Thyroxine is a complex organic compound containing iodine. Thyroxine concentration in the body is kept to the required levels through a negative feedback mechanism. The production of thyroid stimulating hormone is regulated by thyroxine. An increase in thyroxine inhibits the pituitary gland which responds by secreting less thyrotropic hormone. This in turn reduces the activity of thyroid gland leading to a drop in thyroxine production. A low thyroxine level removes the inhibitory influence on the pituitary so that more thyroid stimulating hormone is produced.
There are two major ways that molecules can be moved across a membrane, and the distinction has to do with whether or not cell energy is used. Passive mechanisms like diffusion use no energy, while active transport requires energy to get done.
This is because of how reproduction works in humans. Male and female sex cells are formed by a process called meiosis, where the diploid chromosomes divide and separate. And so the ratio of male to female births is also 50:50.
As we can see from the chart, the diversity of animals in Africa are being affected year after year. In 10 year gap 53,000 lions, 42,500 cheetahs and 12,500 zebras are dead and this is a dangerous sign.
