Download Unit Three - Owen County Schools

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Biology
Unit 8
Evolution
8.1 Natural Selection Causes Evolution
NATURAL SELECTION: organisms with the best traits are
selected by nature to survive and reproduce. These genes
and traits are then passed on to the next generation.
EVOLUTION: change in species over time.
FITNESS: the ability of an organism to survive and
reproduce.
The process of evolution involves changes in populations over
extremely long periods of time. Evolution has occurred on Earth
over many millions of years.
Four conditions for natural selection to happen
1. Overproduction - organisms produce more offspring
than can survive.
2. Genetic Variation - Individual organisms in a
population have slight differences.
3. Struggle for Survival - Individuals compete for
resources.
4. Differential Fitness - Survivors pass on genes for
the best adaptations to their offspring.
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Three Types of Natural Selection:
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Directional Selection – one extreme trait
becomes the most selected trait. (e.g. cheetah speed)
Disruptive Selection – two extreme forms of a
trait become the most selected. (e.g. white/black coloration)
3) Stabilizing Selection – the average form of a
trait becomes the most selected. (e.g. human height)
Example of Natural Selection:
 Beetles living on brown tree bark are either brown
or green.
 Predator (bird) can more easily see green beetles
and will catch them more often than brown.
 Brown beetles live longer and produce more
offspring, to whom they pass the gene for brown.
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8.2 What is the Theory of Evolution?
SCIENTIFIC THEORY: a well-tested scientific explanation
that no evidence contradicts
Theories explain the basic ideas of science. If scientists
find new evidence that contradicts the theory, the theory is
changed.
CHARLES DARWIN: British scientist whose studies of
fossils and different species established the theory of
evolution.
HMS BEAGLE: this ship's voyage allowed Darwin to visit
many different places in the world, and study all of those
locations' native species.
DARWIN’S IDEA - “Descent with Modification:”
Present organisms are changed forms of past organisms.
Traits are inherited from parents.
JEAN-BAPTISTE LAMARCK – thought that acquired
characteristics could be inherited by offspring.
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A real-life application of Lamarck's idea:
Does this seem accurate? Can acquired traits be inherited?
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8.3 Evidence of Evolution
Fossils, Biochemicals, and the study of Comparative
Anatomy provide evidence for change in living species
over time.
FOSSIL EVIDENCE of EVOLUTION
FOSSIL : the remains or traces of organisms that lived in
the past
FOSSIL RECORD: the history of life on Earth, based on
fossils that have been discovered
The fossil record shows how organisms have changed over
time and shows that the Earth is about 4.5 billion years old.
The fossil record shows that some species have lived then
disappeared during the Earth’s history.
EXTINCT: a species no longer living on Earth
EX: pelagornithid
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Extinctions occur when there are major changes in
the environment and the species is not adapted to
survive.
The fossil record helps scientists to discover
relationships between different groups of organisms
and determine common ancestors.
Ex: frilled shark (still present – “living fossil”)
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Ex: Tiktaalik fossil, 375 million years old, 10 fossils
found, a transitional species?
BIOCHEMICAL EVIDENCE
biochemicals - any chemical made by living organisms.
e.g. DNA, amino acids, proteins.
All living things use DNA to provide instructions for the
building of amino acids into proteins.
DNA  amino acids  proteins
Scientists can analyze proteins in different organisms to
determine how similar their DNA is.
The more similar the amino acid sequence in a protein,
the more similar the DNA is between two organisms.
Scientists can determine relationships between organisms
by comparing DNA similarity.
Therefore, DNA is evidence of evolution.
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ANATOMICAL EVIDENCE OF EVOLUTION
COMPARATIVE ANATOMY - a field of biology that
involves comparing the body structures of different
organisms.
Homologous Structures - body parts that are
similar in structure, but have different functions.
Analogous Structures - body parts that are
different in structure, but have the same function.
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Vestigial Structures - body parts in an organism
that have reduced function, or are entirely useless.
e.g. pelvic leg bones in a whale.
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8.4 Disproving Spontaneous Generation
Spontaneous Generation - the idea that living
organisms could be produced from nonliving objects.
Spontaneous Generation was believed to be fact as
recently as 200 years ago, but several scientists
began to challenge the idea.
Francesco Redi (1668), John Needham (1745),
Lazzaro Spallanzani (1745), and Louis Pasteur (1859),
all performed famous experiments testing spontaneous
generation.
Francesco Redi - disproved spontaneous generation
with an experiment involving flies, rotting meat, and
maggots.
In the closed jar, flies could not reach meat to lay eggs,
so no maggots formed.
What was Redi's independent variable?
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John Needham's error experiment supported
spontaneous generation, but
had a major flaw.
Boiling kills microbes, but he
left his jar uncovered. The
microorganisms invaded the
broth, and turned it
cloudy.
Lazzaro Spallanzani disagreed with Needham, and
corrected Needham's error with
his version of Needham's
experiment.
What did Spallanzani do to correct Needham's flaw?
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Louis Pasteur - his famous
experiment in 1859 fully
disproved spontaneous
generation, by using
swan-necked flasks.
Louis Pasteur ended the debate with his famous
swan-neck flask experiment, which allowed air to
contact the broth. Microbes present in the dust were
not able to navigate the bends in the neck of the
flask, and the broth remained clear for days.
With spontaneous generation disproven, a new
question was being debated…
"So how does life start?"
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8.5 How do new species evolve?
SPECIES: a group of organisms that can successfully
produce fertile offspring.
SPECIATION - the formation of new species
Speciation begins with isolation.
GEOGRAPHIC ISOLATION: the separation of a
population into two groups, caused by a change in
the environment.
EX: A barrier, such as a canyon or river, may
form and divide a population in two.
(A) Blue-headed wrasse (Atlantic side of Isthmus) and (B) Cortez rainbow wrasse
(Pacific side of Isthmus) are related by descent from a common ancestral population
that split when the Isthmus formed.
Allopatric speciation - when one species evolves into
different species because of geographic isolation.
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REPRODUCTIVE ISOLATION - a group of
individuals occupy the same area, but are unable to
interbreed.
e.g. different species of frogs occupy the same
forest, but each species breeds at different times of
the year.
Sympatric speciation - when two populations of the
same species, in the same area, evolve into new
species; usually because of reproductive isolation.
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8.6 Speciation Occurs at Different Rates
Gradualism - the idea that speciation occurs at a
regular, gradual rate.
Catastrophism - sudden geological catastrophes
cause mass extinctions of species.
Punctuated Equilibrium - sudden, rapid rates of
speciation; followed by long periods of little
change.