BIOL 1030 – TOPIC 10 LECTURE NOTESTopic 10: Introduction to Animals; Porifera and Radiata (Chs. 32, 33)I. What defines Kingdom Animalia?A. multicellular heterotrophsB. no cell wallsC. monophyletic group (evolved from ancestral protist like modern choanoflagellates)II. What characteristics are associated with animals?A. more than 1 million animal species have been describedB. diversity in form – invertebrates (no backbone; 99% of animals) and vertebratesC. sexual reproduction (few exceptions)1. no alternation of generations (mostly gametic meiosis – haploid cells do not undergo mitosis)2. egg nonmotile, usually much larger than sperm3. sperm typically flagellatedD. most have active movementE. cells move within organism during development (and throughout life)F. typically complex embryonic development for most animals:1. zygote à morula (solid ball of cells)2. morula à blastula (ball becomes hollow)3. blastula à gastrula (ball folds in to form a hollow sac with one opening, the blastopore)4. interior of gastrula eventually forms gut (tube in many)5. blastopore becomes mouth or anusIII. How are animals classified?A. traditional taxonomic grouping based physical characteristics such as body cavities is on the way out (explored below)B. a firm consensus on a new animal classification scheme has not been reached; we will explore some of this on the Tree of Life website in class…Compiled from the Tree of Life (http://tolweb.org/tree/):1 of 7BIOL 1030 – TOPIC 10 LECTURE NOTES...along with a recent publication from Auburn University faculty member Ken Halanych:http://gump.auburn.edu/halanych/lab/Pub.pdfs/Halanych2004.pdf2 of 7BIOL 1030 – TOPIC 10 LECTURE NOTESC. even so, the traditional taxonomy is so firmly entrenched that it is worth knowing and will be referenced in this course along with some of the newer classification schemesD. two subkingdoms: Parazoa and EumetazoaParazoa : no tissues or organs, asymmetricalEumetazoa : definite shape and symmetryIV. Subkingdom Parazoa – Phylum Porifera - the spongesA. actually appears to be a grade1. note Halanych figure above2. somewhat controversial – grades aren’t supposed to be phyla!3. taxon retained largely due to traditionB. asymmetrical3 of 7BIOL 1030 – TOPIC 10 LECTURE NOTESC. cellular level of development – a loose confederation of cellsD. 5150 species, most marineE. larvae free-swimming (motile)F. adults sessileG. filter feeders1. body has numerous small pores – water comes in through these to the interior spongocoel cavity2. water leaves the spongocoel through a large pore, the osculum3. tubes lined with choanocytes (flagellated cells also called collar cells) that move water using their flagellae- 1 cm3 of choanocytes can move 20 L of water/day- to get an ounce of food, a ton of water has to be filtered!H. spicules (calcium carbonate or silica) form scaffolding or “skeleton”I. spongin - a protein - also supports body in someJ. reproduction1. splitting - remove part and it often will grow into a new sponge2. some produce eggs, some spermV. Subkingdom EumetazoaA. rest of the animals; definite shape and symmetry (bilateral or radial) – ~35 living phylaB. key body plan transition: development of tissues, groups of similar cells organized into a structural and functional unitC. Eumetazoa – 1. all with tissue layers2. diploblastic – have two cell layers in embryo- ectoderm – outer layer; source of outer covering(epidermis) and nervous system- endoderm – inner layer; becomes gut (gastrodermis)- found in grade Radiata (radially symmetrical – Phyla Cnidaria and Ctenophora)3. triploblastic – have three cell layers in embryo- mesoderm – middle layer between ecto- and endoderm; most organs form from mesoderm tissue- found in all of clade Bilataria (animals with bilateral symmetry at some point in their life cycle)VI. Eumetazoa have undergone 4 key transitions in body plan during the course of evolutionA. development of bilateral symmetry1. radial symmetry – (found in grade Radiata) any plane through the central axis of the animal will produce two halves that are approximately mirror images of each other2. bilateral symmetry – (found in clade Bilateria) body has left and right halves that are approximately mirror images of each other- body plan has dorsal and ventral regions (back and front)- body plan has anterior and posterior regions (head and rear)3. bilateral symmetry was a major evolutionary advance- bilateral animals move more efficiently able to seek food better4 of 7BIOL 1030 – TOPIC 10 LECTURE NOTES able to better avoid predators- bilateral animals have a central nerve cord(s)- bilateral animals were able to develop a definite head and brain area (cephalization) head is more specialized and efficient head better protects important organsB. development of the body cavity1. evolutionary history unclear; NOT treated as clade-defining synapormorphies anymore2. important for allowing development of efficient organ systems3. cavity makes room for organs and for efficient support of them (both structurally and for transport of materials to and from them)4. acoelomate – no cavity5. pseudocoelomate – have fluid-filled cavity (pseudocoel) between mesoderm and endoderm6. coelomate – have fluid-filled cavity (coelom) within mesoderm and surrounded by mesodermal tissue- parietal peritoneum – epithelium lining outer wall of coelom- visceral peritoneum – epithelium lining covering organs in coelom; also lines inner wall7. body cavities require some form of circulation- pseudocoelomates churn fluid in body cavity- coelomates have a circulatory system circulating fluid = blood open – blood pumps from heart into coelom; used by most invertebrates closed – blood pumps from heart into vessels and back into heart; separation from rest of body fluid allows for greater control of blood contents8. Why is a coelom better than a pseudocoelom?- endoderm and mesoderm are better able to communicate and coordinate during development because they are in direct contact- allows development of a more complex digestive tractC. development of protostomes and deuterostomes (both appear to make clades)1. protostomes – “first mouth”; blastopore becomes mouth2. deuterostomes – “second mouth”; blastopore becomes anus3. cell fate is determined from beginning in protostome embryos, not in deuterostome embryosD. development of a segmented body plan (segmentation) in different