Intro to Zoology What is an animal?

Typical Characteristics:

1) Eukaryotic –each cell has a nucleus

2) Multicellular-Made up of many cells

Cells>Tissue>Organs>Organ Systems

3) Heterotrophic- must eat food to get energy and nutrients- through ingestion and digestion

4) Do not have cell walls

5) Can Move (some are sessile, which means that they don’t move) EX: sponges and barnacles

Origins of animals :

Most likely evolved from colonial protists

Believed to have developed in the water

Phylums Porifera

Cnidaria

Platyhelminthes

Nematoda

Annelida

Mollusca

Arthropoda

Chordata

***There are more than 9 phylums but these represent the most commonly seen animals.

Match the name of phylum with a picture of a member!

http://www.biologycorner.com/resources/animal_phylum_chart.gif

Reproduction and Development

Most animals reproduce sexually.

Some can reproduce asexually.

Fertilization occurs when a sperm penetrates an egg to form a single cell called a zygote.

This may be external (outside male and female) EX: Fish or internal ( inside the female) EX: Horse

Cell DivisionZygote begins dividing by mitosis to form two

new cells.

Each new cell will continue to divide over and over again until a hollow ball called a blastula is formed.

One side of the blastula begins to fold inward, making an inner pouch. At this point, the embryo is called a gastrula.

Germ Layer DevelopmentThe layers that form will eventually form the

tissue and organs of the animal. Most animals possess three layers of tissue (sometimes called germ layers):

1) Ectoderm: outermost layer of cells; eventually forms the outer covering (skin) and nervous system.

2) Mesoderm: middle layer of cells; eventually forms the skeleton, muscles, and circulatory system

3) Endoderm: Inner layer of cells; becomes the digestive tract, internal organs, and respiratory tract

Body CavitiesAs the layers of tissue form organs and organ

systems, some organisms develop a fluid filled space that forms between the digestive tract and the outer wall of the body during development.

Not found in simple animals

May aid in movement

Fluid may act as a reservoir for nutrients and wastes, which diffuse into and out of the animal’s body

Types of Body Cavities Acoelomates: 3 layers of tissue, but no body

cavity is present ( Gut)

Pseudocoelomates- 3 Layers of tissue and a modified body cavity present ( not lined with mesoderm)

Coelomates- a true body cavity present (lined with mesoderm)

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Patterns of Symmetry Asymmetrical – an irregular shape. Some

simple animals do not display symmetry (EX: Sponges)

Radial- Similar parts branch out in all directions from a central line ( like spokes on a bicycle tire)

Bilateral- two halves on either side of a central plane are similar

A. Usually exhibit cephalization –concentration of sensory structures in the anterior (head) end of the animal.

Bilateral Symmetry wordsTerms used to describe location of certain

structures and organs on an animal:

Anterior: head end

Posterior: Tail end

Dorsal: Back

Ventral: Front

http://www.dogsindepth.com/hound_dog_breeds/images/greyhound_h05.jpg

SegmentationA body composed of repeating similar units

In some phyla, segments may look different and have different functions.

Support and Protection of Body

Hydrostatic skeleton- body is supported by the pressure of their fluid filled bodies (EX: jellyfish)

Exoskeleton- A rigid outer covering that protects the soft tissue of many animals ( includes many invertebrates such as crabs and beetles)

Endoskeleton- an internal skeleton that can support a large, heavy body

Vertebrate VS. Invertebrate

Most animals that exist today are classified as invertebrates; animals that lack a backbone

EX: insects, sponges, starfish, jellyfish, clams, worms, etc.

Humans are a type of chordate called a vertebrate, an animal with a backbone.

Chordata is the only phylum that contains vertebrates (although not all chordates are vertebrates)

Digestive System In Sponges, digestion occurs within individual

cells (intracellular)

Gastrovascular Cavity- A digestive chamber with a single opening (incomplete digestive system) Ex: jellyfish and flatworms

Digestive tract (or gut) runs from the mouth to the posterior end or anus. EX: humans, earthworms, and spiders

Respiratory SystemGas Exchange: the process of exchanging

carbon dioxide (in the blood) with oxygen (in the environment)

Gills: Organs that are specialized for gas exchange in water

Lungs: Organs for gas exchange, which are composed of moist, membranous surfaces deep inside the animal’s body

Circulatory SystemMoves blood or a similar fluid through the body

to transport oxygen and nutrients to the cells.

Open circulatory system- blood like circulatory fluid is pumped from vessels in the body into the body cavity ( it bathes the organs) then is returned to the vessels.

Closed circulatory system- blood circulates through the body in tubular vessels.