Integrated
Science
Ch.14
The History
of Life
I. Fossil Evidence of Change
- The fossil record shows that past organisms
were very different from those alive today
and have been affected by several mass
extinctions.
I. Fossil Evidence of Change
- The fossil record shows that past organisms
were very different from those alive today
and have been affected by several mass
extinctions.
Mass Extinction
Events during the
Last 5 Million Years
A. Earth’s Early History
- Earth formed about 4.6 billion years ago.
- Earth’s early atmosphere was very different
and contained almost no free oxygen.
B. The
Geologic
Time
Scale
B. The Geologic Time Scale
1. Precambrian (4,600 – 542 MYA)
- Life (prokaryotes) probably began 3.5 billion
years ago.
- Photosynthesis evolved ~ 3 billion years ago.
Ediacaran
Seascape
2. Paleozoic Era (542- 251 MYA)
- Cambrian explosion marks appearance of
most phyla of living animals.
A Cambrian
Seascape
3. Mesozoic Era (251- 65 MYA)
- Age of dinosaurs (& conifers)
Coastal Cretaceous Scene
- Emergence of
coral reefs
4. Cenozoic Era (65 MYA- Present)
- followed the mass extinctions of many
terrestrial and marine animals
The real reason
dinosaurs went extinct
4. Cenozoic Era (65 MYA- Present)
- followed the mass extinctions of many
terrestrial and marine animals
The Cretaceous mass extinction
was probably caused by a meteorite
and led to the extinction
of the dinosaurs.
- Age of mammals
- Insects and flowering plants diversified
A Pleistocene
Environment
C. Clues in Rocks
1.Fossils
- any preserved remains
of a once-living thing
- examples:
WASP IN
AMBER
PETRIFIED BONE
IMPRINT
PETRIFIED
LOG
SLOTH IN
TAR PIT
2.Fossil Formation
a. An organism dies quickly and is buried under
sediments.
b. Sediments build up over the years.
c. Pressure causes mineralization (organic
tissues replaced by mineral deposits).
3.Dating Fossils
a. Relative Dating
- Law of Superposition: rocks (and fossils)
contained in upper
layers are younger
than those found
in lower layers
b. Radiometric Dating
- determining the age of rock or fossils by
measuring the rate of decay radioisotopes
such as
Carbon-14,
Uranium-238
II. The Origins of Life
- Evidence suggests a
sequence of chemical
events lead to Land plants
Animals
the origin of
the first cells.
- Life has continuously
evolved since then.
Cenozoic
Humans
Origin of
solar system
and Earth
4
1
BYA
Multicellular
eukaryotes
Single-celled
eukaryotes
2
3
Prokaryotes
Atmospheric
oxygen
A. Early Ideas
1. Spontaneous Generation
- The idea that life could arise from
nonliving things.
Mice
Wheat
21 Days
“Recipe” for
Mice (1698)
Sweaty
Underwear
Open-mouthed Jar
A. Early Ideas
1. Spontaneous Generation
Barnacle
Goose Tree
Toads from
emerging
from the soil
2. Biogenesis
- Spontaneous generation disproved by
F. Redi (1668) and Louis Pasteur (1859).
- Living organisms come only from other living
organisms.
Francesco Redi’s
Experiment
2. Biogenesis
- Spontaneous generation disproved by
F. Redi (1668) and Louis Pasteur (1859).
- Living organisms come only from other living
organisms.
Louis Pasteur’s
Experiment
B. Modern Ideas
- Miller and Urey (1953)
showed that simple
organic molecules
could spontaneously
form from inorganic
compounds.
CH4
Electrode
Water vapor
Condenser
Cold
water
Cooled water
containing
organic
molecules
H2O
Sample containing
amino acids and other
organic compounds
C. Endosymbiotic Theory
- Mitochondria and
chloroplasts probably
originated as freeInfolding of
plasma membrane
living prokaryotic
Endoplasmic
cells.
reticulum
- Both organelles have EngulfingNuclear envelope
of aerobic
their own DNA and heterotrophic
ribosomes distinct prokaryote
from eukaryotic
Mitochondrion
host cells.
- Both reproduce
independently from
host cells.
DNA
Plasma
membrane
Ancestral
prokaryote
Ancestral
heterotrophic
eukaryote
Nucleus
Cell with nucleus
and endomembrane
system
Mitochondrion
Engulfing of
photosynthetic
prokaryote in
some cells
Plastid
Ancestral
Photosynthetic
eukaryote
Triassic Landscape, Karen Carr
The End