Most marine fishes broadcast spawn and the parents spend no time feeding and protecting the offspring. On the other hand, whales give birth to well developed calves and will feed and protect the calves for long periods of time. What do you think is the best strategy? Has this strategy paid off in the great whales?

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.