¨       The word biology means the study of life.

(bios means “life” and -logy means “study of”)

¨       Biology is the science that seeks to understand the living world.

¨       A biologist is someone who uses a scientific method to study living things.

Characteristics of Living Things

¨       Living things share several characteristics.  These characteristics include the following:

Ø       Living things are made up of units called cells.

Ø       Living things reproduce.

Ø       Living things are based on a universal genetic code.

Ø       Living things grow and develop.

Ø       Living things obtain and use materials and energy.

Ø       Living things respond to their environment.

Ø       Living things maintain a stable internal environment.

Ø       Taken as a group, living things change over time.

Made Up of Cells

¨       A cell is a collection of living matter enclosed in a barrier that separates the cell from its surroundings.

¨       Cells are the smallest units of an organism being considered alive.

¨       Cells can grow and respond to their surroundings, and reproduce.

¨       Cells are complex and highly organized.

¨       Unicellular describes a living organism made up of a single cell. (uni- means “one”)

Ex) bacteria, algae

¨       Multicellular describes a living organism made up of many cells. (multi- means “many”)

Ex) animals and plants

Reproduction

¨       All organisms produce new organisms though a process called reproduction.

¨       Two types of reproduction:

v      Sexual reproduction – two cells from different parents unite to produce the first cell of the new organism.

v      Asexual reproduction – the new organism has a single parent.

Based on a Genetic Code

¨       Offspring usually resemble their parents.

¨       DNA (deoxyribonucleic acid) is a molecule that carries the directions for inheritance.

¨       The DNA genetic code determines the inherited traits of every organism on Earth.

Growth and Development

¨       All living things grow during at least part of their lives.

¨       Growth for single-celled organisms (bacteria) is a simple increase in size.

¨       Multicellular organisms go through a process called development.

¨       It is a process in which the cells divide again and again to produce the many cells of a mature organism.

¨       Differentiation is when the cells change in shape and structure to form cells such as liver cells, brain cells, and muscle cells.

Need for Materials and Energy

¨       Organisms use energy and a constant supply of materials to grow, develop, and reproduce.

¨       Metabolism is a set of chemical reactions through which an organism builds up and breaks down materials as it carries out life processes.

¨       All organisms take in materials from their environment for energy but the way they do it varies.

v      Plants, some bacteria, and algae obtain energy directly from the sun by photosynthesis.

v      Some organisms eat plants and other photosynthetic organisms.

v      Some organisms eat other organisms.

v      Some organisms obtain energy from the remains of organisms that have died.

Response to the Environment

¨       Organisms detect and respond to stimuli from their environment.

¨       A stimulus is a signal to which an organism responds.

¨       Organisms respond to external changes such as temperature or the amount of light.

¨       Internal stimuli come from within an organism such as the level of the sugar glucose in your blood.

Maintaining Internal Balance

v      Homeostasis is the process by which organisms keep their internal conditions relatively stable.

v      Most organisms must keep internal conditions, such as temperature and water content, fairly constant to survive.

v      Your body works similar to a thermostat in your home.

Ex) If you are too hot, your biological thermostat turns on “air conditioning” by causing you to sweat.

Evolution

¨       Individual organisms many experience many changes during their lives but the traits they have inherited usually do not change.

¨       As a group, any given organism can evolve or change over time.

¨       Over a short period of time, the changes may not seem significant.

¨       Over hundreds of thousands or even millions of years, the changes can be dramatic.

Branches of Biology

¨       Biology is divided into different fields.

v      Zoologists study animals.

v      Botanists study plants.

v      Paleontologists study ancient life.

¨       The study of biology can be approached on many different levels of organization.

¨       Starting with:

Ø       atomsàmoleculesàcellsàtissuesàorgansàorgan systemsàorganismàpopulationàcommunityà

ecosystemàbiosphere

¨       Smaller living systems are found within larger systems.

v      Molecular and cell biologists study the smallest systems.

v      Population biologists and ecologists study the largest systems.

Biology in Everyday Life

¨       Biology helps you understand what affects the quality of your life.

¨       Biology involves:

Ø       Your pets

Ø       Dinosaurs

Ø       Information about food

Ø       Conditions of good health

Ø       Behaviors and diseases that harm you

Ø       Used to diagnose and treat medical problems

Ø       Identifies environmental factors

¨       Biologists do not make decisions about most matters affecting human society or the natural world; citizens and governments do.