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Transcript
Aoccdrnig to a rscheearch at Cmabrigde
Uinervtisy, it deosn't mttaer in waht oredr the
ltteers in a wrod are, the olny iprmoetnt tihng is
that the frist and lsat ltteer be at the rghit pclae.
The rset can be a total mses and you can sitll
raed it wouthit porbelm.
Tihs is bcuseae the huamn mnid deos not
raed ervey lteter by istlef, but the wrod as a
wlohe.
amzanig huh?
Eevyrobdy has seen the Egnilsh
rseaecrh taht sguegtss sepllnig is
irrlevenat. I'd lkie to srtnalge the
rseaecrehrs who did taht sutdy wtih
tehir own itnseitens. The rseaecrehrs
may not hvae to wrok wtih poelpe
who cna't sepll, but I do!
What is
Natural
Selection?
What is
Biological
Fitness?
What is the
relationship
between Biological
Fitness and
Natural Selection?
Turn to to
page 276
of your
Holt Biology
Textbook
Research Darwin and
Natural Selection on pages
276-280 and create a
T-Shirt design detailing
your research
Darwin not the first - Evolution
first proposed by Lucretius, a
Roman philosopher who lived
nearly 2,000 years ago before
the modern theory of evolution
was proposed.
In 1859 Darwin,
published convincing
evidence that species
evolve, and proposed a
reasonable mechanism
explaining how evolution
occurs.
Today almost all
scientists accept that
evolution is the basis
for the diversity of
life on Earth.
Darwin
struggled in school
and repeatedly
skipped lectures to
collect biological
specimens.
In 1831, because of his interest in
nature, one of Darwin’s professors
at Cambridge recommended him
for a position as a naturalist on a
voyage of HMS Beagle.
Darwin’s journey at the
age of 22, would both change
his life and forever change
how we think of ourselves.
In 1809, the French
scientist Jean Baptiste
Lamarck (1744–1829)
proposed a hypothesis for
how organisms change over
generations.
Lamarck believed that
over the lifetime of an
individual, physical
features increase in size
because of use or reduce
in size because of disuse.
Lamarck correctly
pointed out that change in species is linked
to the “physical conditions of life,”
referring to an organism’s environmental
conditions.
As Darwin visited different
places, he also saw things
that he thought could be
explained only by a process
of gradual change.
Darwin found fossils of extinct
armadillos. These fossilized animals
closely resembled, but were not
identical to, the armadillos living in
the area.
Darwin suggested that the
ancestors of Galápagos species
migrated to the islands from South
America long ago and changed after
they arrived. Darwin later called
such a change “descent with
modification”—evolution.
Malthus may
have been
right?
I’ll Call it
Natural Selection
Of Course
I’m Right!!!
Malthus suggested that human populations do not
grow unchecked because death caused by disease,
war, and famine slows population growth.
I’ll bet that this applies to all species, so
individuals that have physical or behavioral traits
that better suit their environment are more likely
to survive and will reproduce more successfully
than those that do not have such traits.
In time, the number of
individuals that carry these
favorable characteristics
will increase in a population.
And thus the nature of the
population will change — a
process called evolution.
It is also my belief that
organisms differ from
place to place because
their habitats present
different challenges to,
and opportunities for,
survival and reproduction.
Each species has evolved
and has accumulated
adaptations in response
to its particular
environment. An
adaptation is a feature
that has become common
in a population because
the feature provides a
selective advantage.
In 1844, Darwin finally
wrote down his ideas
about evolution and
natural selection in an
early outline that he
showed to only a few
scientists he knew and
trusted.
Darwin decided to publish
after he received a letter
and essay in June 1858 from
the young English naturalist
Alfred Russel Wallace (1823–
1913).
Wallace’s essay described a
hypothesis of evolution by
natural selection! In his
letter, he asked if Darwin
would help him get the essay
published. Darwin’s friends
arranged for a summary of
Darwin’s manuscript to be
presented with Wallace’s
paper at a public scientific
meeting.
Darwin’s book On the Origin of
Species by Means of Natural
Selection appeared in November
of 1859. Many people were
deeply disturbed by certain
suggestions of Darwin’s theory.
However, Darwin’s arguments and
evidence were very convincing,
and his view that evolution occurs
gained acceptance slowly from
biologists around the world.
Darwin’s theory of evolution by natural
selection is supported by four major points:
1.Variation exists within the genes of every
population or species (the result of random
mutation and translation errors).
2.In a particular environment, some
individuals of a population or species are
better suited to survive (as a result of
variation) and have more offspring (natural
selection).
3.Over time, the traits that make certain
individuals of a population able to survive and
reproduce tend to spread in that population.
4.There is overwhelming evidence from
fossils and many other sources that living
species evolved from organisms that are
extinct.
• How does natural
variation affect
populations?
• Explain how
natural selection
takes place.