Topic 19
1. Describe the characteristics of animals.
Cell structure and specialization: multicellular eukaryotes; lack cell walls;
extracellular structural proteins; differentiation of cells.
Nutritional mode: chemoheterotrophs; ingest food and digest within their bodies
(internal chamber).
Reproduction and development: sexual reproduction; diploid stage dominating
the life cycle; motile, haploid sperm fertilizes a larger, non-motile haploid egg;
animals are motile at one stage of life cycle; early embryonic development
(blastula, gastrulation); direct development or indirect development (larvae
stages); animal development controlled by conserved Hox genes.
2. Explain the steps in the early embryonic development of animals.
zygote undergoes cleavage to form multicellular, hollow blastula; blastula
undergoes gastrulation; gastrula with two cell layers (ectoderm, endoderm).
Topic 20
The common ancestor of animals (arose 700-670 mya) was a flagellated eukaryote.
Living sister group to animals are Choanoflagellates (heterotrophic protists with
characteristic single flagellum surrounded by a collar of microvilli).
1. Explain the evidence supporting choanoflagellates as the living sister group to
Kingdon Animalia.
Cell morphology of Choanoflagellates and sponge collar cells indistinguishable.
Collar cells identified in other animal phyla, but never in non-choanoflagellate
protists nor in plants or fungi.
Final Exam Study Guide 2
, DNA sequence data indicate that choanoflagellates and animals are sister
groups.
2. Differentiate between animals from the Ediacaran period and the Cambrian
explosion.
Multicellular eukaryotes evolved in multiple lineages (~1.7 bya), giving rise to
algae, plants, fungi, and animals.
Whole-body animal fossils from late Proterozoic (Neoproterozoic era):
Ediacaran biota (565-535 mya) are diverse soft-bodied, mostly sessile marine
organisms; disappeared by Cambrian.
Cambrian explosion (535-525 mya): the origin of most major phyla of living
bilaterian animals.Hypotheses for Cambrian explosion: new predator-prey
relationships; incr. in atmospheric O2; evolution of the Hox gene complex.
3. Identify the shared, derived traits of metazoan clades.
Clade Metazoa: 1. Multicellularity and cell differentiation; 2. Cell adhesion
(extracellular matrix); 3. Sperm and ova; 4. Embryonic blastula.
Topic 21
1. Describe the characteristics of Porifera (sponges).
Sponges are sessile marine animals that lack true tissues; motile larval stage.
Four simple cell types: epidermal cells; porocytes; choanocytes (collar cells)
generate a water current through the sponge and ingest suspended food;
gelatinous acellular mesohyl contains mobile amebocytes and skeletal
elements (spicules or spongin).
Sponges are suspension feeders: water is drawn (by the beating of choanocyte
flagella) through pores (ostia) into a cavity called spongocoel and out through
an opening (osculum); food particles trapped in mucus-covered microvilli and
engulfed by phagocytosis and digested or transferred to amoebocytes.
Final Exam Study Guide 3
, Sponge reproduction: most sponges are hermaphrodites and use internal
fertilization (eggs retained in mesohyl); free-swimming ciliated larvae disperse
from parent sponge; sponge embryonic development highly variable.
2. Describe the characteristics and body plan of Cnidarians.
Simple diploblastic, radial body plan: a sac with a central gastrovascular cavity
with a single opening (functions as mouth and anus) surrounded by tentacles
with stinging cells (subdue prey and/or defence); epidermis (ectoderm),
gastrodermis (endoderm), and mesogloea (acellular 'jelly' matrix).
Two variations on body plan: polyp (sessile form, e.g. sea anemone); medusa
(bell-shaped motile form, e.g. jellyfish).
Cnidarians are predators that use tentacles to capture prey: tentacles armed
with cnidocytes, unique cells that function in defence and capture of prey, that
contain complex endocellular structures (e.g. nematocysts).
3. Differentiate between medusozoan and anthozoan cnidarians.
Medusozoans produce a medusa.Hydrozoans alternate between polyp and
medusa forms.Scyphozoans (jellyfish) and Cubozoans (box jellyfish) have
medusa as the dominant stage in the life cycle.
Anthozoans occur only as sessile solitary or colonial polyps (corals and sea
anemones).
Topic 22
1. Identify animal phyla in clade Lophotrochozoa.
Wide range of animal body plans, but no one unifying trait(s): some develop
lophophore for feeding, others have a trochophore larval stage.
2. Characterize the body plans, morphological features, and life cycles of each phyla
of Lophotrochozoans.
Phylum Platyhelminthes (flatworms)
Final Exam Study Guide 4
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