NATURAL SELECTION
BELL RINGER
Define natural selection
 Define biological evolution
 Acquired Trait
 Define mutation
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OBJECTIVES:
Relate Lamarck to acquired traits and Darwin to
natural selection
 List the principals of natural selection
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LAMARCK’S IDEAS ON EVOLUTION
Jean Baptiste Lamarck (1744-1829) French
biologists
 Supported the idea that populations of organisms
change over time
 Thought that simple organisms could arise from
nonliving matter
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LAMARCK’S IDEAS ON EVOLUTION
Thought that simple organisms inevitably
developed into more complex forms
 Proposed that individuals could acquire traits
during their lifetimes as a result of experience or
behavior – then passed on the traits to offspring
 This idea is known as inheritance of acquired
traits
 Acquired traits (or characters) are those
changes in the structure or function of an
organism that are the result of use, disuse,
environmental influences, disease, or mutilation.
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DARWIN’S IDEA OF EVOLUTION
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In the mid 1800’s Charles Darwin formed a
theory to explain how evolution takes place
Darwin was a naturalist on the H.M.S Beagle
who sailed to the Galapagos Islands
Darwin published a book entitled On the Origin
of Species by Means of Natural Selection
Darwin used the phrase “descent with
modification” to describe the process of evolution
DARWIN’S IDEA OF EVOLUTION
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Darwin saw animals of the Galapagos Islands as
evidence
Islands are home to 13 similar species of finches
– Darwin suspected that all 13 species descended
from and diverged from just a few ancestral finches
– these finches came from the coast of South
America
DARWIN’S FINCHES
DARWIN’S FINCHES
DARWIN’S IDEA OF EVOLUTION
Darwin proposed the theory of natural selection as
the mechanism for descent with modification
Natural selection has four principles:
1. overproduction
 2. genetic variation
 3. struggle to survive
 4. differential reproduction
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PRINCIPLES OF NATURAL SELECTION
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1. overproduction – more offspring can be
produced than can survive to maturity
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Example: in a population of rabbits, female rabbits
can produce a large number of offspring – each rabbit
requires food and is vulnerable to predators and
disease so not all live very long.
2. genetic variation – in a population
individuals have different traits – some deer in a
population may have longer hair which they pass
on to the offspring
PRINCIPLES OF NATURAL SELECTION
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3. struggle to survive – individuals must
compete with each other – some variations
improve an individual’s chance to survive
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A trait makes an individual successful in its
environment
4. differential reproduction – organisms with
the best adaptations are most likely to survive
and reproduce
Natural selection is also known as “the survival
of the fittest”
ARTIFICIAL SELECTION
OBJECTIVES
Relate current organisms to past organisms
based on the included evidences
 Cite examples supporting scientific evidence

FOSSIL RECORD
Fossil is the remains of an organism that died
long ago
 Fossils show that different types of organisms
appeared at different times and places on Earth
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AGE OF FOSSILS
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1669, Danish scientist Nicolaus Steno (16381686) proposed the principle of superposition
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Principle of superposition states that if the rock
strata at a location have not been disturbed, the
lowest stratum was formed before the strata above it.
Geologist put together a timeline for the order in
which group of rocks and fossils were formed
 Time line is known as the geologic time scale
 Geologists can tell a fossils relative age – age
compared to that of other fossils
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AGE OF FOSSILS
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Absolute age of rock is determined by radiometric
dating
Radioactive dating using carbon dating
 Uses radioactive isotopes to determine the age of
fossils – based on half-life of the isotopes
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By using the relative dating and absolute dating
scientist can determine the age of fossils.
DISTRIBUTION OF FOSSILS
1st we can infer that different organisms lived at
different times
 2nd we can infer that today’s organisms are
different from those of the past
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Trilobites were unlike any organism alive today
3rd we can infer that fossils found in adjacent
layers are more like each other than to fossils
found in deeper or higher layers
 4th by comparing fossils and rocks from around
the planet – we can infer when and where
different organisms existed
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BIOGEOGRAPHY AND ANATOMY AND
EMBRYOLOGY
Is the study of the locations of organisms around
the world
 Anatomy is the study of body structure of
organisms
 Embryology is the study of how organisms
develop
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Page 305 figure 15-8
Homologous structures – are anatomical
structures that occur in different species and that
originate by heredity from a structure in the
most recent common ancestor
BIOGEOGRAPHY AND ANATOMY AND
EMBRYOLOGY
Analogous structures have closely related
functions but do not derive from the same
ancestral structure
 Vestigial structures serve no function but
resemble structures with functional roles in
related organisms
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Human tailbone is made of four fused vertebrae that
resemble the bones in an animal’s tail
BIOLOGICAL MOLECULES
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Look at the DNA and RNA of organisms –
scientists compare the DNA of organisms – the
closer related the organisms the closer the DNA
samples are