Transcript Intro to Evolution Powerpoint 2/3

Wednesday, February 3, 2016
• HOMEWORK: None
• OBJECTIVE: I will be able to understand
evolution is learning to recognize variation
within species by examining different
variations.
• DO NOW:
– Define evolution in your own words.
– What do you think a variation in a species is?
 Scientists estimate there are over 8.7 million species
alive on earth.
 This may be less than 1% of all the species that have
ever existed on earth!
How did so many species come about?
How did these species evolve?
A subset of the species Mexican Tetra (Astyanax
mexicanus) lives in dark caves and many, many
generations ago the fish in the population had eyes and
silver color, but now they don’t. Why did this happen?
Other kinds of animals have also lost their sight in caves
over many generations.
Kentucky Cave Shrimp
Texas Cave Salamander
Blind Cave Catfish
Cave Crawfish
Male
Video
Female
The male red back spider
sacrifices himself by throwing
himself into the females fangs
as he mates with her.
Why do you think this
happens?
Male
Female
Male peacocks have long colorful tail
feathers and females do not.
Why do you think they have long colorful
feathers? Why do males have them, but
females don’t?
Many bacteria are becoming
resistant to antibiotics.
MRSA is a kind of bacteria that infects people.
Years ago, MRSA could be killed by many kinds of
antibiotics. Now MRSA is resistant to many of
these antibiotics. How did this occur?
The rough skinned newt produces a toxin that is
unusually strong. It is the most poisonous animal in
the United States. One newt has enough poison to
kill over a dozen people.
Why does the newt produce so much toxin?
The average horn size of bighorn sheep today
is smaller than it was 30 years ago. Why are
their horns smaller?
The average head size of a red-bellied black snake
born in the last few years is smaller than the
average head size of those born 50 years ago.
The average body size stayed the same.
Why has the average head size changed
since 50 years ago?
Male guppies from one stream are very colorful while in
other streams they are less colorful.
More Colorful
Less Colorful
In a severe
drought, some
finches survived
and others
didn’t. Why?
Why has the flower population changed?
But the pesticides are no longer working as
well! Why are more bed bugs surviving
after pesticides are used?
Why are most moths in those
woods lighter today?
Closure
 Based on what you learned so far,
what do you think a variation is?
Closure
 35 million years ago, a large mammal called
moeritherium lived on the earth. Moeritheriums
are the ancestors of elephants.
 Moeritheriums had small ears and a short snout
(or nose). Modern African elephants have big
ears and a long trunk. Write an explanation
about either the ears or the trunk. (You don’t
need to write about both.)
Closure
 Explain why the ears or trunk of a modern
day elephant are different from the ears or
snouts of moeritheriums.
 How did the change occur?
 Also, moeritheriems do not have tusks but
modern African elephants do have tusks.
Why do you think this change occurred?