*The rate at which radioactive decay occurs.
*How much radioactive decay has occurred.
Answer: The body maintains homeostasis by positive and negative feedback mechanism.
Explanation:
The body maintains the internal temperature and metabolism with respect to change in environment.
In case the temperature outside is very cold and the body starts shivering by the movement of skeletal muscles, this is done to maintain the temperature inside body. This is positive feedback.
When the temperature inside the body is maintained, then body stops shivering. This is negative feedback.
This is how the body maintains homeostasis.
Antibiotics damage bacteria by inhibiting their ability to function.
Fertilization is done by germination of pollen on the pistil, without need of moisture as in the case of ferns (character they share with other Spermaphytes).
In Angiosperms fertilization has three essential characteristics:
* it is siphonogamous: the apertured pollen grain possessing two or three cells sees its vegetative cell germinate and form a pollen tube which will convey, with the help of its cytoskeleton, the male gamete (case of the tricellular pollen) where the generating cell ( case of the bicellular pollen) which will carry out its second division of meiosis. In this siphonogamy corresponds to a total franking of water for fertilization.
* it is anisogamous: the female gamete is by far the most massive of the two (the pollen grain is often very dehydrated, the cells it contains have a very small cytoplasmic space).
* it is double: the male gametes conveyed by the pollen grain will merge their nuclei (caryomixis) with those of two different cells. It's a special function for the reproduction of angiosperms. The pollen grain contains two nuclei (all haploids), whereas for example the mammalian spermatozoa contains only one.
