Characteristics of life:

• Organisms are highly organized and contain many complex chemical substances
• Organisms are made up of one or more cells
• *Organisms use energy
• Organisms have a definite form and a limited size
• Organisms have a limited life span
• *Organisms grow
• Organisms respond to changes in the environment
• *Organisms are able to reproduce
• Groups of organisms change over time

8 life functions:

Organisms carry out many different kinds of processes. Some of these processes are also characteristics of life (use of energy, growth, reproduction) and others relate to the functioning of organisms. Many of these life processes are necessary for maintaining a fairly constant environment within an organism in spite of its constantly changing environment.

Homeostasis- The condition of a constant internal environment. The normal condition of balance and equilibrium that exists within cells and organisms. This equilibrium or stability depends on the coordination of thousands of chemical reactions occurring at the same time within cells. Examples of homeostasis: maintaining constant body temperature and blood sugar levels in human beings.

Rudolph The Red Nosed Reindeer Stopped Eating Grapes

Respiration- all life processes require a constant supply of energy. Organisms get their energy by releasing the chemical energy stored in nutrients or food. The process of releasing chemical energy is known as respiration.

• Aerobic respiration- In one type of respiration, sugar or another food substance is broken down to produce water and carbon dioxide. This requires oxygen from the air. (when you do aerobics you need oxygen so you don’t pass out…)
• Anaerobic respiration- when organisms break down food without using oxygen

Transport- process by which substances enter and leave cells and become distributed within the cells. An example of how transport works is the circulatory system. It transports materials to, and wastes away from the cells of the organism.

Regulation- all the activities that help to maintain an organism’s homeostasis make up the process of regulation. It includes the processes by which organisms respond to changes within and around them. It results in the coordination and control of life processes.

Nutrition- organism takes materials from its external environment and changes them into forms it can use. Nutrients are the substances that an organisms needs for energy, growth, repair, or maintenance. Two basic types:

• Organisms can produce complex nutrients from simple substances found in the environment. All green plants and some bacteria and other once celled organisms are able to make their own nutrients in this way.
• Organisms cannot make their own nutrients so they obtain them ready made from the environment. Animals get their nutrients by eating other organisms in their environment.

The taking in of food is called ingestion. The breakdown of complex food molecules into their simpler forms that the organisms can use is called digestion.

Reproduction- the process by which living things produce new living things of their own kind (remember cells are a living thing too). This is either where new cells arise from preexisting cells (cell division, mitosis, meiosis). When cells in a multicellular organism divide to produce new cells, the result may be the growth of the organism or the repair of damaged tissues. Cell division may also result in the production of new organisms of a species. Two types of reproduction:

¨ Asexual- a single individual produces offspring that are identical to that parent.

¨ Sexual- there are 2 parents, the offspring are not identical to either parent.

Synthesis- involves the chemical processes by which large molecules are built from smaller molecules. Organisms are able to combine simple substances chemically to form more complex substances. In animals, the substances used in synthesis are the products of digestion. Synthesis produces materials that can become part of the structure of the organism. this way the organism can repair or replace worn out parts. these materials allow the organism to grow. The incorporation of materials into the organism’s body is called assimilation.

Excretion-the process where waste products of metabolism (when all life functions are considered together, the chemical and biological activities collectively are known as metabolism).are removed from the organism. Every organism produces waste substances that it cannot use and may be harmful if accumulated in the body. These wastes are products of many of the chemical reaction that occur within the cells.

Growth- involves increase in cell number and cell size. Cell growth requires the manufacture of chemical components. Growth results in increase of organism size.

To summarize:

Metabolism- all the chemical reactions occurring within th cells of an organism is called metabolism. It includes processes that build complex substances from simpler ones and processes that break down complex substances into simpler ones. It involves the continuous release and use of energy.