31 pairs
Spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each pair connects the spinal cord with a specific region of the body.
Answer:
Xylem cells have no cytoplasm or end walls, meaning they form a tube through which water can pass freely to allow water transport. Lignin strengthens the cell walls, helping to support the plant.
Directional selection is where one phenotype is favored, so an example would be "a population of madagascar hissing cockroaches suffers heavy predation from lizards. Because their heads are small, the lizards are unable to eat the very largest adult cockroaches, and instead prey upon small and medium sized adults, so as a result the large cockroaches are favored and live".
Meanwhile, disruptive selection is where both extreme phenotypes are favored, an example would be "a population of rabbits can have black fur, white fur or grey fur. This population of rabbits lives in an area of white rocks. When a local volcano erupts, black volcanic rock now dots the landscape amongst the white rocks. Now the black and white rabbits live longer because the black and white spots on the landscape camoflauge them. The two extreme phenotypes are being favored."
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Proteins are the Body's Worker Molecules
Explains structure-function relationship, amino acids, protein folding, genetic code, sickle cell and CF, and computer modeling.
