A whirl-wind tour through the most prominent phyla! Animal Diversity A whirl-wind tour through the most prominent phyla!

Traditional Animal Phylogentic Tree Which animals have a body cavity? What are the possible functions of a body cavity in animals?

Animal Phylogeny – Modern Based on sequences in ribosomal RNA (molecular systematics) Acoelomate flatworms lost their coelom Coelom development happened early Combine phyla with lophophore and trocophore larvae Combine phyla that molt (ecdysis) Fig 32.8

Radiata X X X X X X cnidocytes, unique in the animal kingdom extracellular digestion in a gastrovascular cavity allow food larger than individual cells. Describe the function of a gastrovascular cavity. Tissues allow for different cells to take different roles

Plylum Cnidaria “cnidarians” detect and respond to stimuli from any direction muscles and simple nerve net tissue-grade level of organization Fig 33.6 Fig. 33.5

Polyp vs. medusa 2 tissue layers: 2 body forms: Fig. 33.4 skin (epidermis) gastrovascular cavity lining 2 body forms: polyp medusa Which body form is involved in sexual reproduction, and why? Fig 33.4

Phylum Platyhelminthes – “flat worms” first phyum with organ-system level of organization, and bilateral symmetry with some cephalization gastrovascular cavity; secrete mucus and move by means of cilia and wave-like muscle contractions A thin body between dorsal and ventral surfaces NO coelom (acoelomate) Flatworms, trematodes, tapeworms

Phylum Nemertea - “ribbon worms” Actually acoelomate, but some similarities to the protostomes Complete digestive tract; closed circulatory system What are the advantages of a complete digestive tract? …of a closed circulatory system? What does this predict about size? Photo from: http://www.seaslugforum.net/factsheet.cfm?base=nemertea

Phylum Mollusca – “mollusks” Over 150,000 spp; mostly marine Complete digestive tract; most have an open circulatory system Soft body protected in most by a hard internal or external shell made of calcium carbonate What other organisms manufacture CaCO3? Bivalves: clams, etc. Gastropods: snails, slugs Cephalopods: squid, etc. …and why is this process important to the biosphere? Polyplacophora: chitons

Mollusk anatomy Important consumers: Filter feeders Grazers Carnivores 3 Main body parts: Foot movement Visceral mass internal organs Mantle secretes shell; gas exchange Most use a strap like rasping organ called a radula to scrape food; cephalopods have a beak In many the mantle extends to produce a water-filled chamber, the mantle cavity, which houses the anus and gills (portions of the mantle that increase surface area for gas exchange, making it more efficient).

Phylum Annelida – “segmented worms” ~15,000 species in 3 classes; marine, freshwater and damp soil Body & some organs segmented (division of labor with regional specializations) Polychaetes, earthworms & leeches How do these worms exchange gasses? Fig 33.24bcd

Segmented worm anatomy Front segments contain sense organs and a well-developed brain Complete digestive system and closed circulatory system Complex movement Circular muscles Longitudinal muscles Segmental hydrostatic skeleton Setae Segmentation: having a body built from repeated units (segments) allows a more precise control of the development and function of individual segments or groups of segments.

Summary Important evolutionary trends in body plan: Multicellularity: Porifera True tissues: Cnidaria Bilateral symmetry: Platyhelminthes Coelom: Mollusca (reduced or absent in some) Segmentation: Mollusca (some), Annelida These trends helped animals adapt to different environments or exploit the same environment in a different manner

Exoskeletons must molt to grow (ecdysis) Grasshopper molting Fig 32.8

Phylum Nematoda – “round worms” > 90,000 spp, in aquatic habitats, wet soils, many as decomposers or parasites inside plants and animals Tough, transparent cuticle (mostly collagen) Cylindrical body; longitudinal muscle only; pseudocoelom Complete digestive tract Trichinella Fig 33.25 a, b Muscle cells

Phylum Arthropoda – “arthropods” Jointed appendages (“jointed feet”) > 1 million spp, most of them insects (beetles) Most diverse, widely distributed & abundant of all the animal phyla Hard exoskeleton of chitin Relatively impermeable to water Strong: protection & muscle attachment (striated muscle) Non-living What “problems” does a tough, waterproof exoskeleton create? Fig 33.32

Arthropod anatomy Extensive cephalization Well developed sense organs: sight, “taste” Segmentation some fused and modified into specialized regions (great diversification of form and function) Basic Body Plan: head thorax abdomen Fig 33.26 Lobster: crustacean

Class Insecta - Insects Most successful phylum Mostly terrestrial, but often requiring water for reproduction Only invertebrates with adaptations for flight Fig 33.33 For what purpose(s)? Fig 33.32 Fig 33.34

Class Arachnida – spiders, mites, ticks, scorpions Mostly terrestrial Cephalothorax (fused region) 6 pairs of appendages 2 pairs for feeding 4 pairs of walking legs Fig 33.30b

Scorpions & mites Scorpion in defensive posture cf Fig 33.29 Parasitic mites in honey bee air tube

Class Crustacea – crabs, shrimp, barnacles mostly marine specialized appendages carnivores, detritivores, filter feeders Lobster Barnacles How do these mostly aquatic organisms exchange O2 and CO2? Shrimp

Deuterostomes Protostomes Fig 32.7

Phylum Echinodermata – echinoderms ~ 7,000 spp, all marine “spiny skin” radial symmetry in adults (larvae bilateral)* Endoskeleton plates and projecting elements functions like an exoskeleton Water vascular system sea stars Brittle stars Sea cucumbers *How does this relate to lifestyle in adults vs. larvae? Sea urchins crinoids Fig 33.37

Water vascular system Unique Fluid-filled tubes Tube feet: begin in the madreporite end in tube feet Tube feet: locomotion food gathering gas exchange Fig 33.38