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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

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slide1

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

slide2

Earth History and Macroevolution

  • The fossil record is:
    • The sequence in which fossils appear in rock strata
    • An archive of macroevolution
slide3

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
slide5

Earth History and Macroevolution

Fossils and radiometric dating

Radioactive decay

of carbon-14

100

75

Carbon-14 radioactivity

(as % of living organism’s

C-14 to C-12 ratio)

50

25

0

22.4

33.6

0

11.2

16.8

28.0

39.2

44.8

50.4

5.6

Time (thousands of years)

How

carbon-14

dating is

used to

determine

the vintage

of a

fossilized

clam shell

Carbon-14 in shell

slide6

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 toall present-day life

Atmospheric oxygen

begins to appear due

to photosynthetic

prokaryotes

Origin ofEarth

Earth cool enough

for crust to solidify

Oldest prokaryotic fossils

4,500

4,000

3,500

3,000

2,500

Millions of years ago

slide7

Major Episodes in the History of Life

Cenozoic

Paleozoic

Mesozoic

Bacteria

Prokaryotes

Archaea

Protists

Eukaryotes

Plants

Fungi

Animals

Cambrian

explosion

Extinction of

dinosaurs

Origin of

multicellular

organisms

Plants and

symbiotic fungi

colonize land

Oldest

animal

fossils

Oldest eukaryotic

fossils

First humans

2,000

1,500

1,000

500

0

Millions of years ago

slide8

Major Episodes in the History of Life

Humans

of land

ation

Coloniz

Animals

yotes

Origin of solar

system and Earth

eukar

0

cellular

sent

Pre

Multi

4

1

otes

yotes

kary

Bil

ago

eukar

li

ars

ons

Pro

ye

of

2

3

led

cel

le-

Atmo

Sing

sphe

ric

gen

oxy

  • What if we use a clock analogy to tick down all of the major events in the history of life on Earth?
slide9

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

slide10

Prokaryotes

Bacteria

Prokaryotes

Archaea

Protists

Eukarya

Plants

Fungi

Animals

slide11

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

slide12

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)

Nucleoid (contains DNA)

Pili (attachment structures)

Colorized TEM

slide13

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

slide14

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

slide15

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

slide16

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

Chemoheterotrophs

Photoheterotrophs

Colorized TEM

Organic compounds

Rhodopseudomonas

Little Owl (Athene noctua)

slide17

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

slide18

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.
slide19

Bioterrorism

  • Humans have a long and ugly history of using organisms as weapons.
slide20

Prokaryotes and Chemical Recycling

  • Prokaryotes play essential roles in
    • Chemical cycles in the environment
    • The breakdown of organic wastes and dead organisms
slide21

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

slide22

Protists

  • Protists
    • Are eukaryotic
    • Evolved from prokaryotic ancestors
    • Are ancestral to all other eukaryotes, which are
      • Plants
      • Fungi
      • Animals

Bacteria

Prokaryotes

Archaea

Protists

Plants

Eukarya

Fungi

Animals

Figure 15.UN08

slide23

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

slide24

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

slide25

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
slide26

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

Somatic

cells

Food-synthesizing

cells

Locomotor

cells

Colony

Early multicellular organism

with specialized, interdependent cells

Later organism with

gametes and somatic cells