Survey of the Phyla-Animalia, Invertebrates

1. Survey of the Phyla-Animalia, Invertebrates

2. The Kingdom Animalia is in the domain Eukarya and in the supergroup Unikonta. They are in the group Opisthkonta with fungi. Both groups have different unicellular organisms that are their common ancestor. That fact indicates the groups became multicellular organisms independent of one another.

4. Characteristics of the Animal Kingdom 1. Animals are multicellular, heterotrophic, ingestive and eukaryotic. 2. The cells lack cell walls and are held together by structural proteins which are mostly collagen. They have intracellular junctions such as tight junctions, desmosomes and gap junctions. 3. Animal cells have nervous and muscle tissues found only in this kingdom. 4. Most animals have a diploid life cycle with a sperm fertilizing an egg. The zygote undergoes cleavage forming a blastula (hollow ball of cells). The blastula undergoes mass movement of cells to form a gastrula giving rise to three layers of tissue, endoderm, mesoderm and ectoderm. Often there is a larval stage to the animal which is sexually immature. It often will undergo metamorphisis to become an adult.

5. 5. All animals contain both homeotic genes (any of the genes that control the overall body plan of animal by controlling the developmental fate of a group of cells) and homeobox (a 180-nucleotide sequence with a homeotic gene) encoding the part of the protein that binds to the DNA of the genes regulated by the protein. There is an increase in the number of these genes with an increase in the complexity of the animal. The protists most closely related to animals are the choanoflagellates. It is flagellated with a collar to collect food. It will form colonies.

6. Other interesting points about animals Embryonic development -Deuterostomes versus protostomes. During development many animals first form a hollow ball of cells or blastula. Afterward that there is a mass movement of the cells called gastrulation. This process results in three layers of tissue being established. Ectoderm-becomes skin and nervous tissue Mesoderm-notochord, lining of coelom, kidneys, muscles and bone and circulatory system Endoderm-interior lining of organs and liver, pancreas, lungs and lining of digestive tract. During this process of gastrulation, the first opening to the gut or archenteron forms. In deuterostomes, this opening becomes the anus but in protostomes it becomes the mouth.

7. 1. Among the characteristics unique to animals is A) gastrulation. B) multicellularity. C) sexual reproduction. D) flagellated sperm. E) heterotrophic nutrition.

8. 1. ANS: A The process of gastrulation occurs in animal development (not all animals). It is the mass movement of cells from the hollow ball of cells to establish three embryonic tissue layers, ectoderm, endoderm, and mesoderm. Other organisms such as plants and fungi are multicellular. Many organisms including most protists have sexual reproduction with the production of flagellated sperm cells. Fungi, certain protists and prokaryotes are also heterotrophs.

10. Body plans- Asymmetrical-These animals lack orientation like the sponges. Radial symmetry-The body plan is around an axis and any plane going through the axis will produce opposite halves.

11. -Bilaterial symmetry The body forms a body in a longitudinal plane that divides the body into two equal but opposite halves. It allows the senses to be concentrated in one area (the “head”). Can increase awareness, mobility and predation.

12. Bilateral symmetry in the animal kingdom is best correlated with A) an ability to sense equally in all directions. B) the presence of a skeleton. C) motility and active predation and escape. D) development of a true coelom. E) adaptation to terrestrial environments.

13. ANS: C Bilateral symmetry is associated with an increase in motility, predation and escape.

14. -Bilateral symmetry (animals with this are known as bilateria) The body forms a body in a longitudinal plane that divides the body into two equal but opposite halves. Body cavities (coeloms) -Acoelomate-These animals do not have a body cavity like a flat worm or jelly fish -True coelom-The body cavity is lined with tissue derived from the mesoderm and therefore the cavity is surrounded completely by mesoderm. -Pseudocoelom-The body cavity is lined with mesoderm on the outer part and with endoderm on the inside. Round worms have pseudocoeloms.

16. 3. Acoelomates are characterized by A) the absence of a brain. B) the absence of mesoderm. C) deuterostome development. D) a coelom that is not completely lined with mesoderm. E) a solid body without a cavity surrounding internal organs.

17. 3. ANS: E Animals that do not have a body cavity surrounding internal organs are said to be acoelomate. A gastrovascular cavity is not a coelom. It acts as a digestive cavity in certain organisms.

18. Diagrammed above are the steps thought to have led to evolution of multicellular animals. Lets look at a brief video overview of the invertebrates…

19. Clade Parazoa or sponges-Most closely related to colonial choano-flagellates. These protists and animals have a common ancestor. Phylum Porifera 1. Sessile with no specialized tissue i.e. nerves or muscle. 2. Size 1 cm-2 m. Mostly marine species with few freshwater. The body of a sponge has a cavity called a spongocoel. The body is perforated with pores.

21. 4. The distinction between the sponges and other animal phyla is based mainly on the absence versus the presence of A) a body cavity. B) a complete digestive tract. C) true tissues. D) a circulatory system. E) mesoderm.

22. 4. ANS: C Sponges do not have true tissues. Tissues are composed of a group of cells with a common function such a muscles or nervous tissue.

23. 5.Which two main clades branch from the earliest Eumetazoan ancestor? A) Porifera and Bilateria B) Porifera and Cnidaria C) Cnidaria and Bilateria D) Rotifera and Deuterostomia E) Deuterostomia and Bilateria

24. 5. ANS: C The two main clades that branch from the Eumetazoan ancestor are the clades Cnidaria and Bilateria. Both of these clades have true tissues.

25. Water flows into the pores and into the spongocoel and then out a larger opening called the osculum. There are two layers of cells with a gelatinous layer in between called the mesophyl. The outside of the body is lined with epidermal cells. 3. The pores are lined with cells (porocytes). The inside layer is lined with cells (choanocytes like choanoflagellates ). The flagella of choanocytes beat creating a water current. The choanocyte cell has a collar with a flagella. It also secretes mucus to filter and catch food. There are also amoebocytes which take food from the choanocytes and deliver it to the epidermal cells. 4. Sponges are hermaphrodites. Gametes come from amoebocytes and choanocytes. Eggs reside in the mesohyl and sperm from neighboring sponges fertilize them.

27. 6.Water movement through a sponge would follow what path? A) porocyte -> spongocoel -> osculum B) blastopore -> gastrovascular cavity -> protostome C) choanocyte -> mesohyl -> spongocoel D) porocyte -> choanocyte -> mesohyl E) collar cell -> coelom -> porocyte

28. 6. ANS: A Water movement through a sponge follows the pathway of porocyte -> spongocoel -> osculum

29. Clade Eumetozoa-Animals with true tissues. Two clades are found in CladeEumetazoa-CladeRadiata and CladeBilateria Clade Radiata-Animals with radial symmetry (top and bottom with no head or rear end). Radiata has two tissue layers ectoderm and endoderm and no mesoderm resulting in dipolblastic embryos (no mesoderm). Phylum Cnidaria-Jellyfish and hydra-The basic body plan is a sac with a gastrovascular cavity (GVC). The single opening functions as both the mouth and the anus. Two variations of this body plan-the polyp and medusa. The polyp is a cylinder form that is sessile and adheres to the bottom of the water. The medusa is a "flattened-version of the polyp upside-down". It moves in the water by drifting and contracting its bell shaped body.

30. 7. Although a diverse group, all cnidarians are characterized by A) a gastrovascular cavity. B) an alternation between a medusa and a polyp stage. C) some degree of cephalization. D) muscle tissue of mesodermal origin. E) the complete absence of asexual reproduction.

31. 7. ANS: A All the cnidarians have a gastrovascular cavity. There is no cephalization (some form of head). There is some contractile tissue but is does not originate from the mesoderm. Some cnidarians show alternation between medusa and polyp stage but other lack one or the other. Some cnidarians do have some form of asexual reproduction.

32. Some species exists as polyps and others as medusas and others will have both forms in their life cycles. Both forms have two layers of tissue with a gelatinous layer of material in between called the mesoglea. Surrounding the mouth of these animals are a ring of tentacles. These tentacles have stinging cells called cnidocyte cells. These cells have poisonous, little dart like structures called nematocysts. No muscles but cell will bundles of contractile fibers.

34. There is also nerve net that can detect stimuli causing the organism to react. The gastrovascular cavity has specialized cells that release digestive enzymes to aid in digestion. Class Hydrozoa-(Portuguese man-of-war, hydras, some corals). Mostly marine. Both medusa and polyp forms present. Polyp form usually colonial. Class Scypphozoa-(jellies, sea nettles). All marine. Polyp form greatly reduced. Medusa form up to 2 m in diameter.

35. Class Cubozoa-(box jellies,and sea wasp) All marine. Polyp form greatly reduced. Medusa forms a box like shape with complex eyes and potent venom. Class Anthozoa-(sea anemones, most corals, and sea fans). Medusa stage completely absent sessile, many colonial.

37. Phylum Ctenophora-Superficially looks like cnidarian medusas. These are the comb-jellies. Small and sperical or ovoid. 8 rows of comblike plates fused cilia.

38. Clade Bilateria- These animals have bilateral symmetry. Gives animals dorsal and ventral side as well as an anterior (head) and posterior (tail) end. Cephalization occurred or movement of sensory organs to the anterior end. The anterior end is first to encounter danger, food and other important stimuli. This clade divides up three smaller clades, Deuterostomia, Lophotrochozoa, Ecdysozoa The first clade are the deuterostomes. The deuterostomes are characterizied by their embryonic development and formation of a deuterostome.

39. The second clade are the lophotrochozoans either has a lophophore (a crown of ciliated tentacles function in feeding) or the development of a trochophore larva.

40. 8. The diagram above illustrates a larval form that is characteristic of A) CladeBilateria B) CladeEumetazoa C) CladeLophotrochozoa D) CladeAnimalia

41. 8. ANS: C In the CladeLophotrochozoa, there is either trochophore larva or the organism has a lophophore (a crown of cillia).

42. The third clade is Ecdysozoa. These are animals that form an exoskeleton or thick cuticle. As the animals grow they molt or shed their outer covering (ecdysis).

44. Clade Lophotrochozoa Phylum Platyhelminthes: Flatworms a. Have gastrovascular cavity with pharynx as mouth on ventral side b. Acoelomates c. Nervous system is a pair of ventral nerve cords. Can have eye spots on anterior end that responds to light. In the anterior region one can find a ganglion. d. Nitrogenous wastes removed by a “flame cell” system Four Classes found in this phylum

45. Class Tubellaria-Mosly free-living, most marine, few terrestrial, predators, scavengers; body surface ciliated. Class Mongenea- Marine and freshwater parasites on external surfaces of fish. Class Trematoda- Flukes are parasites of vertebrates. Complicated life history witn intermediate host. Class Cestodea-Tapeworms with scolex. No head or digestive system. Complicated life history.

46. 9. Which of the following will this organism not have? A) true coelom B) nervous tissue C) gastrovascular cavity D) flame cell system

47. 9. ANS: A This organism does not have a body cavity surrounding its organs and is considered to be acoelomate. It does not have a true coelom.