Transcript Slide 1

EVOLUTION – PART 1:
INTRO TO EVOLUTION
On the following slides, the pink sections identify the main
points; Underlined words = vocabulary! Hyperlinks are in
green.
Background Image: http://magickcanoe.com/insects/angry-katydid-3-large.jpg
This katydid is well
adapted to look like
the leaves of its
habitat. In this unit
we will discuss
theories of evolution
and adaptation that
lead to such
phenomenon within
populations.
Background Image: http://magickcanoe.com/insects/angry-katydid-3-large.jpg
Sensitivities
Due to the sensitive nature
of this unit I ask that we keep
in mind that evolution can
often breed tensions
because of religious
teachings about the history
of life.
These theories are part of
understanding the world of
science. Our scientific
discussions will focus on
attempting to explain natural
phenomena (or events).
Differing religious opinions
are okay, but religious based
theories on the history of life
are not the focus of this
class.
Scientific
Theory
• Theory in everyday life is different
from the scientific theory – i.e.
someone has a theory on who will
win the Super Bowl.
• A scientific theory is an
explanation of natural and physical
phenomena that is supported by a
large body of scientific evidence
from multiple, independent
researchers.
• Unlike hypotheses, theories are
well- established and highly
reliable – they are subject to
change as new information is
obtained or technologies
developed.
Evolution
http://www.eurekalert.org/images/release_graphics/yu0926.jpg
• The Earth has millions of
kinds of organisms with an
amazing amount of
diversity, yet, we all share
similarities, the core of
which is DNA. (Every living
organism has it!)
• How are all these different
organisms related to each
other?
• Evolution, or change in a
species over time, is the
process by which modern
organisms have descended
from ancient ones.
• For example, the ancient
horse a was about the size
of a medium dog!
Who is Charles Darwin?
• The British scientist Charles
Darwin is credited the most
in our understanding of
evolution.
• He proposed a hypothesis
about the way life changes
over time .
• That hypothesis, now
supported by a larger body
of modern evidence,
became the theory of
evolution.
Photograph of Charles Darwin by
Maull and Polyblank for the Literary
and Scientific Portrait Club (1855).
Image
After college in 1831, Darwin joined the crew of the ship the H.M.S. Beagle for a
voyage around the world for 5 years!
http://www.anselm.edu/homepage/jpitocch/genbios/22-05-VoyageOfHMSBeagle-L.gif
Darwin Cont.
• During his travels, Darwin kept
journals, took observations, and
made sketches for the variety of
species on this planet.
• When the ship was anchored, he
collected many specimens.
– In one single day in the Brazilian
rainforest he collected 68 different
species of beetles!
• When sailing, Darwin took
observations of the organisms and
kept detailed notes.
http://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/St
riped.love.beetle.arp.jpg/250px-Striped.love.beetle.arp.jpg
Darwin
Cont.
http://english.people.com.cn/200406/07/images/0606_112.jpg
• In his travels, Darwin compared
living organisms to fossil
evidence that he collected
throughout his voyage.
• A fossil is the preserved remains
of an ancient organism.
– Some living organisms he
observed looked like preserved
fossils, while others were unlike
any creature he had ever seen!
EX Dinosaurs
• His evidence posed more
questions.
– Why had so many species
disappeared?
– How are ancient organisms
related to modern organisms?
http://www.cnn.com/EARTH/9707/17/Galápagos /Galápagos .lg.jpg
https://maps.google.com/maps?output=classic
Galápagos
Islands
• Probably his most influential
location on Darwin’s journey
was the Galápagos Islands
off the coast of Ecuador.
• The islands had very different
climates and very different
organisms living there.
http://upload.wikimedia.org/wikipedia/commons/a/a1/Gal%C3%A1p
agos_tortoise_Santa_Cruz.jpg
Darwin learned that each island had a different variety of
land tortoises. One island turtle has a long neck and curved
opening in the shell to allow for the organism to search for
food because of sparse vegetation (or plant life).
Yet, another island with a lot of plant life has a turtle that is
very close to the ground the with a short neck making it
easier to eat.
Galápagos tortoises in Alcedo Caldera, Isabela Island
Photograph by Frans Lanting
"Near the springs it was a curious spectacle to behold many of these
huge creatures, one set eagerly travelling onwards with outstretched
necks, and another set returning, after having drunk their fill."—October
8, 1835
http://rationalrevolution.net/images/darwin_ape.jpg
On the Origin of Species
The political cartoon (1861) is just
one example of the negative
reaction to the theories
explained within the book.
• Charles Darwin used his
notes and other findings to
build his theory of evolution; it
took him years before he was
willing to publish his work
because of the drastic
controversy it would (and did)
cause.
• His book, On the Origin of
Species [By Means of Natural
Selection] was published in
1859.
• In it he argued that life has
been evolving for millions of
years.
Five Basic Concepts
of Origin
• Use the chart to list the 5 themes from On the Origin of
Species.
1. Variation Among Species
• All species have genetic
variation (we now know)
caused by differences in the
DNA and genes of an
organism
– EX color of fur; shape of
teeth; blood type; hormone
levels
• Darwin argued that variation
was normal and was
important.
• Characteristics vary and can
affect the survival of
individuals.
http://www.swarthmore.edu/NatSci/cpurrin1/evolk12/gps/images/sad
dlestretch.jpg
2. Struggle for Existence
•
•
•
•
Organisms produce more offspring than can survive.
Some that survive do not produce offspring.
Organisms are forced to compete for resources.
This is called the struggle for existence; members of
each species must compete for the necessities of life
(food, water, & space).
http://eoimages.gsfc.nasa.gov/images/imagerecords/79000/79553/sandy_goe_2012302
_1745_lrg.jpg
• Survival affected by short-term natural disasters
– EX droughts, fires, floods, snowstorms, hurricanes, etc.
• And affected by long-term changes in the environment
– EX ice ages, biome shifts, etc
3. Adaptations
• Darwin began to realize that
organisms have certain
characteristics or behaviors
that allow them to survive in
their environment.
• An adaptation is an inherited
characteristic (EX a longer
neck) that can increase an
organism’s chance of
survival.
• If they live long enough, they
will reproduce and pass on
their favored genes.
http://www.cedar-foundation.org/uploads/images/300%20Turtle.jpg
Knowledge Check
http://www.pbs.org/wgbh/evolution/library/01/6/images/l_016_02_l.gif
The diagram
below shows
features of the
varieties of finches
in the Galapagos.
How can the
diagram help us
understand the
evolutionary terms
like variation and
adaptation? Turn
and talk to your
neighbor.
4. Fitness
http://farm1.staticflickr.com/49/125046333_7123c38e73_z.jpg?zz=1
• Some organisms are
more suited to their
environment due to
natural variations in the
species.
• Darwin used the term
fitness to define an
individual’s ability to
survive and reproduce.
• Individuals that are fit to
their environment survive
and leave more offspring
than those who aren’t.
5. Descent with Modification
• Living species today are
descended (with modifications)
from common ancestral
species that lived in the past.
• Over time, traits [i.e. genes] for
less favored characteristics will
be eliminated from the gene
pool.
• Species today, therefore, look
different from their ancestors
because of historical changes.
Sketch, Darwin’s
Notebook
Branching “Tree of Life”
Image
Knowledge Check
The diagram below shows descent with modifications for
modern elephants. How can the diagram help us
understand evolutionary terminology like variation and
descent with modification? Turn and talk to your neighbor.
http://www.zo.utexas.edu/faculty/sjasper/images/22.7.gif
What is the gist of the
book?
• Natural selection is the process by which individuals that
are better suited to their environment survive and
reproduce most successfully (AKA survival of the fittest).
• Organisms that are well adapted will be able to survive.
Over time, natural selection leads to changes in the
characteristics of a population.
• New species develop, increasing biodiversity.
– Video
– Video 2
Artificial
Selection
• Darwin understood variation
can be a positive thing!
– EX dairy farmer would
benefit from breeding a cow
that produces a lot of milk
versus a cow that does not.
• He coined the term artificial
selection where nature
provided the variation and
humans selected those
variations that are useful
– EX a pure breed dog, the
best looking horse).
– Animation
http://www.farmlandthegame.eu/images/animals/Dairy-cows-pict-1.jpg
Darwin’s Influences
• Many scientific theories and
observations in the years
before Darwin helped to
influence his theories on
evolution.
• Some scientists long before
Darwin came to similar
conclusions.
• Most people at the time
thought Darwin’s opinions too
radical to accept at the time.
http://www.victorianweb.org/science/darwin/darwin_beard.gif
Linnaeus
http://www.amentsoc.org/images/carl-linnaeus.jpg
• In the 1700s, a Swedish
botanist Carl Linnaeus created
a categorical system to group
animals based on their
similarities (still used today).
• He rejected the idea that
organisms were fixed and did
not change.
– Book - Systema Naturae,
1735
– Darwin sited Linnaeus’s
work in Origin.
Hutton
• Scottish geologist James Hutton
published his hypothesis on the Earth’s
geology formed very slowly over time,
millions of years and are shaped by
natural forces (mainly the weather).
– Most Europeans at the time believed
that the Earth was only a few
thousand years old, but Hutton
proposed that the Earth had to be
much older.
• If the Earth were millions of years old, it
would help to explain the SLOW process
of evolutionary change.
– Book, Theory of the Earth, 1795
http://upload.wikimedia.org/wikipedia/commo
ns/thumb/0/0e/Hutton_James_portrait_Raeburn.
jpg/220px-Hutton_James_portrait_Raeburn.jpg
Erasmus
Darwin
• Darwin’s grandfather,
Erasmus Darwin, an
English doctor, posed
that life descended
from a common
ancestor and had
grown in complexity
over time.
– Book, Zoonomia, or
The Laws of
Organic Life, 1796
http://www.bbc.co.uk/arts/yourpaintings/paintings/erasmus-darwin-1731180219634
• The French scientist Jean-Baptiste
Lamarck observed that life changes
over time; he argued that traits
present in an organism are always
passed on to offspring.
– EX giraffes stretched their necks
to reach food, therefore their
offspring inherited the resulting
long necks.
• Although some of his ideas were
flawed, the idea that species
change and adapt greatly
influenced Darwin.
– Book - Philosophie Zoologique,
1809
– Darwin sited Lamarck’s work in
Origin.
http://en.wikipedia.org/wiki/File:Jean-baptiste_lamarck2.jpg
Lamarck
http://www.anselm.edu/homepage/jpitocch/genbios/22-x3-Lyell.jpg
Lyell
• Charles Lyell’s book was
published just before Darwin
set sail in the Beagle.
• In his book, Lyell proposed
that scientists can observe
the processes that shaped
the Earth millions of year ago
in the present (volcanoes,
earthquakes, etc. all change
how the world looks).
• Darwin wondered if the Earth
can change over time, can
species change too?
– Book – Principles of
Geology, 1830
– Darwin sited Lyell’s work
in Origin.
Wallace
• A contemporary of Darwin,
Alfred Wallace, wrote an essay
on evolution and the process of
natural selection using his
studies of plants and animals a
year before Darwin published
Origins.
– Darwin and Wallace both
presented their findings at
the same scientific
conference.
– Darwin sited Lyell’s work in
Origin.
http://io.uwinnipeg.ca/~simmons/16cm05/1116/22-x5-AlfredWallace.jpg
Extinction
http://www.chrismadden.co.uk/eco/mammoth.gif
• Extinction: the
destruction of a
population.
• If an entire population of
a species cannot adapt,
that species becomes
extinct.
• 99% of all species that
have ever lived are
now extinct!
• Humans contribute to
the extinction of many
plants and animals
because of pollution,
loss of habitat, and
poaching.
Indian tigers, for
example, are a group of
tiger species that had
an original range from
India along Asia's
Pacific rim to northern
China as well as other
sections of Central Asia.
Their range today
outside of protected
areas has been severely
limited.
"Fragmented Habitat." Science Online. Facts On File, Inc. Web. 30 Jan. 2013.
<http://www.fofweb.com/activelink2.asp?ItemID=WE40&SID=5&iPin=SciIllus04661&SingleRecord=True>.
• Many scientists say that the earth is currently experiencing
a mass extinction crisis.
• It is estimated that 1/5 or more of the world’s species will
become extinct if the rainforests alone are destroyed, much
less the coral reefs of the oceans and other habitats.
Mass Extinction
Photo courtesy of Donald E. Davis,
also in public domain from NASA.
• There have been at least 5
mass extinctions during
Earth’s history, when a huge
% of the living species were
destroyed.
• At least one of these has
been attributed to meteor
impact and it’s
consequences.
– Animation
Analyzing the Graphic
Chicxulub Crater, Mexico's
Yucatan Peninsula
180 kilometre (112 mi)
diameter
Most scientists now agree that
this event 65 million years ago
that marked the sudden
extinction of the dinosaurs as
well as the majority of life then
on Earth.
Conclusion
• Evolutionary theory is
constantly changing due
to new information that is
obtained.
– EX The AIDS virus is
changing constantly, and
the flu vaccine must be
modified each year due to
changes.
• Species change, evolve,
over time, and that is
happening now.
http://evolution.berkeley.edu/evolibrary/images/news/avianswineflu.gif