Birds and mammals are endothermic (warm-blooded), maintaining a constant internal body temperature regardless of the environment. Crow is a bird, hence warm-blooded. Fish, frog (amphibian), and snake (reptile) are ectothermic (cold-blooded), their body temperature varies with the environment. Endothermy requires high metabolic rate and insulation (feathers, fur).
Explanation:
The right atrium receives deoxygenated blood from the body via the superior and inferior vena cavae. It then passes to the right ventricle, which pumps it to the lungs for oxygenation. The left atrium receives oxygenated blood from the lungs via pulmonary veins, and the left ventricle pumps it to the body. Thus, the right atrium is the receiving chamber for systemic deoxygenated blood.
Consider statements about human nutrition: 1. Proteins are made of amino acids. 2. Carbohydrates are made of fatty acids. 3. Fats are made of glycerol and fatty acids. Which are correct?
Explanation:
Proteins are complex macromolecules composed of long chains of amino acids linked by peptide bonds. Fats (triglycerides) are lipids composed of one glycerol molecule esterified to three fatty acid chains. Carbohydrates are composed of simple sugars (monosaccharides) like glucose, not fatty acids. Thus, statements 1 and 3 are correct, while statement 2 is false.
Explanation:
Myelin, a lipid-rich sheath formed by Schwann cells (PNS) or oligodendrocytes (CNS), insulates axons, allowing saltatory conduction—impulses jump from one node of Ranvier to the next, greatly speeding up transmission. It also conserves energy. Demyelinating diseases like multiple sclerosis slow conduction.
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