin of
the Species by Means of Natural Selection” in 1859. .
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In this book, he explained that if you look back far enough in time, you would see that all species have a common ancestor. He called this the principle of Common Descent.
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He also explained that because of the
VARIATION that naturally occurs within species, some individuals will have more FITNESS to survive than others. Those individuals will have a better chance of REPRODUCING, and passing on the advantageous GENES.
He called this process ADAPTATION.
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How does a longer neck help a giraffe adapt to its environment?
http://www.hww.ca/hww2.asp?id=94
The mountain sheep is very agile, it has high ability to climb steep terrain
http://www.youtube.com/watch?v=YadP3w7vkJA&feature=related
http://www.gla.ac.uk/~gbza22/jpegs/birds/starling.jpg
Birds keep track of 7 others -gives them ability to stay close together
AdaptationsAdaptations
Inuit people, who live in the extreme cold of the Arctic, have short, stout bodies that conserve heat.
Plant adaptationsPlant adaptations
Venus Fly TrapCaptures animalsAcquires minerals
for photo- synthesis
An example: Bird vocalizationAn example: Bird vocalizationBirds call/sing to
◦Attract mates ◦Defend their territory
SongbirdCawing crow
Owl hoots
Reid et al. (2005) used 20 years of data from song sparrows on Mandarte Island, B.C., Canada
Result: males with larger song repertoires contributed more offspring and grand-offspring to the population◦This was not because females mated to
males with larger repertoires laid or hatched more eggs
◦Rather, these males (1) lived longer; and (2) reared a greater proportion of hatched chicks to independence
http://209.85.173.104/search?q=cache:FQlkM9-WVrIJ:www.sjsu.edu/faculty/fry/123/birdsong2.pdf+bird+songs,+fitness&hl=en&ct=clnk&cd=3&gl=ca
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Where is the evidence?Where is the evidence?
1. Fossil evidence (palaeontology)2. Radioactive dating in sedimentary
rock (stratigraphy)3. Comparative embryology4. Comparative biochemistry
EVIDENCE OF EVOLUTION IN EVIDENCE OF EVOLUTION IN STONESTONEHutton and Lyell proposed that Earth
was very old and had changed slowly and gradually over time.
James HuttonCharles Lyell
FOSSILS:FOSSILS: Geologists have discoveredfossils of organisms that no longer EXIST, but have very similar CHARACTERISTICS to present-day species. QuickTime™ and a
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Many of these fossils could be compared and placed in a plausible SEQUENCE of change from ANCIENT organisms to the present day. This isn’t proof, but it is a piece of EVIDENCE.
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Fossils are formed along with SEDIMENTARY rock. Sometimes, parts of organism’s bodies are PRESERVED.
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Other times, rock forms around the HARDER parts of the dead organisms, (the BONES, WOOD, SHELLS) and it creates a bit of a MOLD. The ORGANIC material from the bodies will eventually be REPLACED by harder, longer lasting INORGANIC compounds inside those “molds”. They call this process PETRIFICATION.
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Fossilization is a tricky process, requiring VERY SPECIFIC CONDITIONS, and so the fossil record has to be put together like a PUZZLE that has many broken and lost pieces!
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Fossil successionof the Trilobite genera
Cambrian
Wherever these fossils are found they always occur in the same succession.
Ordovician
Silurian
Devonian
http://cache.eb.com/eb/image?id=46897&rendTypeId=4 http://www.geocities.com/mrbbug1/meso4.jpg
Discovery of fossilsSome of the fossils resembled living organisms; others did not
The Fossil RecordThe Fossil Record
What are sedimentary rocks?◦ Rock that forms when grains of eroded rock and
other materials are carried to the bottom of a body of water and build up under pressure into layers
http://www.ucmp.berkeley.edu/education/explorations/tours/stories/middle/C7.html
Most fossils are foundin sedimentary rock
B. Sedimentary Rocks and Geology Using the LAW OF
SUPERPOSITION geologists can find the RELATIVE date of fossils.
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The law states that the LOWER layers of SEDIMENTARY rock are OLDER than the upper layers. Fossils found in the layers of rock are the same RELATIVE AGE as the rock itself.
Through RADIOACTIVE DATING geologists are able to tell the ABSOLUTE age of some preserved bones that have been uncovered, or determine the absolute age of some of the ELEMENTS that are found in the IGNEOUS rocks surrounding the fossils.
Using RADIOACTIVE DATING, geologists have calculated that the Earth is about 4.5 BILLION years old.
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The fossil record shows us that change happened first on the EARTH, and then change in the organisms FOLLOWED.
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2. EVIDENCE IN 2. EVIDENCE IN COMPARATIVE EMBRYOLOGYCOMPARATIVE EMBRYOLOGY
When you compare EMBYROS of several species in an EARLY STAGE of their development, they are very SIMILAR in APPEARANCE. Later, the EMBRYOS look vastly DIFFERENT. Why?
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The theory of EVOLUTION explains these different animals had a COMMON ANCESTOR that passed down the sequence of developmental GENES. As the animals evolved, they added steps to the developmental sequence.
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3. Evidence in Comparative Anatomy
Many species have HOMOLOGOUS structures – body parts that have very similar INTERNAL structure but they have different FUNCTIONS.
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Homologous structures: parts of different organisms, often quite dissimilar, that developed from the same ancestral body parts.
Bird Wing
Porpoise Flipper
Homologous structures: body parts that have very similar internal structure but they have different functions
Bird Wing
Porpoise Flipper
Examples include: human arm and BAT WINGS
human arm and WHALE FLIPPERS
One of the classic examples of a homologous structure is the pentadactyl (= five digit) limb.
VESTIGIAL STRUCTURESThere are also
many VESTIGIAL structures – body parts present that are similar to those of other organisms, but are NO LONGER USED.
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Examples include: HUMAN APPENDIX
SNAKE LEGS
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Cassowary
Wisdom teeth
Human tail boneMale breast tissue and nipples
The wings on flightless birds (e.g. The cassowary)◦ Wings of a bird are adapted for flight◦ Not completely useless, use for balance during running
Human tail bone (coccyx)◦ Fused vertebrae, only vestige left of tail that other animals
use for balance, communication, (for some primates as a prehensile limb)
Wisdom teeth◦ Human jaw got smaller over time◦ How may have it been beneficial to our ancestors?
Male breast tissue and nipples◦ Was man descended from a woman? No! During early
stages of fetal development a fetus is sexless. Later in development testosterone causes sex differentiation.
◦ A small number of men have been able to lactate. Cancer can grow on male and female breast tissue
Whiptail lizards
Hind leg bones in whales
Fake sex in virgin whiptail lizards (vestigial behaviour)◦ Only females exist in several species of lizards◦ Reproduce by parthenogenesis (unfertilized egg
develops into a new individual, forming clones of themselves)
◦ They still try copulating, though futile
Hind leg bones in whales◦ Biologists believe that for 100 MYA the only
vertebrates on Earth were water-dwelling creatures with no arms or legs
◦ The “fish” began to develop hips and legs, eventually able to walk out of water
◦ Land dwelling creatures evolved, some mammals moved back into water (50 MYA) ancestors of modern whales
◦ Traces of hind legs—can be seen even now.
The Blind Fish Astyanax Mexicanus
The Sexual Organs of Dandelions
Sexual organs of dandelions◦ Like many flowers that have proper organs (stamen and
pistil) for sexual reproduction, but do not use them◦ Instead, they make clones of themselves◦ Asexual reproduction can be a good strategy in an
environment that is constant, if species are well suited
Blind fish◦ Species of fish dwell in caves deep underground off the
coast of Mexico; they cannot see◦ Has eyes, but as they develop in egg, their eyes
degenerate◦ Born with collapsed remnant of eye covered by a flap of
skin◦ Fish of the same species that live directly above the blind
fish, near the surface where there is plenty of light, have functioning eyes
◦ Scientists have removed lenses from surface water fish, implant them into blind eye fish, can develop functional eye with pupil, cornea, and iris.
Snakes “legs”
Human appendix
Biologists believe it is a vestigial organ left behind from a plant-eating ancestor
**do not confuse HOMOLOGOUS structures with ANALOGOUS structures – ANALOGOUS structures have a similar FUNCTIONS but have very different INTERNAL structure.
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Fly wing
Bird Wing
EXAMPLES: Bird Wings and FLY WINGS
Analogous: Whale fin and Fish Fin
Comparative anatomy structuresComparative anatomy structures
Analogous:1. Different
ancestors2. “analogy”=like3. Different
underlying structures
4. Same Function5. Similar
Environments
Homologous:1. Same ancestor2. “homo”=same3. Same underlying
structures4. Different
Functions5. Different
Environments
Comparative BiochemistryComparative BiochemistryAlmost all living
organisms use the same basic biochemical molecules, including DNA, ATP and many enzymes.
In fact, molecules such as hemoglobin have been used to determine how distantly related some species are.
Haemoglobin is the iron-containing protein attached to red blood cells that transports oxygen from the lungs to the rest of the body
http://www.sciencecollege.co.uk/SC/biochemicals/haemoglobin.jpg
The greater the number of differences in the molecule, the more distantly related the organism are.
http://newsimg.bbc.co.uk/media/images/42343000/gif/_42343831_evolution_tree_2_416.gif
Comparative BiochemistryComparative Biochemistrysimilar DNA
sequences= similar gene segments of the DNA
Code for similar traits in closely related species
NATURAL VARIATION
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