The three changes of state during which energy is absorbed are:
1. Change from solid to liquid - Melting.
2. Change from liquid to gas - Vaporization
3. Change from solid to gas - Sublimation
All these changes of state require heat energy to break the attractive forces that hold the particles of the molecules together, so that they can move into more disorderly states. For instance, when heat is applied to a solid, the solid absorbs the heat and use it to break the attractive forces that are holding the molecules of the solid together. At a particular temperature, the attractive forces will be completely overcome and the solid framework will collapse, thus leading to the melting of the solid.
Answer:
The correct option is: <em>a deficiency of dopamine in the substantia nigra.</em>
Explanation:
The substantia nigra is the principal site involved in the physiopathology of Parkinson´s disease.
Cells from this area degenerate and die progressively causing important degeneration in the central nervous system. The cells that die -with no known reason- are those that produce dopamine and proportionate dopaminergic innervation to the encephalon. In fact, almost all the symptoms exhibited by patients with the disease can be explained by the lack of dopamine in the substantia nigra.
This area uses the neurotransmitter to communicate neurons from the base ganglia. Ganglia are responsible of modulating and modifying movements.
The nigrostriatal system participates in planning and automatic execution of learned movements. When the ganglia activity decreases, so it does the amount and velocity of movements, something typical of the disease.
Answer:
Natural selection is one of the mechanisms by which an organism evolve. In the natural selection when the trait of an organism allows the organism to grow and reproduce in an environment and nature selects it, it is then passed on to the generations and become permanent.
Artificial selection is also one of the mechanism of evolution in which instead of nature, the selection is made by humans like the breeding experiments on dogs and plant crops.
The artificial selection and natural selection are interlinked as in the artificial selection the trait selected by the humans were also selected by nature like the case of crops, the crossing between desired plants produced results which were useful to the humans but grew and reproduced only when the environment selected it to grow and reproduce.
