Download Evolution ppt - Duplin County Schools

Evolution
 Fossils indicated that living things
have changed.
 Several scientists had ideas to
explain how living organism could
change.
1. Lamarck
• French scientist
• Late 1700 early 1800’s
• “Acquired Traits” Theory
traits are not determined by genes
but by “need”.
Ex. Giraffe necks grow longer because
they needed to stretch to reach the
leaves higher up in the tree.
Lamark “Acquired Traits”
2) Charles Darwin
• English scientist
• Developed his theory of “natural
selection” in the mid 1800’s
• Was a naturalist on the HMS Beagle
(traveled around the world, mostly the
southern hemisphere) for 5 years.
• Notice organisms had same similarities
even when they lived far apart.
• Kept records, collected specimens, and
published “The Origin of Species”.
Voyage of the HMS Beagle
Galapagos
Islands
Galapagos Islands played
a big role in Darwin’s thinking!
Darwin’s Finches
• Good example of how evolution occurs
• Each Galapagos Island has its own unique
species of finch
• Each finch had a head and body well-adapted for
life on that island
• The finches were different species, but looked
similar
Adaptive Radiation
Evolutionary Tree (cladogram)
•Darwin realized that the finches
had a common ancestor
•He proposed that originally a few
seed-eating finches had flown to
the islands from mainland. Over
millions of years, the finches
adapted to the foods available on
each island – and evolved into
separate species.
Adaptive radiation is a type of
Divergent Evolution
Adaptive radiation is a type of divergent evolution where a
group of organisms quickly diverges into new species.
Galapagos Tortoises
Adaptive Radiation
Darwin’s ideas that served as a
basis for theory of natural selection
1. All organisms produce more offspring
than can survive.
2. Population numbers remain fairly
constant over long periods of time.
3. Organisms in a species show wide
variation.
4. Some variations are inherited and
passed on to the next generation.
Units of Variation
• Genes carry inheritable characteristics,
also source of random variation
– crossing over
• Mutations cause variation
– missing letters in DNA
Then Darwin made 2 deductions:
1. Since most offspring don’t survive, all
organisms must have to struggle for
survival. (Others are eaten, or die of
disease.)
2. The ones who survive and reproduce
will pass on their genes.
Survival of the Fittest!
Mutations play big role in
natural selection
Rabbit Tale Maybe once upon a
time all rabbits had short
ears and managed OK.
Then one day a mutant with big ears was
born.
She was always the first to dive for cover.
Pretty soon, she had babies; some inherited
her big ears.
They all dived for cover as fast as their mom
– faster than the short earred rabbits.
Eventually, only the big earred rabbits are
left.
Natural Selection
Nature selects those that are best adapted
to survive.
“Survival of the Fittest”
Any adaptive advantage (a favorable trait)
that an organism has
is passed to offspring.
Example of evolution through
natural selection
Cockroaches
Over the centuries, as man and
cockroaches have shared homes,
cockroaches have become smaller and
flatter – easier access to hiding places.
(Large, fat ones more easily stomped.)
Another example – Antibiotic Resistance by
natural selection
• Someone gets sick
• Give them antibiotics
• 99% of the bacteria are killed; only the antibiotic resistant mutants
survive
• They thrive and flourish
• Person gets sick again
• Bacteria cannot be killed by antibiotics
What is this graph telling us?
Testing Bacteria Resistance
All 7 drugs kills bacteria
A
Resistant to 4 drugs
B
The yellow color is bacteria growing on a plate of agar.
Each white dot is a paper disk with a Different Antibiotic on it.
The clear regions around the white disk means bacteria is dead.
Evidence of Evolution
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Fossils
Similarity of embryos
Homologous and analogous structure
Vestigial structures
Similarities in macromolecules
Fossils – tell us that organisms that
once lived on Earth are not here
any more.
Embryoes of all vertebrates
are similar – common ancestor
Homologous Structures – similar
structures with similar functions.
Suggest a common ancestor.
Vestigial Structures
• Examples: appendix, wisdom teeth, human tail
bone
• Interpretation: the vestigial structure was
functional in some ancestor of the modern
organism
• Snakes have pelvic bones; they are known to be
the descendants of four-legged reptiles.
Vestigial Structures in Animals
Vestigial Structures in human
Similarities in Macromolecules
• Natural Selection
Beneficial mutations  new genetic traits
(adaptive traits) advantage in a changing
environment  produce more offspring with those
traits.
• Through time these adaptive traits become more
common in a population.
• Evolution is the change in genetic makeup of a
population through successive generations.
• New species can be formed, or if they cannot
adapt they will die off or become extinct.
• Biodiversity is a result of the ongoing
processes of evolution and extinction.
Adaptive Radiation
Many related species evolve from a single ancestral
species Examples: Galapagos tortoises, Darwin’s
finches, Hawaii Honeycreepers.
Adaptive Radiation
Lonesome
George
Near losses…
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The cheetah, Acinonyx jubatus, is the sole member of its genus.
Twenty thousand years ago, cheetahs roamed four continents.
About 10,000 years ago - because of climate changes - all but
one species of the cheetah became extinct.
With the drastic reduction in their numbers, close relatives were
forced to breed and the cheetah became genetically inbred.
This means all cheetahs are closely related.