Announcements
● Tutoring
Center
SCI I, 407
M 12-3, 5:30-6:30; W 8-9, 5:30-6:30,
Th 8-12, 6-7; F 8-9
● MasteringBiology Assignment due Tuesday 5/31
● Today’s Lecture: Chapters 14 and 15
● Abstract and Lab Reports due this week
● Canned food drive – donation worth 5 extra credit points
Earth History and Macroevolution
– The fossil record is:
• The sequence in which fossils appear in rock strata
• An archive of macroevolution
Earth History and Macroevolution
– Geologists have established a geologic time scale
reflecting a consistent sequence of geologic periods.
– Separated into four broad divisions:
• Precambrian
• Paleozoic
• Mesozoic
• Cenozoic
Earth History and Macroevolution
Radioactive decay
of carbon-14
Carbon-14 radioactivity
(as % of living organism’s
C-14 to C-12 ratio)
Fossils and radiometric dating
100
75
50
25
0
0
5.6 11.2 16.8 22.4 28.0 33.6 39.2 44.8 50.4
Time (thousands of years)
How
carbon-14
dating is
used to
determine
the vintage
of a
fossilized
clam shell
Carbon-14 in shell
Major Episodes in the History of Life
Earth was formed about 4.6 billion years ago.
Prokaryotes
• Evolved by 3.5 billion years ago
• Began oxygen production about 2.7 billion years ago
• Lived alone for almost 2 billion years
Precambrian
Common ancestor to
all present-day life
Origin of
Earth
4,500
Earth cool enough
for crust to solidify
4,000
Oldest prokaryotic fossils
3,500
Millions of years ago
3,000
Atmospheric oxygen
begins to appear due
to photosynthetic
prokaryotes
2,500
Major Episodes in the History of Life
Cenozoic
Paleozoic Mesozoic
Archaea
Fungi
Oldest eukaryotic
fossils
2,000
Origin of
multicellular
organisms
1,500
1,000
Cambrian
explosion
Plants and
Oldest
symbiotic fungi
animal
colonize land
fossils
500
Millions of years ago
Animals
Extinction of
dinosaurs
First humans
0
Eukaryotes
Protists
Plants
Prokaryotes
Bacteria
Major Episodes in the History of Life
Humans
–What if we use a clock
analogy to tick down all
of the major events in
the history of life on
Earth?
Origin of solar
system and Earth
0
4
1
2
3
The Origin of Life
Four-Stage
Hypothesis for the
Origin of Life
Inorganic compounds
Abiotic synthesis
of organic monomers
Organic monomers
Abiotic synthesis
of polymers
Polymer
Formation
of pre-cells
Membrane-enclosed compartment
Self-replicating
molecules
Complementary
chain
Prokaryotes
Bacteria
Prokaryotes
Archaea
Protists
Eukarya
Plants
Fungi
Animals
The Two Major Categories of Cells
● The
● All
countless cells on earth fall into two categories:
Prokaryotic cells — Bacteria and Archaea
Eukaryotic cells — Eukarya
protists, plants, fungi, and animals
cells have several basic features.
1. They are all bound by a thin plasma membrane.
2. All cells have DNA.
3. All cells have ribosomes.
Cytoplasm-the entire contents of a cell
Prokaryotic Cells
● Prokaryotes
Are smaller than eukaryotic cells
Lack internal structures surrounded by membranes
Lack a nucleus
Have a rigid cell wall
Plasma membrane
(encloses cytoplasm)
Cell wall (provides
Rigidity)
Capsule (sticky
coating)
Prokaryotic flagellum
(for propulsion)
Ribosomes
(synthesize proteins)
Colorized TEM
Nucleoid (contains DNA)
Pili (attachment structures)
Prokaryotic Cells
Prokaryotes
•Are ecologically significant, recycling carbon and other vital
chemical elements back and forth between organic matter, the soil,
and atmosphere
•Cause about half of all human diseases
•Are more typically benign or beneficial
Colorized SEM
Prokaryotic Cells
– Prokaryotes come in several shapes:
• Spherical (cocci)
• Rod-shaped (bacilli)
• Spiral
SHAPES OF PROKARYOTIC CELLS
Colorized TEM
Spiral
Colorized SEM
Rod-shaped (bacilli)
Colorized SEM
Spherical (cocci)
Prokaryotic Cells
– Most prokaryotes can reproduce by binary fission
and at very high rates if conditions are favorable.
– Some prokaryotes
Endospore
Colorized SEM
• Form endospores, thick-coated, protective cells that are
produced within the cells when they are exposed to
unfavorable conditions
• Can survive very harsh conditions for extended periods,
even centuries
Prokaryotic Cells
MODES OF NUTRITION
Energy source
Chemical
Photoautotrophs
Colorized TEM
Light
Elodea, an aquatic plant
Bacteria from a hot spring
Colorized TEM
Photoheterotrophs
Organic compounds
Carbon source
CO2
Chemoautotrophs
Rhodopseudomonas
Chemoheterotrophs
Little Owl (Athene noctua)
Prokaryotic Cells
– By comparing diverse prokaryotes at the molecular
level, biologists have identified two major branches
of prokaryotic evolution:
• Bacteria
• Archaea (more closely related to eukaryotes)
Bacteria
Prokaryotes
Archaea
Eukarya
Protists
Plants
Fungi
Animals
Bacteria That Cause Disease
– Bacteria and other organisms that cause disease are
called pathogens.
– Most pathogenic bacteria produce poisons.
• Exotoxins are poisonous proteins secreted by
bacterial cells.
• Endotoxins are not cell secretions but instead
chemical components of the outer membrane of
certain bacteria.
Bioterrorism
Humans have a long and ugly history of using organisms
as weapons.
Prokaryotes and Chemical Recycling
– Prokaryotes play essential roles in
• Chemical cycles in the environment
• The breakdown of organic wastes and dead organisms
Prokaryotes and Bioremediation
– Bioremediation is the use of organisms to remove
pollutants from
• Water
• Air
• Soil
Rotating
spray arm
Rock bed coated
with aerobic
prokaryotes and
fungi
Liquid wastes
Outflow
Protists
– Protists
• Are eukaryotic
• Evolved from prokaryotic ancestors
• Are ancestral to all other eukaryotes, which are
– Plants
– Fungi
– Animals
Bacteria
Prokaryotes
Archaea
Eukarya
Protists
Plants
Fungi
Animals
Figure 15.UN08
The Origin of Eukaryotic Cells
– Eukaryotic cells evolved by
• The infolding of the plasma membrane and
Plasma
membrane
DNA
Membrane
Cytoplasm
infolding
Endoplasmic
reticulum
Nucleus
Ancestral
prokaryote
Nuclear
envelope
Cell with nucleus and
endomembrane system
(a) Origin of the endomembrane system
The Origin of Eukaryotic Cells
– Eukaryotic cells evolved by
• Endosymbiosis – a free-living bacterium, came to reside
inside a host cell, producing mitochondria and chloroplasts
Photosynthetic
prokaryote
Aerobic
heterotrophic
prokaryote
Endosymbiosis
(Some cells)
Chloroplast
Mitochondrion
Photosynthetic
eukaryotic cell
(b) Origin of mitochondria and chloroplasts
The Diversity of Protists
– The classification of protists remains a work in
progress.
– The four major categories of protists, grouped by
lifestyle, are
•
•
•
•
Protozoans
Slime molds
Unicellular algae
Seaweeds
The Origin of Multicellular Life
Multicellular organisms have interdependent, specialized
cells that perform different functions, such as:
feeding, waste disposal, gas exchange, protection
(all are dependent on each other)
Unicellular
protist
Gamete
Locomotor
cells
Food-synthesizing
cells
Somatic
cells
Colony
Early multicellular organism
with specialized, interdependent cells
Later organism with
gametes and somatic cells