Download Chapter 17 The History of Life Section 17

Chapter 17 The History of Life
Section 17-1 The Fossil Record
I.
Fossils and Ancient Life
A. Paleontologists: scientists who study fossils
1. Infer about structure of organisms, what they ate, what ate them, and their
environment
2. Classify fossil organisms and group and arrange them from oldest to most
recent
B. Fossil Record
1. Provides evidence about the history of life on Earth
2. Shows how species have changed (evolved) over time
3. More than 99% of all species that have lived on Earth are extinct (species
died out)
C. How Fossils Form (Special circumstances, so therefore fossil record is
incomplete) Figure 17-2 page 418
1. Water carries small rock particles to bodies of water
2. Dead organisms are buried by the sediment (forms sedimentary rock)
3. The organism is now preserved in the form of a fossil
D. Fossil Types
1. From rock (bones, eggs)
2. Imprints - Mold
3. Cast (wood, shell or bone is replaced by mineral)
4. Amber
E. Age of Fossils
1. Relative dating – comparing the placement of the fossil with that of fossils in
other layers of rock (index fossils)
a. Index fossils – species that existed for a short time with a wide
geographic range and easily recognized
b. Figure 17-3 page 419
c. Used as an estimation for the fossil’s age
2. Radioactive dating – the use of half-lives to determine age of a rock sample
a. Age is calculated based on the amount of remaining radioactive isotopes
a sample contains
b. Half-life is the length of time required for half of the radioactive atoms in
a sample to decay
c. Figure 17-4 page 420
d. Carbon-14 has a half-life of 5730 years, so comparing Carbon-12 with
carbon-14 in a sample will determine age(the more carbon-14 it contains,
the older the sample is)
e. Potassium-40 has a half-life of 1.26 billion years
F. Geologic Time Scale
1. Used to represent evolutionary time
2. Figure 17-5 page 421
3. Eras are divided into periods (time is in millions of years)
4. Precambrian time is about 88% of Earth’s history (very few Multicellular
organisms)
5. Following the Precambrian are three eras:
a. Paleozoic Era (Vertebrate and Invertebrates)
b. Mesozoic Era (Age of Dinosaurs)
c. Cenozoic Era (Age of Mammals)
6. Eras are further divided into periods (tens of millions to less than two million
years)
7. Paleozoic contains: Cambrian, Ordovician, Silurian, Devonian, Carboniferous,
Permian
8. Mesozoic contains: Triassic, Jurassic, and Cretaceous
9. Cenozoic contains: Tertiary and Quaternary
10. Figure 17-6 page 422
Section 17-2 Earth’s Early History
I. Formation of Earth
A. Geologic evidence shows Earth to be 4.6 billion years old
B. Cosmic debris were attracted to each other over a course of 100 million years
C. Including collisions with other objects
D. Dense materials formed the core, moderately dense floated to the surface, and
the least dense formed the first atmosphere
E. Early atmosphere included: hydrogen cyanide, carbon dioxide, carbon
monoxide, nitrogen, hydrogen sulfide, and water
F. 4 billion years age: first solid rocks
G. 3.8 billion years ago: liquid water (oceans)
II. First Organic Molecules
A. Miller and Urey Experiment, Figure 17-8 page 424
B. Used hydrogen, methane, ammonia, and water to represent an early
atmosphere, than electric sparks to simulate lightning to make organic
compounds
C. The experiment showed how organic molecules necessary for life could arise
from simpler compounds on primitive earth
III. The Puzzle of Life’s Origins
A. 200 to 300 million years ago cells similar to modern bacteria existed
B. How did they originate?
C. Formation of Microspheres
1. Proteinoid microspheres are not cells, but have characteristics of living
systems (selectively permeable membrane, store and release energy)
D. Evolution of RNA and DNA
1. RNA can help DNA replicate, process messenger RNA, and catalyze chemical
reactions, can grow and duplicate themselves
2. This may have led to the formation of DNA-directed protein synthesis
3. Figure 17-10, page 425
E. Free Oxygen
1. Microfossils – single-celled prokaryotic organisms that resemble modern
bacteria have been found in rock 3.5 billion years old
2. Photosynthetic bacteria (cyanobacteria found in stromatolites) by 2.2 billion
years produced oxygen (end result of photosynthesis)
3. Oxygen combined with iron in the ocean to form rust (iron oxide) fell to the
ocean floor (iron of today)
4. Oxygen gas started to accumulate in the atmosphere as it increased other
gases (methane and hydrogen sulfide decreased), ozone layer formed, skies
became blue
5. Rise of oxygen caused some forms of life to become extinct, other life forms
evolved using oxygen for respiration
F. Origin of Eukaryotic Cells
1. 2 billion years ago first eukaryotic cells
2. Endosymbiotic Theory – eukaryotic cells formed from a symbiosis among
several different prokaryotic organisms, Figure 17-12, page 427
3. One group of prokaryotes used oxygen to make ATP – evolved into
mitochondria
4. Others carried out photosynthesis – evolved into chloroplasts of plants and
algae
5. Evidence of the Endosymbiotic Theory
a. Mitochondria and chloroplast contain DNA similar to bacterial DNA
b. Mitochondria and chloroplasts have ribosomes whose size and structure
resemble bacteria
c. Mitochondria and chloroplast reproduce like bacteria through the
process of binary fission
G. Sexual Reproduction and Multicellularity
1. Bacteria use asexual reproduction – duplicate genetic material and divide
into two new cells
2. Sexual reproduction allows for genetic variation to mutations in DNA, it
shuffles genes in each generation
3. Favorable gene combinations greatly increase the chances of evolutionary
change due to natural selection
4. This gave way to the development of Multicellular organisms from singlecelled organisms (increase in life diversity)
Section 17-3 Evolution of Multicellular Life
I.
Precambrian Time
A. 90% of Earth’s history
B. Simple anaerobic and aerobic life forms
C. Few fossils exist from this time (animals were soft-bodied)
D. Life existed only in the sea
II.
Paleozoic Era
A. Diversity of marine life, figure 17-14, page 429
B. Cambrian Period: “Cambrian Explosion” (animals with shells and outer skeletons
along with invertebrates) TRILOBITES present
C. Ordovician and Silurian Periods: Ancestors of Octopi and Squid, aquatic arthropods,
some on land, jawless fish, first land plants
D. Devonian Period: “Age of Fishes”, insects, ferns, SHARKS APPEAR, first amphibians
E. Carboniferous and Permian Periods: Reptiles present, winged insects, giant ferns
and trees, remains of these plants formed coal that we use
F. At the end of the Paleozoic era was a mass extinction (95% of all life in the oceans
disappeared)
III.
Mesozoic Era (Age of Dinosaurs and appearance of flowering plants)
A. Triassic period: fish, insects, reptiles and cone-bearing plants (pine trees), first
dinosaurs and mammals appeared
B. Jurassic Period: Dinosaurs “ruled” the Earth, first birds
C. Cretaceous Period: Leafy trees, shrubs, flowering plants, turtles, crocodiles, T-Rex
D. Mass extinction at the end of the Mesozoic Era
IV.
Cenozoic Era (Age of Mammals – now on land, water, and air)
A. Tertiary Period: Climate was warm and mild, marine mammals (dolphins and
whales), grazing mammals, birds, insects, flowering plants, and grasses evolved
(main food source)
B. Quaternary Period: Climate cooled causing series of ice ages, caused oceans to fall
and then rise when glaciers melted, diverse life in oceans and land – bats, dogs, cats,
cattle, mammoths, man appears
I.
Section 17-4 Patterns of Evolution
Macroevolution – large-scale evolutionary patterns and processes that occur over long
periods of time
A. Extinction
1. More than 99% of all species that have ever lived are extinct
2. Extinction can be caused by: food web collapsing, environment
changes, catastrophic events (asteroid)
3. Mass extinction can lead to the loss of some species, but a burst in
evolution that produces new species
4. The extinction of the dinosaurs gave rise to the evolution of birds and
mammals
B. Adaptive Radiation (Figure 17-22, page 436)
1. Studies of fossils or of living organisms show that a single species or a
small group of species has evolved, through natural selection and other
processes, into diverse forms that live in different ways
2. Dinosaurs were the products of adaptive radiation among ancient
reptiles and this allowed them to “rule” the Earth, while mammals
stayed small
C. Convergent Evolution (Figure 17-23, page 437)
1. Process by which unrelated organisms come to resemble one another
2. Different organisms can undergo adaptive radiation in different places
or at different times but in ecologically similar environments
3. Natural selection may mold body structures into modified forms (wings
and flippers)
4. Example: Sharks (fish) and Dolphins (mammals)
5. Some structure look and function similarly but are made up of parts
that don’t share a common evolutionary history (analogous structures)
D. Coevolution (Figure 17-24, page 438)
1. Process by which two species evolve in response to changes in each
other over time
2. Example: Flowers and insect pollinators
3. Example: Plants produce poisons to deter plant-eating insects; the
insects build resistance to the poisons and still eat the plants
E. Punctuated Equilibrium (Figure 17-25, page 439)
1. A pattern of long, stable periods, interrupted by brief periods of more
rapid change
2. Caused by: small population being isolated from the main population,
small group migrates to a new environment, catastrophic event
3. Darwin describe evolution as gradual due to the work of Hutton and
Lyell
4. Gradualism is a slow and steady biological change
5. Evolution can proceed at different rates for different organisms at
different times during Earth’s history
F. Developmental Genes and Body Plans (Figure 17-26, page 440)
1. Changes in genes for growth and differentiation during development
can produce changes in body shape and size
2. Hox genes guide development of major body structures
3. Homologous control genes serve similar functions in animals as
different as insects and humans
4. Small changes in the activity of control genes can affect other genes to
produce large changes in adults
5. Small changes in the timing of cell differentiation and gene expression
can cause change too
6. Example: wing vs. wingless, or small vs. long legs