Flashcards in Animal Origin Deck (60)
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1
Cambrian explosion
rapid diversification of animal body types & lineages
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animal
member of major lineage of eukaryotes (Animalia)
- typically complex, large, multicellular body
- eat other orgs
- mobile
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body plan
basic architecture of animal's body
- including: number & arrangement of limbs, body segments & major tissue layers
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sessile
permanently attached to a substrate
- not capable of moving to another location
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choanocytes
specialized, flagellated feeding cell found in choanoflagellates (closest related living animal relative) & sponges
- most ancient animal phylum
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colonies
assemblage of individuals (semi-independent cells or breeding population of multicellular orgs)
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tissue
group of cells that fcn as a unit
(ie) muscle tissue - animal or xylem tissue - plant
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lophotrochozoans
major lineage of protostomes
- grow by extending size of exoskeletons, not molting
- many phyla = specialized feeding structure (lophophore) or ciliated larvae (trochophore)
(ie) rotifers, flatworms, segmented worms & mollusks
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ecdysozoan
major lineage of protostomes
- grow by molting & expanding bodies
(ie) arthopods, nematodes, etc
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segmentation
body or part of it is divided into series of similar structures
- exemplified by body segments of insects, worms, & somites of vertebrates
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vertebrate
1 of 3 major chordate lineages (Vertebrata)
- animals w/ dorsal column of cartilaginous or bony structures & skull enclosing brain
(ie) fish, amphibians, mammals & reptiles
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invertebrate
paraphyletic group composed of animals w/out a backbone
- includes 95% of all animal species
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benthic
living @ bottom of aquatic environment
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polyp
sessile stage in life cycle of some cnidarians (jellyfish)
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medusa
free-floating stage in life cycle of cnidarians
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cnidocyte
specialized stinging cell found in cnidarians
- used in capturing prey
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Cambrian Explosion diversitfication
(1) increased oxygen levels
(2) predation evolution: sessile to predators w/ shells & skeleton; increased movement
(3) new riches -> new niches (ecological diversification)
(4) new genes, new bodies
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germ layers
embryonic tissue layers
- types: diploblast & triploblast
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diploblast
animals whose embryos have 2 types of tissue
- "two buds"
- ectoderm + endoderm
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triploblast
animals whose embryos have 3 types of tissue
- "three buds"
- ectoderm + mesoderm + endoderm
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ectoderm
skin & nervous system
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mesoderm
circulatory system, muscle & internal structures (bone/organs)
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endoderm
digestive tract lining
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radial symmetry
"spoke symmetry"
- at least 2 planes of symmetry
- older than bilateral
- evolved from phylum Echinodermata
- attracts more prey
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bilateral symmetry
"2 sides symmetry"
- 1 plane of symmetry (lengthwise, down middle)
- occurs in triploblastic lineages
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cephalization
evolution of a head or anterior region
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nerve net
nerve cells organized into diffuse arrangement
- all over body, cover everything
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central nervous system
some neurons clustered into 1 or more tracts/cords that project throughout body
- like a tree w/ roots
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body cavaties
enclosed fluid-filled chamber act as hydrostatic skeleton
(1) coelem
(2) pseudocoelem
(3) acoelmate
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