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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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coelem

fluid-filling cavity btwn inner & outer tubes
- coelemates: bilaterians w/ coelem