A signal cascade is a series of chemical reactions which are triggered by a stimulus acting on a receptor that is then transduced to the intracellular space through second messengers. Finally, effector molecules receive the signal causing a cellular reaction to the initial stimulus. A signal cascade is very useful because it facilitates and accelerates the communication between cells that could be in different parts of a living organism. This communication is vital for cell processes in complex multicellular organisms.
Answer : B ) Visible and infrared light
The heterozygous birds phenotype would therefore be black and white because both parent genes are dominant so they would be fully expressed,none would overpower the other(no dominant or recessive) this is known as Codominance and and example of this is with the blood types.