Answer:
Feathers initially evolved in a role associated with sexual selection.
Explanation:
In species where only males had feathers, these feathers can be considered to have evolved into a role associated with sexual selection. This is because in these species, males used their feathers as a sexual attraction for females, in this case, females chose the males that had more attractive feathers to mate and generate new individuals for the species. An example of this can be seen in the peacock, where the tail with lush feathers is only present in males and is intended to sexually attract females.
<span>Muscle cells are uniquely adapted to contractile function due to three main things. FIrst, they have a large capacity for storage of readily available glycogen to use for work. Second, they contain the actin and myosin cross-bridge cycling structure to perform a contraction of a muscle fiber. Finally, each fiber has central nervous innervation to control contraction and relaxation of the muscle fibers.</span>
Unsaturated fatty acids are a component of the phospholipids in cell membranes and help maintain membrane fluidity. The Phospholipids contain a variety of unsaturated fatty acids, when compressed, the “kinks” in their tails push adjacent phospholipid molecules away, that helps in maintain fluidity in the membrane. Unsaturated fatty acids have at least one double bond, creating a "kink" in the chain, the absence of double bonds decreases fluidity, making the membrane very strong and stacked tightly.
The ratio of saturated and unsaturated fatty acids determines the fluidity in the membrane at a temperature, at appropriate temperatures the phospholipids have enough kinetic energy to overcome the intermolecular forces holding the membrane together, which increases membrane fluidity.
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