1. The History of Life

2. What is Biogenesis?
Biogenesis states that all living things come from other living things
spontaneous generation
Before the 1600’s
A process in which something arises from nothing

3. What Caused the Downfall of Spontaneous Generation?
Redi’s Experiment
It was widely accepted that flies spontaneously generated from rotting meat.
Francesco Redi studied the developmental forms of flies
He saw that maggots were often found places after adult flies had previously landed
He noted that maggots ultimately led to the development of adult flies

4. What Caused the Downfall of Spontaneous Generation?
In 1668 Redi conducted an experiment to prove that maggots could only come from adult flies, and not rotting meat
Maggots Appear
Uncovered Jars
Covered Jars
No Maggots Appear
His results showed that files only came from eggs, in opposition to the idea of spontaneous generation

5. What Caused the Downfall of Spontaneous Generation?
Spallanzani’s Experiment
1700s, Lazzaro Spallanzani tested spontaneous generation of microorganisms
He boiled one flask of meat broth and immediately sealed it after boiling
He boiled another flask of meat broth and let it sit out unsealed
Sealed flasks remained clear
Unsealed flasks became cloudy from microorganisms

6. What Caused the Downfall of Spontaneous Generation?
Broth is boiled.
Flask is
sealed.
open.
Broth becomes cloudy
with microorganisms.
Broth is free of
microorganisms.

7. What Caused the Downfall of Spontaneous Generation?
Pasteur’s Experiment
Louis Pasteur set out to confirm that spontaneous generation is not possible in the mid-1800s
Pasture conducted a similar experiment to Spallanzani
instead of sealing the flask shut, he made a curved-neck flask that allowed air in, but kept microorganisms out
After boiling, the broth remained clear for a year
He broke the neck off of his flask, and the broth became contaminated with microorganisms
The led to the downfall of spontaneous generation, and the acceptance of biogenesis

8. What Caused the Downfall of Spontaneous Generation?
Broth is boiled.
Broth is free of
microorganisms
for a year.
Curved neck
is removed.
Broth is
teeming with microorganisms.

9. Earth’s History

10. What was Earth’s Early History?
The Formation of the Earth
The estimated age of the Earth is over 4 billion years old
Radiometric dating allowed scientists to determine the age of the Earth
Isotopes
atoms of an element with a different number of neutrons
Mass number of an isotope
the total number of protons and neutrons for an atom

11. What was Earth’s Early History?
Some isotopes have unstable nuclei that undergo radioactive decay
Half-Life
The length of time that it takes for one-half of any size sample of an isotope to decay
The age of a material can be determined by measuring the amount of a particular radioactive isotope it contains
Carbon-14 is a radioactive isotope of carbon. Scientists can compare the amount of carbon-14 found in a sample to the amount of carbon-12 (which is not radioactive) to determine the sample’s age
To determine the age of the Earth, scientists use the decay of uranium and thorium isotopes found in rock crystals

12. Radioactive Decay

13. What Were the First Organic Compounds?
All of the elements found in organic compounds are believed to have existed on Earth and in the rest of the solar system when Earth was formed
How did they form the organic compounds found in life?

14. What Were the First Organic Compounds?
Simple Organic Molecule Formation
“The Primordial Soup Hypothesis”
Alexander Oparin thought that Earth’s early atmosphere was VERY different than it is today
He believed it was made of ammonia, hydrogen gas, water vapor and compounds made of carbon and hydrogen
He believed these gases could have produced the first organic compounds in the early oceans

15. What Were the First Organic Compounds?
UV light from the sun, and energy from lightening could have been the energy sources needed to fuel these reactions
As the Earth cooled, and water vapor condensed to form lakes and seas, the organic compounds could be found in the water
Over time, the organic compounds could have undergone chemical reactions (fueled by lightening and UV radiation) to form biological macromolecules

16. What Were the First Organic Compounds?
Stanley Miller and Harold Urey
1953
Used Oparin’s hypotheses to conduct experiments that resulted in the production of organic compounds
Recently, is has been suggested that Earth’s atmosphere was made of CO2, water vapor and N2 gas
These conditions would not allow for the production of organic compounds
Some hypothesize that areas found by undersea hot springs may have produced organic compounds
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17. Miller and Urey Mixture of gases simulating atmospheres of early Earth
Spark simulating lightning storms
Condensation chamber
Cold water cools chamber, causing droplets to form
Water vapor
Liquid containing amino acids and other organic compounds

18. How Were the First Cells Formed?
From Molecules to Cell-like Structures
Cell-like structures that may have led to the first cells
Microspheres
made of many protein molecules in a membrane
Coacervates
collections of droplets that are made of molecules like amino acids and sugars
Both of these form spontaneously in certain kinds of solutions.
Microspheres can bud to form smaller microspheres, while cocervates can grow
These cell-like structures are NOT alive and also lack hereditary characteristics
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19. The First Life-Forms

20. What Were the First Life Forms?
The origin of Heredity
The first molecule that held hereditary information may have been RNA rather than DNA.
serve as a template for protein assembly
some RNA molecules can act as self-replicating enzymes
called ribozymes.

21. What Were the First Life Forms?
The First Prokaryotes
When the first organisms arose, there was no oxygen, which means they were anaerobic
It is believed that the first prokaryotic cells were heterotrophs
feeding on organic molecules
This resulted in the need for autotrophic organisms

22. What Were the First Life Forms?
Chemosynthesis
no oxygen
the first autotrophic cells did not use photosynthesis
These cells used chemosynthesis to produced food
CO2 is used as the carbon source
The energy comes from inorganic substances like sulfur
Archea are prokaryotic cells living today in harsh environments that used chemosynthesis

23. What Were the First Life Forms?
Photosynthesis & Aerobic Respiration
Photosynthetic organisms such as cyanobacteria
produced O2 as a byproduct of photosynthesis
Since O2 could damage enzymes essential for life, organisms developed a way to bond O2 to other compounds to prevent damage
Scientists believe this was one of the first steps in aerobic respiration
It took a billion years for the O2 levels to reach where they are today
As the O2 reached the upper levels of the atmosphere, it reacted with the UV radiation from the sun forming the ozone

24. What is Endosymbiotic Theory?
The First Eukaryotes
Eukaryotes developed from endosymbiosis
a mutual relationship between two prokaryotic cells
A small, aerobic prokaryote entered a larger prokaryote and was able to live and reproduce
modern day mitochondria
There was a second, successful invasion in which a small, photosynthetic cell was able to live and reproduce in a larger prokaryote
chloroplasts

25. What is Endosymbiotic Theory?
Chloroplast
Plants and plantlike protists
Aerobic bacteria
Ancient Prokaryotes
Nuclear envelope evolving
Photosynthetic bacteria
Primitive Photosynthetic Eukaryote
Animals, fungi, and non-plantlike protists
Ancient Anaerobic Prokaryote
Primitive Aerobic Eukaryote

26. What is Endosymbiotic Theory?
Evidence for Endosymbiont Theory
Mitochondria and chloroplasts have their own DNA
Their DNA is circular, similar to prokaryotic DNA
Mitochondria and chloroplasts have ribosomes similar to prokaryotic cells
Mitochondria and chloroplasts reproduce by binary fission, independent from the rest of the cell