1. Announcements SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30,
● 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 1

2. Earth History and Macroevolution
The fossil record is:
The sequence in which fossils appear in rock strata
An archive of macroevolution 2

3. 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 3

5. (as % of living organism’s Carbon-14 radioactivity
Earth History and Macroevolution
Fossils and radiometric dating
Radioactive decay
of carbon-14
100 75
(as % of living organism’s
Carbon-14 radioactivity
C-14 to C-12 ratio) 50 25
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

6. Common ancestor to all present-day life
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
Atmospheric oxygen
begins to appear due
to photosynthetic
prokaryotes
Origin of Earth
Earth cool enough
for crust to solidify
Oldest prokaryotic fossils
4,500
4,000
3,500
3,000
2,500
Millions of years ago 6

7. Major Episodes in the History of Life
Cenozoic
Paleozoic
Mesozoic
Bacteria
Prokaryotes
Archaea
Protists
Eukaryotes
Plants
Fungi
Animals
Cambrian
explosion
Origin of
multicellular
organisms
Oldest
animal
fossils
Plants and
symbiotic fungi
colonize land
Extinction of
dinosaurs
Oldest eukaryotic
fossils
First humans
2,000
1,500
1,000
500
Millions of years ago 7

8. Major Episodes in the History of Life
Humans
Origin of solar
system and Earth 1 4 2 3
Pre
sent
Animals
Coloniz
of land
ation
Multi
eukar
cellular
yotes
Sing
cel
le-
led
Atmo
oxy
sphe
ric
gen
Bil
ars
ons of
ago ye li
kary
otes
Pro
What if we use a clock analogy to tick down all of the major events in the history of life on Earth? 8

9. The Origin of Life Four-Stage Hypothesis for the Origin of Life
Inorganic compounds
Abiotic synthesis
of organic monomers
Four-Stage Hypothesis for the Origin of Life
Organic monomers
Abiotic synthesis
of polymers
Polymer
Formation
of pre-cells
Membrane-enclosed compartment
Self-replicating
molecules
Complementary
chain 9

10. Prokaryotes Bacteria Prokaryotes Archaea Protists Eukarya Plants Fungi
Animals 10

11. The Two Major Categories of Cells
● The countless cells on earth fall into two categories:
Prokaryotic cells — Bacteria and Archaea
Eukaryotic cells — Eukarya
protists, plants, fungi, and animals
● All 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

12. Prokaryotic Cells Are smaller than eukaryotic 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)
Nucleoid (contains DNA)
Pili (attachment structures)
Colorized TEM

13. 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 13

14. Prokaryotic Cells Prokaryotes come in several shapes:
Spherical (cocci)
Rod-shaped (bacilli)
Spiral
SHAPES OF PROKARYOTIC CELLS
Spherical (cocci)
Rod-shaped (bacilli)
Spiral
Colorized SEM
Colorized SEM
Colorized TEM

15. Prokaryotic Cells
Most prokaryotes can reproduce by binary fission and at very high rates if conditions are favorable.
Some prokaryotes
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
Endospore
Colorized SEM

16. Prokaryotic Cells MODES OF NUTRITION Energy source Light Chemical
Photoautotrophs
Chemoautotrophs
Colorized TEM
CO2
Elodea, an aquatic plant
Bacteria from a hot spring
Carbon source
Photoheterotrophs
Chemoheterotrophs
Colorized TEM
Organic compounds
Rhodopseudomonas
Little Owl (Athene noctua)

17. 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
Protists
Eukarya
Plants
Fungi
Animals

18. 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.

19. Bioterrorism
Humans have a long and ugly history of using organisms as weapons.

20. Prokaryotes and Chemical Recycling
Prokaryotes play essential roles in
Chemical cycles in the environment
The breakdown of organic wastes and dead organisms

21. 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
Outflow
Liquid wastes

22. Protists Protists Are eukaryotic Evolved from prokaryotic ancestors
Are ancestral to all other eukaryotes, which are
Plants
Fungi
Animals
Bacteria
Prokaryotes
Archaea
Protists
Eukarya
Plants
Fungi
Animals
Figure 15.UN08

23. The Origin of Eukaryotic Cells
Eukaryotic cells evolved by
The infolding of the plasma membrane and
Plasma
membrane
DNA
Membrane
infolding
Cytoplasm
Endoplasmic
reticulum
Ancestral
prokaryote
Nucleus
Nuclear
envelope
Cell with nucleus and
endomembrane system
(a) Origin of the endomembrane system

24. 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
(Some cells)
Endosymbiosis
Aerobic
heterotrophic
prokaryote
Chloroplast
Mitochondrion
Photosynthetic
eukaryotic cell
(b) Origin of mitochondria and chloroplasts

25. 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

26. 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
Food-synthesizing
cells
Somatic
cells
Locomotor
cells
Colony
Early multicellular organism
with specialized, interdependent cells
Later organism with
gametes and somatic cells