Animals Animal Bodies

Morphology is Symmetry is the branch of biology dealing with the form and structure of organisms. Symmetry is the proper proportion of the parts of a body with respect to one another and with regard to size and form. Body Structure

Radial Symmetry Basic body plan where the organism can be divided into similar halves by passing a plane at any angle along a central axis. Characteristic of sessile and bottom- dwelling animals, as the sea anemone and starfish. Patterns of Symmetry

Bilateral Symmetry – most animals… Basic body plan where the left and right sides of the organism can be divided into approximate mirror images of each other along the midline. Dorsal - back Ventral - tummy Anterior - head Posterior – rear end Bilateral Symmetry – most animals…

Cephalization specialization of the body with sensory and neural organs in an anterior head Bilateral Symmetry…

1. ectoderm = outside layer 2. endoderm = inside layer Germ Layers – layers formed during very early development of most animals 1. ectoderm = outside layer 2. endoderm = inside layer 3. mesoderm = layer in between the above two Patterns of Symmetry

Body Cavities… Most animals have some type of body cavity. Body Cavity Fluid-filled space between the digestive tract and the outer wall of the body Examples: FLATWORM: three germ layers; solid body – lack body cavity. ROUNDWORM: Body cavity aids in movement Provides a firm structure against which muscles can contract Body Cavities…

A body cavity also allows more freedom of movement for the animal The fluid in the cavity is a reservoir for the transport for nutrients and wastes. these diffuse in/out of the animal’s body cells. Body Cavities…

Animal Diversity… ANIMAL DIVERSITY Animal phyla shown on the same branch of the phylogenetic tree are thought to be more closely related to each other than they are to other animals. Likewise, animals shown in different parts of the tree are thought to be more distantly related. Animal Diversity…

Multicellularity and a limited degree of cell specialization – characteristic of sponges Sponges have no organized body shape and no true tissues. True tissues in two layers – found in the cnidarians (hydra, jellyfish, etc.) and the ctenophores (exclusively marine, invertebrates) True tissues in three layers and bilateral symmetry – characterize all of the other animal phyla phylogenetic categories are based on the absence or presence and type of body cavity fundamental patterns of development Animal Diversity…

Animal Diversity… Invertebrates Absence of a backbone Greatest number of animal species Most of the animals alive today Animal Diversity…

Animal Diversity… Chordates Refers to the notochord Dorsal nerve cord A firm, flexible rod of tissue located in the dorsal part of the body (the back). At some stage of development, all chordates have a notochord, dorsal nerve cord, pharyngeal pouches, and a post anal tail. Dorsal nerve cord Hollow tube lying just above (dorsal to) the notochord. Pharyngeal pouches Small outpockets of the anterior part of the digestive tract. Postanal tail Consists of muscle tissue and lies behind the posterior opening of the digestive tract. Animal Diversity…

In most vertebrates… The dorsal nerve cord develops into the brain and the spinal cord. Pharyngeal pouches evolved into gills – used for breathing. In most vertebrates, the notochord is seen only in the embryonic stage. It is replaced by the backbone early in development. Animal Diversity…

Animal Diversity… Vertebrates… Make up only one subphylum of the phylogenetic tree of all animals. Humans are vertebrates. Humans interact extensively with many other vertebrates. fishes birds mammals All of these are primary food sources for humans. Animal Diversity…