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Species could go extinct when their environment changed if they could not adapt to the change.
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ABO blood grouping system is based on presence or absence of three types of antigen on red blood cells. A and B blood group have A and B antigens respectively. AB blood group has both A and B antigens. O blood group does not have any antigen.
A body with particular blood type will consider other blood group foreign ( because it has different antigen ) and produce antibodies against it. A person with blood type A can not be given B type blood because the antibodies in his body will destroy RBCs with B antigen which may even prove fatal.
AB blood type person can receive blood from both A and B blood groups because he has antigens for both of them so it will produce antibodies for neither of them. He can also receive O type blood because O blood does not have any antigen so it can be given to any person without incompatibility reaction.
However, AB individual can only donate blood to AB individual because his blood cells have both A and B antigens. So, he can only donate blood to an individual who does not produce antibodies for both A and B blood groups and that would only be another AB blood type individual.
The geologist time scale was formed when scientists studied rock layers and index fossils worldwide. With this information, they placed Earth's rocks in order by relative age. Later, radioactive dating helped determine the exact age of the divisons in the geologic time scale.
This scale is organized by the 4.6 billion years of earth's history into sections based on important changes seen in the geologic record. The largest intervals are called eons, with each eon containing many millions of years.
In precambarian time the processes that affect Earth's surface have lessened the erosion on the surface. Earth was being hit by meteorites every second. Now there is water erosion and there wasn't back then. The surface changes have lessened over time.
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The characteristic features of the phylum Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a tailgut.
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Oceans will increase in temperature due to global warming. This will adversely effect cold water species such as the humpback whale and increase the territory of larger warm water predetors like sharks.
