The excretory system allows animals to remove metabolic waste their bodies. Many of these substances are potentially toxic. in Mammals nitrogenous toxins like urea are expelled through liquid urine while in reptiles and birds the nitrogenous compounds are expelled as a solid. This allows birds and reptiles to use less water in the processes of metabolism.
Answer: D. Extinctions occur at higher rates during times of ecological stress when populations and species are poorly adapted.
<span>Animals have centrioles to form spindle fibers during prophase. The centriole divides cells. Plants do not have them because they have microtubules instead; they do not need centrioles. Plants are capable of forming a circular loop of microtubules around the future plane of division prior to prophase called the preprophase band, rather than centrosome. Basically- plants don't need it. They have a different way of cell division.</span>
A state of biological balance, or _HOMEOSTASIS_, is important for the survival of individual cells and _the whole organism_ alike.
