BIOLOGY is defined as the study of life. BIO-'life' and LOGY-'the study of'

If you were to take a large number of living things, you would notice that they all have something in common. However, you would also know that they are different as well.

All living things show UNITY (similarities) as well showing a great deal of DIVERSITY (differences).

Here is what all living things have in common...

1) All living things are highly organized and contain many complex chemical substances.

2) All living things contain one or more cells.

UNICELLULAR- contains just one cell
MULTICELLULAR- contains many cells

3) All living things use energy.

4) Living things have a definite form and have a limited size.

5) Living things grow.

6) Living things respond to changes in the environment.

7) Living things can reproduce.

8) Living things eventually die.

Nonliving objects may show one, or even a few of these characteristics but they never show all of them...

We can take these characteristics of life and simplify each...these will make up the 8 life functions.

Scientists classify things as alive if they can carry out these 8 LIFE FUNCTIONS.

R- Respiration
R- Regulation
R- Reproduction
E- Excretion
G- Growth
N- Nutrition
T- Transport
S- Synthesis


Here is a look at the 8 life functions in a bit more detail...

the breakdown of nutrients to yield (or give off) chemical energy
there are 2 types
1) aerobic respiration- uses oxygen
2) anaerobic respiration- doesn't use oxygen

the process where a living thing controls and coordinates its various activities.
in animals--
1) nervous system uses nerve cells
2) endocrine system uses hormones
in plants--
some parts produce hormones

the process by which living things produce new living things of the same kind
there are 2 types
1) asexual reproduction--involves one parent and the offspring are identical to the parent
2) sexual reproduction--involves two parents and the offspring is a combination of both parents

the process by which living things remove waste products produced by cell activities

the process by which living things increase in size or cell number

the process by which living things take in materials from its environment for growth and repair; there are 2 types
1) autotrophic nutrition--where a living thing can make its own food
2) heterotrophic nutrition--where a living thing must ingest (take in) its food

the process by which usable materials are taken into the living thing (ABSORPTION) and distributed throughout the living thing (CIRCULATION)

the process by which smaller, simple substances are combined chemically to form larger, more complex substances

If a living thing has all 8 off these life functions, it is called an ORGANISM!

When we refer to all of the life functions of an organism, we are referring to its METABOLISM--the total of all the life functions required to sustain life (to stay alive)

R + R + R + E + G + N + T + S =

An organism's external (outside) environment is always changing. By keeping the control and regulation of its metabolic activities, an organism can maintain a stable internal (inside) environment. This is called HOMEOSTASIS.

the process by which an organism's metabolic activities are in a state of balance
ex. body temp, blood sugar levels

The 8 Life Functions

a nice introduction clip about biology in general
from, here is a rundown of all the life functions
some life functions listed here in this clip
practice the safety symbols