Download UNIT 8 EVOLUTION READING: Chapter 12 History of Life on Earth

UNIT 8
EVOLUTION
READING:
Chapter 12
Chapter 13
History of Life on Earth
The Theory of Evolution
OBJECTIVES
At the end of this unit of study the student will be able to:
1.
Explain the idea of species
2.
Explain the idea of organisms adapting to their environment
3.
Define evolution and give examples of the four types of evolutionary evidence.
4.
Compare the Lamarckian and Darwinian theories of evolution
5.
Summarize the processes of evolution
6.
Distinguish between convergent and divergent evolution
7.
List several common features of primates
8.
Explain the difference between human beings and other primates
9.
List several early hominids and early humans and state their ages.
10.
Compare Neanderthals and Cro-Magnon Man.
ASSIGNMENTS:
1.
2.
3.
4.
5.
EVOLUTION
UNIT 8
I.
Variation in Living Things
A. SPECIES
1. Group of organisms that interbreed
2. VARIATION - small differences between individuals of a species
a. Some neither helpful nor harmful
b. Some enable organism to be better suited to its environment.
3. Environment constantly changing
a. Some gradual - global warming; change in climates
b. Some sudden - eruption of a volcano; landslide
4. Environmental changes may result in organisms
a. Dying
b. Migrating to a new area
5. Some organisms may have helpful variations that enable them to survive the changes and reproduce.
a. Helpful variation inherited by offspring.
b. Eventually environment contains a large number of individuals that have the helpful variation
B. ADAPTATION
1. Process by which an organism becomes better suited to a change in the environment.
2. Helpful variation - permits survival - individual better suited to its environment.
3. Examples
a. Body Structure or Function - Flat teeth and powerful jaws of horses - chewing grass; Sharp
pointed teeth of tigers - tearing meat.
b. Coloration - Tiger's stripes - camouflage
c. Behavior - Nest building of birds
II. Evidence of Evolution
A. EVOLUTION - Based on present scientific data
1. The theory that describes changes in living things and links them to changes in the environment.
2. Change over a period of time - not rapid.
B. Changes in the Earth and its Environs
1. Earth is about 4.5 billion years old
2. Early planet was ball of hot rock
a. Bombarded by meteorites
b. Volcanic eruptions released gases into the atmosphere
c. In time surface cooled - dropped below boiling point of water
1) Water vapor in air condensed and fell to earth as rain
2) Collected in basins forming oceans - about 3.8 - 3.9 billion years ago.
3. Early atmosphere of the earth.
a. Contained ammonia, methane, hydrogen, and water vapor
b. Bombarded by solar radiation particularly ultraviolet
4. Alexander Oparin - Russian scientist, 1924
a. Proposed that molecules necessary for life were formed from materials in early atmosphere
b. 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.
c. Molecules reformed into larger, more complex organic molecules
d. Molecules washed from atmosphere and collected in shallow pools and oceans - formed an
"organic soup" - complex molecules formed
e. Molecules began to work together forming first cells.
f. Oparin's idea tested by Stanley Miller in 1953.
1) Passed mixture of gases through a flask containing electrodes produced electrical sparks simulated lightning
2) Another flask in setup contained boiling water - provided water vapor for "rain"
3) "Rain" washed molecules in a collecting pool.
4) Miller - organic molecules found - amino acids
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5. The First Cells
a. Quite similar to some present-day bacteria
1) PROKARYOTIC - no true nucleus
2) HETEROTROPHIC - "ate" molecules in organic soup
3) Probably ANAEROBIC - atmosphere had little or no oxygen
b. Primitive cells probably flourished - food supply abundant
c. As numbers increased, food supply used up - competition increased - Cells evolved that could
make their own food out of nonorganic substances - became autotrophic.
1) Most successful autotrophs - those that were photosynthetic.
2) First photosynthetic organisms probably resembled blue-green bacteria - prokaryotic,
chlorophyll but no chloroplast.
3) Autotrophs changed atmosphere - oxygen becomes abundant
d. Eukaryotic Cells
1) Probably appeared about 1.5 billion years ago
2) Popular Theory - began as a small collection or colony of prokaryotic cells; mutual survival
3) Individuals may have become organelles.
a) Mitochondria - aerobic bacteria
b) Chloroplasts - blue-green bacteria
4) Theory doesn't explain all differences between eukaryotes and prokaryotes - doesn't explain
how nuclear membrane came into being.
C. Fossil Evidence
1. FOSSILS
a. Remains or traces of organisms that lived in the past.
b. Found in sedimentary rock - buried in sediment
c. Must be buried in sediments soon after death - slows or stops decay process.
d. Types
1) IMPRINTS - form from soft body parts; usually carbon remains.
2) MOLD - cavity that takes shape of trapped hard body parts
3) CAST - Filled mold.
4) PETRIFIED FOSSILS - Hard parts are replaced by minerals.
5) Whole Organisms
a) Frozen in ground or ice (glaciers)
b) In amber (hardened plant resin)
2. Interpreting Fossils
a. Fossils provide evidence that surface and climates have changed.
1) Fossils of ocean dwelling species in inland areas 2) Coral fossils in cold areas - grow in warm areas
3) Ferns/palm tree fossils in cold areas - warm, humid areas
b. Fossils used as evidence of changes in life forms
1) Example - Horse Fossils
a) Fossils of horses - size of dog to present size
b) Change from 4 toes on foreleg and 3 toes on hindleg to 1 toe (hoof) on each leg.
c. Indicate many different living things have existed in the past.
1) EXTINCT - organisms that no longer lives on earth.
3. Dating Fossils
a. Fossils are useful only if scientists can tell how long ago they lived.
b. RELATIVE AGE - Putting events in their proper sequence
1) No reference to age - which event occurred first, then next, and so on.
2) LAW OF SUPERPOSITION - in sedimentary rocks, bottom layers were deposited before
upper layers - each layer is younger than layers below it and older than the ones above it.
c. ABSOLUTE AGE - Measure of how many years ago an event occurred; measured in actual years.
1) Uses process of RADIOACTIVE DECAY - measure of the half-life of an element.
a) HALF-LIFE - Time it takes for 1/2 of quantity of element to breakdown to another
element.
b) Carbon 14 decays to Nitrogen 14 - half-life = 5730 years.
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4. Geologic Time Scale
a. Set up by scientist using information gained from various dating methods.
b. Divided into 4 large time spans called an ERA
1) Precambrian Era - from formation of earth to about 600 million years ago - 4 billion
years long - little fossil evidence from this era.
2) Paleozoic Era - Lasted about 370 million years
3) Mesozoic Era - (Dinosaurs) - lasted about 160 million years
4) Cenozoic Era - Has lasted about 70 million years - Present
c. 3 most recent ERAS divided into PERIODS
d. Some PERIODS divided into EPOCHS
D. Anatomical Evidence
1. ANATOMY - Study of the structure of living things
a. By comparing structures of organisms, similarities are found
b. Use similarities as evidence of evolution
2. HOMOLOGOUS ORGANS
a. Body parts of different species that are similar in structure
b. Examples
1) Seven neck vertebrae of all mammals
2) Whale's flipper, human's arm, bird's wing, etc.
c. Can't be explained by common function; can be by heredity; indicates common ancestor;
3. VESTIGIAL ORGANS
a. Organs that are reduced in size and appear to have no use.
b. Examples
1) Human appendix
2) Remains of hind limbs in whales
E. Embryological Evidence
1. Early vertebrate embryos look very similar - believed to have common genetic material which
makes their early development similar.
a. Gill slits in vertebrates - remain in fish but form other structures in other vertebrates Eustachian tube in humans
b. NOTOCHORD - stiff rod that forms portion of vertebrae.
F. Biochemical Evidence
1. Similarities between common proteins found in living organisms; More similarities indicate a
closer relationship between the organisms
2. Indicates similarities between DNA of 2 organisms.
III. Theories of Evolution
A. Lamarck's Theory
1. Jean Baptiste de Lamarck, French biologist; early 1800s
2. Believed giraffes' long necks were the result of stretching - as low food supply was consumed, they
stretched their necks to reach higher branches; Disuse of an organ could result in its loss.
3. Based on INHERITANCE OF ACQUIRED CHARACTERISTICS - acquired traits could be passed on
to the next generation
4. Not valid, changes in body cells are not passed to the gametes
B. Darwin's Theory
1. Background
a. British naturalist; Published book;1859 On the Origin of Species by Means of Natural Selection
b. Ideas developed during his 5 year voyage aboard the HMS Beagle
c. Observed many different plants and animals in South America and The Galapagos Islands.
2. Main Hypotheses
a. The world is not static but is changing
b. Living things change through time.
c. Organisms with many common characteristics descended from a common ancestor.
d. Evolutionary change is a result of natural selection.
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3. NATURAL SELECTION - process by which those organisms that are best suited to their
environment survive and reproduce.
a. Overproduction
1) Organisms tend to produce more offspring than could survive.
2) Assumed number of organisms would increase geometrically (1,2,4,8,16,32,64,128,...)
b. Struggle for Existence
1) Noted that even with overproduction, population tended to remain constant.
2) Concluded that populations didn't increase was due to "struggle for existence" - competition
for food, space, etc.,
3) Some individuals will not be successful and will die.
4) Darwin concluded that individuals and species were "selected" by their environment.
c. Variation
1) Individuals of a species vary genetically.
2) Was not able to explain what caused the variations.
d. Natural Selection and Origin of New Species
1) Better suited organisms survived and reproduced; passed these traits to their offspring.
2) Over time many small changes would occur, so that the whole population would change.
3) Eventually populations would become significantly different from past populations - new
species were thus formed.
IV. Processes of Evolution
A. GENE POOL - All the genes of a given population; variations in gene pool cause change in the species.
B. Hardy-Weinberg Law - The frequency of dominant and recessive genes in a population remains the
same from generation to generation.
1. GENE FREQUENCY - indication of relative number of individuals in a population that have a
particular gene.
2. Law applies only under the following conditions
a. Population must be very large
d. Natural selection must not be operating
b. No new genes enter the gene pool
e. Mutations must not occur.
c. Mating must be random
C. GENE MUTATION - change in genetic material; result - change of gene pool
D. ADAPTATION SHIFTS - Changes in frequency of occurrence of certain genes as environment changes.
1. Shift in Color of Peppered Moth in Manchester, England
a. Before 1845, peppered moths were light with dark specks
b. In 1845 during a survey only 1 black moth was observed.
c. Light colored moths were difficult to see on light colored tree trunks - were not eaten by birds.
d. Manchester became an industrial center in mid 1800s - used coal for energy - produced a large
amount of soot; settled on tree bark making it dark
e. By 1895, 99% of moths in area were black - black color permitted hiding while light
coloration made moths stand out on trees - easy food for birds.
E. MIGRATION - movement of organisms into and out of a population brings new genes or removes genes
when organism leaves.
F. ISOLATION - separation of members of a population from other members.
1. Separation may lead to SPECIATION - new and distinct species.
2. GEOGRAPHIC ISOLATION - separation of population members by some geographic barrier river, mountain, canyon, etc.
3. REPRODUCTIVE ISOLATION - separation of members of a population by inability to reproduce.
V. Pathways of Evolution - processes of evolutionary change that have lead to organisms having similarities or
differences.
A. DIVERGENT EVOLUTION
1. Evolutionary pathway where different species have developed from a common ancestor
a. Members of population spread out, adapt to various environments.
b. Different variations are selected
c. ADAPTIVE RADIATION - process where species adapts to set of environmental conditions
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2. DIVERGENT means "moving apart"
3. Example - Darwin's finches on the Galapagos Islands
a. Ancestor inhabited the islands
b. Offspring gradually filled various environments of the islands
c. Some became seed eaters, others ate insects, one even became a type of woodpecker: uses a thorn
as a tool.
B. CONVERGENT EVOLUTION
1. Process of unrelated species developing similar characteristics.
2. CONVERGENT means "coming together"
3. Examplesa. Wings of birds and bats
b. Body shape of whales, porpoises, and dolphins and fish; flippers of the mammals and fins of fish
4. ANALOGOUS ORGANS - organs that are similar in appearance and function but not in origin.
VI. Human History
A. Primate Characteristics - Order of humans, monkeys, apes, etc.
1. Hands adapted for grasping: OPPOSABLE THUMB - touches each finger
2. Well-developed eyes - can see fine detail even in dim light.
3. STEREOSCOPIC VISION - eyes on front of face, can see in 3-D
4. 4 types of teeth - incisors, canines, premolars, molars
5. Most are omnivores
B. Human Characteristics
1. Anatomical Characteristics
a. Posture - permit standing erect; BIPEDAL - walks on 2 limbs
1) Arch of the foot - supports
2) Large toe in line with others; for walking rather than grasping as among other primates.
3) Pelvis provides better support for internal organs and upper body mass - distributes body's
mass onto the legs.
b. Type of Thumb - adapted for refined movements; hand rotates
c. Types of Teeth and Jaw 1) Teeth are smaller than found in the great apes
2) Jaw more bow shaped
d. Brain Capacity - more highly developed brain
2. Physiological Characteristics
a. No definite breeding season (heat) as in other primates
b. Develop and age slower; have longer life span
3. Behavioral Characteristics
a. Brain capacity gives humans ability to learn
b. Makes and uses tools
c. Uses symbols to form languages
C. Biological History of Human
1. Human Fossil Record
a. HOMINID - human like
b. Australopithecus africanus - discovered in 1924 in South Africa; believed to be between 1.5
and 4.5 million years old
c. Australopithecus robustus - 1 to 2 million years old
d. 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
2. Early Human Forms
a. Homo habilis - First discovered by the Leakeys in 1950s; Estimated to have lived 1.5 to 2
million years ago
1) Larger, higher, and rounder skull than australopithecines
2) Erect posture and humanlike hand bones
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b. Homo erectus - Java man - 1891, Peking man - 1929
1) Dated from 1.6 million to 500,000 years ago.
2) Shorter than Homo sapiens thicker and heavier bones
3) Skull structure different - forehead sloped, jaw large, chin small
c. Homo neanderthalensis
1) Lived in Europe and parts of Asia; 200,000 to 35,000 years ago
2) Erect posture; heavier and thicker bones
3) Chinless: Sloping forehead
4) Stone tools; Used fire
d. Homo sapiens
1) Cro-Magnon
a) Fossils found in France in 1868.
b) Estimated to have lived 40,000 years ago.
c) High foreheads, small even teeth, large brain cavities
d) Tools, weapons, and implements found; indicate a complex culture
e) Made pottery, painted on cave walls, carved bones
f) Lived in different places; adapted to different climates.
2) Only species of Homo now living
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