HUMAN EVOLUTION
CHAPTER 26 SECTION 4
SC.912.L.15.1…HIGH (explain how the theory of
evolution is supported by the fossil record,
comparative anatomy, biogeography, molecular
biology, and observed evolutionary change)
SC.912.L.15.10…MEDIUM ( identify basic trends in
hominid evolution from early ancestors six million
years ago to modern humans, including brain size,
jaw size, language, and manufactured tools.)
• A. PRIMATE EVOLUTION. 233 species of mammals
called primates (order primates). Lemurs, monkeys,
apes, humans. Hypothesis supports that human
evolved from a tree dwelling, insect eating ancestor
app. 65mya.
1. CHARACTERISTICS. Now live on the ground, and
retain adapt. For living on trees. EX:
a) Flexible shoulders for swinging.
b) Sensitive fingers instead of claws.
c) Hands can hang and manipulate food.
d) Binocular vision. Eyes in front of the face and the
field of vision overlap enhancing depth perception.
2. -2 MAJOR GROUPS.
First group includes lorises, galagos, and lemurs.
Lemurs live in Madagascar, and lorises live in Africa and
South Asia. They are mostly nocturnal, tree dwellers and
have claws.
Second Group includes tarsiers, new world monkeys, old
world monkeys, apes and humans.
1. tarsiers…live in s. east asia
2. N.W.Monkeys..live in the Americas, tree dwellers,
have prehensile (grasping) tails for swinging.
3. O.W. Monkeys….tree dwellers but tails are not
prehensile.include baboons, macaques, and mandrills
• 4. APES…gibbons, orangutans, gorillas,and
chimpanzees. Larger than other primates, long
arms, short legs, no tails. They can swing.
Gorillas and chimps are highly social of all.
Chimps are the closest relatives from humans
differing in less than 2% of their DNA
sequence.
• ONLINE ACTIVITY 26-4
• B. HOMINID EVOLUTION Members of the human family
are called hominids (Family Hominidae, Order Primates).
Only 1 species of hominids exist : Homo sapiens (modern
man). Earliest man may have lived 6 to 7mya. 2
important developments:
• 1. WALKING UPRIGHT. …Australepithecus aferensis is the
oldest evidence of upright posture and walking on 2
feet……BIPEDALISM (4mya). Became extinct
1.4mya…famous LUCY. Walking upright developed bef.
Big brain.
• 2. ENLARGED BRAINS. First appeared in East Asia 2.5mya.
Large brains found with tools…Homo habilis. Homo
erectus ..taller than habilis, had a larger
brain…app.1200cc.
Increase in intelligence gave them success in Africa.
• C. HYPOTHESES FOR THE ORIGIN OF FULLY MODERN
MAN.
• 1. MULTIREGIONAL HYPOTHESIS. Fully modern
human developed from H.erectus descendents that
spread from Africa 1.5 mya. Interbreeding among
regional H.sapiens evolved as a single species.
• 2. REPLACEMENT HYPOTHESIS. Says that all regional
H.erectus became extinct all over the world and that
humans descended from a group of H. erectus that
remained in Africa. They started spreading out
100,000 ya replacing the other.
• - DNA supports a very recent split from a common
ancestor.
• DRAW FIGURES 26-22 AND 26-23 CHAPTER (26-4)
ORIGINS OF LIFE
SC.912.L14.5 Theory of the origins
of life…High
sc.912.l.14.5 explanations of the
origins. ..moderate
(note: everytime you encounter a
figure you must draw it in your
interactive notebook)
SECTIONS 16-1 AND 17-5
• A. OLDEST FOSSILS
• 1. STROMATOLITES. Oldest fossils about 3.5
million years old, found in domes called
stromatolites. Made of layers of prokaryotic
photosynthetic bacteria also called
CYANOBACTERIA or BLUE-GREEN ALGAE.
• It contain chlorophyll which permits it perform
photosynthesis.
• Page 356
• 2. FORMATION OF ORGANIC POLYMERS. Miller’s
exp. Provided evidence that small organic molecules
could have formed from physical and chemical
processes. How did polymers (long chains of
molecular units [monomers]) formed without living
cells or enzymes being present? Polymers=
polypeptides(amino acids) and polysaccharides
(sugars). DRAW FIGURE 16-2, page 357
• Experiments: solution of amino acids dropped onto
the surface of hot sand, water evaporates and leaves
behind the amino acids then bond together to form
polypeptides. Also, CLAY, concentrate amino acids
and other monomers held together.
• 3.THE RNA WORLD. One important characteristic of
life is inheritance which is based on molecules that
can copy themselves. Cells today TRANSCRIBE
genetic information from DNA to RNA which then
directs the synthesis of enzymes and other proteins.
• One hypothesis of ancient cells is that the first genes
were short strands of RNA that could replicate
without the help of enzymes or other cells. RNA has
shown to make a copy of themselves in solution
containing nucleotides (thymine, adenine, cytosine,
guanine). FIGURE 16-3. PAGE 358.
• Basically an RNA world= included stored genetic
information and directed protein synthesis.
• 4.FORMATION OF PRE-CELLS. Biologist hypothesize that
early organic molecules became organized into increased
level of order by becoming encased in a membrane.
Experiments show that polypeptides can form fluid filled
spheres. If lipids are included in the solution they form
selectively permeable membranes. These are called Precells. They are NOT living but show properties of living
cells. FIG. 16-4.page 358
• SUMMARY
• FIRST. small organic molecules such as nucleotides and
amino acids formed from small organic molecules.
• SECOND. Small molecules joined together to form
proteins and nucleic acids. ONLINE ACTIVITY. 16-1
• THIRD. Molecules that can copy themselves
provide a basis for inheritance.
• FOURTH. These molecules became packaged
with membranes and separated from their
surroundings to form pre-cells.
• -----------------------------------------------------------These exp. Do not say that life originated for
sure this way. They simply show that life COULD
have arisen this way. There is a lot of debate
going on which is part of scientific work.
B. ORIGINS OF LIFE.
WHERE DID LIFE BEGIN?? WHAT CONDITIONS
ALLOWED LIFE ON EARTH??
• Until recent researchers thought that life had
originated in shallow water or moist sediments as
clay.
• But, the early earth was hot and after the
discovery of deep see hydrothermal vents raised
the possibility that similar environments may
have supplied the energy and the chemical raw
materials for the origin of life.
• Ex: Deep sea vents are populated with
prokaryotic organisms.
C. THEORIES OF THE ORIGIN OF LIFE.
• 1. ABIOGENESIS (SPONTANEOUS
GENERATION)
• Until the mid of the 19th century it was thought that
organisms arose from mud or organic matter.
• They thought that maggots arose from meat and
mice from rice..(spontaneous generation)
• In 1968, an Italian Physician Francesco Redi
disproved the believe of SPONTANEOUS
GENERATION at that time with his experiment.
• He performed a controlled experiment:
• DRAW REDI’S EXPERIMENT.(leave space)
• He convinced many scientists that maggots did not
arise from spontaneous generation, but not totally.
They still thought that microorganisms arose from
the air.
• Disproving this was difficult. Finally in the mid 1800s,
LOUIS PASTEUR designed an experiment that
disproved spontaneous generation of
microorganisms.
• DRAW PASTEUR’S EXPERIMENT.(leave space )
• Pasteur set up an experiment in which air but no
microorganisms was allowed to contact a broth that
contained nutrients.
• Pasteur’s experiment showed that microorganisms
do not simply arise in broth, even tin the presence of
air. From time on, BIOGENESIS, the idea that living
organisms come only from other organisms, became
a cornerstone of biology.
• 2. ENDOSYMBIOTIC THEORY. (the origin of
eukaryotes).
• A widely accepted theory is a combination of 2
processes.
• 1. In the first (INFOLDING) one internal membranes
such as endoplasmic reticulum, golgi apparatus, and
the nuclear envelope evolved from the inward fold of
the plasma membrane of ancestral prokaryotic cells.
DRAW FIGURE 17-18 PAGE 395. INFOLDING ONLY!!
These membranes allows the cell to carry out more
complex chemical reactions in separate compartments.
ONLINE ACTIVITY 17-5
• 2. The second on (ENDOSYSMBIOSIS) led to the
existence of mitochondria and chloroplast.
Scientist hypothesize that small symbiotic
prokaryotes lived within other larger host
prokaryotes.
• DRAW FIGURE 17-18.PAGE 395
ENDOSYSMBIOSIS ONLY!!
• Apparently the symbiotic ancestors of
mitochondria were aerobic (use oxygen in cellular
respiration).
• Similarly, the ancestors of chloroplast could have
been photosynthetic bacteria that lived inside a
larger host cell. Since all cells have mitochondria
and only some have chlorophyll, mitochondria
may have evolved first.
EVIDENCE FOR ENDOSYSBIOSIS
• Present day mitochondria and chlorophyll are similar
to prokaryotic cells in at least 2 ways:
• 1). They both contain DNA , RNA and ribosomes.
• 2). They both copy their own DNA and reproduce
within the host cell by a process resembling the
binary fission of prokaryotes.
FIRST ORGANIC MOLECULES
• CYANOBACTERIA AND THE OXYGEN REVOLUTION.
• Earth’s early atmosphere was anaerobic (little or no
oxygen). As cyanobacteria evolved created oxygen as
a by product and bubbled to the surface of lakes and
oceans and entered the atmosphere.
• At first, it was toxic for most organisms and caused
extinctions. Except for the ones that could hide deep
in the mud like some do today.
• Others adapted and extracted oxygen from food
through cellular respiration (aerobic organisms)
• Today atmospheric oxygen is recycled by
photosynthesis is cyanobacteria, algae, and
plants.
• Today many prokaryotes and nearly all
eukaryotes are aerobic.
• The “oxygen revolution” was a major episode
in the history of life.
• Online activity 16-2