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6 Invertebrates.pdf

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6 Invertebrates.pdf

  1. 1. Experiment #6 Kingdom Animalia Invertebrates
  2. 2. Introduction- Animals • All animals are members of the Kingdom Animalia, also called Metazoa. • All members of Animalia are: - multicellular - heterotrophs. • Most ingest food and digest it in an internal cavity. 2
  3. 3. Introduction- Animals • Animal cells lack the rigid cell walls that characterize plant cells. • Most animals are capable of complex and relatively rapid movement compared to other organisms. • Most reproduce sexually, by means of differentiated eggs and sperm. • Most animals are diploid. 3
  4. 4. Introduction- Animals • The development of most animals is characterized by distinctive stages, including: - a zygote, is the product of fertilization; - a blastula, which is a hollow ball of cells formed by the developing zygote; - a gastrula, which is composed of three germ layers: - ectoderm - endoderm - mesoderm. 4
  5. 5. Animals- classification • The classification of animals is based on: • body plan • Symmetry • germ layers • level of organization • coelom (cavity lined by epithelium) • segmentation. 5
  6. 6. Animals- Body Plans • A sac body plan: is one in which the mouth is used as both an entrance for nutrient molecules and an exit for waste molecules. • A tube-within-tube body plan: Animals with a mouth and an anus have this body plan. This plan allows specialization of parts along the digestive canal to occur. 6
  7. 7. Animals- Symmetry • Radial symmetry means that any longitudinal cut that passes through a midpoint gives two equal halves. • Bilaterally symmetrical animals can be cut into right and left halves and generally have well-developed head regions. 7
  8. 8. Animals- Number of Germ Layers • During the embryological development, there may be only two germ layer, ectoderm and endoderm; or three germ layers, ectoderm, endoderm, and mesoderm. • The presence of mesoderm is associated with the development of internal organs associated with higher animals such as skeletons and reproductive organs. 8
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  10. 10. Animals- Level of Organization • Some animals do not have organs and instead have a tissue level of organization. • Most animals have the organ system level of organization. 10
  11. 11. Animals- Coelom • Is the body cavity in which the internal organs are found. • Acoelomates: are animals that do not have a coelom. • Pseudocoelomates: have a body cavity incompletely lined by mesoderm. • True coelomates: have a body cavity completely lined by mesoderm. 11
  12. 12. Animals- Segmentation • When an animal is segmented, it has repeating parts like the vertebrae in the human backbone. Segmentation has led to specialization of parts in advanced animals. • Cephalization, having a well-developed head, is also a characteristic of the most advanced animals. 12
  13. 13. Phylum Porifera (Sponges) • The name stems from the meaning of ("pore bearers"). • are multicellular • Still, they have a very simple grade of organization • the body consists of a loose aggregation of cells embedded in a gelatinous matrix. • They lack any real organs or true tissues, • Nonetheless, they do contain different types of cells. 13
  14. 14. Sponges- Structure • Cells include: • epithelial-like cells called pinacocytes that cover the exterior and non-flagellated interior surfaces • flagellated cells called choanocytes that line inner chambers and canals • amoeboid cells called archeocytes that move about in the mesohyl (the gelatinous matrix within a sponge). • They can differentiate into other types of cells that form parts of the skeleton  composed of collagen and/or spongin fibers often embedded with calcareous or siliceous crystalline spicules). 14
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  16. 16. • Sponges show radial symmetry or none. • A spongocoel is the large, central cavity of sponges. • Water enters the spongocoel through hundreds of tiny pores (Ostia) • Water exits the spongocoel through the larger opening (osculum). 16
  17. 17. Sponges: Ecology • Most species are marine • a few are found in freshwater. • few animals appear to eat sponges, probably because a mouth full of spongin and spicules is not too appetizing! • However, a few reef fish and the hawksbill turtle feed exclusively on sponges. • Sponges provide homes for many organisms, particularly those anchored to coral reefs. 17
  18. 18. Phylum Cnidaria • Cnidarians are radially symmetrical animals that have a circle of tentacles surrounding the mouth. • Cnidarians are characterized by the presence of stinging cells called cnidocytes that are used for the capture of prey and defense. 18
  19. 19. • Cnidarians have two true tissue layers: • an outer epidermis • an inner gastrodermis. • A connective tissue layer called the mesoglea separates the two tissue layers. • The basic body plan includes a mouth that opens into a blind gastrovascular cavity, which is lined with the gastrodermis. 19
  20. 20. Cnidarians can be: - Sessile polyps in which the mouth points upwards (hydra and sea anemones) - swimming medusas in which the mouth points downwards (e.g., jellyfish) 20
  21. 21. Phylum Platyhelminthes (Flatworms) • Members of this phylum are bilaterally symmetrical and dorsoventrally flattened. • They have three embryonic body layers: ectoderm, mesoderm, and endoderm. • The gut is a gastrovascular cavity and has the functions of both digestion and circulation; • the mouth serves as both entrance and exit from the gut. 21
  22. 22. • These animals are the simplest form of animal life to have organ systems, a central nervous system, and a well-defined rostral or head end, with an opposite caudal or tail end. • Flatworms are acoelomate, i.e., the outside of the gut wall is directly continuous with the mesoderm; there is no coelomic cavity and so the gut is not free inside the body. • The mesoderm is muscular and is used for movement. • Ectodermal cells may be ciliated and provide another means of locomotion. 22
  23. 23. Flatworms- Classes • Three classes of the phylum Platyhelminthes exist: - class Turbellaria - class Trematoda - class Cestoda. 23
  24. 24. Class Turbellaria • Members of the class Turbellaria are free living (not parasitic). • Planaria lives in fresh water ponds • is a carnivore (animal eating). • The diet consists of such foods as insect larvae, small crustaceans, and other small living and dead animals. • Planarians reproduce asexually and sexually; individuals have both ovaries and testes. 24
  25. 25. • They glide over surfaces by the action of cilia; muscular contractions wrinkle or bend the body. • There is clearly a head end with a pair of black, light sensitive spots. • The color of planaria would make them blend in and be invisible among the leaves on the bottom of a pond. • The gastrovascular cavity is highly branched, because it serves also for circulation of nutrients to every cell. 25
  26. 26. • A planarian cross section has three or four slices through them. • Most obvious is the one from the middle with the great circular, muscular tube of the pharynx; • around it exists a space. 26
  27. 27. • The gut is continuous with the cells of the surrounding mesoderm. • the gut is lined with cells of endoderm • the outside of the animal is covered with ciliated cells of ectoderm. • The mesoderm is muscular. 27
  28. 28. Class Trematoda • Trematodes are commonly called flukes, and they are parasitic. • The life cycles of parasites are complex, with intermediate hosts and life stages. 28
  29. 29. Liver flukes- Opisthorchis • Opisthorchis is the liver fluke. • The anterior end has a mouth at the end, a sucker disc for holding on; and a ventral sucker, which is somewhat farther posterior. • The intestine divides into two simple tubes near the head end. 29
  30. 30. • The dark organ (colored) in the center of the body is the uterus and it is filled with eggs; the ovary is just posterior to it and appears as a pink mass. • Flukes have a seminal receptacle at the posterior end. The branched organ in the posterior part of the body is the testes. 30
  31. 31. • Trematode life cycle: The liver fluke is an important human parasite that is widely distributed in the Far East. Human infection occurs due to eating raw fish. • The small brown eggs of the fluke exit from a person's body in the feces. The eggs hatch when they are eaten by certain kinds of fresh water snails. • The hatchling is called a miracidium; after several metamorphoses, the parasite leaves the snail and infects fresh water fish; it encysts in their flesh. 31
  32. 32. • When a person eats these fish uncooked or insufficiently cooked, the live parasites enter the digestive system and migrate from the small intestine via the bile duct to the liver. • There they mature into adult liver flukes and in about 3 weeks begin to produce eggs. Eggs return via the bile duct to the digestive system and exit from the body in feces. 32
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  34. 34. Class Cestoda • The Cestoda are parasitic tapeworms. The life cycles are complex. • All tapeworms are extremely flat • the body is divided into segments, and there is no digestive system. • They absorb nutrients across their body walls. 34
  35. 35. The scolex • is the term for the head end of a tapeworm • it has a disc of hooks at the tip, which anchor it into the lining of the host's intestine, and four large suckers for holding on. • New segments or proglottids are generated behind the scolex. 35
  36. 36. • As you move down the worm away from the head, these segments get larger. Each is a complete reproductive machine with testes, ovaries and uterus. • The figure below shows mature proglottids. You can see a branched uterus containing hundreds of eggs in each segment. 36
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