Animal Diversity

Fig Animal Diversity (Ch. 32) Characteristics Animal body plans The tree of animals We are here: multicellular, heterotrophic eukaryotes

Figure 32.4 A traditional view of animal diversity based on body-plan grades

Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA

Animal Diversity (Ch. 32) Characteristics Animal body plans The tree of animals Fig DNA-based tree - the best we have at present. Notice that deuterostomes are not all together. (Echinoderms and Chordates are grouped togther, but some minor deuterostomes (e.g. Brachiopods), are not in the same clade as Echioderms and Chordates. Note: need to know term Metazoa (= animal)

What is an animal? Structure, nutrition, and life history define animals > Animals are multicellular, heterotrophic eukaryotes. >> Animals must take in organic molecules by ingestion; they eat other organisms or organic material that is decomposing. > Animal cells have no cell walls. >> Bodies are held together by proteins, especially collagen. > Animals have two unique types of tissues: a. Nervous tissue b. Muscle tissue

Animal Diversity (Ch. 32) Characteristics Animal body plans The tree of animals Tissues - collections of differentiated, specialized cells, separated by membranes Diploblastic - endoderm and ectoderm Triploblastic - endoderm, ectoderm parazoa- no true tissues metazoa- true tissues ectoderm, mesoderm, endoderm

Fig Animal Diversity (Ch. 32) Characteristics Animal body plans The tree of animals

Figure 32.7 A comparison of early development in protostomes and deuterostomes

Fig. 32.3, 4 Animal Diversity (Ch. 32) Characteristics Animal body plans The tree of animals

Figure 32.5 Body symmetry

Animal Diversity (Ch. 32) Characteristics Animal body plans The tree of animals Fig Body cavities

5. Growth from embryo to adult is modulated (controlled and organized) by Hox genes. Thus, the time sequence of development is controlled by Hox genes.  Many genes are the same or similar in all animals. The sequence in which they are turned on and off during development causes embryos to develop into different animals. Thus, for example, the same genes that give rise to dolphins and humans are in both organisms, but the sequence and time in which they are turned on creates either the dolphin or human. This is controlled by the Hox genes.

III. Origins of animal diversity A. Most animal phyla originated in a relatively brief span of geologic time 1. Modern phyla developed in about 40 million years total. 2. During the Cambrian Explosion (543 to 524 million years ago), nearly all major body plans appeared.

Figure 32.13x Burgess Shale fossils

Figure A sample of some of the animals that evolved during the Cambrian explosion

B. What caused the Cambrian explosion? 1. Development of predators and evolution toward prey escaping/predator hunting. Increased need for speed and better sensory equipment. 2. Oxygen levels reached present levels that allow for rapid metabolism exhibited by animals. 3. Hox genes evolved at that time and allowed for differential development.

Figure 33.1 Review of animal phylogeny

Phylum Porifera Sponges “colony” of flagellated cells individual cells can potentially regenerate into a new individual

Radial

Phylum Cnidaria Hydras, jellyfish, sea anemones, corals gastrovascular cavity stinging cells Radiata (radial symmetry)

Figure 33.4 Polyp and medusa forms of cnidarians

Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms The most obvious shared derived feature of Phylum Cnidaria (you may have been taught to call them Coelenterates) is the cnidocyte, or defensive/prey capture cell, containing stinging organelles called nematocysts (a term I used to refer to the entire cell ). They also all have radial symmetry. Tissues are far more developed in Cnidaria (and in all following Phyla) than in sponges, and in fact a clade called Eumetazoa can be defined based in the presence of true tissues. (I also used this term slightly differently than the book does - again, go with the book for exams.) You do not need to know the Classes of Cnidaria.

Figure 33.5 A cnidocyte of a hydra

Table 33.1 Classes of Phylum Cnidaria

Phylum Ctenophora Comb jellies comblike ciliary plates gastrovascular cavity Radiata (radial symmetry) Coloblasts (sticky cells)

Bilateral Symmetry

Phylum Platyhelminthes Flatworms dorsoventrally flattened no segmentation gastrovascular cavity bilateral, no coelom, protostome

Table 33.2 Classes of Phylum Platyhelminthes

Figure Anatomy of a planarian

Figure Anatomy of a tapeworm

Phylum Rotifera Ciliated crown no digestive system bilateral, pseudocoelomates, protostome

Figure A rotifer

Phylum Nematoda Roundworms unsegmented no circulatory system bilateral, pseudocoelomate, protostome

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Fig a nematode - roundworm - external cuticle needs to be molted for growth. Protostomes, pseudocoelomate

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Ascaris from human intestine (CDC) Pinworm seen in colonoscopy (Tulane)

Lophophorates - several phyla Bryozoans, lampshells (brachiopods) bilateral, coelomate, protostome

Figure Lophophorates: Bryozoan (left), brachiopod (right)

Phylum Mollusca Clams, snails, squids foot, visceral mass, mantle bilateral, coelomate, protostome

Fig Basic mollusc body plan. They are triploblastic (as will be all following phyla), and have bilateral symmetry. The mantle cavity with gills, ventral nerve cord, dorsal circulatory system, and radula (missing in bivalves [clams, etc.]) are among the unique derived characters of molluscs. Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms

Table 33.3 Major Classes of Phylum Mollusca

Figure The results of torsion in a gastropod

Figure Anatomy of a clam

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Fig

Figure Cephalopods Octopuses are considered among the most intelligent invertebrates. Squids are speedy carnivores with beaklike jaws and well- developed eyes. Chambered nautiluses are the only living cephalopods with an external shell. (a) (b) (c) Note the different shells in cephalopods (formally, the class Cephalopoda) - external in Nautilus, internal in squids, and missing in octopuses.

Phylum Annelida segmentation gone crazy! Segmented worms bilateral, coelomate, protostome

Figure Anatomy of an earthworm

Figure Anatomy of an earthworm - Phylum Annelida - segmentation gone crazy! Mouth Subpharyngeal ganglion Pharynx Esophagus Crop Gizzard Intestine Metanephridium Ventral vessel Nerve cords Nephrostome Intestine Dorsal vessel Longitudinal muscle Circular muscle Epidermis Cuticle Septum (partition between segments) Anus Each segment is surrounded by longitudinal muscle, which in turn is surrounded by circular muscle. Earthworms coordinate the contraction of these two sets of muscles to move (see Figure 49.25). These muscles work against the noncompressible coelomic fluid, which acts as a hydrostatic skeleton. Coelom. The coelom of the earthworm is partitioned by septa. Metanephridium. Each segment of the worm contains a pair of excretory tubes, called metanephridia, with ciliated funnels, called nephrostomes. The metanephridia remove wastes from the blood and coelomic fluid through exterior pores. Tiny blood vessels are abundant in the earthworm’s skin, which functions as its respiratory organ. The blood contains oxygen-carrying hemoglobin. Ventral nerve cords with segmental ganglia. The nerve cords penetrate the septa and run the length of the animal, as do the digestive tract and longitudinal blood vessels. The circulatory system, a network of vessels, is closed. The dorsal and ventral vessels are linked by segmental pairs of vessels. The dorsal vessel and five pairs of vessels that circle the esophagus of an earthworm are muscular and pump blood through the circulatory system. Cerebral ganglia. The earthworm nervous system features a brain-like pair of cerebral ganglia above and in front of the pharynx. A ring of nerves around the pharynx connects to a subpharyngeal ganglion, from which a fused pair of nerve cords runs posteriorly. Chaetae. Each segment has four pairs of chaetae, bristles that provide traction for burrowing. Many of the internal structures are repeated within each segment of the earthworm. Giant Australian earthworm Clitellum Protostomes, coelomate, ventral nerve system, dorsal circulatory system - like molluscs

Table 33.4 Classes of Phylum Annelida

Figure A polychaete - mostly marine. Note external “paddles” (parapodia) for swimming. Parapodia

Figure A leech

Phylum Arthropoda Crustaceans, insects, spiders segmented body, jointed appendages, exoskeleton bilateral, coelomate, protostome

Table 33.5 Some Major Arthropod Classes

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Fig Phylum Arthropoda - external skeleton, needs to be molted for growth. Protostomes, coelomate, ventral nerve system, dorsal circulatory system - like molluscs

Figure 33.30b Spider anatomy

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Fig Class Insecta - insects. 3 pairs of legs, one pair antennae, side-ways operating mandibles

Figure A trilobite fossil

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Fig Crustaceans

Invertebrates (Ch.33) Sponges Cnidarians Molluscs Annelids Nematodes Arthropods Echinoderms Fig metamorphosis

Bilateral Deuterostomes

Phylum Echinodermata Starfish, sea urchins bilateral, coelomate, deuterostome

Figure Anatomy of a sea star

Phylum Chordata Lancelets, tunicates, vertebrates notochord, nerve cord bilateral, coelomate, deuterostome

Figure 34.2 Chordate characteristics

Figure 34.3 Subphylum Urochordata: a tunicate

Figure 34.4a Subphylum Cephalochordata: lancelet anatomy