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Chapter 13
The Theory of Evolution
Charles Darwin
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Charles Darwin – visited the Galapagos Islands and
noted that groups of animals varied from island to
island but yet were similar.
He observed 13 species of finches. Each had a type of
beak and coloring adapted to it’s environment/ island.
Upon closer and internal observation, Darwin
concluded that they must’ve come from a common
ancestor.
Evolution – the development of new types of
organisms from preexisting types of organisms over
time. (an inheritable change in characteristics)
Charles Lyell
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(1797-1875) believed in Uniformitarianism –
which states that the geologic processes shaped
Earth in the past continue to operate in the
same way today.
Another belief by Georges Cuvier believed in
Catastrophism – which states that sudden
geologic catastrophes caused the extinction of
large groups of organisms at certain points in
the past
Natural Selection
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Natural Selection – Process by which
individuals that are better adapted to their
enviroment survive and reproduce more
successfully than less well adapted individuals
do: this explains the mechanism of evolution
Adaptation – changes in population over time
Evidence of Evolution
• Fossil – remains or traces of an
organism that died long ago.
• Biogeography – the study of the
locations of organisms around the
world.
• Darwin observed animals that seemed
closely related but yet were adapted to
different environments.
• On the flip side – he also saw animals
that did not seem related but had
similar adaptations to similar
environments that were far apart.
Divergent evolution – process in which
the descendants of a single ancestor
diversify into species that each fit different
parts of the environment (accumulation of
differences b/t populations that once formed a single
population)
Convergent evolution – process by
which different species evolve similar traits
Anatomy & Embryology
• Anatomy – the study of body structure
• Embryology – the study of the development of
•
organisms
Homologous Structures – anatomical structures
that occur in different species, that originated by
heredity from a structure in the most recently
common ancestor of the species
Anatomy & Embryology
Analogous structures – closely related functions but do not
derive from the same ancestral structure
 Example: wings
Butterfly wings
are different from
bat wings which
are different from
bird wings but all
are used to fly
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Anatomy & Embryology
Vestigial structures – structures
that serve no function but
resemble structures with
functional roles in related
organisms (tail bone)
Embryonic development is also
evidence of a common ancestor
– if you look at the development
of vertebrates, they look very
similar in the beginning of their
development.
Anatomy & Embryology
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If a group of animals from similar species have
the same protein in their blood – it can mean
that they are related to a common ancestor
Coevolution – when two or more species
evolved adaptations to each other’s influences
Example: Plants have evolved so that the
animals that eat them also spread their
pollen. As a result, plants and their
pollinators coevolved.
 Artificial selection – when humans chooses
an individual that will parent the next
generation, based on a certain characteristic
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CHAPTER
14
Classification
Classifying Organisms
 Biodiversity – the variety of organisms
considered at all levels from populations
to ecosystems
 Taxonomy – the science of describing,
naming, and classifying organisms
 Taxon – any particular group within a
taxonomic system.
Dichotomous Key
 dichotomous key, is a method of deducing
the correct species assignment of a living
thing. As the alternative name implies, it
works by offering two (or sometimes more)
alternatives at each juncture, and the choice
of one of those alternatives determines the
next step. For each level of distinction, there
is normally a further indent. Some keys use
different numbering systems.
Dichotomous Key
 Are you above or below 5’4.
 Do you have hair below or above your
shoulders?
 Are you right or left handed?
 Do you wear glasses?
 Do you have a job?
 Do you play a sport for the school?
 Then questions get specific with your name.
Levels of Classification
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REMEMBER IT BY
KINGDOM
• KING
PHYLUM
• PETER
• CAME
CLASS
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OVER
ORDER
• FOR
FAMILY
• GRAPE
• SODA
GENUS
SPECIES As you move through the hierarchy
from kingdom to species, animals
become more similar in appearance.
Levels of Organization
• Binomial Nomenclature: the scientific
name with two parts given to an organism:
the genus name followed by species
identifier.
• Example: Human: Homo sapien
Domestic Dog: Canis familiaris
PHYLOGENETICS
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Phylogenetics – the analysis of the
evolutionary or ancestral relationships among
taxa
Phylogenetic diagram or phylogenetic tree –
looks like a family tree and has a branching
pattern that indicates how closely related, by
their evolutionary relationships, a subset of taxa
are thought to be. (can change upon new
discoveries)
Cladistics
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Cladistics – a system of phylogenic analysis
that uses shared and derived characteristics as
the only criteria for grouping taxa
Shared character – feature that all members of
a group have in common – such as scales for
reptiles or hair in mammals
Derived character – a feature that evolved only
within the group under consideration. Only birds
have feathers, among living and extinct animals
– birds are the only animals to have feathers so
you can hypothesize that feathers evolved
strictly within the bird lineage
Cladograms
Clade – organisms that share one or more
derived characters probably inherited from
a common ancestor.
 Cladograms – a phylogenetic diagram
representing common ancestors
 Starts with out-group – an organism that is
distantly related to the other organisms
 Exploring Further pg. 308
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Cladogram
The horse
 Chordata
 Mammalia
 Perissodactyla
 Equidae
 Equus
 Caballus
 Donkey
 Chordata
 Mammalia
 Perissodactyla
 Equidae
 Equus
 Asinus
Crossing
Species
Although donkeys and horses
are similar they are not of the
same species.
 They can produce offspring but
their offspring is sterile.
 The same is true for lions and
tigers which produce sterile
ligers
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