D. A protein catalyst in a living organism
<span>The major structure that supplies the cells with nutrients and removes their waste is the circulatory system. The circulatory system is composed of the heart, the blood vessels going from and back to the heart, and the blood that travels inside them. The blood vessels that carry nutrient and oxygen-rich blood to the cells are arteries. They become the thinner arterioles, and then the thinnest capillaries. With the exception of the pulmonary arteries, which carry non-oxygenated blood from the heart to the lungs, all arteries carry oxygenated blood. The capillaries disburse the nutrients and oxygen to the cells and pick up wastes and carbon dioxide, form into the thicker venules, then to form veins, which lead back to the heart (with the exception of the pulmonary veins, which carry oxygenated blood from the lungs to the heart). Veins also differ from arteries in that veins have valves to prevent blood from flowing backward.</span>
With the actions of the humans the biodiversity is facing a huge problem in most of the world, the habitats are destroyed, forests are cleared, animals are killed, water and air are polluted...
In order to conserve the biodiversity there are certain things that have to be put in action. The methods for conservation can be in-situ methods and ex-situ methods.
The in-situ methods are the preferred ones, as these methods are focused on conserving the environment as it is. This basically means that the ares that have larger biodiversity, and especially where there's species that are rare, should be made national parks, sanctuaries, monuments of nature, thus being protected by law.
The ex-situ methods are the ones that involve the conservation of the species outside of their natural habitat. That is done with gene banks, sperm and ova banks, seed banks, zoos and botanical gardens, collections of In vitro plant tissue and microbal culture, and captive breeding of animals and artificial propagation of plants.
