Hormones because if you think about it. Vertebrates must have backbones and mammals have them. And, humans are basically mammals. And the glands secrete hormones.
Like all other reptiles, birds have scales. Also, birds lay eggs like other reptiles.
The material or substance on which an enzyme acts upon is known as the substrate, they are nothing but reacting molecules and or substances that are able to ultimately be converted to product substances. By the aid of biological enzymes, that lower the energy of activation needed for a chemical reaction to proceed.
The fertilized egg begins a rapid descent to the uterus. The period of rest in the tube appears to be necessary for full development of the fertilized egg and for the uterus to prepare to receive theegg. ... At the end of this transition period, the embryo becomes a mass of very organized cells, called a blastocyst.
