Transcript The History of Life - Grant County Schools

Evolution
Change in a population over time.
 Why
is the Russian prison system
considered to be "ground zero" in the fight
against TB?
 What is responsible for the evolution of TB
strains that are resistant to multiple drugs?
 How does the misuse of antibiotics affect
the evolution of disease-causing bacteria?
Use the theory of natural selection to
explain the growing resistance to
antibiotics.
 Why should we care about a resistant
strain of TB in Russia?
 Anwer

questions while watching video.
http://www.pbs.org/wgbh/evolution/educators/l
essons/lesson6/act1.html
 Discussion.
 http://www.pbs.org/wgbh/evolution/educat
ors/teachstuds/unit6.html
The History of Life
The Origin of Life
 Spontaneous
generation – life arises
from nonlife

Redi – tested idea that flies spontaneously
come from rotting meat.
-Not everyone was convinced of his findings.


Needham – Roman Catholic Theologian
-Heated chicken and corn broths and poured
them in a covered flasks.
-The flasks cooled and microorganisms had
grown.
-Needham believed the microorganisms grew
because of spontaneous generation.
Spallanzani – disagreed with Needham.
- Suggested Needham’s broth had supported
growth because they had been contaminated
before being sealed and heated.
The Origin of Life
Louis Pasteur’s experiment
 disproved spontaneous generation (mid 1800’s)
 Flask 1 – only air was allowed to contact sterile
nutrient broth
• No microorganisms
grew
 Flask 2 – air and
microorganisms were
allowed to contact the broth.
• Microorganisms grew
 Theory of biogenesis – only living organisms can
produce other live orgaisms.

Which came first, the chicken or
the egg?

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Biologists have accepted the concepts of
biogenesis for more than 100 years
Biogenesis does not answer the question of how
life began on Earth
No one will ever know for certain how life began
on earth. We can only make hypotheses about
conditions on early Earth.
Primordial Soup




Step 1: simple organic molecules must
have formed (molecules that contain
carbon)
Step 2: Simple organic molecules must
have become organized into complex
organic molecules (proteins, carbohydrates,
and nucleic acids)
Hypothesized - life began in the oceans

Energy from sun and lightning triggered
chemical reactions to produce small
organic molecules from substances in
the atmosphere
1953 Miller and Urey (American) –
replicated conditions in the lab and
produced amino acids, sugars, and other
molecules
The next step…

How did we get from simple organic
compounds to complex organic compounds?
 In the presence of heat, without oxygen,
amino acids link to from proteins.
 Continue to heat the complex organic
compounds protocells developed.
The Evolution of Cells
 The




first true cells…
Prokaryotes that evolved from a protocell
Anaerobic (no oxygen present in atmosphere)
Autotrophs (photosynthesizing prokaryotes)
evolved to inhabit harsh conditions (ie.
cyanobacteria)
Cyanobacteria produced enough oxygen to
support the formation of an ozone layer.
Endosymbiont Theory


Eukaryotes probably evolved from prokaryote cells
Theory proposes that eukaryotes evolved through a symbiotic
relationship between prokaryotes
 Evidence:
• Chloroplast and cyanobacteria – resemble eachother
• mitochondria and bacteria – some look similar
• Chloroplast and mitochondria contain DNA that is similar to the DNA
in prokaryotes
• Today, some prokaryotes live in close association with eukaryotes
• http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter4/animation__endosymbiosis.html
Selection Activity
*Get into groups of 3’s: 1 recorder, 1 sorter,
1 picker
1. Obtain 2 groups of 1- squares:


Set 1 – 2 red and 8 green
Set 2 – 8 red and 2 green
2. Take set 1. Place the squares numbered
side down randomly on the table. Pick a
red square and record its number.
Replace square.
3. Repeat Step 2 ten times. Clean up set 1.
4. Take set 2. Repeat steps 3 and 4.