practical 3

• The animal kingdom includes multicellular organisms with eukaryotic cells lacking cell walls, plastids, and photosynthetic pigments.
• Most members of the animal kingdome take in nutrients by ingestion, and digestion of those nutrients takes place in an internal cavity. Some take in nutrients by absorption because of their lack of an internal digestive system.
• Reproduction for the animal kingdom is sexual, and except for some of the lowest phyla, haploid cells occur only in gametes.
• Phyla of kingdom Animalia: Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, & Chordata
• Each Phylum must have:

  • the basic body plan of the animals
  • the system employed to obtain nutrients
  • the reproductive systems of the animals
• germ layers: the embryo's triple layers
• germ layers: ectoderm, mesoderm, endoderm
• Ectoderm: outer layer

  • covering the surface of the embryo
• germ layer that gives rise to the outer covering of the animal, and in some phyla, to the central nervous system.

  ectoderm
• the innermost germ layer

  endoderm
• lines the primitive gut, and gives rise to the living of the digestive tract and its out-pocketing such as the liver and lungs of vertebrates

  endoderm
• found between ectoderm and endoderm


  mesoderm
• the germ layer that forms the muscles and most of the other organs between the gut and outer covering of the animal. 


  mesoderm
• 3 body plans

  acoelomate, pseudocoelomate, and coelomate
• the simplest body organization

  acoelomate body plan
• in this body plan, there is no cavity between the digestive tract and the outer body wall

  acoelomate
• The space between the digestive tract and outer body wall of acoelomate organisms is loosely filled with mesodermal cells called parenchyma
• The pseudocoelomate body plan has a fluid-filled cavity called pseudocoelom
• The pseudocoelom is located between the digestive tract and the outer body wall
• There is a layer od mesoderm located underneath the outer body wall of a pseudocoelomate
• There is no mesoderm in a pseudocoelomate, surrounding the organs. Thus, the cavity is not completely lined by mesoderm.
• The internal organs of pseudocoelomate animals are found free within this fluid-filled pseudocoelom.

  • this arrangement is known as the "tube-within-a tube" body plan.
• Coelomates have the body cavity (the coelom) completely lined by mesoderm.
• There is a layer of mesoderm underneath the outer wall of the coelomates and there is another layer of mesoderm surrounding the organs
• The two layers of mesoderm of coelomates connect dorsally and ventrally to form mesenteries that suspend the internal organs in the coelom.
• The fluid within the body cavity cushions the suspended organs, helping to prevent internal injury.
• The body cavity also allows the internal organs to grow and move independently of the outer body wall.
• If it were not for your coelom, every beat of your heart or ripple of your intestine could deform your body surface, and exercise would distort the shapes of the internal organs.
• Members of Phylum Nematoda are worms with long, cylindrical bodies and for this reason, are commonly referred to as roundworms.
• The Phylum Nematoda is among the largest of the animal phyla
• Most nematodes are found free-living within the soil, but a great many are important parasites of plants and animals
• roundworms have a body cavity called a pseudocoelom consisting of a fluid-filled space between the body wall and digestive tract.
• nematodes have a complete digestive tract with a mouth and an anus
• a large nematode that infects the intestinal tract of humans and other vertebrates.

  Ascaris lumbricoides
• It is one of the best-known parasitic nematodes

  Ascaris lumbricoides
• Female Ascaris are larger than males, with straight tails
• male ascaris are thinner than female ascaris, with hooked tails
• At the anterior end of the Ascaris, the mouth is found surrounded by three lobes (lips) of tissue
• At the posterior end of the Ascaris, the anus is located
• The muscular pharynx of the ascaris is found just behind the mouth