Tutorial 31 Animals I

Tutorial 31 Animals I

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Acoelomate An invertebrate lacking a body cavity.
Bilateral symmetry Arrangement of an organism along a central plane, so that the organism can be divided into two equal halves – characteristic of animals that are capable of moving freely through their environments.
Bilateria A taxonomic rank that refers to triploblastic animals with bilateral symmetry.
Cellular differentiation How a cell diverges from its early morphology into a more specialized one.
Cephalization The concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo's development.
Cnidaria A phylum containing bilaterally symmetrical animals found in aquatic environments: they have specialized cells used mainly for capturing prey.
Coelom The body cavity: a fluid-lined space that separates the gut from the outer body wall.
Coelomate Animals with a true body cavity derived from tissue surrounded by mesoderm.
Determinate development The fate of each cell in the adult organism is already determined.
Deuterostome Animals in which the mouth develops from an opening into the embryonic gut other than the blastopore, which develops into the anus.
Development The irreversible processes of growth and differentiation from a zygote through death of the organism.
Diploblastic An animal having a body derived from two embryonic cell layers (ectoderm and endoderm).
Ectoderm The outermost embryonic tissue layer, which forms the central and peripheral nervous systems and epidermis, as well as the heart and other organs.
Endoderm The innermost embryonic tissue layer that will eventually produce the gut and the associated endodermal organs.
Eumetazoa A major division of the animal kingdom in which the organisms have true tissues and comprise all animals except the sponges.
Flatworm Members of Phylum Platyhelminthes with bilaterial symmetry, triploblastic, cephalization, and an incomplete digestive tract.
Ganglion (pl. ganglia) A nerve cell cluster.
Hox genes These control the body plan of an embryo along the head-tail axis and turn other genes on and off.
Indeterminate cleavage The division of a fertilized egg into cells, each of which has the potential of developing into any cell type in the organism.
Larva (pl. larvae) A juvenile form many animals undergo while metamorphosing into adults.
Mesoderm the intermediate embryonic tissue layer that develops into the skeletal system and muscular system.
Parazoa A group of animals that lack clearly defined tissues and organs.
Planaria A freshwater flatworm.
Porifera The phylum that includes sponges.
Posterior The end of an organism opposite to its head.
Protostome Animals in which the oral end of the animal develops from the blastopore.
Pseudocoelomate Animals with a fluid filled body cavity that is derived from mesoderm and endoderm.
Radial Symmetry around a central axis.
Radiata A taxonomic rank that has been used to classify radially symmetric animals such as jellyfish.
Tapeworm Various species of parasitic flatworms.
Tissue Group of similar cells from the same origin that carry out a specific function.
Totipotency The ability of a cell to divide and produce all the differentiated cell types in an organism
Triploblastic Having a body derived from three embryonic cell layers.
What are the three basic features found in all members of kingdom Animalia? They are all motile, heterotrophic, and multicellular.
motility The ability move and/or affect motion in an organisms vicinity.
What do sessile and motile animals share in common? They were motile at least at some point during their development.
In terms of food, all animals are what? Ingestive heterotrophs.
What do most animals have for movement? Muscle and nervous tissue.
Where did the first animals likely originate? From a colonial protests similar to choanoflagellates.
Choanoflagellates Free-living unicellular and colonial flagellate eukaryotes determined to be the closest living relatives of the animals.
What is a similar feature between choanoflagellates and parazoa? A colony of individual cells is anchored to a substrate and each flagellum sweeps food into a cell for digestion.
When did animals first appear in the fossil record? ~750 Ma ago.
Phylogeny Evolutionary history.
Bifurcation Division of an ancestral line into two equal diverging branches.
What does each bifurcation in the phylogenetic tree represent? A character state that is though to clearly separate the lineages at that point.
What is the first major bifurcation of the phylogenetic tree? Animals that lack true tissues (Parazoans) and animals that have true tissures (Eumetazoans).
What do eumetazoans have? Distinct collections of cells arranged for specific purposes.
What is the typical development of sponges? Free-swimming flagellated cells at larval stage and sessile as adults, but will some flagella retained.
What is the second major bifurcation of the phylogenetic tree? The separation of eumetazoans into radial and bilateral symmetry.
What is characteristic of radiata? They have radial symmetry and are diploblastic.
What is characteristic of bilateria? They have bilateral symmetry and are triploblastic.
What is the third major bifurcation of the phylogenetic tree? Acoelomates, pseudocoelomates, and coelomates.
What are the coelomates split into? Protostomes and deuterostomes.
How to protostomes differ from deuterostomes? In the former, the mouth develops first; in the latter, the anus.
What does protos mean? First.
What does deuteros mean? Second.
What does stoma mean? Mouth.
In Anamalia, how are organisms mainly grouped? According to their development.
What is peculiar about groupings in Anamalia according to development? Two animals may appear similar at the early developmental stage but very different as adults.
Morphogenesis How an organism's shape is acquired.
Pattern formation How cells, tissues, and organs are arranged in an organism.
What type of development to protostomes have? Determinate, because their blastomere's fates are determined very early.
Animals with a radial cleavage pattern have what type of blastomeres? Ones that can potentially form all types of tissues.
Dueterostomes have what type of development? Indeterminate.
The early embryonic cells of deuterostomes can be what? Totipotent.
Blastomere Embryonic cell.
What are the three earliest stages of development? Fertilization, zygote, and cleavage.
What is important about early cell divisions? They are not random and can form specific configurations, like spiral and radial patterns.
Blastula A hollow ball formed from the first collection of blastomeres.
How do the ectoderm and endoderm develop? Some cells of the blastula migrate toward the interior, begin to differentiate, and express a different set of genes.
Gastrulation Migration of certain blastomeres to the interior of the blastula.
Induction The process by which certain embryonic cells trigger the differentiation of other embryonic cells.
What mainly happens during the gastrula stage? Cells change their developmental pathway and tissue types arise.
Where is gastrulation singularly observed? In eumetazoans.
What happens at the end of gastrulation? The endoderm and ectoderm have been defined and the mesoderm forms.
Archentron A pouch of cells created by invagination during gastrulation.
Blastopore The opening in the archenteron.
If the blastopore gives rise to a mouth, what is the organism? A protostome.
If the blastopore gives rise to an anus, what is the organism? A deuterostome.
How does the gut form? From the archenteron.
What is particular about Hox genes? They code for transcription factors that control the expression of other genes.
Where are the Hox genes found in animals? In a linear sequence along the chromosome, starting with those that affect structure at the head or an organism and moving down the body.
In which animal were Hox genes first discovered? The fruit fly.
Mice and humans have how many Hox genes? Four clusters.
What can a mutation in the Hox genes result in? A change in the position of body parts.
What are the main questions scientists have about sponges? Are they animals, and is a sponge an individual or a colony of individuals.
What are sponges composed of? A loose collection of cells, though lacking true tissue-level organization.
What symmetry to sponges have? They are asymmetrical.
Do sponges have Hox genes? No, they have Hox-like genes that may be involved in pattern formation.
What are the characteristics of a sponge embryo? It is hollow like a blastula, and it is flagellated, so it is free-swimming.
What eventually happens to a sponge embryo? It anchors to a substrate, the flagellated half inverts, the point where it inverts becomes the osculum, and the space becomes the spongecel.
The phyla Cnidaria and Ctenophora are what? Radiata.
What are some examples of cnidarians? Jellyfish, corals, and sea anemones.
What are the two characteristic body plans of cnidarians? Polyp and medusa.
How is the cnidarian polyp form usually found? Sessile and anchored to a substrate.
How many embryonic tissue layers to radiata have? Two: they lack a mesoderm.
How do the medusa forms of cnidarians move? They have musclelike cells at the base of the epithelial cells that enable them to move by contraction.
How do medusa forms of cnidarians react to the environment? Via a nerve net.
What is peculiar about the gastrovascular cavity of cnidarians? It is used for both digestion and excretion: the mouth and anus are a single structure.
Mesoglea A jellylike substance between the two tissue layers in cnidarians that provides support.
Cnidocytes Specialized cells that function in defense and in the capture of prey.
Nematocysts Organelles in cnidarians that can sting.
What develops in tandem with the single plane of symmetry in bilateria? Advanced sensory material in the anterior part of the body.
What are bilateria in terms of embryonic layers? Triploblastic.
What groups to bilateria comprise? Acoelomates, pseudocoelomates, and coelomates.
In an acoelomate gut, what occurs during contractions? They are not buffered by the fluid-lined body cavity, so all forces affect all internal organs.
What is the main function of the coelem? A mechanical buffer that helps protect internal organs from shock.
What is peculiar to pseudocoelomates? They have a body cavity that is only partially lined by mesoderm-derived tissue.
How is cephalization manifested in flatworms? Eyespots, paired ganglia, and a nervous system.
What are many planarians capable of? Regeneration of a complete body from a small fragment if cut into pieces.
Scolex The head of a tapeworm, which has hooks and suckers.
What is peculiar about flukes? They are parasitic and have complex life cycles.
How does the larvae of schistosoma mansoni find a host? They exhibit chemotaxis and respond to chemical signals from the host's body.
What is the secondmost socioeconomically-devastating disease in the world after malaria? Schistomiasis.
What is the medicine for treating schistomiasis? Praziquantel.

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