BIO-240 FA5 Chapter Notes - Chapter 1.5-1.8: Heterotroph, Outer Core, Archaea

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1.5 How Were Earth and the Solar System Former?
Earth is the third of eight major planets that revolve around the Sun
Evidence shows the Sun and our solar system formed around 5 billion years ago from a
cloud of gas and space dust called a nebula
The Nebular Hypothesis
Nebular hypothesis says that our solar system formed from a cloud of hydrogen and
helium
These gases and dust particles began to contract under gravity, forming the sun
Small amounts of the nebular matter were left behind, forming the protoplanets that
would eventually turn into our planets and moons
Proto-Earth
Proto-Earth was larger than today’s Earth and had no oceans or life
It’s believed that the Moon was formed after a collision between Theia and proto-Earth
The sun condensed core became thermonuclear through thermonuclear fusion
Thermonuclear fusion is when hydrogen atoms becomes tens of millions degrees hot
and combine to form helium and release energy
The sun also releases wind through ionized particles
The protoplanets were gradually cooling, causing them to shrink in size
As they contract, they release radioactivity in their cores
Density and Density Stratification
Density is how heavy something is for its size
Density has nothing to do with thickness, but with its molecular packing
Once Earth became a ball of hot liquid rock, its density became stratified
The highest density materials (iron and nickel) were in the core, where lower density
(rock) formed around the core
Earth’s Internal Structure
Chemical Composition Versus Physical Properties
Earth’s inner structure can be divided by its chemical composition or its physical
properties
Chemical Composition
Earth consists of three layers: crust, mantle, core
Crust has an average depth of about 30 kilometers (20 miles) and is composed of low
density rock (there are two types of crust oceanic and continental)
Immediately below is the mantle, it extends to a depth of 2885 kilometers (1800 miles),
it's composed of high-density iron and magnesium silicate rock
Beneath, the core, its mass from 2885 kilometers (1800 miles) to the center of the Earth
at 6371 kilometers (3960 miles), it’s composed of higher-density metal (iron and nickel)
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Physical Properties
Earth is composed of five layers: inner core, outer core, mesosphere, asthenosphere,
lithosphere
The lithosphere is cool, it extends about 100 km (62 mi), it’s also brittle
The asthenosphere is plastic, which mean it will flow if force is applied, its 100 km (62
mi) to 700 km (430 mi)
The mesosphere expends to a depth of 2885 km (1800 mi)
The core has an outer core (liquid and flowing) and an inner core (rigid)
Near The Surface
Lithosphere
The lithosphere is cool and includes the crust and the top part of the mantle
The two act as a single unit, about 100 km thick
Oceanic versus Continental Crust
Oceanic crust underlies ocean basins and is composed of basalt
Basalt has a density of 3 grams per cubic centimeter
Average oceanic crust is about 8 km thick
Basalt originates as magma from underwater eruptions
Continental crust is made of granite (2.7 grams per cubic centimeter)
Average thickness of continental crust is about 35-60 km
Granite originates as magma that hardens in the Earth’s crust
Asthenosphere
The asthenosphere is hot and can flow with force
It has high viscosity, which means it has a high resistance to flowing
Isostatic Adjustment
Isostatic adjustment is the vertical movement of crust
Oceanic crust is denser, so it floats lower
Continental crust is less dense, so it floats higher
The most recent ice age has caused areas to arise, which is called isostatic rebound
1.6 How Were Earth’s Atmosphere and Oceans Formed?
Origin of Earth’s Atmosphere
Earth’s initial atmosphere came from leftover gases from the nebula
A second atmosphere came from inside Earth through outgassing, low density gases
rose to the surface and were expelled into Earth’s atmosphere
Atmospheric gases consist of: steam, carbon dioxide, hydrogen, and others
This atmosphere, however, was very different from ours today
Origin of Earth’s Oceans
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Document Summary

Earth is the third of eight major planets that revolve around the sun. Evidence shows the sun and our solar system formed around 5 billion years ago from a cloud of gas and space dust called a nebula. Nebular hypothesis says that our solar system formed from a cloud of hydrogen and helium. These gases and dust particles began to contract under gravity, forming the sun. Small amounts of the nebular matter were left behind, forming the protoplanets that would eventually turn into our planets and moons. It"s believed that the moon was formed after a collision between theia and proto-earth. Proto-earth was larger than today"s earth and had no oceans or life. The sun condensed core became thermonuclear through thermonuclear fusion. Thermonuclear fusion is when hydrogen atoms becomes tens of millions degrees hot and combine to form helium and release energy. The sun also releases wind through ionized particles.

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