Living Systems

2. Living Systems

3. Chapter Two: Living Things • 2.1 Is it Alive? • 2.2 What is a Living System?

4. Investigation 2A Plant Growth • What conditions are ideal for the growth of clover plants?

5. 2.1 Is it alive? • An organismis an individual form of life. • Biologists often use five basic rules to classify something as living or nonliving. Yeast is a living organism. Each tiny sphere is an individual living thing.

6. Characteristics of Living Things • All living things respond 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, and gases and use these materials to get energy. • Growth refers to an increase in mass and to an increase in number of cells. • The process of making more of the same kind of organism is called reproduction. • A cell is the smallest unit of a living thing.

7. 2.1 Is it alive? • This is a barnacle. • Read about the five characteristics of life on page 29. • Then decide whether it is alive.

8. 2.1 Is it alive? • Barnacles respondto their environment by closing their shells at low tide, and opening them at high tide. • Barnacles growand develop. They begin life as free-swimming creatures. Once they find a good spot, they “glue” themselves to a rock and form a shell. • Barnacles reproduce. After fertilization from a male barnacle, females hold the eggs in their shells until they hatch. • By waving their legs, barnacles capture food. They use energyfrom the food to move their legs, open and close their shells, and 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 cells.

9. 2.1 Types of energy • Energyis sometimes defined as the ability to cause change or do work. • There are many forms of energy. • Any form can be converted into any other form.