Chp 4 Animal Diversity

• There is life on Earth.
• The cytoplasm of animals is contained within cells in the space between the cell membrane and the nuclear membrane.
• All phyla of the animal kingdom, including sponges, possess collagen, a triple helix of protein that binds cells into tissues.
• The walled cells of plants and fungi are held together by other molecules, such as pectin (a complex starch derived from plants).
• Collagen is not found among unicellular eukaryotes.
• The muscles that distinguish animals from plants or fungi are specializations of the actin and myosin microfilaments common to all eukaryotic cells.
• Mobility limits an animal to maintain the same shape throughout its active life.
• Plants and fungi grow by extension, and their shape is ever-changing.
• Parazoa is a cellular level of organization, with the two phyla in this subkingdom, Porifera (sponges) and Placozoa, lacking clearly defined tissues and organs, their cells specialize and integrate their activities.
• The shape of the creeping flattened placozoans is irregular and changeable.
• Radiata is a tissue level of organization, with the two coelenterate phyla (Cnidaria and Ctenophora) advanced in complexity beyond the parazoans by developing incipient tissues.
• Coelenterates have only two body layers; an inner endoderm for feeding, and an outer ectoderm for protection.
• Between the endoderm and the ectoderm of coelenterates is the mesoglea, a gelatinous mass that contains connective fibers of collagen and usually some cells.
• The cavity between the endoderm and the mesoglea in coelenterates is used for gamete dispersal and waste elimination.
• Cleavage of a fertilized egg produces a hollow sphere of flagellated cells (the blastula).
• Invagination of cells at one or both poles creates a mouthless, solid gastrula; the gastrula is called the planula larva in species in which this stage of development is free-living.
• The inner, endoderm cells subsequently differentiate to form the lining of the central cavity.
• The mouth forms once the planula larva has settled.
• This is characteristic of invagination during the development of all animals.
• All coelenterates are more or less radially symmetrical.
• Protostomes have dividing cells that are oriented at an angle to one another and the ultimate fate of the cells is mostly determined from the beginning.
• Deuterostomes show indeterminate, radial cleavage, with the dividing cells becoming layered and the fate of early cells a product of where they are positioned later in development.
• Coelom formation is schizocoelous in most protostomes, whereas enterocoelous development is typical of deuterostomes.
• For those with a larval stage, the characteristic larval forms also differ.
• Large size is often competitively advantageous but unobtainable by many animals because of constraints of basic body plan.
• The largest known living animals are the whales and elephants.
• The pattern of evolution on Earth has favored sociality in the smallest and the largest, mostly vertebrates.
• The large animals can communicate; they spread out to find food, which all can share, and they protect one another.
• Among the social groups of large animals, only humans have differentiated their functions to such an extent that their societies begin to behave as individuals.
• To stay alive, grow, and reproduce, an animal must find food, water, and oxygen, and it must eliminate the waste products of metabolism.
• A skeleton can support an animal, act as an antagonist to muscle contraction, or do both.
• Muscles can only contract, they require some other structure to stretch them to their noncontracted (relaxed) state.
• Hydrostatic skeletons are the most prevalent skeletal system used by animals for movement and support.
• Hydroskeletons are also important in nonlocomotory muscular systems, such as hearts or intestines, which move blood or food, respectively.
• Hydroskeletons become less efficient when fluid is lost.
• Elastic skeletons do not change shape but simply bend when a muscle contract.
• Jointed skeletons achieve movement through a lever system.
• The speed and force of a movement are determined by the length of the skeletal element and the size of the contracting muscle.
• Short limbs with thick muscles have more power than long limbs with slender muscles, but the latter have more speed.
• A jointed skeleton is ideal for moving on land because of adaptations for protection against dehydration, such as the cuticle.