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Principles of Biology
By
Frank H. Osborne, Ph. D.
Evolution
The Heterotroph Hypothesis
•According to the heterotroph hypothesis, the
first organisms to develop were heterotrophs.
•The autotrophic organisms developed after
the heterotrophic ones.
Primitive Conditions on the Earth
•The age of the Earth is thought to be 4.5 x 109
(4.5 billion) years. Evidence for this estimate
comes from the measurement of the decay of
Uranium. This time is divided into four eons.
•In the earliest eon, there was a reducing
atmosphere, much heat, lightning (electrical
discharge), ultraviolet (UV) light from the
Sun and radiation.
Eons of Time
Eon
Hadian
Archaen
Proterozoic
Phanerozoic
Duration (Millions of Years)
4500-4000
4000-2500
2500- 600
600-Today
Primitive Conditions on the Earth
•There was no ozone layer in the earliest days of
the Earth. To form an ozone layer requires
oxygen. Oxygen is the waste product of
photosynthesis. Photosynthesis did not develop
until after the formation of the first eukaryotic
cells, about 2.5 billion years ago. Therefore,
without an ozone layer, UV light came all the way
down to the surface.
Primitive Conditions on the Earth
•There are no rocks found so far that go back
to the formation of the Earth. Geological
processes of erosion, transport and depostion
have worn away the original rocks.
•There have been rocks found in
Canada and Australia that are dated
in the range of 3.9 - 4.1 billion years.
Synthesis Reactions
•A reducing atmosphere of ammonia (NH3),
methane (CH4), hydrogen (H2) and water (H2O)
has been shown to be able to produce such
molecules as urea, hydrogen cyanide, organic
acids and other molecules under laboratory
conditions by random synthesis reactions with
each other.
Synthesis Reactions
•There was no oxygen in the early atmosphere
but there was some CO2 present. The
molecules produced experimentally in Miller's
spark discharge apparatus were similar to
biological molecules. For example, amino acids
were found.
Miller's Experiment
Aggregates of Organic Molecules
•Aggregates are collections of organic
molecules that may have formed along the
shorelines of primitive seas where the
molecules were exposed to ultraviolet light.
•Radiation on rocks causes them to heat up.
There is evidence that when organic
molecules are heated together dry, they react.
Aggregates of Organic Molecules
•Fox took dry amino acids and heated them
together. Water was released that condensed
on the inside of the test tube at the top. This
condensation resulted from reactions between
the amino acid molecules. Thus the origin of
the term "condensation reaction."
Coascervates
•Certain larger aggregates
(coascervates) might have
begun to divide after reaching
a certain size. Experiments
have shown that CH4, NH3,
and H2O can yield bases like
those found in DNA.
Anaerobic Respiration
•Fermentation is found in all cells, not only the
anaerobic bacteria but even those that use
aerobic respiration. So, anaerobic respiration
must have developed first. The first organisms
probably got their energy by fermenting
organic molecules that were
dissolved in the water.
Development of Autotrophs
•Some organisms must have
developed the means by which to
perform photosynthesis. The
resulting release of oxygen over
time led to the formation of the
oxidizing atmosphere we have
today.
Aerobic Respiration
Those organisms that could tolerate and use
oxygen went on to become aerobic. It is
thought that eukaryotic cells developed as a
result of one kind or prokaryote living inside
another.
Endosymbiosis
•This explanation is called the endosymbiotic
theory. According to this explanation,
mitochondria that we have today were originally
a form of prokaryote that had a knack for
producing energy.
•Similarly, chloroplasts are thought to have
resulted from other prokaryotes that could trap
solar energy.
Endosymbiosis
•Evidence for this theory comes from the fact
that mitochondria and chloroplasts have their
own DNA molecules, independent of the DNA
in the chromosomes of the nucleus of the cell.
This DNA is closely related to bacterial DNA,
not nuclear DNA.
Endosymbiosis
•Also, mitochondria and chloroplasts have
their own ribosomes. These ribosomes are
closely related to bacterial ribosomes and are
distinctly different from the cytoplasmic
ribosomes.
Geologic Time Scale
Geologic Time Scale
•Geologic time is
divided into eras,
periods and epochs.
•Mainly the
distinctions are
based on fossil
evidence.
The Geologic Time Scale
•Life began in the proterozoic eon, about 2.5
billion years ago.
•This is also known as the Pre-Cambrian era.
Each era is a subdivision of an eon. Each era is
also further subdivided into periods. The
periods correspond to major divisions in geologic
(and biologic) history.
The Geologic Time Scale
•Geologists use biology as evidence for different
periods. Up until the discovery of radioactivity
in 1895, there was uncertainty about the age of
the Earth or different layers of rocks.
The Geologic Time Scale
•Geologists then and now use fossils to indicate
information about the age and history of various
rocks. The most recent period, the one we are in
now, is known as the Quaternary Period.
Glaciations of the Quaternary
•There were four major
glaciations (ice ages) in
the Quaternary period.
The earliest ice age began
600,000 years ago.
•Others occurred beginning at 500,000 years
and 250,000 years. The last one began at 70,000
years and ended 20,000 years ago.
The Fossil Record
•The oldest rocks are over 3.5 billion years old.
Fossils are the remains of living things or are
objects that were made by living things. These
are left in sand or mud that will eventually be
turned into sedimentary rock. Teeth and bones
make good fossils as well as tools of primitive
humans and worm burrows.
The Fossil Record
•In undisturbed rock layers, the
oldest fossils (indicating the oldest
rocks) should be found in the oldest
layers. This is the case in the Grand Canyon
that exposes approximately 2.5 billion years of
Earth history in one place.
•Relatedness between fossils is
based on comparative anatomy.
Early Mammals
•The first mammals came into existence as early
as 1.5 x 108 (150,000,000) years ago. The earliest
primates developed about 70,000,000 years ago.
•The earliest monkeys came into being some
40,000,000 years ago. The most primitive of
them already had the same dental pattern as
modern humans.
Fossil Record of Early Humans
•The oldest fossils are found in
Africa. For human archeological
sites, 14C-dating is used.
Fossil Record of Early Humans
•Information about the early ancestors of
humans is derived from the study of fossil bones
and skulls. In the early Miocene lived Proconsul.
Proconsul may have been the common ancestor
of chimpanzees, gorillas and humans. It is 25
million years old and had teeth like those of
apes.
Proconsul
Proconsul
africanus
Early Pleistocene Hominids
•Early Pleistocene hominids lived in the old
stone age. Australopithecus afarensis
(southern ape of the Afar region of
Africa) lived in east Africa at least 3
million years ago. [This makes it the
earliest hominid.]
•It then evolved into the gracile A. africanus and
the robust A. transvaaliensis at about 2 million
years ago.
Australopithecus
afarensis
Australopithecus
afarensis
Australopithecus
afarensis
Australopithecus
transvaaliensis
Early Pleistocene Hominids
•Gracile organisms have delicate boning whereas
robust organisms have heavy boning. The
robust ones lived for about 1 million years then
died out.
•Humans are gracile. The gracile ancestors
evolved into the genus Homo.
Early Pleistocene Hominids
•More recently in the Pleistocene lived Homo
habilis. Homo is the genus that includes
humans. All members of the genus Homo, other
than Homo sapiens sapiens are extinct.
•Homo habilis, like Australopithecus was small
but had distinct differences in the skull bones
and teeth.
Homo
habilis
Homo
habilis
Middle Pleistocene Hominids
•Homo erectus had a more advanced Stone Age
culture called Pre-Moustarian. It had the ability
to use fire and create simple tools. Some
specimens have been given names such as Java
Man. Homo erectus developed in Africa about
1.6 million years ago.
Homo
erectus
Homo
erectus
Homo
erectus
Middle Pleistocene Hominids
•Homo erectus and Australopithecus lived in the
same general areas of Africa and Europe.
Australopithecus may have died out because
Homo erectus was more advanced and could
compete more easily.
Middle Pleistocene Hominids
•The earliest prototype Homo sapiens is dated at
about 300,000 years ago. During the last ice age
it evolved into two sub-species, Homo sapiens
neanderthalis and Homo sapiens sapiens.
Steinheim man is of the Neanderthal type. It has
Mousterian culture which included ritual burial.
Homo sapiens
neanderthalis
Homo sapiens
neanderthalis
The Late Pleistocene
•Homo sapiens neanderthalis lived between
130,000 and 35,000 years ago. In Europe it lived
alongside Homo sapiens sapiens. The two subspecies eventually interbred to form the modern
human, Homo sapiens sapiens.
•Modern humans are most closely related to
chimpanzees, about 90-95%.
Evolutionary Trends in Primates
1.
2.
3.
4.
5.
Primitive five-digit hand and foot pattern
Free mobility of thumb and big toe
Flattened nails instead of sharp claws
Increased facial angle
Perfection of visual apparatus
Evolutionary Trends in Primates
6. Reduction in apparatus of sense of smell
7. Increase in size and complexity of the brain
8. Development of uterus and more efficient
nourishment of the fetus in pregnancy
9. Erect posture and development of
bipedalism
10. Prolongation of post-natal life periods
Biological Taxonomy
Biological taxonomy is most like the address on
an envelope.
• In country, there are more than one states.
In a state there are more than one cities.
• In a city there are more than one streets.
• On a street there are more than one
buildings.
• In each building are one or more occupants.
Biological Taxonomy
The list below contains the taxa from the more
general to the more specific.
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Biological Taxonomy
Each different organism has is own scientific
name. Humans are Homo sapiens.
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Animalia
Chordata
Mammalia
Primates
Hominids
Homo
sapiens
Topics for Third Exam
Cell Division (20)
Mitosis (9)
Meiosis (2)
Reproduction (6)
Embryology (3)
Genetics (10)
Molecular Genetics (6)
Ecology (12)
Evolution (12)
The End
Principles of Biology
Evolution