Life Invaded Land

06/12/2010 § 1 Comment

Our last class was a chance to review the lessons from the previous two classes and was literally an eighty-minute period history session in terms of the biological happenings and events. There was much talk about mass extinctions, different organisms, evolution, and the class mentioned the words ‘period’ and ‘era’ a lot.

As we learned earlier in the week, mass extinctions exist (wow. Irony) so that there is a balance between life and death. Although nature allows for millions of organisms to live, some must die. In my head, it sounds like there cannot be too much of an abundance of life on the earth.

Leaving behind the biochemistry half of this unit just a little bit, the class now has a handful—or more than a handful—of information about the evolution of early life. The majority of the class already understands the origin of eukaryotes, multicellular cells and the eventual rise of different species and organisms. We also understand that life on land could not have existed without oxygen—or else the creatures could not have breathed. Also, I’m pretty sure we get the main idea between the process of making an ozone to protect new land life forms from the UV rays and other harmful natural rays that hit the earth.

Overtime, all of these factors plus unique RNA molecules and division of labor between protists and bacteria lead to the early Palaeozoic life. The first part of the Palaeozoic era was the Cambrian period. (Before the Cambrian period was simply the pre-Cambrian period. All those millions of years were called the pre-Cambrian period). By this point in class, we’d begun learning about the six most important periods we had to know about for this unit.

The Cambrian period was first. During this period, there was a huge explosion of some sort. Afterwards came the Ordovician period where the first fish started appearing. They were, however, jawless. Next was the Silurian period when the first land plants and even a few animals started making it onto land. The Devonian period was a time when insects, vertebrates and amphibians became highly successful in adapting to land and plants. Following the Devonian period was the Carboniferous period where the first real forests ever evolved. To this day, we use these trees for our coal industry, something I didn’t know. Finally, the Permian period can be remembered because during this period, almost 96% of life on earth was almost permanently wiped out. After the Palaeozoic era was the Mesozoic era—the middle era. During this time, the first dinosaurs and mammals appeared during the Triassic period. Then, relating to the famous block-buster selling trilogy, dinosaurs were the dominant species during the Jurassic period. Finally, the Cretaceous period was the most recent mass extinction known to earth’s history, wiping out almost all the dinosaurs (minus birds, whose skeletal structure matches that of a dinosaur’s so much, the two different kinds of animals could have been cousins or even brothers/sisters).

As mentioned earlier, plants, animals, land life cannot exist without the development of the ozone layer and enough oxygen in the air. Because of oxygen and the ozone layer: life was able to come to sea and land, and animals could prosper.

One type of organism that survived well were arthropods because their body armor helped them succeed in their environment with their exoskeleton and appendages. Other organisms with backbones, vertebrates, followed afterwards onto land, such as the first fish (during the Ordovician period) that didn’t have jaws (the fish eventually grew jaws and teeth and became what we know as sharks), amphibians that evolved from fish, except with legs replacing the fins and a variety of other differences, reptiles—which evolved from amphibians—and mammals and birds.

It may be a long shot, but if a student looks at this unit in terms of history and if he or she watches a few animals evolve with their surroundings, where they live, what they need to eat, how they’re going to survive; we can see how their bodies change, how their behavior changes to better suit their surroundings and in a history lesson, we can watch how things change (which is our essay question).

§ One Response to Life Invaded Land

  • Dave Ferguson says:


    With so much information in one post, you did a great job of organizing ideas by paragraph, and then highlighting the key terms with a combination of bold and italicized words.

    Mr. F.

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