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33 Cards in this Set
- Front
- Back
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animals are in the supergroup |
opisthokonta |
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animals are |
heterotrophs |
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animals lack |
a cell wall |
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animals are descended from |
a single common ancestor |
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2 main branches of animal lineage |
vertebrates and invertebrates |
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vertebrates |
are animals that at some stage fo their lives have a spinal cord |
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invertebrates |
do not have a backbone |
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colonial flagellate hypothesis |
states that animals are descended from an ancestor that resembled a hollow spherical colony of flagellated cells |
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what protist most likely resembles the last unicellular ancestor of animals and is closest living relative |
choanoflagellates |
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a choanoglagellate is |
single celled, with a flagellum surrounded by a collar of 30-40 microvilli also exist as a colony of cells |
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how a colonial flagellate might have evolved into an animal |
1 motile flagellates form an aggregate 2. colony of cells form a hollow sphere 3. specialization of cells for reproduction 4. infolding creates tissue |
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all of the various animal body plans we see today were present by |
the Cambrian period |
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what are the possibilities for the reason that animals are so diverse |
shifts in the DNA code and expression of genes called Hox (homeotic) genes |
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symmetry |
pattern of similarity that is observed in objects |
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what are the 3 kinds of symmetry |
asymmetry, radial symmetry, bilateral symmetry |
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asymmetry |
lack of symmetry, seen in sponges |
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radial symmetry |
bodies are organized circularly similar to a wheel such that any longitudinal cut through the central point produces two identical halves, cnidarians and comb jellies |
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bilateral symmetry |
as adults they have a definite left and right half |
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cephalization |
localization of a brain and specialized sensory organs at the anterior end of an animal |
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simplest animals |
sponges |
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first layers of tissue are called |
germ layers |
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animals such as cnidarians that have only 2 tissue layers - the ectoderm and the endoderm are termed |
diploblastic |
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diploblastic animals develop |
tissues but no specialized organs |
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the animals that develop specialized organs are called |
triploblastic |
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as embryos they have 3 tissues |
ectoderm, mesoderm, endoderm |
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tripoblastic animals are either |
protostomes or deuterostomes |
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protostomes |
the mouth develops before teh anus
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deuterostomes |
anus develops before the mouth |
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they develop by differentiation of of 3 major events |
cleavage, blastula formation, and coelom development |
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cleavage |
cell division without cell grouth |
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Blastula |
hollow sphere of cells |
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coelom |
a body cavity lined by mesoderm |
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the interior of a sponge canals is lined with |
flagellated cells that resemble choanoflagellates |
