Early Life On Earth 

By:KyleN 

                                                                                                              http://images.google.com/imgres?imgurl=http://api.fmanager.net/files/fossils/SC0091_trilobite.jpg&imgrefurl=http://www.fossil-museum.com/fossils/index.php

(a Tribolite, an organism that was believed to have lived 400 mya)

   Early life on Earth originated as a small cell, destined to have an ancestor that would become part of a dinosaur, or a winged organism. The basic cells on our planet hadn't come around until about 3.8 bya (billion years ago), before the cyanobacteria's  time, Earth was a giant mass of lava and gases, too harsh to sustain life on the planet. Earth's surface eventually cooled, forming a hard surface over the top of the fiery core. There are many accusations of how life had first started on Earth, but I personally believe that chemical reactions from the air as well as in the water led to the creation of early life.

      The first cyanobacteria (cyanobacteria-the very very early version of the prokaryotic cell which was, in fact, aquatic and can manufacture their own food) had lived in huge mats on ocean floors, or either floated on top the water's surface. These early cells also produced mineralsand substances that glued the cells together to create mats, which were huge collections of cyanobacteria that just stayed together, a giant layey of prokarya cells(prokarya-cells of which have no genetic material or nucleus, such as DNA they are very simple cells, along the category with bacteria and archaea). The cyanobacteria lived well in Earth's early  times,  using a process of photosynthesis, using water, sunlight, and nutrients, that is also used in our modern plants today.

 blue-green algae, a modern day cyanobacteria

http://user.uni-frankfurt.de/~schauder/cyanos/image9.jpg

      Gradually, Earth's atmosphere changed and oxygen filled the air. Eventually, a new type of organism was created: the eukaryotic cell (Eukaryotic cell-a cell that contain of a nucleus and genetic material such as DNA. All living organisms have eukaryotic cells within them that are building blocks to the body; from your skin, hair and blood, to your heart, livers, and kidneys). These new types of cells were created when a prokaryotic and mitochrondia(mitochrondia-organelles that burns sugars from food, that actually benefit the early cells, giving them a more productive way of getting energy from consumed food), and a prehistoric eukaryotic cell was formed.

      The eukaryotic cell was the "special"  type of early organisms on our planet. As you already know, eukaryotic cells are the building blocks of life, so when the first eukaryotic cells were created, they started to group together over time, specializing and creating the first multicellular organism. We, as the human race, do not know about how exactly multicellular organisms arose, but we do know thy started out as very simple organisms, such as algae, a type of cross between plant and animal. It has the characteristics and the genetic material of one, but it also has the genetic material of an animal, so algea is in it's own categories of the six kingdoms of life.But around 600 million years ago, the first jellyfish like organisms had evolved.

     Recall that all the past information that you have seen in this report takes place in water. However, about 460 million years ago, the first living things started moving onto dry land. Think about the challenges organisms would face when they moved to dry land. Cells always need water to carry out their life's processes. Organisms on land needed ways to help them have a sustainable supply of water. Organisms in the water didn't face these problems because they were surrounded by water.

     The first living organisms to wash ashore had features like waxy coverings that prevented them from drying out. These organisms were really algae which were coated with the wax. The algae planted themselves into a moist shore so they had a constant supply of water to live off of. Bacteria also moved onto dry land by using the same technique as the plants, keeping themselves on a moist shore.

     But the first true multicellular animals that moved onto dry land were primitive insets, such as tribolite and mites. The insects colonized in land about 400 million years ago, and probably evolved from hard shelled aquatic animals, such as the Ammonitida, an animal that has a spiral shell. Like early plants, these insects were covered in a waxy substance to prevent them from drying up. They were also able to take in the oxygen from the air, not just from the water. Over time, the bacteria, algae, plants, fungi, and insects spread over and around their new habitat, and conditions changed on the surface as the tectonic plates moved from one place to another on early Earth. New life forms evolved in the new condition while those organisms faced each other and reproduced, making more complex animals, such as sharks or tetra pods (four legged animals).

www.tomno.com/forums/attachment.php?attachmentid=399&stc=1&d=1108541950

Ammonitida

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Angiosperm, a flowering plant.

Major Mass Extinctions

• Permian Extinction-As the populations of organisms on Earth grew in size, both on land and water, Earth was soon teeming with life. But by the end of the period (Permian Period-286-248 mya), roughly 95% of the species on Earth had gone extinct for some unknown reason. Many theories have been put forth to explain the extinction.
• -CO2 levels rising, corrupting the ecosystems
• - Volcano activity rises,sending ash into atmosphere, blocking sunlight and killing animals

• Cretaceous Extinction-Around 145 mya, Earth was again teeming with life and new species. Many types of plants and animals, such as the Archaepteryx and Angiosperm, had evolved. But the dominant group overall were the dinosaurs. However, about 80 million years later, the dinosaurs disappeared, long with many other species, due to a meteorite that hit our planet. More than half of our species died by the meteorite, which created a crater known as the Chicxublub Crater.

• For more mass extinctions, go to this other site-Mass Extinctions

Theories Of The Origins of Life 

• Cells flew through the atmosphere and landed on the surface, therefore putting life on our planet.

• Chemical reactions in the air and water created a cover in which a mitochrondia and other things were encased in it.

The Parts Of A Cell

     The cell which is the basic unit of life, is pretty interesting. So we will look into a Eukaryotic cell, to show you what it is made of. 

williamsclass.com/SeventhScienceWork/ImagesCells/EukaryoticCell.jpg

Eukaryotic Cell

• cytoplasm-most of the work in a cell is carried out in this stuff, which holds everything together

• nucleus-an organelle that carries all of the genetic information, like DNA

• organelle-a fancy word that describes everything within the cell

• mitochrondia-as you already know, it is an organelle that burns sugars from food, to produce energy

• lysosomes-a cartridge that practically just holds waste, which is soon exerted from the cell

• endoplasmic reticulum/golgi apparatus-both are organelles that receive and send information from and to the nucleus

• for more information on cells, go to this other site-Cells , or cell repair

Bibliography 

• California science textbook, McDougal Littell

• www.ucmp.berkely.edu/bacteria/cyaointro.html

• World Book-part O