Transcript Evolution - St. John the Baptist Diocesan High School

Evolution
What is Evolution?
 Evolution
is the change in a species over
time.
 More specifically, it is the change in
inherited characteristics in a species over
the course of generations
Who Was Charles Darwin?
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Charles Darwin was an English scientist who
proposed a theory to explain how organisms
change over time
In 1831 he set sail on a five year voyage
throughout the world and visited several
continents and many remote islands
During these visits he made many
observations of the plants and animals that
he encountered throughout the world
In 1859 he published his famous work “On the
Origin of the Species” in which he proposed
the Theory of Evolution
Theory of Evolution
 Darwin
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based his theory on two ideas:
Variations- Differences among individuals of
a species
Natural Selection- Nature selects any trait
that increases an organism’s ability to
survive and reproduce
Natural Selection
 The
theory of evolution
and natural selection are
based on the following
ideas:
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Overproduction within a
population
Competition within a
species
Survival of the Fittest
Overproduction
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More offspring are born
than can possibly survive
to reproduce themselves
For example, if all the
offspring of bacteria,
insects, dandelions,
rabbits, etc. survived, they
would overrun the earth!
This DOES NOT happen!
Competition
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In our world there is a finite
(limited supply) of resources
As a result, individuals within a
particular species are
constantly competing for
resources such as food, water,
shelter, and mates!
There is simply not enough to
go around!
Survival of the Fittest
 The
individuals who survive are those who
are most adapted to exist in their
environment
 This is due to the possession of adaptations
(differences in form) that maximize their
fitness
 Fitness is the ability for an individual to
survive and reproduce in its specific
environment
Adaptive Value
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Any trait that helps an organism survive and
reproduce under a given set of environmental
conditions is said to have adaptive value
According to Darwin’s theory, a changing
environment will select certain traits and
behaviors of organisms that allow them to
survive and reproduce
Examples of Traits:
Peppered Moths
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The Industrial Revolution in England
covered the trees in dark soot.
Light colored moths were now
more easily spotted by predators
(birds), and were killed off at higher
frequencies.
Dark colored moths were now
camouflaged, and more of them
survived to pass their genes onto
their offspring.
Over time, the majority of
peppered moths in England were
dark colored
Peppered Moth Video Clip
Examples of Traits
 Bacterial
Resistance to Antibiotics
Examples of Traits
 Galapagos
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Finches
The finches on the Galapagos island are
adapted to eating different kinds of food
Examples of Behaviors
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Nest building behavior in
birds- those birds which build
the best nests are able to
reproduce better
Fighting behavior among
walrus populations for a
harem of females- the
stronger, healthier males will
mate with the most females
Correct blinking rate
behavior between male and
female fireflies to find each
other and mate
Kangaroo Boxing
Genetics and Evolution
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As Darwin developed his theory of evolution
following his return to England in 1836, he
worked under a serious disadvantage: He did
not know how heredity worked.
Although Mendel’s work on inheritance was
published in the 1860’s, its importance was
not recognized until after 1900.
Without an understanding of heredity, Darwin
was unable to explain two important factors.
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First, he did not know the source of variation that
was so central to his theory.
Second, he could not explain how inheritable
traits were passed from one generation to the
next.
How are New Traits
Created in Offspring?
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During meiosis (remember
crossing over!) new
combinations of genes occur.
This is called genetic
recombination. These genes
can be passed on to the
offspring.
Random mutations of genes in
the gametes can create new
traits in the offspring. The
mutations are changes in the
base pairs of DNA that can
occur randomly or from
exposure to radiation.
Genetics and Evolution
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If a random mutation or a product of genetic
recombination creates a new trait in an
offspring that is advantageous for survival,
that offspring will have a much greater
likelihood of reproducing and passing its
genes on to future generations
As time and generations continue, this
advantageous trait (or variation) will increase
in frequency in the population, and may even
lead to the creation of a new and species.
This is called speciation.
Anole Lizards Speciation
Evidence for Evolution
 Geologic
Record
 Geographic Distribution of Living Species
 Homologous Body Structures
 Vestigial Structures
 Comparative Embryology
 Comparative Biochemistry
Geologic Record
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Some evidence for
evolution comes from
fossils.
Fossils are traces or
remains of once-living
organisms that have
been preserved by
natural processes
Fossils that have formed
in different layers of rock
show how species have
evolved over time
Evolution of the
Chambered Nautilus
Geographic Distribution
 Different
species on different continents
look and behave in similar manners
 These species evolved into similar
organisms because they were exposed to
similar pressures of natural selection
BeaverNorth
America
CapybaraSouth
America
Homologous Body Structures
 Structures
of different organisms that are
similar in form but may differ in function
 They show that these organisms may have
shared a common ancestor
Vestigial Structures
A
structure that no longer serves a
purpose in an organism but is present
because it once was useful in the
organisms evolutionary past
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Ex: Whales with tiny pelvic bones, species of
snakes with tiny legs, birds that have wings
but cannot fly (penguins, ostriches)
Vestigial Structures
Vestigial Structures
Comparative Embryology
 Comparing
embryos of
different
organisms can
indicate they may
have shared a
common ancestor
Comparative Biochemistry
 Comparing
the molecular makeup of an
organism such as proteins, enzymes, and
other body chemicals
 The greater the similarity, the more closely
related the organisms are and the greater
the likelihood they share a common
ancestor
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Ex: Every organism on this earth contains
genetic material in the form of DNA or RNA
Comparative Biochemistry
Comparing DNA Sequences
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The more similar the DNA
sequence is between two
species, the more closely
related they are
For example, humans and
chimps share about 98% of
the same DNA!
Even stranger, humans share
50% of their DNA with fruit flies!
Human vs. Chimpanzee
Genome
 Comparing
Human and Chimp Genome
Origin of Life on Earth
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All life on earth is said to have
evolved from one common
ancestor
In Earth’s primitive environment,
the first organisms to evolve were
simple single-cellular organisms
3.8 billion years ago
Those single-cellular organisms
evolved into multi-cellular
organisms that became
increasingly more complex
Today, every living species is a
descendant of this first life form
Animation: Origin of Life
Evolutionary Models
 Simple
branching
diagrams can be used to
represent the
evolutionary relationships
among different species
 These diagrams are
called phylogenetic trees
Branching points represent ancestors common to species
at the ends of these branches. Ends of branches represent
species that are alive today.
Based on this tree, are lizards more closely related to
turtles or to birds?
1. List the letters of species that are presently alive:
2. Which species is the one common ancestor to all the other
species?
3. Which two species are more closely related, F and G, or F
and L?
4. List all of the common ancestors of species L and N:
Human Influence on Evolution
 Selective
Breeding, or artificial selection, is
when humans, not the natural
environment, select the organisms that
have certain advantageous traits and
decide which ones will survive and pass
on those traits to their offspring. This results
in livestock breeds and crops that are
different from their wild ancestors
Human Influence on Evolution
 Genetic
Engineeringhumans manipulate
genes (ex: cloning,
recombinant DNA) to
produce new
varieties of plants
and animals
Lamarck’s Theory of
Acquired Characteristics
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An organism can pass on characteristics that
it acquired during its lifetime to its offspring
Proposed by Frenchman Jean-Baptiste
Lamarck in the early 1800s
Two Parts:
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Use and Disuse- individuals lose characteristics
they do not require and develop characteristics
that are useful
Inheritance of acquired traits- individuals inherit
the traits of their ancestors
Example of Lamarckism
 Giraffes
stretching their necks to
reach leaves high in the trees are
able to strengthen and gradually
lengthen their necks
 Any offspring produced by these
giraffes will inherit these
characteristics and also have long
necks
Extinction
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Extinction is the disappearance of an entire
species
It typically occurs when the environment
changes
Sometimes, the environment changes so much
that there are no longer any members of the
species that are adapted to survive
Based on the fossil record, the majority of the
species that have ever lived on Earth, are now
extinct
Resurrecting the Extinct