Describe the characteristics of sponges, unique features that distinguish them from other phyla, and how they impact humans.
Sponges (Phylum Porifera) are the simplest animals -
sessile animals that suspension feed on bacteria using specialized cells called choanocytes (collar cells) -
distinguishing characters: one cell layer with no true organs, generally asymmetrical, acoelomate -
structure: incurrent ostia, filtering chamber, excurrent osculum -
sponges are important economically for chemical prospecting, ecologically for water filtration
Describe the characteristics of cnidarians including several example animals, unique features that distinguish them from other phyla, and how they impact humans.
Jellyfish, corals, anemones, and hydroids (Phylum Cnidaria) -
distinguishing characters: radially symmetrical, acoelomate animals with only two (true) tissue layers. -
many species with two body forms to life cycle: the medusa and polyp, many reproduce asexually as well as sexually -
all posess specialized stinging cells called cnidocytes -
cnidarian guts have only one opening that leads to a gastrovascular cavity, which functions for digestion, circulation and support -
cnidarians are important medically for some stings, ecologically as fish predators, or coral reefs
Describe the characteristics of flatworms including several example animals, unique features that distinguish them from other phyla, and how they impact humans.
Flatworms (Phylum Platyhelminthes)
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simplest bilaterally symmetrical animals with organ system level of organization -
includes free-living groups and two parasitic groups (flukes and tapeworms); parasites typically have attachment structures (e.g. a scolex), larger reproductive systems, and complex life cycles -
characters: three tissue layers, flat body to allow transport by diffusion, incomplete digestive tract (gastrovascular cavity), simple nervous system, acoelomate
Describe the characteristics of roundworms including several example animals, unique features that distinguish them from other phyla, and how they impact humans.
Roundworms (Phylum Nematoda) -
abundant, simple, pseudocoelomate worms -
includes free-living and parasitic forms, some important human parasites (Trichinella, pinworms), agricultural pests and study organisms for genetics (C. elegans) -
characters: three tissue layers with organ systems, exoskeleton/cuticle that they must molt, flow-through gut with specialized regions, often fixed number of cells in adult
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