There are two classifications of watershed pollution, point source, and nonpoint source. With pollution, the source of chemicals or other is readily apparent, such as a treatment plant or a factory that releases directly into the water. With pollution, no single source is evident, but still exist, such as or pet waste running off from into storm drains.

*point source
*non-point source
*pollution
*contaminants
*waste
*Water pollution
*fertilizer
*suburban yards

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.