First, preexisting rocks must weather/erode, forming the sediment that will eventually form the sedimentary rock. Then, that sediment must settle someplace, and over a long period of time, pressure begins to build. This causes the sediments to become compacted. After a long period of time (and a lot of pressure), the sediments cement together and form a sedimentary rock. In a nutshell, sedimentary rocks form through compaction, cementation, and eventually... lithification.
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Answer: B and C
Explanation: Both are below 6 on the scale so their not as hard or tough.
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.
That would be false. The Ozone layer is what protects Earth from UV radiation. The Ozone is part of the Stratosphere.
Answer:
The cells found in the root of the plant normally lacks chloroplasts, as roots do not perform photosynthesis. The main function of chloroplast is photosynthesis.
Explanation:
The plant cell contains nucleus, cell wall, cell membrane, mitochondria, chloroplasts, vacuole, endoplasmic reticulum, ribosomes etc. Chloroplasts contain green pigments which give green color to the plants. The main function of chloroplast is photosynthesis. During photosynthesis, the plants produce glucose and release oxygen by using carbon dioxide from the air, and absorbing water and nutrients from the soil. Using the glucose in the plants and oxygen, mitochondria produce energy.
The root system of the plants absorb water and nutrients from the soil. The absorbed water and nutrients are then transported to various parts of the plant to carry out processes like photosynthesis, maintaining turgor pressure etc. They have different types of cell which perform some specific functions. These cells also contain cell wall, cell membrane and mitochondria. Mitochondria provides energy for the active transport of water and nutrients. But chloroplasts are absent in root cells as they do not perform photosynthesis.
