Download Adaptations over Time Chapter 12

Section 1: Ideas about Evolutions
Section 2: Clues about Evolution
Section 3: Evolution of Primates
There are millions of species on earth
 Species is a group of organisms that share similar
characteristics and can reproduce among themselves to
produce fertile off springs
 Changes in inherited characteristics over time is evolution
 Modern day horse has changed in size and hoof shape in
the past 50 million years
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1809, Babtiste Lamarck proposed hypothesis to explain how
species change over time
His proposal became known as inheritance of acquired
characteristics which states that characteristics or traits developed
during a parent organisms’ lifetime are inherited by its offspring
◦ If cut tail on dog, its offspring will not have a tail
◦ If lift weights and build muscles, offspring will have large
muscles
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Charles Darwin (1831-1845) traveled around world taking
samples of over 2000 species
He drew pictures of organisms, tried to classify them and noticed
small but obvious changes in organism on his trip
Galapagos Island was visited by his ship where he noticed 13
species of finches were similar but had slight differences in body
size, beak shape, and eating habits and were similar to one species
he had seen on continent of South American Coast
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Darwin reasoned that the Galapagos finches must have had to
compete for food.
Finches with beak shapes that allowed them to eat available
food survived longer and produced more offspring than
finches without those beak shapes
After many generations these groups of finches became
separate species
Darwin returned to England and wrote a book that
changed our thought of how and why traits are passed on
the offspring
 He developed the Theory of Evolution by Natural
Selection
 It states that organisms with traits best suited to their
environment are more likely to survive and reproduce
 Page 337 (applying science)
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Darwins Theory emphasizes differences among
individuals
 These differences are called variations
 Variations are inherited traits that make an individual
different from other members of its species
 Variations result from mutations and may be small (shape
of human hairlines) or large (albino)
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Those variations over time allow a gene pool that is a
little different
 Those differences can be beneficial and if so those traits
are carried thru to offspring
 An adaptation is any variation that makes an organism
better suited to its environment
 Variations can result in changes of color, shape, behavior,
or chemical makeup
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 When organisms move into an area
or leave they
bring or take with them characteristics that may
change the gene pool
 When
separated geographically from
other organisms of the same species,
variations of the isolated species may
occur due to gene mutations
 Overtime to two populations may
become different so they can not
reproduce amongst themselves
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Gradualism: slow process of change where
one species changes to a new species
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Punctuated equilibrium: one species changes
rapidly to another (penicillin resistant bacteria)
Clues From Fossils
 Study of Embryology
 Homologous structures
 Vestigal structures
 DNA evidence
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◦ Fossils are living organisms preserved by natural
means
◦ They tell us a lot about the climate, how they obtain
their food, sometimes how they died
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Fossils can be preserved by
◦ Petrified remains caused by minerals replacing wood or
bone.
◦ Imprint fossils are caused by organisms leaving imprint in
sedimentary rock that later hardens.
◦ Casts and Molds where minerals fill in the area of a dead
organism and tracks are recorded.
◦ Ice trapped organisms preserved in whole form.
◦ Amber or Tar pits preserve whole organisms trapped and
hardened.
◦ Most fossils are found in sedimentary rock(layers of
sediment cemented together or mineral deposits from a
solution
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Relative Dating: Dating of fossils by looking
at position fossils lies in relation to each other
◦ Layers of rock are deposited in layers and lower
layers will be older than layers above
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◦ It is not an accurate time but relative, so fossils at
lower levels were deposited before fossils found
above and are older than those above
Accurate dating of fossils based on radioactive
decay of certain radioactive rocks
 Radioactive elements give off a steady
amount of radiation and they decay are steady
rates
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◦ Scientist can determine age of rock that fossils are
found by calculating that decay
◦ This method gives more accurate dates of fossil
preservation
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Fossils can show a gradual change of an
organism
Those changes are preserved in rock and you
can follow the evolutionary development of
them
Fossils can also show extinction of some
species
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Embryology: study of embryos and their
development
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Relationship among species (vertebrates) have
similar embryo development
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Homologous structures: body parts that are similar in
origin and structure are call homologous
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Scientists studies these similarities in structure and
function to see if two or more species share common
ancestors (thus indicating similar evolutionary paths)
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Vestigal structures: structures that no longer seem to
have a function (appendix, tail bone in humans, ear
wiggling, wisdom teeth)
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Thought that in earlier times they did have a function,
but no longer was needed in an organism and could be
related to ancestors with similar structures
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This can track evolutionary changes from a species
ancestors
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By comparing DNA amongst species, similarities are
shown between organism
Scientists can determine how closely related
organisms are to each other
Similar DNA suggest common ancestry
Humans and other primates
◦ Humans have 23 pairs, primates have 24, but two of an apes
chromosomes when laid side by side match chromosome #2 on
the human genome
◦ Blood proteins are similar between humans and apes
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The Order of the Primates are composed of
apes, monkeys, and humans
Characteristics they share
◦ Opposable thumb, binocular vision, flexible
shoulders
◦ Believed to share common ancestor
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Primates are divided into 2 groups
◦ Strepsirhines: lemurs and tarpsier
◦ Haplorhines : monkeys, apes, humans
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Hominids: early human-like ancestors that shared
characteristics with gorillas, orangutans but had larger
brains (4-6 millions years ago)
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African origins: Lucy (Australopithecus) oldest
hominid found (2.9-3.4 mya) in Africa : small brain,
walked upright indicating ancestors to present
humans
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Homo habilis: handy man who used tools ( 1.5-2 mya)
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Gave rise to Homo erectus had larger brain (1.6 mya)
traveled from Africa to SE Asia, China and maybe
Europe
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Larger brain and more human like than Lucy
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Homo sapiens: (400,000 ya) evolved and broke into two
early human groups Neantherthal and Cro-Magnon
and lived during the same time
Neanderthal: lived in caves, used stone tools,
hunted large animals, disappeared 30,000 ya, short,
thick bones, small chins and heavy browridges.
Probably not direct ancestor of humans but a branch
Cro-Magnon: fossil found between 10,000-40,000
ya : Thought to be ancestor of human, walk upright,
tall, used tools, buried their dead
Homo sapiens means wise human