Transcript Evolution – Part I

Evolution – Part I
Chapters 1-2,15,17
EVOLUTION =
Change in hereditary
features in a species over
time
Origin of Life – 2 Theories
1. Spontaneous Generation belief that living things come
from nonliving
• Before 17th century
• Ex: worms form in rain,
rotting meat made maggots,
etc.
2. Biogenesis = all living
things come from living
things
• Widely accepted today
Evidence for Biogenesis
a. Redi – covered one jar of
meat & left one jar uncovered
maggots formed only on
uncovered meat
OBSERVATIONS: Flies land on uncovered meat.
Later, maggots appear on meat.
HYPOTHESIS: Flies produce maggots.
PROCEDURE
Uncovered jars
Controlled Variables:
jars, type of meat,
location, temperature,
time
Covered jars
Several
days pass
Manipulated Variables:
gauze covering that
keeps flies away from
meat
Responding Variable:
whether maggots
Maggots appear
appear
No maggots appear
CONCLUSION: Maggots form only when flies come in contact with meat.
Spontaneous generation of maggots did not occur.
b. Spallanzani – boiled two
flasks of broth, covered one
only uncovered had
microorganisms in it
Spallanzani’s Experiment:
Gravy is boiled.
Flask is
open.
Gravy is teeming
with microorganisms.
Gravy is boiled.
Flask is
sealed.
Gravy is free of
microorganisms.
c. Pasteur – boiled broth in
curved-neck flask
air gets in but microorganisms
trapped in curve of neck;
none in broth
Pasteur’s Experiment
Broth is boiled.
Broth is free of
microorganisms
for a year.
Curved neck
is removed.
Broth is
teeming with
microorganisms.
Earth’s Early History
• Earth formed 4.6 billion
years ago (bya)
•
st
1
prokaryotes formed ~2 bya
•
st
1
eukaryotes formed ~1.5 bya
Geologic Timeline
* Divides history of life into
significant time periods
Eras: Precambrian,
Paleozoic, Mesozoic,
Cenozoic (present)
Periods: subdivisions of
eras (12)
The Fossil Record
Chapter 17-1
I. Fossils
A. Paleontologists study
and date fossils to create
a fossil record
B. Fossil record- evidence
of the history of life on
earth
II. Fossil Formation
A. Fossil-
any remains of
an organism that has
been preserved.
B. Most fossils are found
in sedimentary rock
Buried by layers of
sediment which forms
new rock
Quality can vary
III. Fossil Dating
A. Two methods- Relative
dating & radioactive
dating
1. Relative Dating- age
of fossil is determined
by the layer of rock it
was found in
Index fossils are
used to estimate
age.
2. Radioactive datingmethod to determine
absolute age of fossil.
measures age by
amount of radioactive
elements; i.e. Carbon-14
and Potassium-40
Half-life
= finds age of
sample by measuring
time for ½ radioactive
element to decay.
Radioactive problem
Half
life of Radium-226 is
1600 years. What is the
age of a fossil containing
1/32 the original amount
of Radium-226?
8,000 years old
Early Earth
Chapter 17-2
I. Primitive Earth’s Atmosphere:
1. Carbon Monoxide (CO)
2. Hydrogen sulfide (H2S)
3. Hydrogen cyanide (HCN)
4. Nitrogen gas (N2)
5. Water vapor (H2O)
* No Oxygen (O2)!!
II. Earth’s Conditions
a. Hot! Hot! Hot!
Hit
by asteroids and
comets, & many volcano
eruptions
III.First Macromolecules of Life
a. Hot temperature combined
gases in atmosphere = simple
organic compounds
b. AFTER ~ 1 b.y. Earth
cooled & H2O vapor turned
into liquid - organic compounds
collected in lakes/seas
c. Lightning & UV radiation
charged chemical reactions
to make macromolecules
-nucleic acids
-proteins
-carbohydrates
-lipids
d. Evidence?
Miller & Urey created
“early atm.” conditions
in lab &
macromolecules
formed