. Groups of specialized cells cooperate to form a tissue, such as a muscle.
.This requires that they take in nutrients, which they use to provide energy for the work that cells do and to make the materials that a cell or an organism needs. Specialized cells perform specialized functions in multicellular organisms.
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Fossil hunters can be good stewards by respecting the area around the dig site. Instead of getting big machinery to do the dig and ruining the area around the fossil, they can instead be careful in obtaining the fossils.
If a star of 50 solar masses were to supernova. It would most likely become a black hole.
A star is a hot body of glowing gas which starts its life in Nebulae. The stars vary in size, mass and temperature. The mass of a star ranges from 1/20 times to 50 solar mass.
The stage one of the stars is born in nebula, which is a region of very high density and then it gets condensed to a huge globule of gas and dust that contracts under its own gravity.
The next stage is a region of the condensing matter which starts heating up and glowing is known as Protostar. At stage three, hydrogen fuses and forms helium as the nuclear reactions start. Stage four is a Main Sequence star when it starts to release its energy, contraction stops and it begins to shine.
Some of the stars have mass more than 3 times of the Sun and up to 50 times the mass of the sun.
When the surviving core is between 1.5-3 solar mass, with higher contraction making it tiny and dense a Neutron star is formed. If the core is greater than 3 solar masses then the core further contracts to become a Black Hole.
The human immunodeficiency virus (HIV) that causes the disease known as aids selectively infects helper T cells (CD4+).
This retrovirus also infects macrophages and dendritic cells. When CD4+ T cell numbers decrease below a critical level (due to the killing of this cells with different mechanisms), cell-mediated immunity is lost. As a result, the body becomes progressively more susceptible to infections, leading to the development of AIDS.
<span> HIV can be transmitted only via body fluids like blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk, which means that people usually get or transmit HIV through sexual behaviours and use of the needle. For HIV infection, these fluids must come in direct contact with a mucous membrane or damaged tissue. Another way is to be directly injected into the bloodstream (from a needle for example).</span>
