Levels of Organization The smallest unit of matter is an atom. The cell is the basic unit of structure and function in living things. While there are unicellular organisms, multicellular organisms are made of many cells that are specialized to perform particular tasks. Multicellular organisms are made up of specialized cells that work together to make tissues, followed by organs, then organ systems, and finally an organism.

Cell Specialization All cells carry the same DNA information but they do not perform the same functions and may not look the same. The process of a cell becoming a particular type of cell is called cell differentiation.

Regeneration Regeneration is the process where a body part is replaced or regrown. Ex: Salamanders can regrow limbs that have been amputated. The human liver is the only human organ that has the ability to regenerate. Human fingertips also have a limited ability to regenerate.

Stem Cells Every cell in our bodies originally came from a small group of stem cells. A stem cell is an unspecialized cell. It has the potential to become any type of cell. Under the proper conditions the stem cells can become specialized cells. The ability to direct stem cell development could help to treat many injuries and diseases.

Embryonic Stem Cells These come from human embryos (either from umbilical cords, placenta or from aborted embryos). At this point in the development of a human, these cells have not differentiated and can become anything.

Adult Stem Cells There are few examples of adult stem cells in the body because most cells have specialized. There are some in skin, blood and neural tissues. Currently, these are being used in research for the treatments of many diseases like cancer, Alzheimer’s and Parkinson’s.

Meristematic Stem Cells These are stem cells found in plants. Located in the growing root tips. They continually produce new cells of various types for the life of the plant.

Animal Tissues Groups of cells that function together and are specialized for common tasks are called tissues. There are 4 types of animal tissues: epithelial, connective, muscle, and nervous tissue.

Specialized Cells 50 – 75 Trillion cells in your body 220 specialized cells Muscle Nerve Blood (red and white) Sperm Egg

1) Epithelial Tissue Lines the body cavities and outer surface of the body. They form a protective barrier. It can be one cell thick or several layers thick. Forms glands that produce hormones, enzymes, and sweat. Ex: skin

2) Connective Tissue Main purpose is to join other tissues together. They also store fat and fill empty space. Tendons, ligaments, bones, cartilage and blood are all types of connective tissue. Blood is made of plasma, red blood cells, white blood cells, and platelets.

3) Muscle Tissue 3 types: cardiac, skeletal, and smooth. Skeletal muscles are used for movement of our appendages. Smooth muscle lines many organs. Cardiac muscles is the muscle of the heart. Smooth and Cardiac muscles are involuntary, meaning they move without conscious control.

4) Nervous Tissue Tissues capable of creating and sending messages throughout the body. They send and receive information and respond to stimuli.

Plant Tissues 4 types: epidermal, vascular, ground, and meristematic. They all originate from meristematic tissue because it is unspecialized.

1) Meristematic Tissue Unspecialized tissue capable of becoming any kind of cells. Responsible for growing new parts of the plant.

2) Epidermal Tissue The protective outer covering of the plant. Has specialized guard cells that from pores called stoma allowing molecules like water, CO2 and O2 to pass in and out.

3) Ground Tissue In the stem, provides strength and support. In the leaves, photosynthesis and gas exchange occur in a specialized mesophyll layer. In the roots, stores water and nutrients.

4) Vascular Tissue Used for transporting substances like water and nutrients throughout the plant. 2 types: xylem and phloem. The xylem moves water and minerals up from the roots to the leaves. The phloem transports sugar produced during photosynthesis in the leaves to other parts in the plant.