DIFFERENT LIFE FORMS

By Mariyam

HAS ANY ONE WONDERED HOW LIFE BEGAN ON EARTH? Some believe it was specially

created.

Some scientist believe that life formed because of the chemical reactions billions of years ago.

WHERE DID LIFE FIRST APPEAR? First forms of life appeared in the ancient seas of the earth, when the planet was readying itself to nurture life.

WHICH ANCIENT CREATURES LIVED BILLIONS OF YEARS AGO?

HOW DO WE KNOW ABOUT ANCIENT CREATURES, IF THEY LIVED WHEN NO ONE WAS AROUND?

When an animal or plant dies , it sometimes leaves a mark or it remains in a rock.

This is fossil. Scientists study fossils to help them

learn about the kinds of creatures that lived in the past.

Many of these creatures are extinct to day.

This is how the dinosaurs and many other interesting life forms were discovered.

LIFE IS THOUGHT TO HAVE ORIGINATED THROUGH SOME SYSTEM OF REPLICATION(REPEATING ITSELF)

THOSE WHICH REPLICATED DEVELOPED INTO SIMPLE CELLS LATER, BECOMING THE BACTERIA AND BLUE ALGAE IN THE OCEANS.

bacteriaBlue-green algae

THE BLUE GREEN ALGAE PLAYED AN IMPORTANT ROLE AS THEY STARTED TO PRODUCE OXYGEN , WHICH SETTLED IN THE ATMOSPHERE AND WAS ESSENTIAL TO THE LATER DEVELOPMENT OF ALL AIR BREATHING HIGHER ANIMALS.

LATER THOSE SIMPLE CELLS SOMEHOW CHANGED INTO CERTAIN CELLS WITH AN ENCLOSED NUCLEUS AND OTHER ADVANCED FEATURES.

FROM THE UNI-CELLULAR STRUCTURES WERE FORMED. SOME MULTI- CELLULAR STRUCTURES AND EVENTUALLY SOFT BODIED MARINE INVERTEBRATES CAME INTO BEING.

MARINE INVERTEBRATES CALLED TRILOBITES ABOUNDED IN THE SEA.

LATER THE FIRST VERTEBRATES, SOME SIMPLE FISH APPEARED.

LIFE FOR A LONG TIME AFTERWARDS ONLY EXISTED IN THE WATER, WITH THE LAND BEING COMPLETELY BARREN.

THE FIRST VASCULAR PLANTS VENTURED ONTO LAND TO BE THE FIRST LAND BASED LIFE FORM.

AMPHIBIANS EVOLVING FROM FISH FOLLOWED LATER TO BECOME THE FIRST ANIMALS ON LAND.

SOME AMPHIBIANS ,WHICH CAME TO DEPEND LESS AND LESS ON WATER, BRANCHED LATER INTO REPTILES, WHICH WERE THE FIRST TRUE LAND ANIMALS.

REPTILIAN CREATURES ALONG THE ALMIGHTY DINOSAURS WERE DOMINANT TILL THE MASS EXTINCTIONS OCCURRED, WITH ONLY A FEW OF THEM SURVIVING IT.

HUMANS AS KNOWN TODAY , ARE VERY LATE ARRIVALS IN THIS WORLD.