Answer:
(D). lungs
Explanation:
Cladograms are diagrams that show cladistic relationship between organisms of different species on the basis of their characteristics. The cladograms may include characteristics to make two organisms different from each other.
In given cladogram, characteristic that separates bony fish from amphibians is 'lungs', as lungs are absent in bony fishes, while present in amphibians.
Thus, the correct answer is option (D).
Answer: Brain stem
Explanation:
The brainstem can be defined as a structure which is present in between the midbrain and the cerebrum. This controls the flow of information from the brain and the rest of the body. It also controls the functions like breathing, heart rate, consciousness, sleep and wake cycle and blood pressure. The brain stem consists of pons, midbrain and medulla oblongata.
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:
RNA contains an additional oxygen atom on the ribose sugar. (Ans. C)
Explanation:
RNA contains a sugar which is known as ribose, and which contains an extra group of hydroxyl (OH-) while DNA contains deoxyribose sugar.
RNA contains four nitrogenous bases cytosine, adenine, guanine, and uracil, while DNA contains cytosine, adenine, guanine, and thymine.
Double helix means two stranded structure like DNA, while RNA is single stranded.
DNA molecule is much longer polymer than RNA molecule.
Nucleic acid is the macromolecule that carries code for building our body.
