2.  Make a list of life activities of a pond organism that can only be seen under a microscope.  Make a list of the life activities of a fish.  Which organism do you think can adapt to a wider range of conditions? Why?

3.  You are a many-celled organism because your body is made up of more than one cell.  Human body is made of more than a trillion cells  There are single-celled organisms such as an amoeba, that has only one cell.  Can only be seen with a microscope

4.  In many-celled organisms, cells are specialized to perform different tasks in the body  They must be organized to work together and keep the organism healthy  5 main levels of organization  Cells  Tissues  Organs  Organ systems  Organisms

5.  In many-celled organisms, cells perform many different functions.  These cells are specialized; that is, different types of cells that do different kinds of work

6.  Each group of specialized cells is organized into tissues  Muscle cells make up three different kinds of muscle tissue in the human body: smooth, skeletal, and cardiac.

7.  Tissues are organized into groups called organs  An organ is a group of tissues that work together to perform special functions.  Both plants and animals have tissues and organs.  A heart is one of many organs in a many-celled organism  Heart is mostly made of cardiac muscle tissue  Also contains nerve and connective tissues ▪ Muscle, nerve, and connective tissues work together to pump blood through the heart and body

8.  A group of organs that work together make up an organ system  Some organisms, such as sponges, have no organ systems  Some organisms, such as flatworms, have only a couple organ systems  Complex organisms, such as dogs and humans, have ten organ systems

9.  Highest level of cellular organization  All organisms carry out life processes  In most organisms, the different organ systems work together to keep the organism alive

10.  Circulatory: pump blood throughout the body  Skeletal: enables support, protect, and movement  Muscular: enables support, protect, and movement  Skin: protects organism from the outside environment  Endocrine: deals with hormones in the body  Reproductive: enables organisms produce more organisms like themselves  Digestive: enables you to process the nutrients your body needs  Respiratory: enables you to breathe  Excretory: removes waste  Nervous: receives and sends electrical and chemical signals

11.  List at least one example of each of the following: cell, tissue, organ, organ system, and organism.  Describe the difference between a cardiac muscle cell, cardiac muscle tissue, and the heart.  Can a single-celled organism contain tissue? EXPLAIN.  Classify the following as a tissue, organ, or organ system:  Brain  Spinal cord  Nerves  Heart  Group of muscle cells