In HIV-infected patients, there is a gradual loss of CD4+ T cells over time. These cells, also called T helper cells, organize the immune system's attack on disease-causing invaders, like Salmonella.
Homologous and analogous structures are two types of evolutionary evidence, taken together, provide strong evidence for when extinct species most likely diverged from common ancestors, relative to other events happening on Earth.
Several types of evidence support the theory of evolution: If two or more species share a unique physical feature, such as a complex bone structure or body plan, they can all inherit this property from the common ancestor. Physical traits shared through evolutionary history (common ancestor) they say they are homologous. Not all physical properties that look similar are signs of common ancestry. Some physical similarities instead are analogous: they evolved independently in different organisms because organisms lived in similar environments or experienced similar selective pressures.
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Answer:
Through simple diffusion, down the concentration gradient.
Explanation:
The phospholipids of the membrane are amphipathic with hydrophillic heads and hydrophobic tails. Other polar molecules cannot go through this hydrophobic interior. Since small uncharged lipids are non polar and hydrohobic, they are able to go through the membrane without the help of transport proteins. Therefore, the last two options can be ruled out because facilitated diffusion includes the use of a protein. Diffusion involves molecules moving down the concentration gradient so the second option can be ruled out.
