Is it alive? An organism is an individual form of ___________. Biologists often use five basic rules to classify something as ____________ or _________________. Yeast is a living organism. Each tiny sphere is an individual living thing.

Characteristics of Living Things All living things _________________ to a stimulus. The sunlight is a stimulus and the frog’s choice to sun himself is called a response. All living things take materials from their surroundings such as food, water, & gases and use these materials to get _____________. Growth refers to an increase in _____________ and to an increase in number of cells. The process of making more of the same kind of organism is called _____________________________. A ________________________ is the smallest unit of a living thing.

Is it alive? This is a barnacle. Read about the five characteristics of life on page 42. Then decide whether it is alive.

Is it alive? Barnacles respond to their _______________ by closing their shells at low tide, and opening them at high tide. Barnacles ____________ & ____________. They begin life as free-swimming creatures. Once they find a good spot, they “glue” themselves to a rock and form a shell. Barnacles _________________. After fertilization from a male barnacle, females hold the eggs in their shells until they hatch. By waving their legs, barnacles capture food. They ________________ ________________ from the food to move their legs, open and close their shells, & carry out all life processes. If you examined the legs of a barnacle with a microscope you would see that they are made of individual _______.

Types of energy Energy is sometimes defined as the ability to cause change or do ___________. There are many _________ of energy. Any form can be _______________________ into any other form.