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.
The boundary between conducting zone and respiratory zone structures occurs at the terminal bronchiole/respiratory bronchiole junction. The major respiratory structures span the nasal cavity to the diaphragm. Functionally, the respiratory system can be divided into a conducting zone and a respiratory zone. The conducting zone of the respiratory system includes the organs and structures not directly involved in gas exchange. The gas exchange occurs in the respiratory zone.
The continual input of energy, mostly from sunlight, sustains the process of life. Sunlight allows plants, algae and cyanobacteria to use photosynthesis to convert carbon dioxide and water into organic compounds like carbohydrates. This process is the fundamental source of organic material in the biosphere. There are a few exceptions to this, such as ecosystems living around hydrothermal vents on the ocean floor, which derive their energy from the chemical compounds such as methane and hydrogen sulfide. In either case, the overall productivity of an ecosystem is controlled by the total energy available.
Answer:
Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.
Explanation:
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years (for the most massive) to trillions of years (for the less massive), considerably more than the age of the universe. ^
Small, relatively cold, low mass red dwarfs burn hydrogen slowly and will burn for hundreds of billions of years
Massive hot supergiants will live for just a few million years.
A mid-sized star like the Sun will remain on the main sequence for about 10 billion years. Hope tis helps!!
