What did the discovery of radioactivity do to change the geological time scale?

Which organisms have pharyngeal arches that develop from all three germ layers and go through the same development stages as embryos? 1.bird 2.ladybug 3.starfish 4.snake

An organ system consists of a group of organs that performs specific functions necessary for the survival of an organism. humans have eleven different organ systems: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive. discuss the function of neurons, the brain and the spinal cord within the human nervous system while explaining the interrelationship of each organ.

During which phase does earth see more than half of the moon's surface? 1)first quarter2)third quarter3)waxing gibbous4)waning crescent