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>
The route sperm take through the human male reproduction by C. Vas deference, epididymis then the Urethra.
Answer:
fossils depict how our bones have changed from past year to today.
Explanation:
for example, wisdom teeth were use to eat raw meat and crush bones as shown in fossils like Lucy. Another example would be extinct animals preserved, they were not able to survive and adapt to the earths changing conditions.
Answer:
<em>Evolution</em>
Explanation:
Evolution can be described as the changes which occur in a population over a period of time. Over a period of time, organisms tend to evolve those characteristics which make them better adapted to live in an environment. Such changes which occur over a long period of time are termed as evolution. Charles Darwin was the scientist to bring forward the theory of evolution.
The change in the tail length of a rat over a course of many years is an example of evolution.
Answer:
a move from the fundamental niche to the realized niche for both species.
Explanation:
The niche of an organism is the functional role of the organism in the community or the ecosystem as a whole. This include the environment an organism lives and all the jobs it does in it.
Fundamental niche refers to all the possible functional roles of an organism in an ecosystem while realized niche refers to the specific roles the organism is limited to as a result of resource limitation, competition or other factors.
Resource partitioning involves the division of limited resources among organisms so as to avoid competition within the niche.
<em>Hence, resource partitioning causes a move from the fundamental niche of an organism to the realized niche of that organism. </em>
