28 terms

Biology Chapter 18

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annelids
segmented worms, have a closed circulatory system
arthropods
have jointed appendages and an exoskeleton that must be shed to permit growth
cnidarians
exhibit 2 radial body forms, the polyp and the medusa, and use stinging cells to capture prey
echinoderms
"spiny skin", have a water vascular system that functions in locomotion, feeding, and gas exchange
flatworms
simplest bilaterian animals, lack a body cavity; live in marine, freshwater, and damp terrestrial habitats
molluscs
have a body plan with 3 main parts: a visceral mass, a mantle, and a foot
nematodes
have a pseudocoelom and are the simplest animals that have a complete digestive tract
sponges
sessile animals that have specialized cells called amoebocytes and choanocytes
choanocytes
a flagellated feeding cell found in sponges. Also called a collar cell, it has a collar-like ring that traps food particles around the base of its flagellum
amoebocyte
an amoeba-like cell that moves by pseudopodia and is found in most animals; depending on the species, may ingest and distribute food, dispose of wastes, form skeletal fibers, fight infections, and change into other cell types
notochord
a flexible, supportive, longitudinal rod located between the digestive tract and the nerve cord
pharyngeal slits
located in the pharynx, the region just behind the mouth
deuterostomes
a mode of animal development in which the opening formed during gastrulation becomes the anus. Animals with this pattern of development include the echinoderms and the chordates
pseudocoelom
a body cavity that is not lined with mesoderm and is in direct contact with the wall of the digestive tract
cnidaria and platyhelminthes (flatworms)
Both _________ possess a gastrovascular cavity that has only one opening.
mid to late Precambrian (1 billion years ago or less)
All animals can probably trace their lineage to a common ancestor that lived in the _______.
protostomes
a mode of animal development in which the opening formed during gastrulation becomes the mouth. Animals with this pattern of development include the flatworms, molluscs, annelids, nematodes, and arthropods
blastula
the zygote divides by mitosis to form a hollow ball of cells called _____
gastrula
one side of the blastula folds in and cells become rearranged to form a _____ that establishes three embryonic layers
endoderm
forms a lining of the future digestive tract
ectoderm
forms an outer layer that will give rise to the skin and nervous system
mesoderm
forms a middle layer that will give rise to muscle and most internal organs
radial symmetry
have a top and bottom but lack back and front or right and left sides
bilateral symmetry
mirror image right and left sides
eumetazoans
animals with true tissues
cnidarians
radial symmetry, two tissue layers, polyp, medusa; carnivores that use their tentacles to capture prey and to push prey into their mouths
nematodes
roundworms; are abundant and diverse, with an estimated 500,000 species; have bilateral symmetry, three tissue layers, a nonliving cuticle covering the body that prevents them from drying out, a pseudocoelom body cavity that functions to distribute nutrients and as a hydroskeleton, and a complete digestive tract with a mouth and anus
gastropods
the largest group of mollusks; found in freshwater, salt water, and terrestrial environments; only of the mollusks that live on land, using the mantle cavity as a lung, and often protected by a single, spiral shell