An Introduction to Animal Diversity and Invertebrates By Genetically Superior™

Common Characteristics of Animals 1. multicellular 2. no cell wall 3. heterotrophic eukaryotes 4. sexual reproduction 5. tissues develop from embryonic layers

Cambrian Explosion 1. Occurred in the Paleozoic Era ( mya) 2. Animal diversification accelerates 3. Possible causes a) new predator-prey relationships emerge that trigger natural selection -forms of locomotive had to evolve (for predators) and shell defensees (for prey) b) 02 in atmosphere c) evolution of the Hox Gene Complex provided developmental flexibility that led to variations 4. Arthropods begin to adapt to terrestrial habitats (example: millipedes and centipedes)

Cambrian Explosion Neoproterozoic Era (1 bya-542mya) -Generally accepted fossils of animals are only 575 mya (known as Ediacaran fauna) -Related to cnidarians and corals, soft- Neoprotozoic bodied molluscs -Numerous tunnels and tracks indicate forms of worms -570mya embryos discovered in China show basic structural organization of present-day embryos (scientists not certain which clade)

Embryonic Development 1. most animals produce sexually 2. diploid stage dominates life cycle 3. zygote undergoes cleavage

Characterization of Invertebrates 1. grade: group of animal species that share same level of organizational complexity 2. body plans: a set of morphological and developmental traits that define a grade a) symmetry -radial -bilateral - cephalization: bilaterally symmetrical animals (anthropods and mammals) have trait of sensory equipment concentrated at anterior end - symmetry of animal fits its lifestyle

Diploplasts vs. triploblasts 1.diploplasts 1.animals with two germ layers (endoderm and ectoderm) 2.cnidarians 3.jellies, corals 1.triploblasts 1.three germ layers (third one being the mesoderm) 2. bilateral symmetry animals and cephalization 1. three categories of triploblasts based off of coeloms: 2. acoelomates 3. do not have coeloms 1.coelomates 2.have a true coelom 3.body cavity formed from mesoderm 4.HUMANS! 1.pseudocoelomates 2.have a false coelom 3.body cavity formed from blastocoel Invertebrates

All Triploblasts

1.two ways of development of chordates (have spinal cord) 1.protostome development 1.mouth develops from blastopore (opening of gastrula) 1.deuterstome development 1.anus develops from blastopore; Some Triploblasts are Chordates...

Chordates

Sponges (Porifera) - Are sessile (fixed in one place, immobile) Symmetry: -none Diploplast: -2 germ layers and no coelom Cephalization: -none Special adaptations: -unlike eumetazoans (all other animals), sponges lack true tissues Examples: -azure vase sponge (Callyspongia plicifera)

Cnidarians Symmetry : -radial Diploblast : -2 germ layers and no coelom Cephalization : -none Special Adaptations: -tentacles sting, thread punctures prey Examples: -jellies, sea anemones Hydrozoa: Man O' War

Flatworms -In addition to many free living forms, some are also parasitic Symmetry : -bilateral Triploblast : -triploblastic development -acoelomates (lack body cavity) Cephalization : -is evident (head ganglion attached to nerve cords) Special Adaptations: -Their flat shape/thin bodies enables gas exchange and elimination of nitrogen waste to occur through diffusion Examples : Tapeworm Marine flatworm

Annelids (segmented worms) -life cycle includes the trochophore stage (ciliated larval stage) Symmetry : -bilateral Triploblastic : - 3 germ layers -pseudocoelomates Cephalization : - have some (pair of cerebral ganglia at their anterior end) Special Adaptations: - well-developed coelom provides a hydrostatic skeleton Examples : - Earthworm -Bristleworm

Molluscs -are soft-bodied animals, some have protective shell -four classes: 1. Polyplacophora (chitons) 2. Gastropoda (snails and slugs) 3. Bivalvia (clams, oysters, other bivalves) 4. Cephalopoda (squids, octopuses, cuttlefish, chambered nautiluses) Symmetry: -depends upon the organism Triploblasts : -3 germ layers -coelomates Cephalization : -is evident Special Adaptations: - share same body plans: -foot (muscular, used for movement) -visceral mass (contains most internal organs) -mantle (fold of tissue that drapes over visceral mass and secretes a shell if one is present)

Nemotodes (round worms) -most are parasitic Symmetry : -bilateral Triploblastic: -3 germ layers -pseudocoelomates Cephalization: -some (only two small anterior “cerebral” ganglia from which neural chords split) Special Adaptations: -digestive system is complete (has both anus and mouth) -can redirect some cellular functions of their host Examples: -Parasitic Trichinella spiralis

Echinoderms -slow moving or sessile marine animals Symmetry -radial as adult (not perfectly), bilateral as larvae Triploblastic : -3 germ layers -coelomates Cephalization : -none Special Adaptation: -water vascular system (tube-like extensions that function in locomotion, feeding, and gas exchange) Example: -star fish -sea urchin

Arthropods (insects, arachnids, crustaceans) Symmetry : -bilateral Triploblastic : -3 germ layers -coelomates Cephalization : -is extensive (concentration of diverse sensory structures at the anterior end) Special Adaptations: -hard, external shell (exoskeleton or cuticle) and the molting process Examples :

Grasshoppers

Arthropods coelomates

Earthworms coelomates Annelids