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cleavage
the first few cell divisions of a zygote
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Cleavage patterns
- many exist among animals
- influenced by the configuration of the yolk
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radial cleavage
- in echinoderms
- yolk is evenly distributed through the egg's cytoplasm
- "complete" cleavage
- the fertilized egg is divided into an even pattern
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spiral cleavage
- a permutation of radial cleavage
- in lophotrochozoans
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diploblastic
embryos that have 2 cell layers (ectoderm and endoderm)
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Triploblastic
embryos that have 3 cell layers (ectoderm, mesoderm, and endoderm)
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Protosomes
in the blastopore that the mouth forms first then anus
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Deuterostomes
in the blastopore that the anus forms first then the mouth
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bilaterians
- contains the groups protostomes and deuterostomes
- have bilateral symmetry
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body plan
the general structure, arrangement of organ systems, and function of its parts
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body cavity
- the presence/structure of an internal, fluid filled space
- based on acoelomates, coelomate, and psuedocoelomate
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acoelomate
- non enclosed, fluid filled cavity
- space filled with mesachyme
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psuedocoelomate
- a fluid filled space in which organs are suspended
- enclosed by muscles on the outside
- lacks an inner layer around organs
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coelomate
- contains a coelom
- the body cavity develops within a mesoderm
- has peritoneum lining the walls and organs
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hydrostatic skeleton
- the cavities function as this most of the time
- muscles move the fluid which moves the body parts
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segmentation
- the division of animal's bodies into segments
- this facilitates specialization of different body regions
- allows animals to alter the shape of the body in complex ways
- segments can move separately
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motile
the ability to move from place to place
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sessile
non moving, they stay in one place, usually attached
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filter feeders
- animals that use a straining device to get food from the environment
- water currents are essential for these
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choanocytes
- specialized feeding cells
- flagellated
- help bring food towards them
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nematocysts
- specialized cells containing stinging organelles
- on tentacles
- inject prey with toxins
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dispresal
the movement of organisms from a parent organism or from existing populations
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trochophore
a radially symmetrical larval form
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nauplius
a bilaterally symmetrical larval form
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Bilateria
- a large monophyletic group embracing all animals EXCEPT sponges, placozoans, ctenophores, and cnidarians
- triploblastic
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eumatozoans
everything not included in bilateria
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Sponges
- simplest animals
- no cell layers
- no true organs
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Spicules
- hard skeletal elements in sponges
- can be large or small
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placozoans
- simple animals
- have few distinct cell types
- asymmetrical
- attach to surfaces
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ctenophores
- "comb jellies"
- radially symmetrical
- diploblastic
- >outer layer is the mesoglea
- have beating cilia
- >contain ctenes
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cnidarians
- sea anemones, jellyfish, corals, and hydrozoans
- has one opening for mouth/anus
- has gastrovascular cavity
- has 2 stages (motile and sessile)
- motile-medusa
- sessile-polyp
- larvae is the planula
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gastrovascular cavity
- a blind sac
- functions in digestion, circulation, and gas exchange
- acts as hydrostatic skeleton
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medusa
- free swimming stage of the cnidarians
- produced from budding of polyps
- used for sexual reproduction
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polyp
- the unmoving stage of cnidarians
- attached to substratum
- produce medusae by budding (asexual)
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planula
- ciliated larval stage of the cnidarians
- develops into polyps
- formed from fertilized egg
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anthozoans
- a clade
- sea anemones
- solitary
- consists of 1+ polyps
- polyps become specialized for feeding and reproducing
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