Science Ch 7 Section 3-6

the process in which the nuclei of radioactive elements break down releasing fast, moving partices and energy

the time it takes for half of the atoms of a radioactive element to decay

a record of the geologic events and life forms in Earth's history

one of the three long units of geologic time between the Precambrian and the present

a horizontal row of elements in the perodic table or oneof the units of geologice time into which geologist divide eras

a loose collection of ice and dust that orbits the sun, typically in a long narrow orbit

an animal without a backbone

an animal with a backbone

a vertebrate whose body temperature is determined by the temperature of its environment and that lives its early life in water and its adult life on land

a vertebrate whose temperature is determined by the temperature of its environment, that has lungs and scaly skin, and that lays eggs on land

when many types of living things become extinct at the same time

a vertebrate whose body temperature is regulated by its internal heat, and that has skin covered with hair or fur and glands that produce milk to feed its young