Fossil Evidence of Change Land Environments The History of Life Section 1 Earth formed about 4.6...
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Fossil Evidence of Change Land Environments The History of Life Section 1 Earth formed about 4.6 billion years ago. Gravity pulled the densest elements to the center of the planet. The planet began to cool after about 500 million years. A solid crust formed on the surface. Water vapor condensed and formed the oceans. Most scientists believe life began in the oceans
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Transcript of Fossil Evidence of Change Land Environments The History of Life Section 1 Earth formed about 4.6...
Fossil Evidence of Change
Land Environments
The History of LifeSection 1
Earth formed about 4.6 billion years ago. Gravity pulled the densest elements to the
center of the planet. The planet began to cool after about 500
million years. A solid crust formed on the surface. Water vapor condensed and formed the
oceans. Most scientists believe life began in the
oceans
Fossil Evidence of Change
Atmosphere
The History of Life
The gases that likely made up the atmosphere are those that were expelled by volcanoes. Water vapor, Carbon dioxide, Sulfur dioxide,
Carbon monoxide, Hydrogen sulfide, Hydrogen cyanide, Nitrogen, and Hydrogen
NO Oxygen (O2)
Section 1
Uses the decay of radioactive isotopes to measure the age of a rock
Radioactive dating is the method used to determine the age of the earth and of fossils.
Radiometric Dating
The History of Life
Fossil Evidence of Change
Section 1
Clues in Rocks
The History of Life
A fossil is any preserved evidence of an organism. Examples of fossils include bones, shells,
and impressions of dead organisms left in rocks.
Most organisms decompose before they have a chance to become fossilized.
Fossil Evidence of Change
Section 1
Fossil Formation
The History of Life
Nearly all fossils are formed in sedimentary rock.
The sediments build up until they cover the organism’s remains.
Minerals replace the organic matter or fill the empty pore spaces of the organism.
Fossil Evidence of Change
Section 1
Dating fossils
The History of Life
Relative dating is a method used to determine the age of rocks by comparing them with those in other layers.
Fossil Evidence of Change
Section 1
The History of LifeSection 1
Plate tectonics describes the movement of several large plates that make up the surface of Earth.
These plates, some of which contain continents, move atop a partially molten layer of rock underneath them.
The History of Life
Fossil Evidence of Change
Section 1
The History of LifeSection 1
The Origin of Life
Origins: Early Ideas
The History of Life
Spontaneous generation is the idea that life arises from nonlife.
Francesco Redi, an Italian scientist, disproved the idea that flies arose spontaneously from rotting meat.
Section 2
The theory of biogenesis states that only living organisms can produce other living organisms.
Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms.
The History of Life
The Origin of Life
Section 2
Simple Organic Molecule Formation
The History of Life
Life may have began at the surface of the ocean where UV light from the Sun and lightning were the primary energy sources.
Many scientists believe life began at the depths of the ocean where geothermal vents provided the energy for organic molecule formation.
The Origin of Life
Section 2
The Primordial Soup Model
The History of Life
In the 1920’s Oparin and Haldane both suggested that the early Earth’s oceans contained large amounts of organic molecules. This hypothesis became known as the
primordial soup model. In 1953, the primordial soup model was tested
by Miller and Urey.
The Origin of Life
Section 2
Stanley Miller and Harold Urey were the first to show that simple organic molecules could be made from inorganic compounds.
Later, scientists found that hydrogen cyanide could be formed from even simpler molecules in simulated early Earth environments.
The History of Life
The Origin of Life
Section 2
The Bubble Model
The History of Life
In 1986, the geophysicist Louis Lerman suggested that the key processes that formed the chemicals needed for life took place within bubbles on the ocean’s surface.
The Origin of Life
Section 2
The Bubble Model
The History of Life
The Origin of Life
Section 2
The History of LifeSection 2
Genetic Code
The History of Life
Some RNA sequences appear to have changed very little through time.
Many biologists consider RNA to have been life’s first coding system.
Other researchers have proposed that clay crystals could have provided an initial template for RNA replication.
The Origin of Life
Section 2
Cellular Evolution
The History of Life
Scientists hypothesize that the first cells were prokaryotes.
Many scientists think that modern prokaryotes called Archaea are the closest relatives of Earth’s first cells.
The Origin of Life
Section 2
Photosynthesizing Prokaryotes
The History of Life
Fossil evidence of cyanobacteria has been found in rocks as old as 3.5 billion years.
Cyanobacteria eventually produced enough oxygen to support the formation of the ozone layer. Ozone blocks the sun’s UV rays
With oxygen and the ozone layer in the atmosphere, life could migrate onto land.
The Origin of Life
Section 2
The Endosymbiotic Theory
The History of Life
The ancestors of eukaryotic cells lived in association with prokaryotic cells. It has been suggested that a large prokaryote
engulfed a smaller one, which continued to live and provide energy to the larger prokaryote
The relationship between the cells became mutually beneficial, and the prokaryotic symbionts became organelles in eukaryotic cells.
This theory explains the origin of chloroplasts and mitochondria.
The Origin of Life
Section 2
The History of Life
The Origin of Life
Section 2
The History of LifeSection 2
