An organism that others may depend on for survival is called a

keystone species

Explanation:

a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically.

answer; ///i believe the correct answer is (aids) acquired immune deficiency syndrome;

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.