Intro to Animals

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Biology

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43 Terms

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Key traits of animals
all multicellular. lack cell walls but have extracellular matrix
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Extracellular matrix (ECM)
structural support. composition depends on tissue type. fibrous component contains collagen
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All animals are
heterotrophic and motile at some life stage
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Most animals feed by
ingestion
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all but sponges have
nerve cells and muscles
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Most animals are
diploid and form gametes via meiosis
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Metazoans
all animals
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Eumetazoans
animals with tissues
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When did animals originate?
700 mya. chemical evidence of steriods by sponges same as today around 710 mya
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First animal fossils
about 560 mya. soft-bodied, resembled sponges, cnidarians and mollusks
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Ediacaran biota
first animal fossils named after time period they date to
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What was the protistan ancestor of animals?
Choanoflagellates. DNA evidence shows sister taxa
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Choanocytes
collar cells of sponges, resemble choanoflagellate cells
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Animals are what kind of phylogenetic group?
monophyletic
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Basal phylum
diverged early from root of the tree. in animals this is Porifera
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Most animals are in the groups
Bilateral, and most are invertebrates.
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Radial symmetry
multiple planes of symmetry (i.e. jellyfish) can sense environment from all sides because uniform distribution of nerve/sensory cells
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Bilateral symmetry
single plane of symmetry. Central NS and Cephalization
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Central NS and Cephalization
concentration of nerves/senses at anterior (head). can coordinate complex movements & sense environment when entered
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Tissue
group of cells organized into structural and functional units.
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Tissues form as
germ layers (embryonic tissue layers)
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ectoderm
gives rise to skin and nervous system
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endoderm
gives rise to lining of digestive system
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Diploblasts
animals with two germ layers (i.e. jellyfish)
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Triploblasts
animals with three germ layers
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Endoderm in triploblasts
leads to lining of digestive, respiratory, reproductive systems
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Mesoderm
gives rise to muscles, bones and most organs. allows for development of complex muscles for movement
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Coelom
Fluid filled body cavity between inner and outer tubes. Chamber acts as hydrostatic skeleton
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Hydrostatic
Involves fluid filled cavity
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Hydrostatic skeleton
muscles work against fluid filled cavity
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Body cavity allows
space for organ development, support and movement of larger bodies that lack limbs, and circulation of nutrients, gases and wastes.
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Acoelomates
No body cavity
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Psuedocoelomates
Body cavity partially lined with mesoderm
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Coelomates
body cavity completely lines with mesoderm
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Cambrian explosion
appearance of ancestors of several modern day phyla
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Diversification of animals in Cambrian
time period in which animals could have larger bodies thanks to more O2, and could make more ATP in aerobic metabolism

evolution of predation
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Non-bilaterian phyla
Porifera and Cnidaria
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Sponges
benthic: freshwater and marine species. sessile. filter feeders. covered with pores for water intake
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Choanocytes in sponges
drive water flow and engulf food. amoebocytes also engulf food
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Spicules
provide support to sponge. made of CaCO3, SiO2, or spongin
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Cnidaria
radially symmetrical diploblasts. mesoglea (inner gelatinous layer). jellies, sea anemones, corals and hydrozoans. polyp and medusa stages of life.
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Synapomorphy of cnidarians
cnidocytes. specialized in capturing prey. possess gastrovascular cavity
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Nematocyst
coiled structure, discharges when disturbed. grabs prey. part of cnidocyte.