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Answer:
The correct answer is leaves, spines are modified leaves.
Explanation:
Cactus have spines, the thorn-like thing, in which replace leaves. These spines lower the surface area of the cacti reducing water loss. These spines are actually advance modified leaves which rise according to their environmental conditions.
The stem of a cactus is also thick and fleshy which allows it to store water. The cacti's stem also has a waterproof waxy kind of layer to help retain more water.
Thus, the spines of a cactus plant are nothing but a modified leaf.
The LDL receptor and transferrin receptors are examples of receptors that function by receptor-mediated endocytosis. The LDL receptor is a transmembrane protein of the plasma membrane. Occupancy of the ligand binding site of the LDL receptor in the extracellular domain of the receptor by LDL initiates endocytosis.
Answer:
Evolution of the Dog. Recent molecular evidence shows that dogs are descended from the gray wolf, domesticated about 130,000 years ago.