introduction

WHAT IS ZOOLOGY? Zoology is the study of animal life
 * **CHAPTER 1**

GENERAL PROPERTIES OF LIVING SYSTEMS Macromolecules found in living organisms are much more complex than those found in non-living things Living systems demonstrate a unique and complex hierarchical organization: Cells>Tissues>Organs>Organ Systems>Organisms Heredity of characteristics is due to the transmission of traits from parents to offspring A genetic program provides similarity of inheritance Living organisms maintain themselves by obtaining nutrients from their environments All organisms pass through a characterisitic life cycle In some animals, metamorphosis causes the development of an adult that is completely different from the juvenile The study of the interactions between organisms and their environments is called ecology
 * CHEMICAL UNIQUENESS
 * Living systems demonstrate a unique and complex molecular organization**
 * These molecules include nucleic acids, proteins, lipids, and carbohydrates
 * COMPLEXITY AND HIERARCHICAL ORGANIZATION**
 * REPRODUCTION
 * Living systems can reproduce themselves**
 * Variation is apparent in sexual reproduction and reduces the transmission of deadly disorders such as cystic fibrosis and hemophilia
 * POSSESSION OF A GENETIC PROGRAM**
 * The genetic code found in DNA causes very specific proteins, such as hemoglobin and insulin, to be produced
 * METABOLISM**
 * Cellular respiration takes place in the mitochondria of animal cells to produce ATP (energy)
 * DEVELOPMENT**
 * This cycle begins with the fertilization of an egg by a sperm in most animals, followed by a very specific sequence of changes that lead to the development of a mature adult**
 * ENVIRONMENTAL INTERACTION
 * All animals interact with their environments**

ARCHITECTURAL PATTERN OF AN ANIMAL Based upon the number of cells, there are two major groups of animals:
 * CHAPTER 10**
 * PROTOZOANS--single-celled (unicellular) animals
 * METAZOANS--many-celled (multicellular) animals consisting of cells, tissues, organs, and organ systems


 * The larger body size of metazoans promotes a more efficient use of energy**

WHAT IS SYMMETRY? The arrangement of body parts with reference to some axis of the body is symmetry. There are four basic body plans found in animals:
 * Asymmetry
 * Spherical symmetry
 * Radial symmetry
 * Bilateral symmetry

ASYMMETRY
 * These organisms are irregular in shape
 * There is no obvious body plan
 * Sponges are asymmetrical in shape

SPHERICAL SYMMETRY
 * This type of symmetry is rare and is only found in some protozoans

RADIAL SYMMETRY
 * These forms can be divided into two halves by more than one plane passing through a main axis
 * Another way of describing radial symmetry is that there is a center to the body, surrounded by several "arms" that extend equally from the center
 * Jellyfish are radial animals

BILATERAL SYMMETRY
 * These body forms can be divided into two mirror-image halves: left and right
 * Movement is much easier than in other body plans
 * Most animals exhibit bilateral symmetry and can be grouped according to their body cavity type. This body cavity is called a **coelom.

ANIMAL GROUPS WITH BILATERAL SYMMETRY**
 * ACOELOMATE ANIMALS, such as the flatworms, have no body cavity
 * PSEUDOCOELOMATE ANIMALS, such as roundworms, have a "false" coelom which is a body cavity formed in a different manner from the true coelom
 * EUCOELOMATE ANIMALS have a true coelom which consists of a body space lined with a membrane called the **peritoneum

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 * METAMERISM (SEGMENTATION)--repetition of similar body segments along a longitudinal axis. Thses segments are called **metameres,** or **somites.** Within the somites, repetition of blood vessels, muscles, and nerves is found
 * CEPHALIZATION--The existence of a head is found basically in bilaterally symmetrical animals ||  ||
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