Easter Island is a small 63-square-mile patch of land — more than a thousand miles from the next inhabited spot in the Pacific Ocean. In A.D. 1200 (or thereabouts), a small group of Polynesians — it might have been a single family — made their way there, settled in and began to farm. When they arrived, the place was covered with trees — as many as 16 million of them, some towering 100 feet high.
These settlers were farmers, practicing slash-and-burn agriculture, so they burned down woods, opened spaces, and began to multiply. Pretty soon the island had too many people, too few trees, and then, in only a few generations, no trees at all.
Answer:
Answer for the question:
Which of the following statements about the phosphorus cycle is false? The main abiotic reservoir for phosphorus is in the soil. Plants release dissolved phosphate ions into the soil. Guano can be used by farmers to add phosphorus to the soil. Phosphates that drain from soils into the sea becomes part of new rock and will cycle back into living organisms.
is given below.
Explanation:
The correct answer is given below.
Soil is not the main reservoir for the phosphorous. The main antibiotic phosphorous is in the rocks.
Answer:
Blood clothing is an example of positive feedback.
This type of feedback mechanism is useful to the body because it multiplies the factor that intervenes in clotting accelerating the process.
If a toxin affects the molecules that signal for platelets the feedback will not be effective enough to produce clotting and the body will keep bleeding.
Explanation:
Blood clotting is an example of positive feedback due to the fact that when the vascular endothelium is damaged platelets will go to this area and activate themselves once they are in contact with the collagen fibers of the damaged structure. When the platelets are activated they will release the contents that is stored in their granules. One of the contents is a Gq-linked protein receptor cascade, that will increase the concentration of calcium in the platelets. Calcium activates protein kinase C, which, in turn, activates phospholipase A2 (PLA2). PLA2 will modifies an integrin membrane increasing its affinity to bind fibrinogen. The activated platelets change their shape , and the fibrinogen cross-links with the integrin membrane aiding in the aggregation of adjacent platelets. After this the coagulation cascade takes place. there are two pathways the extrinsic and the extrinsic one.
The extrinsic pathway will be activated due to tissular factor released by the platelets and the intrinsic pathway will be activated due to endothelial collagen. The final product of both pathways is factor x.
Factor x will transform prothrombin into thrombin will activate the conversion of fibrinogen into fibrin. Thrombin will form a net of fibrin that will the clot.
A cascade reaction is useful because every component of the cascade are related making a quick reaction once that one of then is activated and can activate other or more factors.
If a toxin affects the molecules that signals for platelets, platelets will not go to the damaged area and in consequence there will not be thrombin and fibrin to form the clot together with platelets.
Answer: Example for multiple alleles is human blood type
Explanation:
Blood types exsist as four possible phenotypes A,B,AB, and O .
Its found in the body's tissues.
Hope that helps. I can give a more detailed answer if you need one. <span />
