Explain why evolution by natural selection can not occur if there is no variation in a characteristic

What is the mitochondria

8. What is used for support in plant cells?

which of these technological advances has improved flu vaccines? A. virus strains multiplied in cell cultures B. sonograms C. antiviral drugs D. blood typing

The movement of a magnetic pole away from the actual pole

Each part and area of the ear have specific functions in the hearing process. In which of the following parts of the ear are sound waves changed into a signal the brain can understand? A. inner ear B. none of these C. middle ear D. outer ear

Why might it be particularly beneficial for the giant spider crab to be so large?

In which stage of growth do plants rest or grow very little?

Scientists have debated the evolution of three life forms: reptiles, birds and dinosaurs. After many years of reviewing fossil records scientists proposed the evolutionary relationship seen above in the cladogram.

The PNS is divided into several subsystems. What two subsystems form the first major division of the PNS? sensory and motor somatic and autonomic parasympathetic and sympathetic CNS and brain

Consider the model of the food chain. Imagine there is a herbicide poison spill and all the grass is killed. How will this influence the food chain model? A) The grasshoppers will die out. B) All of the consumers will decrease.