Introduction to Animals

Characteristics Multicellular Organization Heterotrophic Sexual reproduction and development Movement

Multicellular Organization Most animals contain large numbers of cells. Humans contain 50 trillion cells. In most animals, there is a division of labor. Specialization is the adaptation of a cell for a particular function. Tissues are the organization of cells. Cell are able to organize by the joining of cells by cell junctions. Cell specialization has allowed organisms to evolve and adapt to many environments.

Animals are Heterotrophic They must obtain complex organic material from other sources. Most accomplish this through ingestion. Digestion is accomplished within the animal. This process extracts the carbohydrates, protein and lipids from the food eaten.

Sexual Reproduction and Development Sexual reproduction restores the diploid number and increases genetic variation. During the developmental process, the zygote undergoes many mitotic divisions. These identical cells must undergo differentiation. Differentiation is process of cell becoming different from each other and being specialized.

Movement Most animal are able to move. The ability to move results from the interrelations of two types of tissues found only in animals: nervous tissue and muscular tissue. There are a few animals that are sessile.

Origin and Classification The first animals probably arose from the sea. Taxonomists have grouped animals into several phyla based on evolutionary relationships. Many taxonomist recognize 30 or more animal phyla. We will investigate 11 phyla. Ten of the phyla include invertebrates and only Chordata includes the vertebrates.

Animal Body Structure Symmetry Germ layers Body Cavities

Symmetry Asymmetry refers to the consistent overall pattern of structure of an animal. Animals have three patterns of symmetry. Asymmetry – no symmetry Radial Symmetry – similar parts branch in all directions from a central point Bilateral Symmetry- similar halves on either side of a central plane.

Patterns of Symmetry

Identify the Type of Symmetry

Most animals have a dorsal, ventral, anterior and posterior side or orientation. Dorsal – top Ventral – bottom Anterior – head Posterior - tail Most animals exhibit cephalization, the concentration of sensory and brain structures in the anterior. Animals with cephalization have a head!

Germ Layers Germ layers are fundamental tissue types found in all animals except sponges (no true tissues). Ectoderm Mesoderm Endoderm

Body Cavities Most animals have a fluid filled space that forms between the digestive tract and the outer wall of the body during development. This space is known as a COELOM.

Acoelomate (without a coelom) 2 germ layers ectoderm and endoderm not separated by a cavity least complex body plan sponges and cnidarians 3 layer acoelomate 3 germ layers endoderm, mesoderm and ectoderm flatworms Pseudocoelomate pseudocoelom cavity formed between mesoderm and endoderm roundworms and rotifers Coelomate cavity developed within the mesoderm most complex body plan mollusks, annelids, arthropods, echinoderms, and chordates

Animal Diversity Invertebrates Chordates 10 phyla 95% of animals Notochord Dorsal nerve cord Pharyngeal pouches Postanal tail Vertebrates Include fishes, birds and mammals

What is the difference in a vertebrate and an invertebrate? A vertebrate is an animal with a backbone and invertebrates do not have a backbone.

Comparison of Invertebrates and Vertebrates symmetry germ layers Body cavities Segmentation support Respiratory/ circulatory Digestive/excretory Nervous reproduction