WHAT IS THE EVIDENCE FOR EVOLUTION?

Evolution through time periods:

Precambrian time is divided in three times:

Hadean: in this time, the solar system was forming, surrounded by a cloud of gas and dust around the sun. This gas, is supposed to be derived from a supernova (the explosion of an old, massive star). Particles surrounding the sun began to coalesce by gravity into larger lumps, or planetesimals, which continued to aggregate into planets. Left-over" material formed asteroids and comets - like asteroid Ida. The oldest meteorites and lunar rocks are about 4.5 billion years old, but the oldest Earth rocks currently known are 3.8 billion years old. Sometime during the first 800 million or so years of its history, the surface of the Earth changed from liquid to solid. Once solid rock formed on the Earth, its geological history began.

Archaean: The atmosphere was very different from what we breathe today; at that time, it was likely a reducing atmosphere of methane, ammonia, and other gases which would be toxic to most life on our planet today. Also during this time, the Earth's crust cooled enough that rocks and continental plates began to form. It was early in the Archaean that life first appeared on Earth. Our oldest fossils date to roughly 3.5 billion years ago, and consist of bacteria microfossils. In fact, all life during the more than one billion years of the Archaean was bacterial.

This is an artist's depiction of what an Archaean coast might have looked like 3.5 billion years ago.

Proterozoic era: Many of the most exciting events in the history of the Earth and of life occurred during the Proterozoic -- stable continents first appeared and began to accrete, a long process taking about a billion years. Also coming from this time are the first abundant fossils of living organisms, mostly bacteria and archaeans, but by about 1.8 billion years ago eukaryotic cells appear as fossils too. With the beginning of the Middle Proterozoic comes the first evidence of oxygen build-up in the atmosphere. This global catastrophe spelled doom for many bacterial groups, but made possible the explosion of eukaryotic forms. These include multicellular algae, and toward the end of the Proterozoic, the first animals.

Phanerozoic Eon is divided in three times :

Paleozoic Era: The Paleozoic is bracketed by two of the most important events in the history of animal life. At its beginning, multicelled animals underwent a dramatic "explosion" in diversity, and almost all living animal phyla appeared within a few millions of years. At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species. The Paleozoic took up over half of the Phanerozoic, approximately 300 million years. During the Paleozoic there were six major continental land masses; each of these consisted of different parts of the modern continents. For instance, at the beginning of the Paleozoic, today's western coast of North America ran east-west along the equator, while Africa was at the South Pole. These Paleozoic continents experienced tremendous mountain building along their margins, and numerous incursions and retreats of shallow seas across their interiors.

Mesozoic Era The Mesozoic is divided into three time periods:

the Triassic (245-208 Million Years Ago), the Jurassic (208-146 Million Years Ago), and the Cretaceous (146-65 Million Years Ago). Mesozoic means "middle animals", and is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic. Dinosaurs, which are perhaps the most popular organisms of the Mesozoic, evolved in the Triassic, but were not very diverse until the Jurassic. Except for birds, dinosaurs became extinct at the end of the Cretaceous. Some of the last dinosaurs to have lived are found in the late Cretaceous deposits of Montana in the United States. The Mesozoic was also a time of great change in the terrestrial vegetation. The early Mesozoic was dominated by ferns, cycads, ginkgophytes, bennettitaleans, and other unusual plants. Modern gymnosperms, such as conifers, first appeared in their current recognizable forms in the early Triassic. By the middle of the Cretaceous, the earliest angiosperms had appeared and began to diversify, largely taking over from the other plant groups.

Cenozoic era The Cenozoic is the most recent of the three major subdivisions of animal history. The other two are the Paleozoic and Mesozoic. The Cenozoic spans only about 65 million years, from the end of the Cretaceous and the extinction of non-avian dinosaurs to the present. The Cenozoic is sometimes called the Age of Mammals, because the largest land animals have been mammals during that time. The Cenozoic is divided into two main sub-divisions: the Tertiary and the Quaternary. Most of the Cenozoic is the Tertiary, from 65 million years ago to 1.8 million years ago. The Quaternary includes only the last 1.8 million years.

B.To calculate your birthday related to the earth´s age you must do the following instructions:

I am 15 years old

My birthday: December 13

1) The earth is: about 4.6 billion years old

It has: 4.6 billion /365 = 12,602,740 days

2) Number of days from January 1st until my birthday:

31+28+31+30+31+30+31+31+30+31+30+13=347 days

3) Number of days substracted from the total number of days in a year:

365-347= 18 days

4) Equivalent number of years on the geologic time scale:

18 x 12602740= 226,849,320 years

5) Millions of years ago: 227 MYA

6) Name of the geological period that corresponds to this year:

MESOZOIC, TRIASSIC

7) A card for the Earth!

Happy Birthday, Earth!

During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator, called Pangaea.

The climate was generally hot and dry.

Both the start and end of the Triassic are marked by major extinction events, which were particularly severe in the oceans. It was accompanied by huge volcanic eruptions that occurred as the supercontinent Pangaea began to break apart.