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• Did you ever wonder why ostriches have
wings when they cannot fly?
• Answer: Ostriches EVOLVED from other
birds that can fly.
• Ostriches share a COMMON ANCESTOR
that could fly, but then they evolved into
birds that cannot fly.
• We have all heard of Charles Darwin, who
is named the Father of Evolution.
• Before Darwin, however, science was
heavily influenced by religion.
• God created the world and all organisms in
the world and nothing has changed since
• In the 1700’s things began to change.
• Europeans began to explore the earth: Asia,
• They began to notice that there were many more
species, or types of organisms, than anyone ever
• Patterns began to emerge:
– Each geographic area has its own unique species
– Scientists began to think that perhaps organisms
changed or evolved to live in their unique habitat
– Perhaps species weren’t fixed, they changed…..
• Next was the discovery of fossils: preserved remains of organisms that
died long ago.
• As people began building roads and more modern buildings, they
began to dig up rocks that looked like bugs, birds, and other animals.
• Scientists began to understand that fossils were buried in different
layers of the earth, and these layers corresponded to how long ago the
organisms lived and died.
• Fossil remains also revealed that fossils from shallow layers in the
earth resembled modern organisms more so than those fossils in
deeper layers and those fossils in deeper layers were of simple, less
complex organisms and often represented species that were no longer
alive in the present.
• Next up was the proposal that the Earth’s
present landscape was produced by past
action of things like volcanoes, flooding
rivers, movement of tectonic plates under
the ground, etc. This led to the belief that
the Earth was very old.
• Modern geologists estimate that the Earth is
4.5 billion years old.
The Evolution of Evolutionary
• Lamarck, 1800’s: younger fossils are more
complex than older ones, so perhaps species are
changing and becoming more complex over time
AND PERHAPS these more complex organisms
INHERITED their complexity from their parents.
• Later in the 1800’s Darwin and Wallace began the
real work on evolutionary thought.
Darwin & Wallace
• Both traveled extensively and studied plants and
• Both observed that there was an increasing
complexity in the fossil record.
• Both observed that some organisms that may not
be related nevertheless had similar features.
• Both suggested that ORGANISMS CHANGE
Darwin & Wallace
• Both wrote papers about this new theory.
• Descent with modification: individual
organisms in each generation differ slightly
from organisms in the previous generation.
• Over long periods of time, these small
differences accumulate to produce MAJOR
the mechanism of evolution*
• 1.) Individual members of a population differ from one
• 2.) Some of those differences are due to characteristics that
can be passed from parent to offspring.
• 3.) In each generation, some individuals in a population
survive and reproduce, but others do not.
• 4.) Whether an individual lives or dies is not by
chance/luck. Those who have inherited advantageous traits
survive the longest and have the most offspring. This
process is called NATURAL SELECTION.
1.) Members differ from one another
• Look around the room….we are all
different: height, weight, skin color, eye
• We now know that this is because of
changes in our DNA (what might be called
mutations) which produce different
2.) Traits passed on to offspring
• No “proof” of this was available in the early
1800’s (Mendel didn’t come along until late
• But now we know that traits are passed to
3.) Some survive, some don’t
• Darwin knew that, for instance, one pair of
elephants could produce 19 million
offspring if they lived a full life and
reproduced as often as they could….but
there aren’t 19million elephants…so some
4.) Survival and reproduction are not
• Evidence suggests that survival and reproductive success depends on
an individual’s characteristics.
– Large male elephant seals have more offspring, because females
are attracted to larger males
– Snapdragon flowers produce more white offspring than yellow
ones because pollinators are attracted to the white flowers more
– Antibiotic resistant bacteria grow faster than non-resistant ones
– The “winners” in the competition to survive win because they
have specific traits.
– Over time, the population changes as these specific traits are
Proof of Evolution*
• 1.) Fossils
• 2.) Comparative Anatomy
– Homologous Structures
– Vestigial Structures
• 3.) Embryologic Similarity: all vertebrate
structures look similar to each other early in
• 4.) Biochemical proof: DNA
• new species evolved from, and replaced,
• Ex: whales evolved from four-legged land
2.) Comparative Anatomy
• Homologous Structures: body structure is
modified by evolution to serve different
functions in different species, but all of
these organisms have a COMMON ancestor
from which they evolved.
– Forelimbs of birds/mammals (Fig 14-8) have
all of the same internal anatomy, but look very
different (paws, feet, wings, flippers)
• Vestigial Structures: structures that serve no
apparent purpose in a more advanced organism,
but was useful in an earlier organism
– Appendix: no use in humans, helped in digesting plants
back when humans and their predecessors ate only
– Pelvic bones in whales: they don’t need them to swim,
but have them
– Other examples: wisdom teeth, arrector pili muscles,
These vestigial bones are similar in
structure to those of the salamander
but serve no function; all three animals
inherited the bones from a common
The bones of a salamander’s hindlimb
function in support and locomotion
(c) Boa constrictor
(b) Baleen whale
3.) Embryologic Similarity*
• Ancestral vertebrates possessed genes (HOX
genes) that directed the development of gills and
tails. All of their descendants still have those
• In fish, those genes are active (protein synthesis)
all the way through development and fish are
BORN with gills and tails.
• In humans and chickens, these genes are shut off
at some point in development, because we are
born without gills/tails.
Proof of natural selection
• The breeding of domestic plants and animals to produce
desirable features is something humans have done for
thousands of years.
• We have artificially bred dogs to the point that there are
breeds of dogs that look COMPLETELY different (Great
Dane vs Chihuahua) yet they belong to the same species.
This was done by selecting the individuals from each litter
that had more of the desirable traits and breeding them
(Great Dane: bred the biggest puppies of the litter or
Chihuahua: bred the smallest dogs, etc)
It’s still happening
• Roaches in Florida resistant to Combat:
developed a mutation that caused them to
Two final points*
• The variations on which natural selection
works are produced by random mutations.
• Natural selection favors organisms that are
best adapted to a particular environment at a
particular time. (If environment changes,
then the traits that organisms need to
survive may change too.