Transcript Evolution

SPECIES - Group of organisms that interbreed
VARIATION - small differences between individuals
of a species
 Some neither helpful nor harmful
 Some enable organism to be better suited to its
environment.
Environment constantly changing
 Some gradual - global warming; change in climates
 Some sudden - eruption of a volcano; landslide
Environmental changes may result in organisms
 Dying
 Migration to new area
Some organisms may have helpful variations that enable them to
survive the changes and reproduce.
 Helpful variation inherited by offspring.
 Eventually environment contains a large number of individuals
that have the helpful variation
ADAPTATION
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Process by which an organism becomes better suited to a change in
the environment.
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Helpful variation - permits survival - individual better suited to its
environment.
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Examples :
Body Structure or Function
Flat teeth and powerful jaws of horses - chewing grass
Sharp pointed teeth of tigers - tearing meat.
Coloration - Tiger's stripes - camouflage
Behavior - Nest building of birds
EVOLUTION - Based on present scientific data
 The theory that describes changes in living
things and links them to changes in the
environment.
 Change over a period of time - not rapid.
Changes in the Earth and its Environs
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Earth about 4.5 billion years old
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Early planet was ball of hot rock
Bombarded by meteorites
Volcanic eruptions released gases into the atmosphere
Surface cooled - below boiling point of water
Water vapor condensed and fell to earth as rain
Collects forming oceans - 3.8 - 3.9 billion years ago.
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Early atmosphere of the earth.
Contained ammonia, methane, hydrogen, and water vapor
Bombarded by solar radiation particularly ultraviolet
Alexander Oparin - Russian scientist, 1924
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Proposed that life molecules formed from materials in early atmosphere
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Theorized that energy from lightning, volcanic eruptions, ultraviolet
radiation from sun, and natural radiation of earth may have split some of
the molecules of the early atmosphere.
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Molecules reformed - larger, more complex organic molecules
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Molecules washed from atmosphere; collected in shallow pools and
oceans - formed an "organic soup" - complex molecules
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Molecules worked together forming first cells.
Oparin's idea tested by Stanley Miller - 1953.
Passed mixture of gases through a flask containing
electrodes - simulated lightning
 Another flask contained boiling water - provided
water vapor for "rain"
 "Rain" washed molecules in a collecting pool.
 Organic molecules found - amino acids
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The First Cells
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Quite similar to some present-day bacteria
Prokaryotic - no true nucleus
Heterotrophic - "ate" molecules in organic soup
Probably Anaerobic - atmosphere had little or no oxygen
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Primitive cells flourished - food supply abundant
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Numbers increased, food supply used up - competition increased Cells evolved that could make their own food - autotrophic.
Photosynthetic organisms most successful autotrophs
Resembled blue-green bacteria - prokaryotic, no chloroplast.
Autotrophs changed atmosphere - oxygen becomes abundant
Eukaryotic Cells
Probably appeared about 1.5 billion years ago
Began as a small colony of prokaryotic cells; mutual
survival
 Individuals may have become organelles.
Mitochondria - aerobic bacteria
Chloroplasts - blue-green bacteria
 Theory doesn't explain all differences between
eukaryotes and prokaryotes - doesn't explain how
nuclear membrane came into being.
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Major Types of Evidence
 Fossil Evidence
 Anatomical Evidence
 Embryological Evidence
 Biochemical Evidence
Fossil Evidence
Fossils
Remains or traces of organisms that lived in the past.
Found in sedimentary rock - buried in sediment
Must be buried in sediments soon after death – slows/stops decay
Types
Imprints - from soft body parts; usually carbon remains.
Mold - cavity takes shape of trapped hard body parts
Cast - Filled mold.
Petrified Fossils - Hard parts are replaced by minerals.
Whole Organisms
Frozen in ground or ice (glaciers)
In amber (hardened plant resin)
Interpreting Fossils
Fossils provide evidence that surface/climates have changed.
Fossils of ocean dwelling species in inland areas Coral fossils in cold areas - grow in warm areas
Ferns/palm tree fossils in cold areas - warm, humid areas
Fossils used as evidence of changes in life forms
Example - Horse Fossils
Fossils of horses - size of dog to present size
Change from 4 toes on foreleg and 3 toes on hindleg
to 1 toe (hoof) on each leg.
Indicate many different living things have existed in the past.
Extinct - organisms that no longer lives on earth.
Dating Fossils
Fossils are useful only if scientists can tell how long ago they lived.
Relative Age - Putting events in their proper sequence
No reference to age - order event occur
Law of Superposition - sedimentary rocks, bottom layers
deposited before upper layers - each layer is younger than layers
below it and older than the ones above it.
 Absolute Age - how many years ago an event occurred; measured in
actual years.
Uses Radioactive Decay - measure of half-life of element.
Half-Life - Time it takes for ½ of quantity of element to
breakdown to another element.
Carbon 14 decays to Nitrogen 14 - half-life = 5730 years.
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Geologic Time Scale
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Set up by scientist using information gained from various dating
methods.
Divided into 4 large time spans called an ERA
Precambrian Era - formation of earth to about 600
million years ago - 4 billion years long - little fossil evidence
Paleozoic Era - Lasted about 370 million years
Mesozoic Era - (Dinosaurs) - lasted about 160 million years
Cenozoic Era - Has lasted about 70 million years - Present
3 most recent Eras divided into Periods
Some Periods divided into Epochs
Anatomical Evidence
 Anatomy - Study of the structure of living things
By comparing structures of organisms, similarities are found
Use similarities as evidence of evolution
 Homologous Organs
Body parts of different species that are similar in structure
Examples
Seven neck vertebrae of all mammals
Whale's flipper, human's arm, bird's wing, etc.
Can't be explained by common function; can be by heredity; indicates common
ancestor;
 Vestigial Organs
Organs that are reduced in size and appear to have no use.
Examples
Human appendix
Remains of hind limbs in whales
Embryological Evidence
Early vertebrate embryos look very similar
Believed to have common genetic material early development similar.
Gill slits in vertebrates
Notochord
Biochemical Evidence
Similarities between common proteins found in
living organisms
Similarities indicate a close relationship
Indicates similarities between DNA of organisms.
Lamarck's Theory
Jean Baptiste de Lamarck, French biologist; early 1800s
Believed giraffes' long necks result of stretching
Low food supply was consumed
Stretched their necks to reach higher branches
Disuse of an organ could result in its loss.
Based on Inheritance of Acquired Characteristics
Acquired traits passed on to the next generation
Not valid, body cells changes not passed to gametes
Darwin's Theory
Background
British naturalist
Published book;1859
On the Origin of Species by Means of Natural Selection
Ideas formed during 5 year voyage aboard the HMS Beagle
Observed many different plants and animals in South
America and The Galapagos Islands.
Main Hypotheses
The world is not static but is changing
 Living things change through time.
 Organisms with many common characteristics
descended from a common ancestor.
 Evolutionary change is result of natural selection.
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Natural Selection –
Process by which those organisms that
are best suited to their environment
survive and reproduce.
Factors Working in Natural Selection
 Overproduction
 Struggle for Existence
 Variation
Overproduction
Organisms tend to produce more offspring than
could survive.
 Assumed number of organisms would increase
geometrically (1,2,4,8,16,32,64,128,...)
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Struggle for Existence
 Even with overproduction, population tended to
remain constant.
 Concluded lack of population increase was due
to "struggle for existence" - competition for
food, space, etc.,
 Some individuals not successful; will die.
 Concluded that individuals and species were
"selected" by their environment.
Variation
 Individuals of a species vary genetically.
 Not able to explain cause of variations.
Natural Selection and Origin of New Species
Better suited organisms survived and
reproduced; passed traits to their offspring.
 Over time many small changes would occur, the
whole population would change.
 Eventually populations become significantly
different from past populations
New species formed.
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Gene Pool
All the genes of a given population
Variations in gene pool cause changes in
the species.
Hardy-Weinberg Law
The frequency of dominant and recessive genes in a population
remains the same from generation to generation.
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Gene Frequency - indication of relative number of individuals in a
population that have a particular gene.
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Law applies only under the following conditions
Population must be very large
No new genes enter the gene pool
Mating must be random
Natural selection must not be operating
Mutations must not occur.
Major Processes at Work
 Gene Mutation
 Adaptation Shifts
 Migration
 Isolation
Gene Mutation
Change in genetic material
Result - change of gene pool
Adaptation Shifts
Changes in frequency of occurrence of certain
genes as environment changes.
Shift in Color of Peppered Moth in Manchester, England
Before 1845, peppered moths were light with dark specks
In 1845 during a survey only 1 black moth was observed.
Light colored moths were difficult to see on light colored
tree trunks - not eaten by birds.
Manchester - industrial center in mid 1800s
Used coal for energy - large amount of soot;
Settled on tree bark making it dark
By 1895, 99% of moths in area were black
Black color permitted hiding
Light coloration moths stand out on trees - easy
food for birds.
Migration
Movement of organisms into and out of
a population
Brings new genes or removes genes
when organism leaves.
Isolation
Separation of members of a population from other
members.
Separation may lead to Speciation
Formation new and distinct species.
Geographic Isolation - separation of population
members by some geographic barrier
River, mountain, canyon, etc.
Reproductive Isolation - separation of members
of a population by inability to reproduce.
Processes of evolutionary change
that have lead to organisms having
similarities or differences.
Divergent Evolution
Evolutionary pathway where different species have developed from a
common ancestor
Members of population spread out, adapt to various
environments.
Different variations are selected
Adaptive Radiation - process where species adapts to set of
environmental conditions
 Divergent means "moving apart"
 Example - Darwin's finches on the Galapagos Islands
Ancestor inhabited the islands
Offspring gradually filled various environments of the islands
Some became seed eaters, others ate insects, one even
became a type of woodpecker: uses a thorn as a tool.
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Convergent Evolution
 Process of unrelated species developing similar
characteristics.
 Convergent means "coming together"
 ExamplesWings of birds and bats
Body shape of whales, porpoises, and
dolphins and fish
Flippers of the mammals and fins of fish
 Analogous Organs - organs that are similar in
appearance and function but not in origin.
Primate Characteristics - Order of humans, monkeys, apes
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Hands adapted for grasping: Opposable Thumb touches each finger
Well-developed eyes - can see fine detail even in dim
light.
Stereoscopic Vision - eyes on front of face, see in 3-D
4 types of teeth - incisors, canines, premolars, molars
Most are omnivores
Human Characteristics
Anatomical Characteristics
Posture - permit standing erect; Bipedal - walks on 2 limbs
Arch of the foot - supports
Large toe in line with others; walking rather grasping
Pelvis provides better support for internal organs and
upper body mass - distributes body's mass onto the
legs.
Type of Thumb - adapted for refined movements
Hand rotates
Types of Teeth and Jaw Teeth are smaller than found in the great apes
Jaw more bow shaped
Brain Capacity - more highly developed brain
Human Characteristics
Physiological Characteristics
No definite breeding season (heat) as
in other primates
Develop and age slower
Have longer life span
Human Characteristics
Behavioral Characteristics
Brain capacity gives ability to learn
Makes and uses tools
Uses symbols to form languages
Biological History of Human
Human Fossil Record
Hominid - human like
Australopithecus africanus
Discovered in 1924 in South Africa
Believed between 1.5 and 4.5 million years old
Australopithecus robustus
1 to 2 million years old
Australopithecus afarensis
Discovered 1977; 40% complete skeleton
Female; nicknamed "Lucy“
Thought to be 3.5 million years old
Theorized as common ancestor of modern humans and
the two above mentioned species
Early Human Forms
Homo habilis
First discovered by the Leakeys in 1950s;
Estimated to have lived 1.5 to 2 million
years ago
Larger, higher, and rounder skull than
australopithecines
Erect posture and humanlike hand bones
Early Human Forms
Homo erectus
Java man - 1891, Peking man - 1929
Dated from 1.6 million to 500,000 years ago.
Shorter than Homo sapiens thicker and
heavier bones
Skull structure different - forehead sloped,
jaw large, chin small
Early Human Forms
Homo neanderthalensis
Lived in Europe and parts of Asia
Lived 200,000 to 35,000 years ago
Erect posture; heavier and thicker bones
Chinless: Sloping forehead
Stone tools; Used fire
Early Human Forms
Homo sapiens
Cro-Magnon
Fossils found in France in 1868.
Estimated to have lived 40,000 years ago.
High foreheads, small even teeth, large brain cavities
Tools, weapons, and implements found; complex culture
Made pottery, painted on cave walls, carved bones
Lived in different places; adapted to different climates.
Only species of Homo now living