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Biology Example Essays

Example Biology Essays

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A collection of Example Biology Essays

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Biology: The Fossil Record and Theories of Evolution

In general, the term 'evolution' can imply a drastic orgradual change from a very broad perspective. Life on earth, the universe,galaxies, as also the earth in general have evolved through millions of years.In this essay we consider only one aspect of evolution emphasizing on evolutionas a biological tool for change among species and consider fossil record assupportive of both evolution theories and also the other theories contrary toevolution.


Biology: Xenotransplantation Organ Transplantation

Xenotransplantation is a very useful surgical method to be used nowadays which is "the transplantation of living cells, tissues or organs from one species to another species such as from pigs to humans." ( The transplantation can be between the same species (human to human) or different species (animal to human) which causes more problems.

There are some steps before a recipient can carry out xenotransplantation. Firstly, there has to be a donated organ that will less likely to cause rejection inside the recipient's body which is the hardest part.The organ has to be checked carefully. Then the recipient can carry out organ transplantation. After the surgery there are some things that the recipient needs to be careful with. Many people desperately need more organs, therefore that is why xenotransplantation has developed between the same species and different species.

Transplant surgery is defined as "the surgical removal of an organ(s), tissue, or blood products from a donor and surgically placing or infusing them into a recipient." ( The purpose of transplant surgery is to give a chance to recipients who do not have any other ways to cure the diseases, because they are at the very last stage for their organ diseases.


Biology: Muscle Fibre Solution

If the skinned muscle fibre is immersed in the salt solution similar to intracellular muscle cytoplasm and also contains Ca2+, the cell membrane of the fibres will become impermiable for small molecules like ATP because the permeability of the cells depend on the concentration of free ionized calcium Ca2+ in cytoplasm. This can be explained with the help of an example. Put the whole muscle fibres in the Ca2+ indicatorfura-2 conjugated to high molecular weight dextran.

The fluorescence when measured from cytoplasm was found 17 degrees C (Isaevaand & Shirokova, 2003). The fluorescenceexcitation spectrum of fura dextran was turned slightly red in resting fibers compared with the spectrum of the Ca (2+)-free indicator inbuffer solutions. If we compare the spectra in the cytoplasm and inthe vitro solutions, we find an apparently "negative" cytoplasm (Ca2+), which probably reflects an alteration of the indicator propertiesin the cytoplasm.

To change the indicator's fluorescence signal in termsof cytoplasm [Ca2+], we applied beta-escin to permeabilize the cellmembrane of the fibers immersed in fura dextran. After treating this fibre with 5micro M beta-escin for 30 to 35 minutes, the cell membrane becomes permeable to smallmolecules like Ca2+, ATP, etc, whereas the 10-kD fura dextran only slowlyleaked out of the fibre.


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