Transcript Introduction to Evolution

Introduction to Evolution
• Question #1
• What is your definition of evolution?
– This is your definition, not anyone else in class.
• Take about 2 minutes to think about what you are
going to write (don’t write anything yet!).
• Take 2-3 minutes to write your definition on a
blank piece of paper.
Introduction to Evolution
• Evolution can be
described as “change
over time”.
• The evolutionary
process is by which
modern organisms
have descended from
ancient organisms.
Introduction to Evolution
• Our definition of evolution:
– The change in allele frequency (genetic
make-up) in a population over time.
• This can be caused by many factors in
which we will discuss later.
Introduction to Evolution
• Question #2:
• Did humans evolve from monkeys?
Explain.
Introduction to Evolution
• Explanation:
• Humans did not evolve from
monkeys.
• Humans are more closely
related to modern apes than to
monkeys, but we didn't
evolve from apes, either.
• Humans share a common
ancestor with modern African
apes, like gorillas and
chimpanzees.
• Humans are probably most
closely related to two
chimpanzee species: the
common chimpanzee and the
bonobo.
Introduction to Evolution
• Scientists believe this
common ancestor
existed
5 to 8 million years ago.
• Shortly thereafter, the
species diverged into two
separate lineages.
• One of these lineages
ultimately evolved into
gorillas and chimps, and
the other evolved into
early human ancestors
called hominids.
Introduction to Evolution
• We are not the king of all species.
• We all come from ONE common ancestor.
Introduction to Evolution
• Key points to understanding the
process of evolution:
• This is not a religious topic.
• This is a theory that is well-supported.
• Remember, this is the explanation of a
process that happens (and has been
happening) to all biological organisms.
• Have an open mind!!!!!!!
Charles Darwin
• The individual who
contributed more to
our understanding
of evolution than
anyone was
Charles Darwin.
Charles Darwin
• Born in England in
1809 (same day as
Abraham Lincoln).
• In 1831 set sail from
England around the
world on the HMS
Beagle.
• This would become
one of the most
important voyages in
the history of science.
Charles Darwin
• During his travels, Darwin
made numerous
observations and collected
evidence that led him to
propose a revolutionary
hypothesis about the way
life changes over time.
• That hypothesis, now
supported by huge body of
evidence, has become the
theory of evolution.
Charles Darwin
• On this voyage, Darwin
made many stops and
observed and collected
many species of plants
and animals.
• He began to realize that
an enormous number of
species inhabited the
Earth.
Charles Darwin
• Darwin was intrigued by
the fact that all species
were so well adapted to
whatever environment
they inhabited.
• He was also fascinated
by the many ways
organisms survived and
produced offspring.
Charles Darwin
• Darwin was also
puzzled by where
different species
lived and did not
live.
– Australia and
Argentina have the
same grassland
ecosystem but are
inhabited by
completely different
animals.
Ring-tailed Coati
Charles Darwin
• For Darwin, these
patterns posed
challenging
questions:
• Why were there no
rabbits in Australia
(yet) despite the
perfect habitat?
• Similarly, why were
there no kangaroos in
England
Charles Darwin
• Darwin soon realized that
living animals represented
just part of the puzzle
posed by the natural
world.
• Darwin collected many
fossils on his voyage.
– Some resembled
organisms that were alive.
– Some looked completely
unlike any creature ever
seen.
Charles Darwin
• As Darwin studied
fossils, new
questions arose:
– Why had so many
of these species
disappeared?
– How were they
related to living
species?
The Galapagos Islands
• These island
located about
1000km west of
South America
influenced Darwin
more than any stop
made during his
voyage.
The Galapagos Islands
• These island are located
very close together but
have completely different
climates and ecosystems.
• The smaller, lower islands
are hot, dry, and barren of
most vegetation.
• The bigger, higher islands
have greater rainfall and a
higher abundance of
plants and animals.
The Galapagos Islands
• Darwin was fascinated with the land tortoises
found in the Galapagos.
• Darwin learned that these tortoises varied in
predictable patterns from one island to
another.
The Galapagos Islands
• The dome-shaped shell tortoises are found
on wetter islands such as Isabela.
• The intermediate shell tortoise are found on
islands with a mixture of dry and vegetative
ecosystems.
• The saddle-backed tortoises are found on
drier islands such as Hood.
• Why?
The Galapagos Islands
Saddle-Backed Tortoise
The Galapagos Islands
• Darwin also examined
many different types of
brown birds foraging for
seeds.
• He noted a difference in
beak shapes on many of
these birds and thought
they were all different
species of brown bird
(wrens, warblers, etc) at
first.
The Journey Home
• While heading home,
Darwin spent a great deal
of time thinking about his
findings.
• Darwin had observed that
the characteristics of many
animals and plants varied
noticeably among the
different islands of the
Galapagos.
The Journey Home
• After returning to
England, Darwin began
to wonder if animals
living on different islands
had once been members
of the same species.
• According to this
hypothesis, these
separate species would
have evolved from an
original South American
ancestor species after
becoming isolated from
one another.
The Journey Home
• Was this possible?
• If so, it would turn
people’s view of the
natural world upside
down.