Evolution of life
Story of life.
Charles Darwin.
Life.
Reproduction.
Adaptation.
Diversity of life.
Tree of life.
Geological time scale.
Hadean Eon.
Continents.
Land marks of life.
Prokaryotes.
Cynobacteria.
Eukaryotes.
Multicellular life.
Diversification of life.
Plants.
Animals.
Fish.
Tetrapods.
Amphibians.
Insects.
Reptiles.
Dinosaurs.
Birds.
Mammals.
Human beings.
Story of Life.
About 500 years back, all of mankind believed,
that the Earth was the centre of the Universe.
The Sun they believed revolved around the Earth.
They also believed that all the planets, even all the stars, revolved around the Earth.
Learned people, even drew scientific diagrams, to illustrate this, to the ignorant.
Copernicus, Galileo and other scientists, broke this illusion from which we suffered.
When we have a pattern of thinking, for generations, sometimes for centuries,
it is difficult to break the belief, that we hold on to.
But we eventually realised that the Earth, is not the centre of the Universe.
The Sun is at the centre of the solar system.
The Earth and the other planets, revolve around the Sun.
The Sun itself, is one of the stars, in the periphery of our galaxy, the Milky way.
Our galaxy, the Milky way, is one of the billions of galaxies, in the Universe.
This fact, was so dramatically different, from what was believed.
There is no wonder, that people did not believe it, at first.
In fact, Galileo was persecuted for propagating the Sun centric,
or heliocentric theory.
Of course, today we unquestioningly accept our position, in the Universe.
There is a interesting analogy, in the story of life.
About 200 years earlier, they believed that,
human beings are the centre, of all life.
This anthropogenic thinking persisted, since the dawn of civilisation,
till about 200 years back.
We regarded all other forms of life as peripheral to our own life.
In fact a real science of Biology, did not exist, before that.
In fact a good deal of our investigations, of other forms of life,
was to determine what we could eat, and what we could not eat.
It was Charles Darwin, who seeded the concept, that human beings,
were not the centre of life.
Charles Darwin.
Charles Darwin really did not set out, to unravel the mystery of life.
He got into this mission, quiet by accident.
In 1831, an expedition was planned to chart many parts of the world.
Charles Darwin was appointed, as a companion for the captain of the ship, H M S Beagle.
Apparently, he got a little bored with this job.
He started observing the different forms of life, in the places, that the ship visited.
He was a keen observer, and he noticed many similarities, and some differences,
in the same form of life.
For example, he observed that the same birds, looked different, in different islands,
that the ship landed in.
This aroused his curiosity.
He started collecting samples, of different forms of life.
His interest extended, to all forms of life.
Plants, animals, birds, Insects, etc.
He noticed a consistent pattern.
These forms of life, seem to adapt, to a specific environment that they lived in.
He hit upon the idea that, life forms adapted, to the environment.
He also got a clue, that one form of current life, evolved from another form of life,
which existed earlier.
He started wondering.
Did all forms of life, evolve from an earlier formof life?
Are all forms of life related?
Did all forms of life originate from, some unknown earlier forms of life?
He suspected that the answer was - yes.
He did not jump to conclusions.
For the next 20 years, he started studying all forms life,
and their relationship to each other.
He not only studied living life forms, but also fossils of life, which existed earlier.
The evidence kept mounting, in favour of his theory.
But he was hesitant to publish his findings.
This was partly due to the fact, that he knew that he needed very strong evidence,
to present his theory.
He was also little worried, that he will be ridiculed for his theory,
since it was against the established religious belief of that time.
He finally published his book, “On the Origin of Species” in 1859.
There was initial resistance, to accept his theory.
Some people joked, that it was a “Monkey to Man” theory.
Darwin latter grew a beard.
Cartoonists caricatured him, as a “Ape”.
After some time, people realised, that it was not a joke.
They began to accept, the theory of evolution.
Now there is a broad scientific consensus,
of the basic principles of evolution.
The theory has been further improved, and refined.
When Darwin outlined his theory, DNA had not been discovered.
After the discovery of DNA, many of the principles of evolution,
could be validated more scientifically.
Life.
We all have a intuitive idea, of what is a living being.
Basically, a living being is born, and grows, it replicates, and it dies.
It also ingests food, and spends energy to live.
This simplified definition, would be more than sufficient,
to appreciate what is a living being.
We can easily identify a living being, that we can see.
We just need to extend it, to include microorganisms, like bacteria,
which we cannot see.
Bacteria is also a living organism.
When we add a small teaspoon of curds or yogurt to milk, after sometime,
the whole of the milk, turns to curds.
This is due to the work of microscopic bacteria.
The bacteria replicates many many times in this process.
The story of life is a very long one.
Life originated somewhere around 3.6 billion years ago.
The first forms of life, were simple single living cells.
But these cells were alive.
They replicated, and created new cells endlessly.
How exactly, lifeless, inorganic chemicals, became living cells,
is a mystery.
There are some theories, but nothing is definitive.
For about a billion years, life on Earth was mostly cellular.
It is as if nature, was perfecting the design of the living cell,
over a billion years.
But it was worth the wait.
Even today, all living organisms, including human beings, have the same
basic function of a living cell, designed billion of years ago.
If the living cell is a marvel,
the DNA inside it is a miracle.
If there is one critical component, which is present in all forms of life,
it is DNA.
DNA is short form of Deoxyribonucleic acid.
This molecule is present in all living cells, of all forms of life.
We commonly call it as Genes.
It is the master plan, complete instruction manual, and encyclopaedia,
all rolled into one, double helix molecule.
The crowning glory of nature’s design is that the DNA replicates itself.
Once it replicates, it knows everything, required to build a cell.
If we have to choose, one defining feature of life, we have to choose reproduction.
Reproduction has ensured the continuity of life, for about 3.6 billion years.
DNA is the common thread, of the entire fabric of life,
that exists now, and existed, throughout the 3.6 billion years of life.
It is the centre of the story of life.
Reproduction.
Death is a common feature, of all forms of life.
It is reproduction, which has maintained the continuum, of life,
for 3.6 billion years.
In the very beginning simple cells, were the only forms of life.
But these cells could replicate themselves.
Nature experimented with many forms of reproducing life.
One main form was asexual reproduction.
In this form the DNA, just replicates by itself.
It then goes on to build the new cell.
This is possible because, the DNA has the master plan,
complete instruction manual, and encyclopaedia, to build the new cell.
In this form of reproduction, the new cell has identical genes, to the original cell,
most of the time.
Sometimes, by mistake, accident, or design the genes can be very slightly different.
Microorganisms, and many forms of plant life, use asexual reproduction,
to continue life.
Another form of reproduction, is sexual reproduction.
In this form two egg cells from a male and female parent,
decide to meet and get fertilised.
The resultant cell takes some features from the male parent cell,
and some features from the female parent cell.
The resultant DNA is unique, and different from both the parent.
This is at the core of the new baby cell,
it then grows, into a form of life.
Most animals and some plants, use sexual reproduction, to continue life.
There are some variants, but these are the main forms of reproduction.
But nature always has the habit of experimenting with new methods.
Some species, like the bacteria in the curds just replicate themselves.
Some species of life, lay eggs, and take care to hatch it.
Some species of life, lay eggs, but don’t bother to hatch it.
Some species, give birth to babies, and feed and nurture it.
Some species, give birth to babies, and leave it to fend for themselves.
Nature designed many experiments.
A Kangaroo even had a built in pouch, to carry the baby.
Plant life also reproduces, in many ways.
Some species, develop seeds, and let the wind distribute it.
Some species, enclose the seed, in an enticing fruit.
Birds and animals like squirrels, eat the fruit and distribute the seeds.
Some plants develop beautiful flowers, to attract the bees, to spread its pollen.
Some plants can produce a new offshoot, from its roots.
The extent to which plants and animals go, to reproduce is truly amazing.
Some whales will swim thousands of kilometres to mate and then leave for a new journey.
Some species die immediately after reproduction.
Though there are many variants and styles of reproduction,
there seems to be a inbuilt instinct, in all living forms to reproduce.
Adaptation.
When a new life is born, it could have a characteristic,
slightly different from the parent.
The genes of the new life, could be slightly different from that of the parent.
This results in a natural variation.
In the story of life, nature created more and more variants.
Some variants could not adapt well to the environment.
This could be due to many factors.
Climate, availability of food, type of food, predators,
are some examples of environmental factors.
The variants which could not adapt, did not reproduce, and became extinct.
Many of the species that existed, in the 3.6 billion years of life,
are now extinct.
We only know of them, through fossil records.
Fossils are preserved remains, of forms of life, that once existed.
Some variants could adapt to their environment.
They survived and reproduced.
It is as if nature was having a selection process.
This selection process, resulted in, continuing the lineage of the variants,
which could adapt.
This is the process of natural selection.
Natural selection was happening through out the history of life.
Over a few generations, the variants created by nature,
were not significantly different.
But when this variant generation, and natural selection,
happened over many, many generations,
a new variant developed, which was significantly different from its ancestors.
It then became a new species.
Every new species, as a distinct DNA signature.
By mapping and comparing the DNA of different species,
from currently living species, and extinct fossils,
we can track, the evolution of species over time.
We are familiar with wolves.
Over many, many generations, they created a variant,
which is, a dog.
A dog is considered as different species, though it descended from wolves.
Over many generations, a species, can create a new species.
In many ways, a new species, is a series of successful accidents.
The new species will have distinct characteristics, compared to the original species.
The new species will breed, only among themselves.
For example, dogs will breed with dogs,
wolves will breed with wolves,
but dogs will not breed with wolves.
In the course of evolution of life, many forms of life,
evolved to adapt to many different environmental conditions.
The more obvious examples are -
Fish adapted to living in water.
Animals adapted to living in land.
Birds adapted to living in air.
But within animals, different animals adapted to different ways of life.
Nature designed Camels, to adapt to water scarcity in the desert.
Camels have a inbuilt large pouch, to carry water.
Cactus plants also adapted to water scarcity, and stored water.
Polar bears adapted to hibernating in winter,
since there was no food in winter.
Giraffe developed a long neck, to reach leaves, which were at a height.
And so it goes on.
Every species of Life, adapted to some specific conditions of life.
It might be of special interest to us, to know that apes adapted to living in trees.
Diversity of Life.
If we look around us, we can see many forms of life.
If we look a little more carefully, we can observe, even more forms of life.
When we visit a zoo, we can see many more forms of life.
When we visit a museum, we are introduced to many extinct forms of life,
like Dinosaurs.
If we spend a vacation, in a jungle resort, we will come across,
many fascinating forms of life.
Our planet Earth, is filled with, millions of species of life.
Many more millions, of species of life, is now extinct.
The characteristics of these species, vary very widely.
We know of plants, trees, animals, fish, birds, insects, bacteria, etc.
There are about 320,000 species of plants.
There are about 100,000 species of trees.
There are about 2000 types of fruits.
There are about 5500 species of mammals.
There are about 31000 species of fish.
There are about 10000 types of birds.
When it comes to insects, the estimates becomes more fuzzy.
There are 10 to 30 million species of insects.
When it comes to microorganisms, we can only make a guesstimate.
There are several millions of species, of microorganisms.
Each species have a unique character.
All species of animals move, but trees don’t move.
However, the tallest living thing, is a tree.
They are more than 115 meters in height.
The galapagos tortoise moves, but very slowly.
This is a tortoise that Charles Darwin observed.
It moves at a leisurely speed of 0.3 km per hour.
Among moving species, the cheetah is the fastest.
It can reach speeds up to 120 km per hour.
The peregrine falcon, is the fastest bird,
it can reach speeds up to 390 km per hour.
The arctic tern, a bird, migrates, from the arctic region,
to the antarctic region, and back, every year.
It covers about 90,000 km every year.
To navigate it has a built in GPS, designed by Nature.
Termites live mostly underground.
They eat dead vegetation and wood, and fertilise the soil.
They build mud palaces, whose design, is a architectural marvel.
They live as a society, so harmoniously, it will put any politician to shame.
Some species eat certain type of plants.
Some species eat certain type of other animals.
Some species like a mouse, have a life span of 3 years,
an elephant has a life span of 80 years.
But there is a bristlecone pine tree called Methuselah,
which is approaching, its 5000th birthday.
Most animals are diurnal, they sleep during the night.
Some animals are nocturnal, they stay awake during the night and sleep during the day.
The shark requires to continuously move to live.
It does not sleep at all, at least in the conventional sense.
An ant hardly weighs anything.
But a blue whale, can weigh upto 180 tons.
Its baby, however weighs only a modest 2.7 tons.
Let us not under estimate, the light weight ant.
It can carry 10 to 50 times, it’s own weight.
If we human beings could do that, we could carry our car, and walk out,
if we find ourselves in a traffic jam.
Sometimes we wonder about the wide variety, of the forms of life.
It is as if nature designed, millions of jobs,
and life evolved and diversified to fill all the job openings.
It seems as if life, not only adapted to the environment,
but also, made use of all opportunities, available to it.
Tree of Life.
When it comes to physical elements, we can identify each one of them.
The periodic table, has one unique element, for each atomic number.
There are 118 known elements.
But no such periodic table, exists for the species of life.
They are so diversified, and so large in number,
We are yet to identify, and classify, all the species of life.
Taxonomy is a science, which deals with classifying, known forms of life.
A seven level classification, is commonly used,
to classify all forms of life.
The first level, is the kingdom.
The second level is the phylum.
Phylum, is a division of a kingdom.
The third level is class.
Class, is a division of phylum.
Fourth level is order.
Order, is division of a class.
Fifth level is family.
A family is a division, of an order.
Sixth level is genus.
A genus is a division, of family.
Seventh level is species.
Species is a division, of genus.
Let us imagine, a big tree.
At the base we have a trunk,
the trunk has some main branches,
each main branch, has many sub branches,
each sub branch, has many sub, sub branches,
and so on, and so on.
We need to stretch our imagination, to keep doing this,
till we arrive at many million, final sub branches.
As you can imagine, this tree is really a very, very, big tree.
But, that is the tree of life.
Life started around 3.6 billion years ago.
Life started out as simple single cellular organisms.
It then diversified into other forms of life.
Each new form of life, was a new species,
it took many many generations, to become a new species.
Natural selection and adaptation played a big role,
in the evolution of life.
During the course of evolution, many species went extinct.
However, the surviving species, went on to create new species.
If we travel back in time, we will not recognise, most of the species,
that once existed in life.
They will all seem very strange to us, like dinosaurs.
Evolution was a continuous experiment in life.
Sexual reproduction played a large role, in creating variety.
By slightly shuffling the DNA of each parent,
nature was able to create, a slightly new variant,
in the next generation.
It appears, that every variant, is a little bit of an accident.
Successful variants survived.
Unsuccessful variants died.
The successful variants, over many generations, created a new species.
A new species, was like a completely new model,
incompatible with the previous model.
A new species will only breed among themselves.
This process of creating new species, went on for 3.6 billion years.
If we look around today, all the forms of life, are the grand result,
of 3.6 billion years, of nature’s experiments.
It seems like a long time, but the result justifies it.
All forms of life, in the tree of life, are related to each other,
in some distant past.
The cow and the goat, had a common ancestor.
The apple tree and the orange tree had a common ancestor.
So far, it is not hard to imagine this.
An ant, a crocodile, a dove, and a elephant,
had a common ancestor.
We just have to travel back, much further in the tree of life,
to find this common ancestor.
A tree, a fish, an animal, and a bird,
had a common ancestor.
We really have to travel, long long back in the tree of life,
to discover this ancestor.
If we travel long enough, we will finally arrive, at our greatest ancestor,
a simple living cell.
This will hopefully make us understand, that all forms of life,
are inter related.
We always marvel, at the things human beings invented.
All the inventions of human beings, would pale in comparison,
with the designs of nature.
The designs of nature, are complex, sophisticated, advanced and elegant.
Hopefully, we will be inspired, by nature’s design,
to design our own future.
We can view the tree of our life, as a continuous diversification,
and improvement in design.
All the millions of branches, in the tree of life,
are winners, of 3.6 billion years, of design competition.
We human beings sit in one of the many million branches,
of the tree of life.
When we look around, at the other branches, which are other forms of life,
we will appreciate, that we are all related.
We all share a common ancestor.
Geological Time Scale.
The Earth is about 4.5 billion years old.
Geologists measure the time, since the beginning of the Earth,
using a special time scale.
The largest unit, is the supereon.
A supereon, has many eons.
A Eon is a very large period of time, that is typically many million of years.
A Eon is divided into many periods.
A period is divided into many epochs.
A Epochs is divided into many ages.
When discussing the history of Earth, this kind of time scale is useful.
Hadean Eon.
The very first period, of the existence of the Earth,
is called the Hadean Eon.
Hadean refers to the conditions, that existed on Earth, in the beginning.
The conditions on Earth at that time, was really hellish.
The Earth had a large number of active volcanoes.
The Volcanoes used to spew out molten lava.
The oceans were boiling.
The atmosphere was filled with poisonous gases.
The Earth used to get regularly bombarded, by meteorites, big and small.
The moon is believed, to have split away from the Earth,
when one such meteorite, hit the Earth.
It used to rain, not with water but with acids.
In summary, Life was not worth living.
As we can imagine, there was no life on Earth, in the beginning.
Continents.
Earlier, all the land mass, on the Earth, was a super continent.
It was called Pangaea.
It is only much later that land masses, separated from the super continent Pangaea,
and drifted out, to different parts of the Earth.
India for example was attached, some where near south America.
It split up, drifted away and hit, another break away continent, Asia.
The force of the impact was so heavy that, the whole himalayan range,
including Everest, was formed during that time.
The continents spread to all parts of the planet Earth.
Today, we have the known 7 continents,
Asia, Africa, North America, South America, Antarctica, Europe and Australia.
These continents were isolated from each other.
The environment in each continent was very different.
Antarctica become very very cold, and is a frozen continent.
This had a some bearing, on the way life evolved, in the different continents.
This geological phenomena, had a bearing, on the evolution of life.
India for example, which was close to Antarctica, drifted away,
to become a tropical country.
These geological changes, had some influence,
on the evolution of life.
When continents drifted to a new location, living species had to adapt,
to a new environment.
Land marks of life.
For the 1st 900 million years, are so, there was no life on Earth.
The conditions were too hellish, for life to exist.
About 3.6 billion years ago, life was born on planet Earth.
The story of life, since then, is a long story.
We will only discuss a few land marks, or highlights, of this story.
3.6 billion years, is a long period of time.
To help us visualise this time period, we will formulate, a simple time scale.
We will say that one year, is equal to 3.6 billion years.
This means that one day, is equal to about 10 million years.
10 days is equal to 100 million years.
One month is equal to 300 million years.
Hundred days is equal to 1 billion years.
We have to remember, that all time periods that we discuss,
are very approximate.
More precise dates, is neither known nor important.
The land marks for highlights, make a exciting stories by themselves.
When we mark a time, for example like, 550 million years ago,
we mean starting from about 550 million years ago.
We should remember evolution was a long and continuous process.
The time we mention, is only a convenient book mark.
Prokaryotes.
About 3.6 billion years ago, something very strange,
and exciting happened.
In our time scale, this would be one year ago.
From the primordial chemical soup, in the ocean,
a living cell emerged.
Some lifeless inorganic chemicals, combine to form a living cell.
How exactly this transition happened, is still a mystery.
There are some theories, but nothing is certain.
However, that life was born, around this time, is a fact.
The first living cells were called, prokaryotes.
They had a cell membrane.
Inside the cell, they had DNA, mitochondria,
and some more primitive organelles.
The chemical elements, in the cell, are very familiar.
There were elements like carbon, hydrogen, oxygen, nitrogen etc.,
These elements are the same, that we study in the periodic table, today.
But the living prokaryotes, did something that, no element in the periodic table,
was able to do, till today.
The cell replicated itself.
This qualifies as something, as a miracle.
If there is one most important feature of life,
it is the ability to reproduce.
This was possible, thanks to a design marvel, called DNA.
DNA stands for Deoxyribo Nucleic Acid.
DNA had the intelligence to divide, rebuild itself and also build a new cell.
DNA is the common thread, always present, in the tree of life,
and the story of life.
Life was able to expand, and diversify.
Prokaryotes, were able to replicate and reproduce themselves.
This was the beginning of the 3.6 billion years, of the story of life.
This microscopic, humble cell was our most ancient ancestor.
Cyanobacteria.
About 3.4 billion years ago, life came up with a very interesting invention.
It was called photosynthesis.
In our time scale, of one year, this will be equivalent, to January 3rd week.
Cyanobacteria, is a type of bacteria which learnt to harvest the sun’s energy,
through photosynthesis.
Energy from the sun, was captured by cyanobacteria,
and stored as chemical energy, in molecules like ATP.
ATP stands for Adenosine TriPhosphate.
Photosynthesis was a significant invention, since it acted,
as a crucial microbiological conduit, for solar energy, to life.
This basic design of photosynthesis, is still used by plant life.
There was another dramatic change, that took place.
Cyanobacteria, released oxygen into the atmosphere.
Earlier the atmosphere was filled with carbon dioxide, and other gases.
Over a period of time, cyanobacteria, change the atmosphere,
to an oxygen rich atmosphere.
Every time we breathe, we need to be thankful for photosynthesis,
for the oxygen, that we have in the atmosphere.
Even today forests, use this design, to produce oxygen for us.
Without it, we need to use oxygen masks, to live.
We need to take care of nature’s design, in our forests.
Eukaryotes.
About 2 billion years ago, nature came up, with a new cell design.
In our time scale of one year, we have already reached, the second week of June.
It is 1.6 billion years, since the first living cells appeared.
This new type of cell is called eukaryotes.
One of the major design changes, in eukaryotes, was that the genetic material,
was enclosed in a nuclear envelop.
This cells also developed membrane bound organelles.
For example. The mitochondria, Golgi apparatus etc.,
were membrane bound.
Earlier forms of cellular life, used to reproduce, by replication.
The DNA split into two, and then rebuilt itself, into a new cell.
Eukaryotes introduced a revolutionary new concept, for reproduction,
called sexual reproduction.
In this process, DNA from two different parent cells, merged to form a new DNA.
This new DNA, rebuilt the new cell.
This was a dramatic development.
Combining two different DNA’s, could create, a larger number of variants.
Life could now, think of diversifying faster.
Eukaryotes, also created a foundation, to develop multi cellular organisms.
Eukaryotes, are a major branch, or domain, of life.
All multi cellular organisms, are eukaryotes.
But for eukaryotes, we will all be some kind of bacteria.
1.6 billion years seems like a long time, to bring out a new model cell.
It is almost as if, nature took extraordinary care, to design the basic cell.
It was worth the wait.
The basic cell design, developed by eukaryotes, was carried forward,
to all future branches, that evolved from it.
In the tree of life, all branches, in the eukaryote domain, is the same.
This is true till today.
Multicellular Life.
About 1 billion years ago, mark the beginning, of multi cellular organisms.
In our time scale of one year, we have already reached, September 3rd week.
Earlier, all forms of life were unicellular.
In multi cellular life, many cells combine to form a single living organism,
This had some major advantages.
Life could grow into larger organisms.
Unicellular living organisms, like bacteria, are microscopic, we could not see them.
Multicellular organisms, grew large enough to be seen.
The earliest multicellular organism was a sponge like creature.
It had no particular form or shape.
It had no organs like plants and animals have.
It is only much later, that nature started to build, specialist cells.
This way each cell could perform a specialised, but different function,
and all the cell together could combine, to form more complex living organisms.
This basic idea, was incorporated into all plant, animal and fungi life.
As life evolved, more and more specialised cells came into being.
One of the earliest specialisation, which happened,
resulted in the creation of kingdoms.
Specialised plant cells, and specialised animal cells,
resulted in the formation of two distinct kingdoms.
The plant kingdom, and the animal kingdom.
The plant and the animal kingdom, are more familiar to us.
The other kingdoms were Fungi, Protozoa, and Monera.
Within the plant kingdom, later on, more specialised cells evolved,
like the cells in branches, leaves, roots, flowers, seeds etc.
Within the animal kingdom, later on, more specialised cells evolved.
like the cells in bone, muscle, blood, brain etc.
Specialised cells helped to build specialised organs.
This helped to design more sophisticated living organisms.
This however happened much later.
Diversification of Life.
About 550 million years ago, something dramatic happened,
when we say 550 million years ago, we mean starting from 550 million years ago.
You would have noticed, that for more than 3 billion years,
in the story of life, there were no familiar forms of life.
Life was mostly cellular, multicellular at best.
550 million years ago, which is November 1st week, in our time scale,
a biological revolution started happening.
We are familiar with the industrial revolution.
Within a relatively short span, of about two centuries,
we invented many things.
Steam engines, trains, motor cycles, electricity, bulbs, telegraphs, cars, telephones,
fans, pumps, elevators, machinery, aeroplanes, radio, transistor, rockets, satellites,
computers, nuclear reactors and so on.
We invented so many things, that we called the period,
starting in the 19th century, as the industrial revolution.
A similar biological revolution took place, in the story of life.
However, these changes, took place, over millions of years.
It was as if, nature decided, that it was time to diversify.
Using the basic cell design, it started, inventing new forms of life.
Most of the basic branches of life, started out during this period.
This basic branches are called phylums.
Phylums are divisions of kingdoms.
The kingdom of animals, developed about 35 phyla.
Phyla is plural for phylum.
The kingdom of plants, developed about 12 phyla.
These basic branches, were a defining feature, in the story of life.
All future species, in the plant and animal kingdom,
evolved from these phyla.
Compared to the earlier billions of years, these evolutions,
happened over millions of years.
We will briefly discuss, a few forms of life, that evolved.
The list is only a sample, but enough to give us,
a fair idea of what happened.
The evolution of these branches, happened in parallel.
While the plant kingdom was diversifying, the animal kingdom was also diversifying.
Plants.
Some of the earliest plants, were some kind of algae, or sea weed.
They were floating around, in the ocean.
They were aquatic plants.
Most of the early plant life, evolved in the ocean.
Plants were autotrophs.
They harvested sun’s energy, by photosynthesis, to produce their own food.
Even today plants are autotrophs.
About 475 million years ago, plants started exploring,
land as a habitat.
They apparently liked land, because many species of plants,
evolved as land plants.
Some of the early plants, were,
Hornworts.
Mosses
Liverworts.
Ferns & Horsetails.
Conifers.
Ginkgo, Maidenhair.
The most significant, invention, in the evolution of plants, was the seed.
Early Plants, like ferns, mosses and liverworts did not have seeds.
The seed was an important means, of reproduction.
Plants with seeds evolved into many branches of plants that we see today.
About 320,000 species of plants, have evolved.
Trees also evolved from plants.
About 100,000 species of trees, have evolved.
The plant kingdom, in the tree of life, is rich with diversity.
Plants and trees adapted very well, to land life.
Many species grew together, in dense forests.
Forests are a habitat, for many flora and fauna.
Flora is a common name for plant species.
Fauna is a common name for animal species.
A large portion, of the habitable land mass,
was once covered with forests.
Sadly, human beings destroyed or degraded, a large proportion of the forests,
that once existed in our planet.
Forests are a source of oxygen, and is essential to our well being.
We need to conserve, what is left of our forests.
Animals.
Another branch of life, that evolved, was the kingdom of animals.
Let us look at a few samples, of the early branches, in the kingdom of life.
Segmented worms.
Thorny worms.
Arrow worms.
Goblet worms.
Jaw worms.
Horsehair worms.
Ribbon worms.
Velvet worms.
Horseshoe worms.
Flat worms.
Peanut worms.
Looks like nature was fond of worms.
If it had stopped, it’s design experiments, with these branches,
we would all be crawling around.
Fortunately it did not.
It also designed some other branches, like
Mollusks.
Sponges.
Arthropods.
Chordates.
We evolved from chordates, branch of life.
One of the significant difference, of animals,
is that they do not produce their own food.
Animals, seem to have decided, that plants or autotrophs, will produce food,
and they will eat the plants, for food.
Animals are called heterotrophs.
Interestingly, the sun’s energy reach heterotrophs, via autotrophs,
which they eat.
All species which developed, in the animal branch, are heterotrophs.
Early animals had no particular form and shape.
It is only later, that they developed a front and a back side.
Before that, we could not make out, head or tails of animals.
They went one step further.
They developed a small brain, in the head.
This was a break through.
Another important feature, of animals, is that they are motile.
That is they are able to move.
This was a great advantage.
They could move around, and search for food.
Plants species, used to reproduce, mostly with its seeds.
Plants and trees, used to distribute the seeds, and hope for the best.
Animals on the other hand, were able to move around, and find a mate.
This helped in reproduction.
Animals diversified, into many interesting branches.
Sponges, a formless floating species.
Annelids, like earthworms and leeches.
Arthropods, like millipedes, centipedes, insects, spiders, scorpions,
crabs, lobsters, shrimps, etc.
Mollusks, like clamps, octopuses, oysters, squid, snails.
Vertebrates, like fish, reptiles, amphibians, mammals, and birds.
Fish.
The sea, was the habitat of the earliest animals.
One branch of animals, called vertebrates, developed a prototype of a spine.
They are called notochords.
Many bony fish developed with these early spines.
The spine gave a structure, and a definite form and shape, to early forms of fish.
Many species of fish developed with this basic design.
Fish were able to breathe oxygen, present in dissolved form, in water.
They also moved around, with the help of fins.
Nature developed about 31000 species of fish.
We all evolved, from the species of fish.
Tetrapods.
Tetrapod means four footed.
These animals were, four limbed vertebrates.
The limbs developed from the fins, the fish had.
Early tetrapods, possibly used the limbs, to help them swim.
We can speculate that some tetrapods, experimented with walking ,
on the ocean floor with these limbs.
Tetrapods however, remain loyal to the water habitat.
Amphibians.
We can now indulge in some more speculation.
Some tetrapods near the shore, peeped out of the water.
They saw land and possibly liked it.
Some enterprising young tetrapods, tried to climb on to the land.
But there was a major problem.
These animals were used to breathing in water.
Now they had to learn to breathe oxygen, in the atmosphere.
Over many generations,they learnt to do this.
These animals learnt to breathe, both in water and land.
They evolved, to live partly in water, and partly in land.
They are called Amphibians.
An example of the amphibian species, which exist today, is the frog.
Insects.
One branch of animals, which evolved, were insects.
This branch of evolution, seem to believe that small is beautiful.
We discussed that, nature threw up many job opportunities.
Some of them required very small sized life forms.
Many species of insects, evolved to fill these gaps.
Small size, does not mean inferior design.
Some of the best design features, of nature, is present in insects.
For example, an ant can carry 10 to 50 times, its own weight.
We have a common perception, that insects are pests.
All insects are not pests.
A number of insects species, play a beneficial role in the biosphere.
Termites, Earth worms, Bees, are a few examples.
Reptiles.
Reptiles evolved, about 300 million years back.
We have already reached December, in the story of life.
Reptiles are cold blooded animals.
They make use of the environment, to warm or cool themselves.
They have very small limbs, and move very slowly.
Many of them seemed to specialise, in developing a thick skin.
Some example of reptiles are turtles, tortoises, lizards,
crocodiles and alligators.
Reptiles were the ancestors of dinosaurs.
Dinosaurs.
A dinosaur evolved about 230 million years ago.
Dinosaurs have captured our imagination.
We possibly imagine dinosaur, as large and ferocious creatures.
Actually dinosaurs developed in many shapes and sizes.
Many of them were harmless, gentle, plant eating animals.
Dinosaurs were once abundant, in the planet.
But the whole dinosaurs species went extinct, about 65 million years ago.
But other species, evolved from dinosaurs.
Some type of dinosaurs, evolved into birds.
Birds.
Birds evolved, about 150 million years ago.
Early animals knew how to swim.
Later, animals learnt to move around in land.
It was only much later, that nature decided to experiment with flight.
Some type of dinosaurs, changed their design, of two of their limbs, to wings.
Over a period of time, a long period of time, they eventually learnt to fly.
Now we have, about 10000 types of birds.
Most of them are beautiful, graceful and elegant.
It is difficult to imagine, that they evolved, from dinosaurs.
But nature always had a tendency to experiment with new designs.
Mammals.
Mammals are familiar animals to us.
Cows, goats, sheep, deer, lions, are mammals.
Mammals evolved only about 200 million years ago.
We are already in December 2nd week, in our story of life.
It is then this interesting branch, called mammals started evolving.
Mammals belong to the kingdom, Animalia.
They belong to the Phylum, Chordata, and to the class, Mammalia.
Mammals evolved some interesting characteristics.
They invented a new way of giving birth.
Earlier animals used to lay eggs, and hatch them.
Life used to emerge, from the egg.
Mammals started developing, the embryo of the baby, in the womb.
Much of the development of the baby, took place,
in the safe environment of the womb.
They then gave birth to a well developed baby.
This had a evolutionary advantage.
The chances of the survival of the baby, dramatically improved.
This success resulted in evolving a number of species, with this design.
Mammals did not stop, with developing the baby in the womb.
Even after it was born, they nurtured the baby, till it was fully grown.
They protected the young ones,
and taught them the art of living.
In the wild, the art of living is very important,
it is the art of survival itself.
Since the young ones are protected and tutored,
their chances of survival, further improved dramatically.
In the story of life, mammals were the one branch,
which took so much care, of the young ones, and even pampered them.
We could imagine, that the young ones of mammals,
even had time to play.
This luxury was never available to other species.
Mothers also developed a way, to feed the young ones.
They developed mammary glands.
The word mammals comes from this.
Animals have to search, and find food.
Sometimes they could find it, and sometimes they could not.
But the mothers of the mammals, always supplied food to the young,
when ever they needed it.
This luxury also was not available, to other species.
Mammals also had some interesting physiological features.
They developed a better brain, heart, and a circulatory system.
They were much better adapted, to the conditions in the environment.
About 5500 species of mammals evolved.
We can see many of them today, in the forest, or in the zoo.
One branch of mammals, learnt to climb trees.
They learnt to live in trees.
It possibly helped them, to escape from predators,
who would have liked to, have them for breakfast.
This branch called the hominidae, is of special interest to us.
The hominidae branch, is commonly known as the great apes.
This branch developed other branches, like Gorillas, orang-utans, and chimpanzees.
The chimpanzees are our great ancestors.
Human Beings.
The story of life is about 3.6 billion years.
For convenience, We have used a scale of one year, to represent 3.6 billion years.
So, one day represents approximately, 10 million years.
We have reached December 31st, in the story of life.
May be its time to end the story.
But wait.
Something happened, on the evening of December 31st, which might be of interest to us.
The genus homo, came into being.
Homo, means Human.
We just made it to the story of life,
in the evening of December 31st.
About 2.5 million years ago, the new genus of homo appeared.
It descended from the family of Hominidae, which refers to great apes.
This family consisted of Orangutans, Gorillas, Bonobos, and Chimpanzees.
In this family, our closest relative, are Chimpanzees.
We share more than 95 % of our genes with Chimpanzees.
We will pause, to trace our origins, from the beginning of life.
We belong to,
Domain of Eukaryota.
Kingdom of Animalia.
Phylum of Chordata.
Sub phylum of Vertebrata.
Super class of Tetropoda.
Class of Mammals.
Order of Primates.
And the family of, Hominidae.
We belong to the genus of Homo.
Homo Habilis.
One of the early species of the genus homo, is Homo habilis.
If you look at a picture, of a homo habilis,
it might look more like an ape, then a human being.
We probably behaved like one.
But, we could make simple tools.
Nature had to start somewhere,
and this was a good beginning.
Homo Erectus.
About 1.8 million years ago,
the homo erectus species evolved.
This mastered the art of walking.
It might not appear to be a big deal, to us.
But actually, it is a revolutionary design.
Animals use all four limbs to walk.
When we learnt to walk on two legs, it freed our hands.
Our hands evolved, from the forelimbs of animals.
Initially we had, nothing to do with our hands.
We probably started making tools, with our hands.
These tools are made of stone.
Since there is no machines, we can imagine,
how difficult it would have been to make a stone tool.
But, it was worth it.
It helped us to hunt, and gather food.
Once we had enough food, we had more time, to develop better and better tools.
This gave us an advantage, over other species.
Over a period of time, as your are aware,
our tools, gave us the power to dominate, our planet.
Homo Antecessor.
This species homo antecessor, evolved about 1.2 million years ago.
Scientists have identified a gene, related to speech, in this species.
May be we began to start speaking, in a primitive way, around this time.
Languages is one of the important features, which differentiates us,
from other animals.
Through it we were able to communicate knowledge and ideas.
Animals teach their young, by demonstrating.
We possibly also started, by teaching them, through language.
Homo sapiens.
Sapien means wise.
We are Homo sapiens.
We are wise humans.
Homo sapiens, is the species,
that anatomically modern Human Beings are called.
They evolved about 200 thousand years back.
This is about 20 min before midnight, in our story of life.
We just about made it, to the story of life.
Some people may think, that our planet, always had human beings.
Some people may think, that our planet, was created for us.
The truth is, that we are very, very, very recent guests of the planet.
We checked in, into the planet Earth, in our story of life, a few minutes ago.
We are related to all other forms of life.
We have descended from other forms of life.
Knowing this, will make us feel connected to other forms of life.
Does this mean, that we are just another animal?
In a physiological sense, yes we are.
But we are much more, in the intellectual dimension.
Human beings, have a relatively larger brain, compared to other species.
That is, given our body size, we have a disproportionately larger brain.
Some scientist speculate, when our hands became free,
and started to develop tools, it helped to develop the brain more.
We are the only species, which cooks the food we eat.
Some theories suggest, that eating cooked food, being more efficient,
helped the brain to develop more.
We do not know exactly why, but we do know, that we have a relatively larger brain.
But it not only the size, of the brain,
it is also the quality of the brain.
We have the most highly developed intellect, among all species.
It is quite obvious, we have certain qualities which clearly differentiates us.
A few of them are:
We can think.
We can communicate our thoughts through language.
We take care of our young, and nurture them, for the longest period of time.
Thanks to Mom and Dad for that.
Thanks to our more sophisticated brain, we can do a long list of things,
which animals cannot do.
We can speak, we can sing, we can dance, we can write books, we can write poetry,
we can invent, we can joke, we can understand science, and so on and so on.
We can even smile.
We are a truly gifted species.
We are wise humans.
We hope, we can use our wisdom responsibly.