Answer:
<u>Luteinizing hormone </u>(LH) stimulates Leydig cells to secrete testosterone
<u>Follicle stimulating hormone (FSH)</u> stimulates Sertoli cells to secrete protein and other molecules required for spermatogenesis
Explanation:
Under the influence of gonadotropin-releasing hormone, the anterior pituitary releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In males, LH stimulates interstitial cells of testes (Leydig cell) to secrete the hormone testosterone. FSH acts indirectly to stimulate spermatogenesis by causing the release of androgen-binding protein (ABP) from the Sertoli cells. The function of ABP is to maintain the higher concentrations of testosterone to stimulate the final steps of spermatogenesis in the seminiferous tubules.
The hypothesis by Coleman was that the product of the ob+ gene was the appetite suppressing hormone. Hence, the homozygous ob/ob mutant are in a position to synthesize that hormone, and its circulating level would be zero. He also hypothesized that the product of the db+ gene was the receptor for the appetite-suppressing hormone. Thus, the homozygous db/db mutant would be able to synthesize the hormone but would not be in a position to respond to it. It would eat excessively and produce large amounts of body fat, which in turn would produce large amounts of appetite-suppressing hormone . In the absence of a receptor, the db/db mutant's hormone level would remain abnormally high.
Coleman's hypothesis were confirmed when the precise functions of the ob+ and db+ genes were determined. The peptide hormone encoded by the ob+ gene was named Leptin.
There are five levels of cell organization recognized by biologists.
Answer:
The correct answer would be C. The tortoises provided evidence that different species have adaptations suited to their particular environments.
Darwin observed that how different environment on different island lead to the development of different species as a result of adaptations and natural selection.
For example, tortoise inhabiting well-watered islands which used to have short and cropped vegetation had developed a dome-shaped shell.
In contrast, the tortoise inhabiting the arid islands had developed saddle-shaped shells. It is because they needed to stretch their necks in order to reach branches of cactus and other vegetation available in the area.
Consequently, they developed long necks and high peak to the front edges of their shells. It made it possible for them to stretch their heads vertically.
Answer:
Option A: True
Explanation:
Insectivorous birds such as bluebirds, dippers and flycatchers prefer to eat medium-sized insects. This is because like most birds, they love easy and satisfying meals. To the birds, a medium-sized insect is a good compromise because it is quite easy to chew and digest and at the same time, easy to find.
As a result, most insectivorous birds prefer to get their daily ration of proteins from the medium-sized birds.
