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_phylu m_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 Division Zygote 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 Development The 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 Cavities As 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) http://pulpbits.com/wp-content/uploads/2013/12/threefunctions-of-a-body-cavity.jpg 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 words Terms 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/image s/greyhound_h05.jpg Segmentation A 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 System Gas 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 System Moves 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.