This document provides an overview of fossils and how they help scientists understand the history of life on Earth. It discusses how fossils are formed, the different eras defined by fossils, and examples of specific fossil findings, including the first cell, a spider trapped in amber, a triassic bird, ceratites fossils, plant fossils, the skeleton of a prehistoric rat, and a symmetrodonta fossil. Fossils have allowed scientists to reconstruct the evolution of life, determine when organisms appeared and went extinct, and divide Earth's history into eras and periods.

2. INDEX
-The first cell.
-How are eras and periods formed?
-The eras.
-What are fossils?
-How are fossils formed?
-How fossils help us?
-History of a spider.
-The triasic bird.
-Life started in the sea.
-Ceratites.
-Plants fossils.
-Model of an primitive rat.
-Head and body of a primitive rat.
-The symmerodonta.

3. THE FIRST
CELL


Since living
things first
appeared on the
planet, they
have changed
to adapt to the
conditions of
their
enviroment
 We call this
biodiversity.
This is one example of the first
cell, a bacteria.

4. The bacterias evolutionated and reproduct. In this
way appeared lots of species.
The appeared the cells. Their join together and
form firsts organisms.

5. How eras and periods formate?
We dont know when life appeared in the planet, but we have an
idea of the periods and eras thanks to the fossils, that helped
scientist to separate the rests of the bodys and the footprints in
different millions of years.
Fossils also related the eras to different epochs of appearing
and desapearing of the several species.

6. The eras .
There are five eras:
Archaic : 5.000 millions of years ago the Earth
is formed , but there is no life.
Primary : 2.600 years ago appeared firsts
molluscs.
Secundary: 240 millions of years lived the
dinosaurs.
Terciary: 65 millions of years ago firsts
mammals were born.
Cuaternary : 2 millions of years ago the men
has appeared.

7. What are the fossils?
Fossiles are the body, or footprints of this
living thing, mineralized and converted in
stone.
The footprints can be excrements, tracks,
or evrything that show us the activity of a
living thing.
e
Here we can see
one axample.

8. How fossils are formed?
The fossils can be formed in different ways. Here is the
more common one:
1.First, the body is burried under the mud.
2.Years later, there are just the bones under the layers of
mud converted in sedimentary rocks.
3.Past some millions of years the sedimentary layers of
rock have moved and the bones have mineralized.
4.Then, the layers bagan to move and the fossil comes to
light.

9. How fossils help us?
Fossls a a very important data about the history of our planet.
It helpes us in many ways:
Reconstruct an important part of the history of life because
scientists have learned about the characteriatics of many
extinct organisms.
Obtain information of the history of Earth: we can know
when an organism appeared and when it extinct.
Make a calendar of the history of Earth, to divide it in eras
and periods.

10. History of a spider.
This was a spider caught in the
resine of a tree. It is called ambar.
The ambar conserved the body of
the spider perfectly, so we can see
the animal in the same conditions
than when it died.
A lot of other insects were caught
in this tipe of resine, so we have a
small part of many millions of
years ago.

11. The triasic bird.
The skelet of this triasic bird was found after millions of years .
It is very important because it conserved some of its feathers.
Thanks to that we know a dinosaur put the first bird egg. And
that responds the questions ``who was first, the egg or the
chicken´´. Today we know that it was the chicke.

12. LIFE STARTED IN
THE SEA
There are a lot of theories about how
life started, but all them says that life
started in the sea. This is why we have
found lots of fossil shells and
bacterias in the sea.

13. Ceratites.
The Ceratites is an extint genus of the ammonite
cephalopod that lived in marine habitats in what is now
Europe, Asia and North America during the triasic.
It is named Horn Stone because
of its form. All other different
species of its family have the
same form.

14. Some plants
get incrusted
in the stone
.When the
plant
discompaund
s it leaves
the siluet of
its leaves on
the rock .
PLANTS FOSSILS

15. This plant is very similar of its
ancestor a primitive fern .
The leaves are identic to the
primitive plant .
That give us the idea that this plant
hasnt evolutionated practically
nothing.

16. This is the model of the skeleton of
a rat found after a lot of time.

17. THE HEAD
AND THE
BODY OF A
PREHISTORIC
RAT
This is part of the restant body of a prehistoric rat.
It was found in Timor Oriental, and it was 40 times
bigger than a normal rat. This kind of rats
desappeares 1.000 years ago, but scientists say the
species was born in prehistory.

18. Symmetrodonta
This fossil was found in
South America and it is
procedent of a family of
mammals characterized for
the triangular molars. The
scientists say that although
there were many
individuals, there are few
fossils.

19. And this was how
the biodiversity
expanded, and the
evidence the
fossiles that left us.

20. This presentation was made by :
NATALIA HERNANDEZ
SOSNOWSKA
&
GABRIELA CAROLINA
STANCU