<u>Answer:</u>
Recent evidence suggest that feathers evolved from scales and suggest that 'feathers and pycnofibers' could be homologous.
<u>Explanation:</u>
- One of the major difficult issue related to bird evolution is the evolution of feathers.
- Feathers are considered as the most 'complex integumentary structures' which are found in vertebrates.
- Evolutionary developmental biology suggests that the 'planar scale structure' is been modified for developing into feathers by 'splitting' to form web like structures.
- Scales and Feathers consist of 'two distinct form of keratin' so it was thought that 'each type was exclusive skin structure' but recent study suggests that they are developmental expressions of same skin structures.
Electron microscopes use _beam of electrons___ in order to allow for higher magnification and more detail when viewing specimens.
Explanation:
A beam of electrons has a shorter wavelength than normal light used in light microscopes, by approximately a factor of X 100000. Therefore, electrons microscope have the inherent attribute of having a very high resolution. They have been used to discover very small organelles in cells such as the ribosomes and mitochondria that cannot be clearly viewed even with the highest resolution in light microscopes.
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Answer:
The reactivity greatens the farther you go down on the periodic table. Lithium will have the weakest reaction, and cesium will have the greatest reaction. Patterns like this are useful to scientists because it shows which elements are the most reactive and which aren't. The farther down and to the left you go within the periodic table, the more reactive the elements become. The farther up and to the right you go, the less reactive they become.
Explanation:
D. Proteins help control substances by making trans-membrane channels.
