Animals

Parthenogenesis

A type of reproduction in which females produce offspring from unfertilized eggs.

Notochord

A longitudinal, flexible rod that runs along the dorsal axis of an animals body in the future position of the vertebral column.

Neural Crest

A band of cells along the border where the neural tube pinches off from the ectoderm. The cells migrate to various parts of the embryo and form the pigment cells in the skin, bones of the skull, the teeth, the adrenal glands, and parts of the peripheral nervous system.

Vertebrate

A chordate animal with a backbone: The mammals, reptiles (including birds), amphibians, sharks and rays, ray-finned fishes, and lobe-fins.Chordates

Tracheal System

A gas exchange system of branched, chitin-lined tubes that infiltrate the body and carry oxygen directly to cells in insects.

Eumetazoan

A member of the clade Eumetazoa, animals with true tissues (all animals except sponges).

Chordate

A member of the phylum Chordata, animals that at some point during their development have a notochord; a dorsal, hollow nerve cord; phryngeal slits or clefts; and a muscular, post-anal tail.

What are the four characteristics of the Chordates?

A notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail.

Identify the signifance of the amniotic egg and the amniote.

Amniotes are named for the major derived character of the clade, the amniotic egg, which contains specialized membranes that protect the embryo. Called extraembryonic membranes because they are not part of the body of the embryo itself, these membranes develop from tissue layers that grow out from the embryo. They function in gas exchange, waste storage, and the transfer of stored nutrients to the embryo. The amniotic egg is named for one of these membranes, the amnion, which encloses a compartment of fluid that bathes the embryo and acts as a hydraulic shock absorber. The amniotic eggs of most reptiles and some mammals have a shell. The shell significantly slows dehydration of the egg in air, an adaptation that allowed amniotes to occupy a wider range of terrestrial habitats than amphibians, their closest living relatives. Amniotes also acquired other adaptations to terrestrial life, including less permeable skin and the ability to use the rib cage to ventilate the lungs. Whereas earlier tetrapods and living amphibians generally sprawl their legs out, living amniotes display a more elevated stance.

Parazoan

An animal belonging to a grade of organization lacking true tissues; a Sponge (phylum Porifera).

Coelomate

An animal that possesses a true coelom (fluid-filled body cavity lined by tissue completely derived from mesoderm).

Pseudocoelomate

An animal whose body cavity is not completely lined by mesoderm.

Cephalization

An evolutionary trend toward the concentration of sensory equipment on the anterior end of the body.

Gastrovascular Cavity

An extensive pouch that serves as the site of extracellular digestion and a passageway to disperse materials throughout most of an animal's body.

Outline the major characteristics that define an animal.

Animals are multicellular, heterotrphic eukaryotes with tissues that develop from embryonic layers.

What is the significance of cephalization as an evolutionary trend?

Bilateral animals generally move actively from place to place. Their central nervous system enables them to coordinate complex movements.

Deuterostomes

Deuterostomes are characterized by radial cleavage, enterocoelous, and the mouth deriving from the secondary opening while the bloastopore usually forms the anus.

What is the importance of segmentation?

Early arthropods had pronounced segmentation, but their appendages showed little variation from segment to segment. As arthropods continued to evolve, the segments tended to fuse and become fewer in number, and the appendages became specialized for a variety of functions. These evolutionary changes resulted not only in great diversification but also in an efficient body plan that permits the division of labor among different regions.

What is the evolutionary significance of the coelom as seen in the Annelids?

Earthworms eat their way through the soil, extracting nutrients as the soil passes through the alimentary canal. Undigested material, mixed with mucus secreted into the canal, is egected as castings through the anus.

What are some evolutionary advancements we see in the Platyhelminthes?

Flatworms have bilateral symmetry and a central nervous system that processes information from sensory structures.

Diploblastic

Having two germ layers.

Compare Lophotrochozoa and Ecdysozoa

Lophotrochozoan: Member of a group of animal phyla with protostome development that some systematists hypothesize form a clade, chaacterized by lophophores or trochophore larvae. Ecdysozoan: Member of a group of animal phyla with protostome development that some systematists hypothesize form a clade, including many molting animals.

What are the three major body regions of a Mollusc?

Molluscs have a muscular foot, a visceral mass, and a mantle.

Why are the Arthropoda regarded as the most successful of all animal phyla?

On the criteria of species diversity, distribution, and sheer numbers, arthropods must be regarded as the most successful of all animal phyla.

In what way are Platyhelminthes significant to humans?

Platyhelminthes can parasitize humans.

Triploblastic

Possessing three germ layers: the endoderm, mesoderm, and ectoderm. Most eumetazoans are triploblastic.

Protostomes

Protostomes are characterized by spiral cleavage, schizocoelous development, and the mouth generally developing from the blastopore, and it is for this characteristic that the term protostome derives (from the Greek protos, first, and stoma, mouth).

What is unique in the structure and function of the Pseudocoelomates.

Pseudocoelomates have body cavities that are not completely lined by mesoderm. They do, however,have fully functional body cavities.

Radial, indeterminate cleavage

Radial: A type of embryonic development in deuterostomes in which the planes of cell division that transform the zygote into a ball of cells are either parallel or perpendicular to the polar axis, thereby aligning tiers of cells one above the other. Indeterminate: A type of embryonic development in deuterostomes, in which each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo..

Describe the two forms of symmetry of the Eumetazoa.

Radial: The parts of a radial animal radiate from the center. Any imaginary slice through the central axis divides the animal into mirror images. Bilateral: A bilateral animal has a left side and a right side. Only one imaginary cut divides the animal into mirror-image halves.

How do the germ layers of Radiata and the other Eumetazoa differ?

Radiata have only two germ layers, the Endoderm and the Ectoderm, and are diploblastic. Other animals have athe mesoderm, between the ectoderm and the Endoderm.

Identify a characteristic that was most significant to Arthropod success.

Segmentation, being coelomates, having an exoskeleton, jointed appendages, having well-developed sensory organs, having an open circulatory system and having a variety of organs specialized for gas exchange.

Spiral, determinate cleavage

Spiral:A type of embryonic development in protostomes, in which the planes of cell division that transform the zygote into a ball of cells occur obliquely to the polar axis, resulting in cells of each tier sitting in the grooves between cells of adjacent tiers. Determinate: A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early.

How does the structure of a sponge relate to its method of nutrition?

Sponges are suspension feeders, trapping particles that pass through the internal channels of their bodies.

In the evolution of vertebrates, identify the significance of being tetrapod.

Tetrapods have limbs that can support their weight on land and feet with digits that allow them to transmit muscle-generated forces to the ground when they walk. The bones of the pelvic girdle, to which the hind legs are attached, are fused to the backbone, permitting forces generated by the hind legs against the ground to be transferred to the rest of the body. The pharyngeal clefts give rise to the ears, glands, and other structures. The ears are adapted to the detection of airborne sounds.

Endoderm

The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract.

Gastrulation

The formation of a gastrula from a blastula.

Blastula

The hollow ball of cells marking the end stage of cleavage during early embryonic development.

Mesoderm

The middle primary germ layer of an early embryo that develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, and most of the circulatory system.

Blastopore

The opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterstomes.

Ectoderm

The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye.

Cleavage

The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane. Also, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.

List and describe an example of an invertebrate chordate.

The urochordates, the cephalochordates, and the hagfishes.

What characterizes the subphylum Vertebrata?

The vertebrates derive their name from vertebrae, the series of bones that make up the vertebral column, or back bone. Vertebrates are craniates that have a backbone. Vertebrates have a more complex nervous system and a more elaborate skeleton than those of their ancestors.

What is a unique characteristic common to the Cnidarians?

These animals share a distinctive body plan that includes a gastrovascular cavity with a single opening that serves aboth mouth and anus.

List ways in which Nematodes impact humans.

These extremely numerous free-living worms play an important role in decomposition and nutrient cycling. phylum Nematoda also includes many important agricultural pests that attack the roots of plants. Other species of nematodes parasitize animals.

Germ Layers

Three main layers that form the various tissues and organs of an animal body.

What traits are particularly unique to the Echinoderms?

Unique to echinoderms is the water vascular system, a network of hydraulic canals branching into extensions called tube feet that function in locomotion, feeding, and gas exchange.

List a hypothesis for the origin of animals.

Various studies suggest that animal diversification began more than a billion years ago. The common ancestor may have resembled modern choanoflagellates, protists that are the closest living relatives of animals, and was probably itself a colonial, flagellated protist.

List the stages of early embryonic development of an animal

Zygote, Eight-cell stage, Blastula, Gastrulation, Gastrula

Acoelomates

solid-bodied animals that lack a cavity between the gut and outer body wall.

What are the two forms of shape within the Cnidarians?

the sessile polyp and the floating medusa.