Transcript Chapter 17: The History and Diversity of Life

Chapter 17: The History and
Diversity of Life
Section 17-3: Bacteria – The First
Organisms
Ancient Prokaryotes
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Scientists have found simple,
prokaryotic microfossils from about
3.5 bya
The first prokaryotes did not need
oxygen, then over time some
organisms developed the ability to
do photosynthesis
Ancient Prokaryotes
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Photosynthetic prokaryotes began
producing large amounts of oxygen
by 2.2 – 2 bya
As oxygen accumulated in the
atmosphere, some early life forms
went extinct while others were
forced into deep, airless hiding
places
Ancient Prokaryotes
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Some evolved the ability to USE
oxygen to make energy by cellular
respiration
Living Prokaryotes
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Only organisms for about half of
Earth’s history
Modern prokaryotes so diverse
because they have had the longest
time to evolve
Bacteria are everywhere – from the
coldest mountains, to the bottom of
the ocean floor, and even in volcanic
hot springs
Living Prokaryotes
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Very adaptable because they are
small and simple
Many are necessary for human
survival
What are Bacteria?
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They are prokaryotes that have a
cell membrane surrounded by a cell
wall, whose genetic material is
contained in a single circular strand
of DNA
No nucleus, no organelles
Bacterial Kingdoms
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Kingdom Eubacteria
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Called “true” bacteria because they
have a thick, rigid cell wall made of the
carbohydrate peptidoglycan
Very diverse, some photosynthetic
Kingdom Archaebacteria
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“Ancient” bacteria that live in extreme
conditions (intense temperatures, very
salty water, no oxygen)
Cell walls made of lipids
Bacterial Reproduction
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Asexual reproduction by binary
fission
Chromosome duplicates and one
cell divides into two cells
Even simpler than mitosis
Bacterial Reproduction
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Some bacteria, like E. coli,
sometimes undergo conjugation
Simple form of sexual reproduction
that allows for genetic material to
be exchanged between two bacteria
Some can also go through
transformation, where bacteria
pick up DNA pieces from other
bacteria