Transcript Two Views of Adaptation

Two Views of Adaptations
Pages 109-114
Ideas About How Adaptations
Occur
Inheritance
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of Acquired Characteristics
The idea that organisms can change themselves was
accepted by scientists in the 1800s
Individual parents can try to change, and the changes
they make are passed on to the next generation
(inherited)
The population then changes over time
Individuals acquire characteristics because they want or
need them
Jean-Baptiste Lamarck, French scientist, thought that
change occurred as acquired characteristics were
inherited
Natural Selection: A Population View of Adaptation
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Charles Darwin and Alfred Russell Wallace presented “natural
selection” using the following logic
 More offspring are born than can survive
 Organisms within a population vary from one another in specific
characteristics
 Heritable variation – Some variations among individuals can be
passed from parents to offspring
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Individuals that have inherited traits that better enable them to
survive and reproduce will leave more offspring.
 The frequency of these traits will increase in future
generations
 Population will change over time
 Beneficial traits are called adaptations.
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Describes how POPULATIONS change over time
Characteristics that become more frequent in a
population are the very ones that help individuals survive
and reproduce… Natural Selection is not random
Natural Selection A Powerful Idea Pages 112-114
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Why Scientists accept natural
selection
 If there are no limits on
population growth organisms
would reproduce very rapidly.
 Our observations tell us that
most populations in the wild
stay fairly constant in size.
 Resources available in any
natural environment are
limited.
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Specific DNA changes cause
variation in populations
agriculture has been changed
using artificial selection
Used to develop flu vaccine
and treatment for HIV
Explanation for phenomena
such as why spiders eat their
mate
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Why Scientists reject the
inheritance of acquired
characteristics
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Variations that occur during
an organisms lifetime are
often not heritable and can
not affect the course of
evolution
agriculture in the Soviet Union
did not improve from
treatments based on the idea
of the inheritance of acquired
characteristics
The Finch Scientists of the Galapagos pages 105-106
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Daphne Major gets only 10 inches of rain a year
Many species of plants, insects, birds, tortoises, iguanas
ancestors traveled from other Galapagos islands or
traveled 600 miles from South America to Daphne Major
Darwin’s Finches are a species of bird that all have a
common ancestor (some 3 million years ago) yet they
have a variety of beak sizes and shapes which are key in
allowing them to specialize on certain food during the
dry season.
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Hard seeds, soft seeds, insects, fruits, cactus pads, etc.
Why is Daphne Major an Ideal Place to Conduct Biological Studies
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Species have been evolving undisturbed for several million years on
this island.
Dr. Rose Mary and Peter Grant did detailed and thorough studies of
Finches on Daphne Major and got a glimpse of evolution in action.
HMS Beagle
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Darwin was 22 years old in 1831 when he boarded the research
vessel HMS Beagle for a five year trip.
He was supposed to collect organisms as the boat traveled around
the world.
The mission of the crew was to make a detailed map of the coast of
South America
Darwin’s job was to collect as many organisms as possible and
make detailed observations of them on the boat.
 He observed fossils that were much larger than modern species.
 He observed that tortoise shell patterns varied from island to
island
 Observations led Darwin to question where some of the
organisms came from and how to explain all the variation he
saw within a species.
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After he returned from his voyage Darwin spent 20 more years
collecting observations and testing his ideas
Finally he published “On the Origin of Species”
Evolution was not a phrase Darwin used instead he used Descent
with Modification
 Modification is a change in a feature of an organism
 Descent means organisms are linked to the past through their
ancestors
Used Natural Selection as his explanation for how modification
occurred
Descent with Modification helped explain the diversity in organisms
he observed and why closely related species tend to be found on
the same continent
Human Skin Color Adaptations
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Vitamin D in the Body
 A nutrient crucial to bone
and immune system health
 Vitamin D deficiency can
cause abnormal bone
growth called rickets in
children
 Women who had rickets
will have abnormal pelvic
bone structure and could
die during child birth
 Linked to a high
susceptibility to disease
and cancer
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Folate in the Body
 A nutrient used when the
critical molecule DNA makes
copies of itself when new cells
are being made
 Supports the growth and
development of an
embryo/fetus/baby
 Folate deficiency can cause
anemia (a condition where the
blood does not make enough
red blood cells), infertility (due
to a reduced ability to produce
mature sperm and egg cells),
and birth defects that can be
fatal to the fetus (such as
malformation of the spine
called spina bifida)
Foods
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Vitamin D rich foods
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Fatty fish, mushrooms, eggs
Added to milk, bread, and
cereal
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Folate rich foods
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Leafy green vegetables,
beans, peas
Added to some cereals
Ultraviolet radiation and Nutrients
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Humans can synthesize (make)
their own vitamin D when
ultraviolet light penetrates the
skin
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The human body can not
make its own folate
Exposure to ultraviolet
light can cause a 43%
drop in folate in the
bloodstream
Folate that has been
broken down by UV
exposure is unable to
perform it’s biological
functions
Skin Color and Ultraviolet Light
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Darker Skin Colors absorb
ultraviolet light before it
reaches the bloodstream
The darker a person’s skin the
less ultraviolet light penetrates
deep enough for vitamin D
synthesis
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Lighter Skin Colors do not
absorb much ultraviolet light
before it reaches the
bloodstream where it can
destroy folate
The lighter a person’s skin the
more ultraviolet light
penetrates deep enough for
vitamin D synthesis
Skin color, sunburn, and skin cancer
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Skin is the largest human organ
Functions in the regulation of
temperature through sweating
Severe sunburn
 can damage the sweat
glands and reduce the
body’s ability to stay cool
 Sun-blistered skin can
become infected
Skin Cancer
 Caused by exposure to UV
radiation over long periods
of time
 Typically appears in older
individuals, past their
reproductive years
 If untreated some skin
cancers can be fatal
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Exposure of light-skinned
individuals t UV radiation
causes sunburn over a short
period of time
Darker-skinned individuals take
more exposure to burn
Individuals born in Africa with
albinism (complete lack of skin
pigment) are at high risk for
skin cancer
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90% die before the age of 30
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One function of the skin
When do people usually develop skin cancer?
What is the life expectancy of an individual with albinism in Africa?
What health concern might a darker skinned person have?
What health concern might a lighter skinned person have?
What benefit does darker skin give?
What benefit does lighter skin give?
What are health issues with low folate levels?
What are the health issues with low vitamin D levels?
Identify the selective pressure in the human skin color adaptation.
Which nutrient can the skin make?
What foods naturally contain vit D?
What foods naturally contain folate?
What is the function of vit D?
What is the function of folate?
What is anemia?
What is Rickets?
What skin color absorbs more UV radiation letting only some through?
What skin color absorbs less UV radiation letting more through?