The video talks about how the lipid bilayer was discovered. The cell membrane has to be able to allow certain molecules in and others to go out of it. The cell membrane protects the cell. It is a bilayer that is two sided.
Starting with cells, homeostasis is needed to sustain balance. Cells take in and expel matter to create the desired balance. Organs are made of cells, and also can only have certain amounts of matter in the organ. (i.e. blood in the heart) organ systems have a similar need to maintain homeostasis. (air in respiratory system) Then, organisms such as humans need to maintain homeostasis as well. (i.e. having nutrients in body) air diffuses to different places, creating wind, to maintain the balance of equal distribution. Planets maintain homeostasis by keeping certain amounts of matter on them and not having the matter fall off into space. Solar systems and galaxies all have a trend to be made up of different bodies of matter which orbit the larger ones to keep the inertia and gravity in balance.
One thing I learned in this three class unit is that plants have a central vacuole. This vacuole is key to help them survive when they are not near water, just as camels keep water in their humps, plants keep water in their vacuoles. These vacuoles are at the center of plant cells.
The video went into more detail about some scientists that were discussed in the book. The speaker spoke about cell theory, and the debates about whether cells come from other cells or not. A cool fact from it was that the Robert Hooke and Issac Newton had fights in the science world.
Organelles are not considered alive because most of them do not contain their own DNA. For example, a lipid serving as a plasma membrane would not have its own DNA. Also, organelles are not found out in nature on their own just as cells are. They have to be part of a host cell, which they help function in a relationship that is beneficial to both. For something to be alive, it has to be made of cells, organelles are not made of cells. They are a part of something that is alive.
During this three class lesson I learned that there is no definition agreed upon for life. This was extremely surprising because biology is a widely studied science that focuses on life. I learned that some biologists have different guidelines for life, but there is no consensus. There is no definition of life yet, but I found it very interesting that a subject so widely studied could have no definition of the thing it focuses on.
Summary
The article "Defining Life," from Astrobiology Magazine, is a compilation of several views on the definition of life. The article uses views of several scientists to come to a conclusion that we can only define what we understand. Without chemistry, defining water is tough. We have no clear way to define life yet. The most comprehensive view in the article is that life can reproduce, use energy, and do so by following a set of instructions. Commentary This article was very interesting. The views of several scientists who studied life for a living were all flawed because as the article points out, there is no way to define life. There may be another set of science that we need to understand before comprehending what life is is possible. I found Benton Clark's analysis to be the most "accurate." Bibliography Mullen, Leslie. "Defining Life." Astrobiology Magazine. Nasa, 19 June 2002. Web. 9 Sept. 2013. <http://www.astrobio.net/exclusive/226/defining-life>. Post on tardigrades
I learned a lot about tardigrades, but the most interesting fact was their ability to perform cryptobiosis. The idea that a living thing could turn practically dead, using very little energy to stay alive and doing very little to save energy, is incredible. The tardigrades had to curl up when put in the acidic lemon juice, but they returned to normal in the basic solution because of their ability to perform cryptobiosis. Tardigrades are very interesting creatures, but their most remarkable feature is that they can "die and come back to life." |
AuthorMichael Tellini Archives
May 2014
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