Which is a requirement for natural selection to occur?
a. heritable variations for some traits
b. the ability of an organism to improve a trait during its lifetime
c. equal probability of survival for all offspring
d. fewer offspring than the environment can support

The right answer is A. heritable variations for some traits .

Natural selection per is simply a sort of the individuals most likely to survive or reproduce, regardless of the reason why they possess such an ability. To induce the evolution of a particular biological trait in a population under the effect of natural selection, this biological trait must vary from one individual to another, whether this individual variation is heritable, and that this variation correlated with that of reproductive success or the probability of survival of individuals.

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation:

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.