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Early history of Earth
 Earth is thought to have formed about 4.6 billion
years ago.
 Oldest rocks are about 3.9 billions years old.
 About 3.5 billion years ago, the first living organisms
appeared.
 Bacteria, Prokaryotic, Anaerobic
Fossils
 Fossils: any preserved remains of an organism
that lived long ago.
Paleontologists
 Scientists who study ancient life
Relative dating technique
 Based on the premise that the deeper an organism is
buried in sediment, the older it is.
Spontaneous generation
 Aristotle proposed the theory of spontaneous generation.
 The idea that life was produced from nonliving matter.
 Idea lasted almost 2000 years
Francisco Reid
In 1668, he disproved the theory of spontaneous
generation of larger organisms.
 Evidence against spontaneous generation:
 1. Unsealed – maggots on meat
 2. Sealed – no maggots on meat
 3. Gauze – few maggots on gauze, none on meat
Biogenesis
 Louis Pasteur
 In the mid-1800s, he disproved the
“air theory” and established the
concept of biogenesis.
 The idea that living organisms
come only from other living
organisms.
John Lamarck
 1809
 One Of First Scientists To
Understand That Change
Occurs Over Time
 Stated that Changes Are
Adaptations To Environment
acquired in an organism’s
lifetime
 Said acquired changes were
passed to offspring
Lamarck’s theory of evolution
 Idea called Law of Use and
Disuse
 If a body part were used, it
got stronger
 If body part NOT used, it
deteriorated
 Blacksmiths & Their Sons
(muscular arms)
 Giraffe’s Necks Longer
from stretching)
 Inheritance Of Acquired Traits
 Traits Acquired During Ones Lifetime Would Be
Passed To Offspring
Clipped ears of dogs could be passed to offspring
11
Lamarck’s Mistakes
 Lamarck Did NOT Know how
traits were inherited (Traits are
passed through genes)
 Genes Are NOT Changed By
Activities In Life
 Change Through Mutation
Occurs Before An Organism Is
Born
Evolution
 A change in a population of organisms over time
Charles Darwin
 Scientist who is considered the founder of
modern evolutionary theory.
 Astounded by variety of life (biodiversity)
 Naturalist
Charles Darwin
 Darwin used his theory
of natural selection to
explain how organisms
evolve.
HMS Beagle’s Voyage
 In 1831, he sailed on the HMS Beagle to South America
& the South Pacific and returned 5 years later.
The Galapagos Islands
 Small Group of Islands 1000 km West of South
America
 Darwin studied & compared the anatomy of many
organisms.
 Very Different Climates
 Animals On Islands Unique



Tortoises
Iguanas
Finches
The Galapagos Islands
 Island species varied from mainland species & from
island-to-island species
 Each island had long or short neck tortoises
The Galapagos Islands
 Finches on the islands resembled a mainland finch
 More types of finches appeared on the islands where the available
food was different (seeds, nuts, berries, insects…)
 Finches had different types of beaks adapted to their type of food gathering
Natural selection
 The process by which individuals that are better
adapted to everything around them survive and
reproduce more successfully.
Natural selection
 Those with less favorable variations are less likely to
survive and pass on traits to the next generation.
 Each new generation is largely made up of offspring
from parents with the most favorable variations.
 Natural selection is also known as “the survival of the
fittest.”
Natural Selection is driven by 4
important points:
 1. All populations have genetic variation
 2. The environment presents challenges to successful
reproduction

Naturally, an organism that does not survive to reproduce or whose offspring die
before the offspring can reproduce does not pass its genes on to future
generations.
 3. Individuals tend to produce more offspring than the
environment can support.

Individuals of a population often compete with one another to survive.
 4. Individuals that are better able to cope with the challenges
presented by their environment tend to leave more offspring
than those individuals less suited to the environment.
Adaptation
 An anatomical, physiological or behavioral trait or
characteristic that improves a population’s ability to
survive.
Evidence for evolution

The following provide evidence for evolution:
1.
2.
3.
4.
Fossil Records
Anatomical Studies (homologous, analogous, vestigial)
Embryological development
Biochemistry: DNA Sequences
Fossil evidence
 Scientists use fossil records to understand the general
pathway of evolution.
A model of evolution
from small-toed to
one-toed horses.
Anatomical studies
 Homologous
Structures are….
 Similar structures
that show a
common ancestor.
Anatomical studies
 An analogous structure is any body part that is similar
in function but different in structure.
 Example: Insect and bird wings have the same function but
are not similar in structure (bird wings are made up of a set
of bones while insect wings are mainly made of chitin).
Anatomical studies
 A vestigial
structure is any body structure that is
reduced in size and function in a living organism but may
have been used in an ancestor.
Legs on skinks
Appendix in humans
Pelvic bones
of a baleen
whale.
Embryological development
 In the earliest stage of
embryological
development in a fish,
reptile, bird and
mammal, a tail and gill
slits can be seen in all
species.
 As development
continues, the embryos
become more & more
distinct, & in the stages
before birth, they attain
their distinctive forms.
Biochemistry
 Scientists use DNA, RNA and proteins to determine levels of
relationships among species within major taxonomic groups.
Speciation
 It is the process by which a new species
is formed.
 This can only occur when either interbreeding or the
production of fertile offspring is somehow prevented.
 Isolation and divergence can lead to speciation.
Patterns of evolution
 Divergence is the build up of differences between groups
of living things as a result of natural selection
 Divergence leads to the formation of new species
Types of isolation
 Geographic isolation occurs if a physical barrier
separates a population into groups.
 Reproductive isolation occurs when formerly
interbreeding organisms are prevented from
producing fertile offspring.
Speciation rates
(evolution tempos)
 Gradualism is the idea that species
originate through a gradual buildup of
new adaptations.
 It is supported by fossil evidence, such as those for the
slow & steady buildup of adaptations of camels &
horses.
Speciation rates
(evolution tempos)
 Punctuated equilibrium states that speciation
occurs quickly in rapid bursts, with long periods of
stability in between.
Patterns of evolution
 Convergent
evolution is the
process by which
unrelated species
become more
similar as they
adapt to the same
kind of
environment.
Evolution of pesticide resistance
Selection against small guppies results in an
increase in average size
Other Vocabulary
 Gene Flow – the movement of genes into
or out of a population due to
interbreeding
 Genetic Drift – the random change in
allele frequency in a population