Oxygen, it takes in Carbon Dioxide and releases Oxygen as a waste :)
Answer:
Because natural selection selects for it. Thus it persists.
Explanation:
You have to understand heterozygote advantage. Basically, it's where heterozygotes have an advantage over homozygotes. In the case of sickle cell disease, heterozygotes have an advantage, and natural selection favors whatever is advantageous. Thus, because heterozygotes each have one recessive sickle-cell allele, as natural selection favors the heterozygotes, the recessive sickle-cell allele persists and remains in the gene pool.
1) Muscle Cell*myosin filament: changes shape and pulls on and releases actin filament allowing movement*If the myosin filament was missing or injured, it would be cause difficulty in movement2) Flagellum*Dynein arms: uses energy from ATP to "grab" the attached droplet allowing a wave like movement when pulling the droplets together* If the dynein arms was missing or injured the flagellum would have no possible way of moving causing it to stuck in mid-air
Hormones
The endocrine system includes various glands in the body that are responsible for secreting hormones into the bloodstream. Hormones are chemical substances produced by the body that regulate certain functions of cells and organs. Hormones can regulate sleep, sex, growth, stress, huger, metabolism, etc.
Theory ----> not proved yet
Law --------> a theory which is proved and universally accepted
