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10.2 Darwin’s Observations
Origin of Life• The origin of life, 4.6
billion years ago.
10.2 Darwin’s Observations
History of Life on Earth
• The Universe came into being about 15 billion years ago.
• Big Bang Theory: The sudden appearance of all the matter and energy in the Universe as a single very hot and dense point.
History of the Worldhttps://www.youtube.com/watch?v=m1R8-E71wAc
10.2 Darwin’s Observations
Formation of Organic Molecules
• Fairly complex organic molecules will form spontaneously under conditions that existed on the primitive Earth.
• Results in a “primordial soup”: • Oceans filled with a dilute solution of organic
molecules of all kinds.
10.2 Darwin’s Observations
Age of the Bacteria
• Prokaryotes dominated the Earth for most of its history.
• Bacteria can live under a much
wider variety of conditions than eukaryotes.
• They use many different sources of energy and carbon, and they can grew at very high temperatures, high pressures, acidic conditions.
• They were called Archaebacteria.
10.2 Darwin’s Observations
The Onset of Oxygen
• The atmosphere of the primitive Earth was probably like that of Mars today: nitrogen, carbon dioxide, water vapor, but no free oxygen.
• Cyanobacteria is credited with creating the oxygen in the atmosphere.
• About 2 billion years ago, the
oxygen level in the atmosphere started to rise.
10.2 Darwin’s Observations
Rise of the Eukaryotes
• Endosymbiont hypothesis: mitochondria were once free-living bacteria that developed an intracellular symbiosis with a primitive eukaryote.
• Today all eukaryotes have mitochondria.
• Chloroplasts: another endosymbiont, of a cyanobacteria. Found in plants and algae.
10.2 Darwin’s Observations
Early scientists proposed ideas about evolution.
• Evolution is the process of biological change by which descendants come to differ from their ancestors.
10.2 Darwin’s Observations
Self Check
1. Which of the following is a term for a group of similar organisms that can reproduce and produce fertile offspring?
a. individual
b. population
c. species
d. fossil
10.2 Darwin’s Observations
Self-Check
2. Biogeography is the study of the
a. distribution of organisms around the world.
b. environments around the world.
c. different types of rocks around the world.
d. age of fossils around the world.
10.2 Darwin’s Observations
Theories of geologic change set the stage for Darwin’s theory.
• There were three theories of geologic change.– catastrophism– gradualism– uniformitarianism
10.2 Darwin’s Observations
• Uniformitarianism is the prevailing theory of geologic change.
10.2 Darwin’s Observations
• Indirect Evidence1. Fossil Record2. Geography3. Comparative Anatomy4. Comparative Embryology5. Comparative Biochemistry
• Direct Evidence– Current observations
Ch 12.1
Evidence of common ancestry(Evolution Theory) among species comes from many sources.
10.2 Darwin’s Observations
Evidence for evolution in Darwin’s time came from several sources.
• Fossils provide evidence of evolution.
• Fossils in older layers are more primitive than those in the upper layers.
10.2 Darwin’s Observations
In which rock layer would you find the oldest fossils and why?
Law of Superposition
10.2 Darwin’s Observations
• The study of geography provides evidence of evolution.
– island species most closely resemble nearest mainland species
– populations can show variation from one island to another
10.2 Darwin’s Observations
• The study of anatomy provides evidence of evolution.
– Homologous structures are similar in structure but different in function.
– Homologous structures are evidence of a common ancestor.
10.2 Darwin’s Observations
Human hand
Bat wing
Mole foot
Fly wing
– Analogous structures are not evidence of a common ancestor.
• The study of anatomy provides evidence of evolution.
– Analogous structures have a similar function.
10.2 Darwin’s Observations
• Vestigial structures are remnants of organs or structures that had a function in an early ancestor.
• Ostrich wings are examples of vestigial structures.
Structural patterns are clues to the history of a species.
Hip bone in pythonAppendix in humanTail bone (cocyx) in human
10.2 Darwin’s Observations
• Embryology provides evidence of evolution.
Larva
Adult barnacleAdult crab
– identical larvae, different adult body forms– similar embryos, diverse organisms
10.2 Darwin’s Observations
Poll
Which of these embryos is that of a human?
A B C D
10.2 Darwin’s Observations
10.2 Darwin’s Observations
Comparative Biochemistry
• All living things contain similar biochemical compounds
• Examples would include: structure and function of DNA, RNA, and proteins (including enzymes) are similar in all organisms
10.2 Darwin’s Observations
Self-Check
3. What is suggested by the similarity of early embryos of different species of vertebrates?
a. no evolutionary relationship between the groups
b. recent common ancestry
c. similar environments in the past
d. evolution from a distant common ancestor
10.2 Darwin’s Observations
Self-Check
4. Some organisms that share a common ancestor have features that have different functions, but similar structures. These are known as
a. vestigial structures.
b. analogous structures.
c. homologous structures.
d. fossil structures.
10.2 Darwin’s Observations
Self-Check
5. If an organism has a vestigial structure, that structure likely once had a function in a(n)
a. close relative.
b. early ancestor.
c. unrelated organism.
d. embryological stage.
10.2 Darwin’s Observations
Self-Check
5. Which of the following is an example of a vestigial structure?
a. the wings of red-tailed hawks
b. the hind limbs of a house cat
c. the fins of a shark
d. the wings of an ostrich
10.2 Darwin’s Observations
KEY CONCEPT Darwin’s voyage provided insight on evolution.
10.2 Darwin’s Observations
Charles Darwin and the HMS Beagle
10.2 Darwin’s Observations
Darwin observed differences among island species.
• Variation is a difference in a physical trait.– Galápagos tortoises that live in areas with tall plants
have long necks and legs.– Galápagos finches that live in areas with hard-shelled
nuts have strong beaks.
10.2 Darwin’s Observations
• An adaptation is a feature that allows an organism to better survive in its environment.
– Species are able to adapt to their environment.
– Adaptations can lead to genetic change in a population.
10.2 Darwin’s Observations
• Variation:
• Adaptation:
10.2 Darwin’s Observations
• Darwin found fossils of extinct animals that resemble modern animals.
• Darwin found fossil shells high up in the Andes mountains.
Darwin observed fossil and geologic evidence supporting an ancient Earth.
10.2 Darwin’s Observations
• He saw land move from underwater to above sea level due to an earthquake.
• Darwin extended his observations to the evolution of organisms.
10.2 Darwin’s Observations
• Fossils:
10.2 Darwin’s Observations
Self Check
The difference in the physical traits of an individual from those of other individuals in a group is called a(n)
a. change.
b. adaptation.
c. species.
d. variation.
10.2 Darwin’s Observations
Over time, adaptations can lead populations to experience
a. environmental changes.
b. genetic changes.
c. geologic changes.
d. extinctions.
10.2 Darwin’s Observations
What did Charles Darwin observe in finch populations on the Galápagos Islands off the coast of South America?
a. different species on different islands
b. all species on one of the islands
c. identical species on all the islands
d. the same species as in North America
10.2 Darwin’s Observations
What did Charles Darwin learn from the fossils of a giant armadillo that he found in Argentina?
a. An earthquake led to the armadillo’s extinction.
b. Armadillos used to be marine organisms.
c. Modern animals may be related to fossilized organisms.
d. Fossils do not resemble modern animals.
10.2 Darwin’s Observations
Fossils of marine organisms high in the Andes Mountains led Darwin to conclude that
a. Earth is 6000 years old.
b. interspecific variation had taken place.
c. great change can happen over time.
d. an earthquake had taken place.
