The Animal Kingdom Invertebrates The Animal Kingdom Characteristics

The Animal Kingdom Invertebrates

The Animal Kingdom Characteristics: Eukaryotic (have a nucleus) Heterotrophic: must consume their food All are multicellular Possess no cell wall Typically have nerve tissue to conduct impulses and muscle tissue for movement Sexual reproduction is typical

The Animal Kingdom The animal kingdom evolved from a colonial protist. That common ancestor lived over 700 mya in the Precambrian oceans. One hypothesis for animal evolution:

The Animal Kingdom Of ~43 animal phyla, perhaps 9 are common. Animals: heterotrophic, multicellular, no cell wall

The Animal Kingdom Traditionally, the separation of animal phyla is based on body plans. The 1 st branch point is the presence or absence of tissues. The simplest animals today are choanoflagellates. Aquatic, no tissues Colony of simple cells Eat bacteria by endocytosis

Phylum Porifera Sponges Bodies are loose federations of cells - not true tissues because cells are relatively unspecialized. They lack nerves or muscles, but individual cells sense and react. Porous bodies have no symmetry (asymmetrical). Sessile (attached to substrate).

Phylum Porifera Sponges Body resembles a perforated sac. Multicellularity allows cell differentiation. Choanocytes filter food.

Phylum Cnidaria The 2 nd branch point for animal taxonomy is what type of symmetry they possess: radial or bilateral. Radial symmetry: a cut in any direction creates equal halves. Bilateral symmetry: there is only one direction where a cut creates equal halves.

Phylum Cnidaria Corals, jellyfish, hydras Body plan: double-layered bag. They have a gut but only one opening to the outside (the mouth). Specialized tissues coordinate cellular activity like digestion (gastrodermis). Extracellular digestion: enzymes are released into the body cavity allowing animals to digest things bigger than single cells. Radial symmetry: like a wheel – slice anywhere along the body axis and get a mirror image.

Phylum Cnidaria Corals, jellyfish, hydras Cnidos: Greek for stinger; these animals contain nematocysts cells that eject barbed threads tipped with poisons.

Phylum Cnidaria Corals, jellyfish, hydras Coral polyps live inside skeletons of calcium. They have a symbiotic relationship with brown algae called zooxanthellae

Phylum Platyhelminthes The 3 rd branch point is based on the type body cavity. Flatworms have no body cavity; they are acoelomate. Ex: tapeworm (below) of Solid all the way through

Phylum Platyhelminthes Flatworms Bilateral symmetry: cut lengthwise – get 2 equal halves. Cephalization: a definite head concentrates sensory organs & develops on active animals. Organs: collections of different tissues dedicated to one function.

Phylum Platyhelminthes Flatworms Digestive systems: mouth is only opening (no anus) so food in & waste out of mouth; nutrients must diffuse. Flatworms are small (~ ½ inch) or thin; no circulatory system means all cells must be near the branched intestine to get food & to exchange O 2 and CO 2. Hermaproditic: both sexes in each animal. Asexual reproduction Lung fluke

Phylum Nematoda Roundworms Bilateral symmetry; body plan = tube within a tube. Digestive tract with two openings (these have an anus, so food moves in one direction only). Microscopic to 1 meter in length. Parasites live in body tissues Examples of human diseases: Elephantiasis (right) Trichinosis from uncooked meat like pork, bear.

Phylum Annelida Segmented worms Bilateral symmetry. Body plan: tube within tube (a body cavity). Contains a mouth and an anus, plus specialized organs for digestion, circulation (five hearts), reproduction. Body segmentation: repeated body units (segments) can evolve over generations. Hydrostatic skeleton. a

Phylum Annelida Segmented worms Hermaphroditic leech (above) earthworm (right) marine worm (top)

Phylum Mollusca Mollusks - snails, slugs, clams, mussels, squids, octopi Have the innovations of previous groups: Bilateral symmetry A body cavity Tissues and organs Body segmentation

Phylum Mollusca Mollusks - snails, slugs, clams, mussels, squids, octopi A circulatory system moves nutrients (food & gases aren’t moved just by diffusion), and a coiled intestine can be longer, more efficient.

The Animal Kingdom Review the branch points in animal evolution. Presence or absence of tissues. Type of symmetry: None: sponges. Radial: cnidarians. Bilateral: worms, mollusks. Presence of a body cavity (a coelom). None (acoelomate): flatworms. Present (coelomate): nematodes, annelids, mollusks. Fills with water to provide support (a hydrostatic skeleton).

The Animal Kingdom Review the branch points in animal evolution. Animals: heterotrophic, multicellular, no cell wall