How did Plants Originate

For more than half the earth’s history nothing living existed upon any part of the globe.  That means, for millions of years the surface of our planet was nothing but bare rocks, without soil or sand, swept by hot winds exceeding in violence the wildest tornadoes, of today.  It was drenched by torrential downpours of tropical rain, which gradually tore away the surface to form sandy sediments at the bottom of the seas.
According to the theories of science, there was a time when there were no plants on earth.  Then, hundreds of millions of years later, tiny specks of protoplasm appeared on the earth.  Protoplasm is the name for the living material that is found in both plants and animals.  these original specks of protoplasm, according to this theory, were the beginnings of all our plants and animals.
The protoplasm specks that became plants developed thick walls and settled down to staying in one place.  They also developed a kind of green colouring matter known as “chlorophyll”.  this enabled them to make food from substances in the air, water and soil.
These early green plants had only one cell, but they later formed groups of cells.  Since they had no protection against drying out, they had to stay in the water.  Today, some descendants of these original plants still survive, though they have changed quite a bit.  We call them “algae”.

Image Source: thestockmasters.com
One group of plants that developed obtained their food without the use of chlorophyll.  these non-green plants are the “fungi”.
Most of the plants on earth today evolve from the algae.  Some of them came out of the sea and developed rootlets which could anchor them in the soil.  They also developed little leaves with an outer skin covering, as protection against drying.  these plants became mosses and ferns.
All the earliest plants are reproduced either by simple cell division or by means of spores.  Spores are little dust-like cells something like seeds, but containing no stored food in them as seeds do.  As time went on, some of these plants developed flowers that produced true seeds.
Two different types of plants with seeds appeared; those with naked seeds and those with protected seeds.  Each of these two types later developed along many different lines.
Plants have “factories” to manufacture their food, and these factories are the leaves.

How do Seeds Germinate

Among the seed bearing plants, the flowering plants are far more successful and numerous than others.  Virtually all species of plant cultivated are flowering plants.
The seed of this group consists of an embryo with its associated storage materials. Growth of the seed begins with early division of the zygote within the tissues of the parent plant.  There is hardly any specialization of cells at this point.  But a pair of embryonic organs, the root and the shoot become evident.  The root exhibits a positive response to gravity and the shoot which is the forerunner of the stem and leaves, are phototropic.

Image Source: www.wikipedia.org
The seeds of many plants are obliged to undergo a period of dormancy.  There are some species whose seeds remain dormant only until proper conditions of moisture, temperature and oxygen supply are such, as to initiate embryonic growth.
After the root and shoot have grown for a short time, some of their cells differentiate to form the tissues characteristic of the mature plant.  New growth occurs at the tip.  As a consequence of gradual differentiation, certain tissues come to characterise the mature plant.

What are Viviparous

We know that most fishes lay eggs.  These eggs are fertilized outside the body.  Fishes that emit eggs are described as oviparous.  But some fishes give birth to living young.  These are described as viviparous.

Image Source: www.diverosa.com
Among the viviparous fishes are guppies, platies, swordtails and mollies.  The eggs are fertilized inside the body of the female and grow into baby fish there.  At the appropriate time, they are born.  In platies it is 21 days after fertilization.
The number of eggs that are laid and fertilized vary a great deal from one kind of fish to another.  some fishes expel their eggs and then abandon them, showing no more interest in them.  These kind of fishes lay great numbers of eggs.  Those fishes that watch over their developing young lay far fewer eggs.
Fishes also lay two types of eggs.  One type floats and the other sinks.  Eggs that float are called pelagic eggs.  They are usually tiny and transparent and do not have much yolk.  Eggs that sink are called demersal eggs.  They are usually heavier and yolky.
As an example, herring lay demersal eggs and show no care for these eggs.  They may deposit 20,000 to 40,000 eggs.  Cod, on the other hand, lay pelagic eggs.  An average-sized cod can lay one hundred million eggs!
Mackerel lay 400,000 to 500,000 eggs in a season, but they never lay more than 50,000 at a time.  Large halibut can lay over two million eggs!
Eggs vary in size, too.  Herring eggs are one millimetre in diameter.  Cod eggs are about 1.5 millimetres.  Halibut eggs are 3 millimetres.  eggs that are guarded until the young are larger have greater chance for survival.  But millions and millions of fish eggs are eaten by other creatures.

Dolphins

Dolphins are small whales, ranging in length from about 1 to 3.5 metres.  Whether they are called “dolphins” or “porpoises” seems to be a matter of preference.  Either name is correct.

Image Source: www.wikipedia.org

There are several reasons why  scientists consider the dolphin to be an unusually intelligent animal.  Many of them have been known to imitate human speech quite distinctly and without even being urged to do so.  They can also learn to understand human words and respond to them.
Students of animal behaviour have two other reasons for considering the dolphin intelligent.  Dolphins are able to invent and play games.  For example, suppose there is a feather floating about in a tank of water, a dolphin will get the feather and bring it near the jet of water entering the tank.  The feather drifts into the jet and goes shooting off.  The dolphin pursues it, catches it, brings it back and again releases it into the jet.
Dolphins have invented games with small rubber inner tubes.  They will toss the tube to someone standing by the tank and wait for the person to toss it back to them so they can catch it.  This kind of play is considered a sign of intelligence.
Dolphins can also solve problems.  If a piece of food is stuck under a rock, they can find a way to “blow” the food out from under the rock.
Just how intelligent dolphins are has not been tested.  This is because there is no intelligence test by which animals as different as dogs and chimpanzees and dolphins can be rated.

Sea Mammals

Mammals are the only animals which have milk producing glands.  They are the only ones that nourish their young with milk.  They also possess hair on their body.

Marine mammals have several independent lines of evolution.  But, they offer an excellent example of convergent adaptations in different groups, resulting in a similar mode of life.

Image Source: www.wikipedia.org

The main group are: the Cetacea, Sirenia and Pinnipedia.  Of these the last group is not found in Indian waters.  The whales, dolphins, and porpoises belongs to the first one, while seals, sealions and walruses are of the second one.  As such we have in our waters whales and dolphins.  But, if we take the whole list, porpoises, seals, sealions and walruses will also be there among the marine mammals.

Most Venomous Snake

The most venomous land snake is a native of Channel country, Queen’sland, Australia named Paradamansia microlepidotus.  It is a snake of about two metres in length.

The Indian Cobra (Naja naja) is found from Caspian across Asia, South of the Himalayas to Southern China and Philipines and south to Bali in Indonesia.  It is regarded as being one of the most dangerous snakes and death has been recorded as little as 15 minutes after the bite.

Ant's Cows

The little aphides are also known as plant lice. They feed on the juices of plant stems, leaves and roots.

Image Source: www.wikipedia.org

They are small, soft bodied and weak. But they have one characteristic that has stood them in good stead for millions of years. They suck more fluid from plants than they need. This surplus oozes out of their bodies in the form of a sweet excretion known as honeydew.

Image Source:www.wikipedia.org

This is delicious food for ants.  So the ants and aphides have developed a sort of mutual accommodation.  The ant strokes the aphid and is rewarded with a drop of honeydew.  In return the aphid enjoys a body guard of attendant ants that may keep away predatory insects etc.

In summer there are many generations of short lived females each of which can reproduce up to 100 young, without fertilization.  The ants do not herd the aphides like cattle.  The aphid form herds of their own, sometimes numbering 80 – 100 individuals, whether or not ants are present.  The ants merely locate these aggregations and take advantage of them.  Nor do ants put the aphides out to pasture, except in a few ant species.

Hence aphides are also described as "ant's cows".