Answer:
a.energy source ,either sunlight or chemicals
Explanation:
the animals using sunlight are known as photoautotrophs and the animals using chemicals are known as chemoautotrophs.
<span>D. That they variable is staying the same.
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The walls of a villi are only one cell thick, composed of thin epithelial cells, to allow dissolved molecules to pass through quickly.
The epithelial cells of the villi are further covered by even smaller finger-like projections known as microvilli. These microvilli further increase the surface area for absorption.
Close association of the blood capillaries in the villus and the epithelium create a minimal distance for diffusion of food molecules.
Mitochondria in the epithelium provide the ATP for active transport.
The lacteal branch at the center of villi carry away fats after absorption.
Answer:
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The variety of compounds would decrease, since four violence charge give carbon the possibility to form single bond, double bond and triple bond. Where as a atom with 7 violence charge can only form single bonds.