The Origin and Evolution of Earth - Chapter 2 Geography NCERT Class 11

Summary

This educational video delves into the formation and evolution of Earth, exploring both early and modern theories. It discusses the universe's expansion, the formation of stars and planets through accretion and gravitational forces, and the solar system's structure. The video also covers the Earth's layered structure, the evolution of its atmosphere and hydrosphere, and the origin of life. It highlights the significance of photosynthesis in creating Earth's oxygen-rich atmosphere and the geological timeline that traces life's development from simple organisms to complex life forms.

Takeaways

• 🌏 The Earth's formation and evolution are central to understanding its origin and the physical changes it underwent over time.
• 🌌 Two main theories exist for the origin of Earth: early and modern, with separate videos explaining each theory in detail.
• 📈 The universe is expanding, with an increase in space between galaxies, and our solar system is part of the Milky Way galaxy.
• 🌌 Stars were formed around 5 to 6 billion years ago, prior to the formation of planets, through the process of fusion where hydrogen and helium atoms combine, releasing energy.
• 🌍 Planets formed from localized lumps of gases that, due to gravitational force, created a core and a rotating disk of gas and dust, eventually leading to the formation of planets.
• 🌐 The solar system consists of the Sun, eight planets, moons, asteroids, comets, and other celestial bodies, with terrestrial planets being closer to the Sun and Jovian planets further away.
• 🌘 The difference between terrestrial and Jovian planets lies in their composition and proximity to the Sun, with terrestrial planets being rocky and Jovian planets being gas giants.
• 🌕 The Moon, Earth's only natural satellite, is believed to have formed from a giant impact, where a Mars-sized object collided with Earth, ejecting debris that coalesced into the Moon.
• 🌋 The Earth's layered structure, including the crust, mantle, outer core, and inner core, resulted from the process of accretion and the separation of materials based on density.
• 🌬️ The evolution of Earth's atmosphere and hydrosphere involved stages such as the primordial atmosphere, volcanic activity releasing gases, and the formation of oceans, which allowed life to evolve.
• 🌱 The origin of life on Earth is attributed to complex chemical reactions that led to the formation of organic molecules capable of self-replication, eventually giving rise to all life forms.

Q & A

What are the two theories about the origin of Earth mentioned in the video?

The two theories about the origin of Earth mentioned are the early and modern theories. The video creator has made separate videos on both, which are linked in the description for further understanding.

What is the significance of the universe's expansion in relation to galaxies?

The expansion of the universe refers to the increase in space between galaxies. It's important to remember that a universe consists of more than one galaxy, and each galaxy contains moons, asteroids, planets, and stars. The solar system we are part of is one such galaxy, and the Milky Way is the name of our galaxy.

How long ago are stars believed to have been formed, and how does this relate to the age of Earth?

Stars are believed to have been formed about 5 to 6 billion years ago. Since Earth is estimated to be 4.6 billion years old, it's clear that stars were present before the formation of planets.

What is the process called where two light nuclei combine together, releasing a vast amount of energy?

The process where two light nuclei combine together, releasing a vast amount of energy, is called fusion reaction.

Can you explain the formation of a core in a gas cloud as described in the video?

The formation of a core in a gas cloud is described using the example of spinning a bucket of water with sand in it. The sand particles gather at the center due to the centrifugal force, similar to how the core of a gas cloud forms due to gravitational forces within the cloud.

What is the difference between terrestrial and Jovian planets?

Terrestrial planets are those that lie between the Sun and the asteroid belt, composed mainly of rock and metal. Jovian or gas giant planets are those outside the asteroid belt and are characterized by their thick atmospheres of helium and hydrogen.

Why does the Earth's atmosphere contain mostly nitrogen and oxygen?

The Earth's atmosphere contains mostly nitrogen (about 78%) and oxygen (about 20-21%) due to a series of evolutionary stages, including the initial composition after the formation of the Earth, the effects of volcanic activity and degassing, and the introduction of oxygen through photosynthesis by early life forms.

How were the Earth's oceans formed according to the video?

The Earth's oceans were formed as the planet cooled down, releasing gases and water vapor from its interior. Volcanic eruptions contributed to the continuous release of water vapor, which condensed and rained down, collecting in depressions to form oceans.

What is the 'Big Splat' theory mentioned in the video regarding the Moon's formation?

The 'Big Splat' theory suggests that the Moon was formed as a result of a giant impact, where a Mars-sized object collided with the Earth. The debris from this collision eventually coalesced due to gravitational attraction to form the Moon.

How does the video explain the origin of life on Earth?

The video explains that the origin of life on Earth is attributed to complex chemical reactions that generated complex organic molecules. These molecules were capable of duplicating themselves, leading to the formation of living organisms from inanimate matter.

Outlines

00:00

🌏 Origin and Evolution of Earth

This paragraph introduces Chapter 2, which discusses the formation and evolution of Earth. It mentions two theories regarding Earth's origin: early and modern, with separate videos provided for further understanding. The script explains the expansion of the universe and the structure of galaxies, including our own Milky Way. It also delves into the formation of stars around 5 to 6 billion years ago, which is prior to the formation of Earth, estimated at 4.6 billion years old. The process of star formation involves the fusion of hydrogen and helium atoms, releasing energy. The video also covers the measurement of light and the stages of planet formation, including the aggregation of gas clouds into cores and the eventual development into planets through accretion.

05:01

🚀 Formation of Solar System and Planets

Paragraph 2 elaborates on the formation of the solar system, starting with the nebula core around 5 to 5.6 billion years ago, leading to the formation of planets 4.6 billion years ago. The solar system is composed of the Sun, eight planets, moons, asteroids, comets, and other celestial bodies. Inner planets (Mercury, Venus, Earth, Mars) are distinguished from outer planets (Jupiter, Saturn, Uranus, Neptune), with the latter also known as Jovian or gas giant planets. The paragraph explains the difference between terrestrial and Jovian planets based on their composition and proximity to the Sun. It also touches on the theory of moon formation, suggesting that the current scientific consensus is that the Moon was formed from debris after a large body the size of Mars collided with Earth, known as the Giant Impact Theory or Big Splat.

10:02

🌋 Earth's Layered Structure and Evolution

Paragraph 3 discusses the evolution of Earth from a hot, rocky object with a thin atmosphere to its current state. It highlights the layered structure of Earth, including the crust, mantle, outer core, and inner core. The process of accretion, which led to the formation of Earth's layers, is explained, along with the role of temperature and density in material separation. The paragraph also covers the formation of the Moon and its impact on Earth's evolution, including the Giant Impact event. Additionally, it provides an overview of the lithosphere, which includes the crust and mantle, and how the Earth's early volatile state led to constant changes and the eventual formation of a crust.

15:04

🌤️ Evolution of Atmosphere and Hydrosphere

This paragraph details the evolution of Earth's atmosphere and hydrosphere. It describes the initial atmosphere composed mainly of hydrogen and helium, which was later lost due to solar winds. The current atmosphere's composition, dominated by nitrogen and oxygen, is a result of three stages: the premod atmosphere from the supernova explosion, the thermal radiation from Earth's hot interior, and the photosynthesis process by early life forms. The paragraph also explains the process of degassing, where gases and water vapor were released as Earth cooled, leading to the formation of oceans. The oceans are estimated to be around 4 billion years old, and their formation marked the beginning of life on Earth, which evolved in the oceans before spreading to land.

20:04

🌱 Origin of Life and Geological Time Scale

Paragraph 5 explores the origin of life on Earth, suggesting it began as complex chemical reactions that led to the formation of organic molecules capable of self-replication. These molecules transformed inanimate matter into living organisms. The paragraph connects the presence of fossils in rocks to the early life forms, such as blue algae, indicating life evolved around 3.8 billion years ago. It mentions the geological time scale, which charts the major events in the history of life on Earth, and how it shows the transition from unicellular bacteria to modern humans. The speaker expresses fascination with these processes and considers creating additional content to delve deeper into these topics.

Keywords

💡Origin of Earth

The 'Origin of Earth' refers to the formation of our planet, which is a fundamental aspect of understanding Earth's history. In the video, it is mentioned as the starting point for discussing Earth's evolution, highlighting the importance of knowing how our planet came into existence. The script discusses both early and modern theories of Earth's origin, suggesting a comprehensive exploration of the subject.

💡Evolution

Evolution, in the context of the video, refers to the physical changes that Earth underwent over time. It is central to the video's theme as it helps viewers understand how Earth transformed from its initial state to what it is today. The script mentions the evolution of Earth's atmosphere, hydrosphere, and life, illustrating the dynamic nature of our planet's development.

💡Universe Expansion

The 'Universe Expansion' is a concept that describes the increase in space between galaxies. It is relevant to the video's theme as it sets the stage for discussing the broader cosmic context in which Earth's formation and evolution took place. The script emphasizes that the universe consists of multiple galaxies, each with its own celestial bodies, providing a backdrop for Earth's story.

💡Formation of Stars

The 'Formation of Stars' is a key concept in the video that explains how stars, including our Sun, came into existence. It is crucial for understanding the video's narrative as stars are the birthplaces of solar systems, including ours. The script describes the process of star formation through the fusion of hydrogen and helium atoms, which is a fundamental aspect of cosmic evolution.

💡Accretion

Accretion is the process by which celestial bodies grow by accumulating mass, layer by layer. In the video, this term is used to describe how Earth and other planets formed from smaller bodies. It is a critical concept for understanding the physical development of Earth, as it explains the transition from a collection of smaller bodies to a single, cohesive planet.

💡Terrestrial Planets

Terrestrial planets are those that are composed mainly of rock and metal, and are located between the Sun and the asteroid belt. The video uses this term to differentiate between the inner planets, which have Earth-like compositions, and the outer, gas giant planets. This distinction is important for understanding the diversity of planets within our solar system and their unique characteristics.

💡Jovian Planets

Jovian planets, also known as gas giants, are large planets with thick atmospheres primarily composed of hydrogen and helium. The video contrasts these with terrestrial planets to highlight the differences in composition and characteristics among the planets in our solar system. Understanding Jovian planets is essential for grasping the variety of celestial bodies that exist.

💡Moon Formation

The 'Moon Formation' theory discussed in the video suggests that the Moon was created as a result of a giant impact between Earth and another celestial body. This concept is significant for understanding Earth's natural satellite and its influence on our planet. The script mentions the 'Big Splat' theory, which is a widely accepted explanation for the Moon's origin.

💡Atmosphere Evolution

The 'Atmosphere Evolution' refers to the changes in Earth's atmospheric composition over time. This is a key aspect of the video's theme as it discusses how the early atmosphere, rich in hydrogen and helium, transformed into the current atmosphere with a higher concentration of nitrogen and oxygen. Understanding this evolution is crucial for appreciating the development of life-supporting conditions on Earth.

💡Origin of Life

The 'Origin of Life' is a central topic in the video that explores how life began on Earth. It is presented as the culmination of Earth's evolution, with complex chemical reactions leading to the formation of organic molecules capable of self-replication. This concept is essential for understanding the emergence of living organisms and the development of biodiversity on our planet.

Highlights

The chapter discusses the origin and evolution of Earth, including its formation and physical changes over time.

Two main theories on the origin of Earth are presented: early and modern theories, with separate videos provided for further understanding.

The universe is expanding, with an increase in space between galaxies, and our solar system is part of the Milky Way galaxy.

Stars are believed to have formed around 5 to 6 billion years ago, prior to the formation of planets like Earth.

Matter and energy in the universe were unevenly distributed, leading to the formation of hydrogen and helium atoms through fusion reactions.

The formation of planets involves stages such as core formation, gas cloud condensation, and the development of planetesimals into planets.

Our solar system consists of the Sun, eight planets, moons, asteroids, comets, and other celestial bodies.

The terrestrial planets (Mercury, Venus, Earth, Mars) are rocky and metallic, while Jovian planets (like Jupiter) are gas giants.

The Moon is Earth's only natural satellite, and its formation is believed to be the result of a giant impact.

Earth's early atmosphere was different from today's, consisting mainly of hydrogen and helium.

The evolution of Earth's atmosphere involved stages including the primordial atmosphere, volcanic outgassing, and the addition of oxygen through photosynthesis.

The oceans on Earth formed around 500 million years after the planet's formation, providing a habitat for the earliest life forms.

Life on Earth is thought to have originated from complex chemical reactions that led to self-replicating organic molecules.

The geological timescale provides a framework for understanding the major events in the evolution of life on Earth.

The chapter concludes by emphasizing the importance of understanding the origin and evolution of life as a crucial part of Earth's history.

Transcripts

this video is about chapter 2 the origin

and evolution of Earth in this chapter

we will read about the story of the

origin that is the formation of Earth

and evolution that is how Earth evolved

over time meaning what were the physical

changes that the Earth went through now

the origin of Earth has two theories

basically the early and modern theories

I've made separate videos on both the

theories I'll be posting the link in the

description as well as you can click on

the link here on the screen so watch

that video and you will understand these

theories well the expansion of universe

means increase in space between the

galaxies always remember this order a

universe consists of more than one

Galaxy and one Galaxy consists of moons

asteroids planets and stars so the solar

system that we are part of is one Galaxy

like that there are many other galaxies

and the name of a galaxy is Milky Way

though we know there are many other

galaxies but we do not know whether

there is another universe so the

scientific Community only believes in

the theory that the universe is

expanding

now we will read about how the stars

were formed now the formation of stars

is believed to have taken place some 5

to six billion years ago Earth is

believed to be 4.6 billions years old so

clearly stars were there before the

planets previously we spoke about how

matter and energy was scattered in the

universe due to the big explosion of the

singular atom one thing to know is that

the matter and energy were uneven

meaning there were differences in the

densities in every matter because of

that there was attraction between these

matters and that's how hydrogen and

helium atoms were formed basically

hydrogen and helium are a gas like this

there are many tiny groups of hydrogen

and helium gases constantly colliding

with each other and producing energy

this process is also called as fusion

reaction where two light nuclei combined

together releasing vast amount of energy

and this energy gave rise to formation

of stars let's quickly understand how to

measure a light here again I've made a

separate video on this topic as well the

link is there in the description you can

also click on The annotation on the

screen so follow the link and watch the

video now we are going to talk about the

formation of planets now there are again

some stages in the development of

planets as well so let's go through them

so just moments back we have read that

stars are localized lump of gases now

the gravitational force within those

lump leads to the formation of a core to

the gas cloud and a huge rotating disc

of gas and dust envelopes around the gas

core

so let me just show it to you with the

help of an illustration because it's

very difficult to make you understand

with words so a good example to

illustrate this is uh take a bucket of

water a little water not much and put

some sand in it now spin the water in

that bucket in a circular fashion soon

you'll notice that so all the mud

particle that you had poured it will

come in the center and gather so that's

how it forms a core and the same thing

happens in these gas clouds inside a

star and then after a long time layers

of of layers starts forming and that's

how a rotating dis of gas is formed and

then in the next stage the gas cloud

starts getting condensed meaning it gets

very concentrated and due to this

phenomena the matters that are around

the core develops into small rounded

objects then again after time what

happens these small objects by the

process of cohesion meaning they form

group sort of a thing and develops into

what is called Planet decimal

so you see most of the things happen

because of collision and gravitational

attraction because of these phenomena

the materials stick together and that's

what makes these large number of small

bodies now in the final stage these

large number of small bodies they

accrete to form a few larger bodies so

the meaning of accrete is forming layer

after layer so these smaller bodies that

were formed due to Collision and

gravitational attraction with time what

happens is layers several layers are

formed on it as a result from a small

body it becomes a large body and that's

how planets are formed I hope you

understood somewhat how the planets are

formed if at all you did not follow up I

recommend that you go back a little bit

and watch it again because it can get

difficult to explain by using these

words that are given in the book so I'm

trying my best to use illustrations and

examples and you know refining the words

into simpler terms so just go back a

little bit and watch it again and I'm

sure you'll get get it now we're going

to read about our solar system so here

it says our solar system consists of

nine planets now this is a fairly old

book so as of now there are eight

planets in the solar system so that

means Pluto is no longer a planet and

the reason behind that is because it has

been classified as dwarf so the meaning

of dwarf planet is it is a round mass of

metal and rock or gas moving around the

Sun that is not large enough to be

considered as as a planet okay some of

the 12w planet in our solar system

includes Pluto then we have series and

Aries so as I've told you before that

everything right from planets and stars

and everything has been formed out of

this Cloud called nebula so the core

formation of this nebula started

somewhat around 5 to 5.6 billion years

ago and the planets were formed about

4.6 billion years ago so clearly it

means that stars were there before

planets now don't forget this just

remember this our solar system consists

of sun that is the star sun is a star

basically and then we have eight planets

then 63 moons then millions of smaller

bodies like asteroids and comets and

huge quantity of dust grains and gases

and if you see it is because of these

two last terms that is dust grains and

gases there are new stars and planets

that are coming up so there's always a

new discovery by NASA about all these

planets and stars so out of the eight

planets Mercury Venus Earth and Mars are

called as the inner planet so if you

look at the solar system after Mars the

Jupiter planet comes and in between Mars

and Jupiter there is a big asteroid belt

so those planets which are out of

asteroid belt including Jupiter they are

known as outer planets and those which

are inside they are called inner planets

so these planets which are inside the

asteroid belt they are called as

terrestrial planets meaning they have

earthlike

similarities in other words they consist

of rock and metals and the planets that

are outside the asteroid belt they are

called Jovian or gas giant planets so

basically they are like Jupiter and they

are huge planets but they have very

thick atmosphere mostly of helium and

hydrogen and this is another cool fact

all the planets were formed in the same

period sometime about 4.6 billion years

ago so when we hear something like this

that all the planets were formed in the

same period it clearly proves the fact

that whatever phenomena that caused

these planets to exist is actually true

which is the Big Bang Theory the

universe being expanding whilea Theory

because just for argument sake had it

been the fact that all the planets came

into existence at their own time then it

would be difficult to argue that what

actually happened because there there's

going to be very different kind of data

of you know something happened because

of something else and then something

happened because of something else if

everything happens because of one reason

then it is easier to study and

understand I hope you're getting what

I'm trying to say now let's try to

understand what is the difference

between terrestrial and Jovian Planets

so let me quickly tell you this

terrestrial planets are those planets

which are in between the Sun and the

asteroid belt and the ones that are

outside the asteroid belt they are known

as Jovian planets or outer planets so as

we know that most of the testile planets

are full of rock and

so that means it has very less gas and

dust and if you look at the Jovian

Planets they have lot of gas present

dust and gas present so the theory goes

like this Newton realized that the

reason the planets orbit around the Sun

is related to why objects fall to earth

when we drop them the Sun's gravity

pulls on the planets just as Earth's

gravity pulls down anything that is not

held up by some other force and keeps

you and me on the ground so heavier the

objects produce a bigger gravitational

pull than lighter ones so as the heavy

weight in our solar system the sun is

the strongest gravitational pull now

with this Theory you know that the

terrestrial planets which are between

the Sun and asteroid belt they are

nearer to the Sun and because of that

they exert a lot of gravitational pull

and because they are nearer to the sun

meaning the heat of the sun blew away

all the gases and dust but then the

Jovian planets which are outside the

asteroid belt they are far away from the

Sun so the solar winds were not that

intense that's why these planets still

have a lot of gas and dust particles so

that's the reason between the inner

planets and the outer planets or in

other words the terrestrial planets and

the Jovian

Planets now we're going to talk about

the moon moon is the only natural

satellite of the earth meaning Moon just

revolves around the earth now there is a

theory behind how the moon was formed so

if you see a lot of the time we are

reading about theories in this chapter

so this chapter is full of theories so

let's understand the theory behind the

moon as well so in 1838 Sir George

Darwin he suggested that the Earth and

the moon they were combined okay they

were joined together like a dumble

shaped so if you have seen a dumble it

looks like this now what happened was it

eventually broke and the material that

was forming the Moon it got separated

from the earth and to support this

Theory Darwin went on to say that if you

look at the depression in the Pacific

Ocean so Pacific Ocean is the largest

ocean and the deepest ocean so the

depression that occupies the Pacific

Ocean that depression is due to the

separation of the Moon object from the

earth so this is the theory of George

Darwin now the present scientist they do

not accept this Theory what we now

believe is that the formation of moon as

a satellite of Earth is an outcome of

giant impact now this theory has another

name which is called the big Splat now

big splat that means Big Splash a giant

impact now what this Theory says is

there was an object of the size of Mars

so that object that body it collided

into the Earth sometime shortly after

the earth was formed so when two objects

Collide there are these debris so these

portions of small blasted material they

continue to orbit around the Earth and

due to gravitational attraction and

collision these small particles

eventually formed into the present Moon

so this theory is now widely accepted

about the origin of moon now we're going

to read about the evolution of the earth

so once upon a time the planet Earth was

a baring Rocky and hot object with a

thin atmosphere of hydrogen and helium

and today when we see a picture of the

Earth it does not look like that so

obviously there must have been some

events some processes which has caused

this change so let's go ahead and

understand what led to the evolution of

life on the surface of the planet

so we know that all the celestial body

were formed with a process called

accretion meaning a layer after layer

after layer that's how they became from

small body to a large body similarly

Earth is no different the Earth has a

layered structure so from the outermost

end of the atmosphere to the Center of

the Earth the material that exists is

not uniform meaning they are not same so

right from the outside of the earth as

we go towards the interior of the Earth

the density increases

that's why we also know that there are

five layers in atmosphere and then we

also know that the Earth's interior is

divided into four parts that is the

crust mantle outer core and inner core

and that's why in geography we also have

different disciplines to understand the

Earth we have the lithosphere then we

have the study of atmosphere hydrosphere

so they have been nicely categorized in

different subjects so that we can read

about Earth in a much more better sense

now we are going to read about

lithosphere when we hear the word

lithosphere it it means the outer layer

of the Earth consisting of crust and

mantle so initially the Earth was in a

volatile State meaning there was

constant change taking place everything

was going through Rapid change so all

the particles that were involved in the

creation of Earth their densities were

increasing as well there was so much

Collision taking place and energy was

increasing as a result temperature was

also increasing rapidly in chemistry if

you want to extract or refine any metal

you need to put the metal in a furnace

where the temperature is extremely high

the idea is to turn the metal into a

molten state so that the properties of

the metal get separated similar thing

happened here as well when the

temperature was so high all the

materials started getting separated

depending on their densities heavy

materials like iron started sinking

towards the center of the earth forming

the coal and the lighter ones moved

towards the surface with time the

temperature cooled and the outer layer

in the form of a crust was formed and

then there was another big impact that

is the cre creation of moon which we

also call the giant impact even that

further heated the Earth and that's how

materials got separated into different

layers we know Earth has four layers

like the crust mantle outer core and

inner core always remember from the

crust to the core the density of the

material increases in the coming

chapters we will discuss about the

properties of each of the Earth's layer

now we're going to read about the

evolution of atmosphere and hydrosphere

so in the Earth's atmosphere you will

mostly find nitrogen and oxygen nitrogen

consists of some 78% of the entire air

and 20% or 21% is oxygen there is a

separate chapter that is chapter 8 which

deals with the composition and structure

of Earth's atmosphere so we will read in

depth about all these things in that

chapter so there are three stages in the

evolution of the present atmosphere it

is because of these three stages the

present atmosphere came into being so in

the premod atmosphere the Sun and its

planet formed about 5 billion years ago

where there was an explosion of a

supernova which is a big star so that

before bursting had generated heavy

elements starting from hydrogen and

helium so that was the first stage of

the present atmosphere I mean to say

atmosphere initially looked like that

and then comes the second stage we have

read that the Earth was a very volatile

object there were constant changes rapid

development was going on and the

temperature was so high that the

interior of the Earth was super hot so

when an object is super hot it will emit

heat which is also called as thermal

radiation so we have to say that these

thermal radiation they will also

contribute to the evolution of the

atmosphere so every single aspect

together contributed towards present

atmosphere that's why we have to count

every single thing and now comes the

final stage that is the third stage

today when human beings and living

organism came into existence in this

world there was a process called photo

synthesis so photosynthesis is a

chemical process through which plants

some bacteria and algae produce glucose

and oxygen from carbon dioxide and water

using only light as a source of energy

before even humans arrived on this

planet There Were Trees plants and all

sorts of grasses and Etc so we can say

that the process of photosynthesis has

already begun before the humans arrived

and we know that plants take carbon

dioxide and emits oxygen so again there

is a emission of oxygen involved and

that is the final and the third stage of

the composition of present atmosphere

always remember the premod atmosphere

which is the initial atmosphere when the

Earth was beginning to form that

atmosphere consisted only of hydrogen

and helium so that atmosphere went away

and the reason behind that is because it

is not just Earth all the terrestrial

planets so we have spoken about what the

terrestrial planets are these are the

planets that are in between Sun and and

the asteroid belt so basically there are

only four planets Mercury Venus Earth

and Mars now these planets the

terrestrial planets since they are

closer to the Sun these planets received

a lot of solar wind coming from the Sun

it stripped off the hydrogen and helium

atmosphere and that's why these planets

don't look like the jovial planets the

planets which are outside the asteroid

belt and finally when the Earth was

cooling down the gases and the water

vapor they were released from the

interior of Earth now this thing is very

easy to imagine whenever you're trying

to boil water in an utensil at your

place you will see that if you put a

cover on it or if you put some kind of a

plate on it you'll see that the plate

will gather all the water vapor so the

similar thing happened when the Earth

was cooling down all the heat was

released upward and in the atmosphere

the water vapor was collected and that

is how the present atmosphere started

the early atmosphere largely contained

water vapor nitrogen carbon dioxide

methane ammonia and very little of free

oxygen so the process through which the

gases were outpoured from the interior

is called degassing now you must be

wondering that okay the gases were

degased so how did it still continue to

form water vapor and the answer to that

question is the continuous volcanic

eruption so volcanoes are like a

ventilator of the earth so from these

ventilators the inner core the heated

substance of the earth starts pouring

out and again if there is a a substance

which has a high temperature there will

be heat and because of this continuous

volcanic eruption there was a lot of

water vapor and gases generated and as

these water vapor were released they

started getting condensed and then the

carbon dioxide in the atmosphere got

dissolved in rain water and the

temperature further decreased causing

more condensation and rain and then once

rain started happening the rain water

falling onto the surface got collected

in the depression to give rise to oceans

and that's how the ocean iodes of the

earth were formed so these Earth's ocean

were formed within 500 million years

from the formation of the earth now that

tells us that the oceans are as old as

4,000 million years and then once the

oceans were formed life began to evolve

and if you notice bacteria were among

the first life forms to appear on Earth

and if you see humidity is perfect for

any bacterial growth and humidity is

formed due to heat and water hence it is

obvious that once the oceans were formed

L life began to evolve and once life

began to evolve the process of

photosynthesis also started so for a

very long time life was confined to the

oceans that means there was no presence

of life on a land form it was only

confined to Ocean because ocean had the

perfect combination of oxygen through

the process of

photosynthesis and eventually this big

ocean was saturated with oxygen and

after that oxygen began to flood to the

atmosphere and that's how oxygen contain

started increasing in the atmosphere now

comes the last topic of this chapter the

origin of life because once the earth

was formed it is necessary to know about

the life on Earth otherwise the entire

big picture is incomplete that's why the

origin and evolution of life is regarded

as the last phase in the evolution of

Earth so far after reading all of this

we are clear about the fact that

initially it was impossible to live on

Earth because the conditions were not

ideal you know Earth was w vertile it

was super hot there was very little

oxygen so all these things were going on

hence the modern scientist they think

that the origin of life is due to the

complex chemical reaction that generated

complex organic molecules and because of

their assembly we came into present and

this assembly of complex organic

molecules is such that it duplicates

themselves it is just like amoeba how it

splits into two equal copies of itself

similarly this organic molecule it

started copying itself and that got

converted into inanimate matter and that

converted some matters which were

lifeless which had no sign of life into

living organism so when you look at a

rock you'll find fossils in it fossils

are the dead decay of animals and plant

organism hence when we look at a rock

the record of life that existed on this

planet can be seen across different

periods so when you look at Blue algae

which is found in lakes and water bodies

and if you look at the microscopic

structure closely you will find that

these formations are present in rocks

that are much older and are some 300,000

million years ago and that is how we can

assume that life began to evolve

sometime 3,800 million years ago and if

you want to know how a unicellular

bacteria turned into a modern man then

you have to look at this geological time

scale so this geological time scale

shows some life major events and it is

very fascinating to see how this thing

happened it is almost like a magic but

there's a huge deep science involved and

that is why it makes geography

interesting you know I'm so fascinated

to read all of this maybe I will make a

separate short videos on these smaller

Concepts as to how human came into

existence how Earth was formed how this

ocean were formed moon were formed Etc

anyways with this we have come to an end

of this chapter and this chapter has

been a real eye opener till now for me

and it's so interesting and fascinating

to read this I hope you understood

whatever that I told you though in

between it was kind of difficult for me

to comprehend because the words that

were used they were not very simple to

be able to convert them into a real

metaphor or a simpler example I hope you

found this video informative and let me

know what you think about this so as

usual question answers can be found on

the website so thanks for watching and

I'll see you in the next one if you

enjoy these videos and see a purpose

behind watching them please like the

video and comment down below until then

catch you guys later and talk to you

guys on the next one peace