Most fish exchange gases using gills<span> on either side of the </span>pharynx<span> (throat). Gills are tissues which consist of threadlike protein structures called </span>filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia.<span>Each filament contains a </span>capillary<span> network that provides a large </span>surface area<span> for exchanging </span>oxygen<span> and </span>carbon dioxide<span>. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing </span>countercurrent exchange<span>. The gills push the oxygen-poor water out through openings in the sides of the pharynx. Some fish, like </span>sharks<span> and </span>lampreys<span>, possess multiple gill openings.</span>
CD4 and CD 8 are molecules present on the surface of T cells where they interact with major histocompatibility (MHC) Molecules.
CD4 and CD8 improve T cell signalling by attaching to MHC class II (CD4) or MHC class I (CD8) molecules on APCs.
- The association of CD4 with MHC class II significantly decreases the number of antigenic peptides necessary for T cell activation (5) and significantly boosts cytokine output by helper T cells.
The MHC molecules' wide polymorphism is their distinguishing trait.
- This polymorphism is crucial for T cell antigen recognition.
- A T cell detects antigen as a peptide bound by a specific allelic variation of an MHC molecule and will not identify the identical peptide bound by other MHC molecules.
- This type of T cell activity is known as MHC limitation.
Hence, the correct answer is option C
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The correct answer is:
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C.asthenosphere </span><span>
If I made a mistake feel free to tell me ^-^
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Answer:
Secondary succession is usually faster than primary succession because soil and nutrients are already present due to 'normalization' by previous pioneer species, and because roots, seeds and other biotic organisms may still be present within the substrate.
Explanation:
that's all i got really i hope it helped a little.
Diffusion is important to organisms because it is the process by which useful molecules enter the body cellsand waste products are removed. Digested food molecules (amino acids, glucose) move down a concentration gradient from the intestine to the blood.
