Introduction to Animals

Think of an animal… Did you think of an organism that has fur or a bony skeleton? MOST animals have neither bones nor hair!!! So…what are the characteristics that all animals have in common?

Animal Characteristics Multicellular Eukaryotic (with no cell walls!) Heterotrophic

Dividing Animals Based on Habitat Animals that live in the water are AQUATIC Animals that live on land are TERRESTRIAL

Multicellular Organization Most animals contain large numbers of cells Humans contain 50 trillion cells! In most animals, cells are specialized to perform different functions cells  tissues  organs  organ systems Cell specialization has allowed organisms to evolve and adapt to many environments

Animals are Heterotrophic Heterotrophs must obtain complex organic material from other sources The animal eats (ingests) and then digests. Digestion extracts the carbohydrates, protein and lipids from the food eaten

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

Gastrulation: step in development when major tissues (germ layers) begin to develop Endoderm, Mesoderm, Ectoderm

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

Origin and Classification First animals arose from the sea Taxonomists have grouped animals into several phyla based on evolutionary relationships 95% of animals are invertebrates! (We will investigate 9 major phyla. Eight of these phyla include invertebrates and only Phylum Chordata includes the vertebrates)

Divisions of Animal Body Structure Symmetry Cephalization Germ layers Body Cavities

Symmetry Symmetry refers to the consistent overall pattern of structure of an animal Animals have three patterns of symmetry: Asymmetry – no symmetry Examples: Fiddler crabs, Sponges (porifera)

Symmetry, Continued Radial Symmetry – similar parts branch in all directions from a central point Ex: sea star, anemones Bilateral Symmetry- similar halves on either side of a central plane Ex: Butterflies, humans

Patterns of Symmetry

Most animals have a dorsal, ventral, anterior and posterior side or orientation. Dorsal – top (topside or back) Ventral – bottom (underside or belly) Anterior – head Posterior – tail

Cephalization Most animals exhibit cephalization Cepahlization: the concentration of sensory and brain structures in the anterior (near the head) Animals with cephalization have a head!

Germ Layers Germ layers are 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 body cavity is known as a COELOM

Human Body Cavities

After Gastrulation Deuterostome: blastopore becomes the anus Protostome: blastopore becomes the mouth

Animal Diversity 95% Invertebrates (animals without a backbone) Phylum Porifera (sponges) Phylum Cnidaria (jellyfish & corals) Phylum Platyhelminthes (flatworms) Phylum Nematoda (roundworms) Phylum Annelida (segmented worms) Phylum Mollusca (mollusks) Phylum Echinodermata (spiny sea creatures) Phylum Arthropoda (insects & spiders) 5% Vertebrates (animals with a backbone) Phylum Chordata (Fishes, birds, reptiles, amphibians and mammals)