Answer:
D. Activated platelets release chemicals that activate more platelets.
Explanation:
When a stimulus or a change in some condition triggers a response that intensifies the changing condition, the mechanism is called a positive feedback mechanism.
Any damage to tissues makes the platelets to contact and stick to parts such as collagen fibers of the connective tissue present under the damaged endothelial cells. This process of platelet adhesion activates the platelets and brings about changes in them. The activated platelets grow many projections to contact and interact with one another. They also release ADP and thromboxane A2 which in turn activates the nearby platelets. The ADP makes other platelets in the area sticky. The stickiness of the newly recruited and activated platelets causes them to join the originally activated platelets. Eventually, the accumulation and attachment of large numbers of platelets form a platelet plug.
Here, release of chemicals from the activated platlets to activate more platlets represents the positive feedback mechanism.
Answer:
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Most people know that a major function of the kidneys is to remove waste products and excess fluid from the body. These waste products and excess fluid are removed through the urine. The production of urine involves highly complex steps of excretion and re-absorption.
The phylogenetic tree is commonly used by biologists to study evolutionary relationships between organisms and their ancestors. To add up, it is a diagram that branches the "phylogeny" of a single organism which could be very significant and determining on how genetically different or similar they are to their ancestors.
