Is It Alive? Characteristics of Living Things & Necessities of Life

Characteristics of Living Things What makes something living or nonliving? Is a rock living? What about a piece of grass? Or an icicle? There are 6 characteristics of living things

#1: Living Things Have Cells All living things are composed of one or more cells What is a cell? A cell is a membrane- covered structure that contains all the material necessary for life Unicellular = one cell; multicellular = more than one cell

#2: Living Things Sense and Respond to Change A stimulus is a change that affects the activity of an organism. -Examples: chemicals, gravity, light, sound, hunger, or anything else that activates a response Homeostasis is the maintenance of a stable internal environment Allows us to keep our internal environment in check when external environment is changing Example: When it gets cold outside, our internal temp still stay 98.6 degrees

Homeostasis is kind of like a see-saw, which your body wants to keep balanced. -Outside temp is cold, but our bodies don’t plunge into a low body temp—it works hard to balance our temp at 98.6 degrees, no matter what the outside weather!

#3: Living Things Reproduce Sexual reproduction: two parents produce offspring that is similar to both parents Asexual reproduction: single parent produces offspring that is identical to the parent

#4: Living Things Have DNA The cells of ALL living things contain the molecule “deoxyribonucleic acid, or DNA DNA controls structure and function of the cells Heredity: passing copies of DNA from parent to offspring

#5: Living Things Use Energy Organisms need and use energy to carry out activities in life Metabolism: the total of all the chemical activities that the organism performs

#6: Living Things Grow and Develop We all GROW! It doesn’t matter if you are a multicellular or unicellular organism We all develop! As we grow, we go through different stages in our lives. Example: US! Baby->child->teen- >adult Acorn  seedling  sapling  tree

Necessities of Life Organisms need 4 things to live: Water Your body is made up of 70 % water Most of the chemical reactions involved in metabolism require water

Air A mixture of gases (oxygen and carbon dioxide) Organisms on land get oxygen from the air Marine animals get dissolved oxygen from the water or by coming up for air Green plants, algae, and some bacteria need carbon dioxide in addition to oxygen to undergo their food making process called photosynthesis

Food Gives us energy and raw materials needed to carry on life processes such as replacing cells Producers: make their own food Consumers: get food by eating other organisms Decomposers: break down nutrients of dead organisms or animal wastes

5 Building Blocks of Cells 1) Proteins: Molecule made up of amino acids; helps build and repair body structures. Example: protein hemoglobin is in red blood cells and binds to oxygen to deliver it throughout the body

2) Carbohydrates: molecules made up of sugar A) Simple carbohydrates: one sugar molecule, like table sugar B) Complex carbohydrates: hundreds of sugar molecules, such as plants (potato, whole wheat)

3) Lipids: do not dissolve in water; include fats and steroids A) phospholipids are the molecules that form much of the cell membrane; the head is attracted to water but the tail is not—the tails attract to form two layers

4) ATP: “Adenosine Triphosphate”; major energy- carrying molecule in the cell; provides energy for the cell

5) Nucleic Acids: have all the information a cell needs to make proteins; DNA is a nucleic acid

Shelter (a place to live) All living things need a place to live that has all of the necessities of life (enough space, food, water, etc)