Biology+Intro

Biology is the study of living things.

Different types of living things include: plants, animals, bacteria, fungi and protists

There are approximately five recognized **Characteristics of Life**
 * cells - all living things are made of cells
 * reproduction - all living things are capable of creating more organisms like themselves
 * growth - all living things increase in size and/or complexity
 * irritability - all living things are able to respond to different stimuli in the environment
 * metabolism - all living things consume energy




 * Biological Organization**

From simplest to most complex, living things are put together in the following manner:
 * **atoms** - the most basic building blocks of matter - organisms consist mostly of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) as well as phosphorus (P), sulfur (S), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg)
 * **molecules** - elements combine to form the basic molecules of life such as carbohydrates, proteins, lipids and nucleic acids
 * **organelles** - small functional units within the cell such as the nucleus, ribosome, cell membrane, endoplasmic reticulum, golgi bodies, chloroplasts, vacuoles, lysosomes, mitochondria and others
 * **cell** - the most basic unit of life
 * **tissues** - groups of cells which perform a similar function - epithelial, connective, nervous and muscle
 * **organs** - groups of tissues which perform a similar function - e.g. heart, lungs, stomach, kidney, etc.
 * **organ systems** - groups of organs which perform a similar function within the body - e.g. digestive, respiratory, circulatory, nervous, endocrine, excretory, skeleto-muscular, immune,
 * **organism** - a complete functional living thing consisting of organ systems