Animal kingdom


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Animal kingdom

  1. 1. 1 General Biology II Lab Lab #6: Introduction to the Kingdom Animalia ______________________________________________________________________________ OBJECTIVES: 1. Understand hierarchical organization of animal complexity. 2. Learn the differences between acoelomate, pseudocoelomate and coelomate organisms. 3. Learn the advantages of cellular specialization to form tissues and organs. 4. Learn how to classify organisms based on body symmetry. 5. Understand the major differences between protostomes and deuterostomes. 6. Learn and employ the directional terms used to identify body positions on different types of organisms. ______________________________________________________________________________ INTRODUCTION: The multicellular organisms that make up the 32 phyla of Kingdom Animalia have evolved from the nearly 100 phyla produced during the Cambrian explosion about 600 million years ago. During this time, an unprecedented variety of novel body plans and architectures arose (Fig. 1). Figure 1. Diversity of members belonging to the Animal Kingdom In the upcoming labs, we will examine the different levels of complexity and organization in representative phyla of Kingdom Animalia (See Fig. 2). We will consider the environmental
  2. 2. 2 constraints that led to the evolution of particular body plans and the adaptations that certain animals evolved in order to survive in their respective environments. In general, members of Kingdom Animalia are eukaryotic, multicellular, motile (at least during certain developmental stages), heterotrophic and unlike plants, lack a cell wall. Additionally, most animals reproduce sexually and have a characteristic pattern of embryonic development. Similar to alternation of generations observed in previous phyla, organisms in the Animal kingdom undergo stages of development, starting from the fusion of an egg and a sperm and ending with a multicellular adult phase. While the morphology of the adult organism is highly species-specific, the genes that regulate organismal development are often conserved across species. In addition, the life cycles of members of Kingdom Animalia vary considerably, i.e., the stages may look completely different from each other (metamorphosis), they may last for different periods of time (hours vs. years) and can occur in different habitats (e.g. dragonflies - adults live in air while larvae are aquatic). Figure 2. Phylogenetic tree of members of Kingdom Animalia NOTE: Make sure that you fully understand EVERY term used to characterize animals because these terms will appear again in the upcoming labs.
  3. 3. 3 ______________________________________________________________________________ Task 1: Understanding the hierarchical organization of animal complexity The common descent of animals within Kingdom Animalia can be observed in the organization of body plans and the fundamental building blocks that all animals share. Unicellular protozoans, one of the simplest and most ancient groups, limit all their metabolic, sensory, and reproductive functions to one cell. By varying the organization and specialization of organelles within this cell, they are able to achieve all the same functions as more structurally complex organisms. Protozoans, which display cellular organization, are described as protoplasmic while multicellular animals (e.g. sponges) characterized by the same cellular level of organization are collectively referred to as parazoans. In this simplest level of the hierarchy, cells may be functionally differentiated, i.e. certain sets of cells are devoted to perform a specialized role within the body. Over time, cellular organization led to the evolution of a cell-tissue level of organization, where groups of similar cells aggregated into layers (tissues) enabling them to perform a common function(s). The nerve net in jellyfish (Fig. 14.7 in your dissection atlas) is a good example of this level of organization. Following in complexity is the tissue-organ level of organization, produced when different types of tissues combine to form organs. In general, organs perform more specialized functions than tissues and can be composed of different tissue types (e.g. the heart, which is composed of cardiac muscle, epithelial, connective and nervous tissues). This level of organization is observed exclusively in metazoans, most of which also exhibit an organ-system level of organization, where multiple organs operate together, forming a system that has a specific function (Fig. 3). In metazoans, there are eleven organ systems: skeletal, muscular, integumentary, digestive, respiratory, circulatory, excretory, nervous, endocrine, immune and reproductive. We will examine some of these systems in greater depth during Labs 8-11. Figure 3. Hierarchical organization
  4. 4. 4 The major patterns of organization of animal complexity are described below in Table 1. As you examine the organisms today, note which level of organization is present in each. Make sure to sketch the organisms listed for each level of organization, noting the phylum, genus and species of each. Table 1 Level of organization Protoplasmic Cellular Cell-tissue Tissue-organ Organ- system Description All functions are confined to a cell Aggregation of cells that are functionally differentiated. Cells are aggregated into patters/layers = tissues. Different tissues are organized into organs; more specialized than tissues. Organs work together as a system to perform a coordinated function Representative group Protista **not a part of Kingdom Animalia. We will NOT examine them today** Parazoa Radiata Bilateria Bilateria Example: a. phylum b. genus c. common name a. Porifera b. Grantia c. Sponges a. Cnidaria b. Metridium c. Sea anemone a. Platyhelminthes b. Dugesia c. Planarian a. Chordata b. Perca c. Perch Drawing of whole organism Questions: 1. Can you suggest why, during the evolution of separate animal lineages, there has been a tendency for complexity to increase when body size increases?
  5. 5. 5 2. Sponges have folded walls. What advantage could this trait have for the sponge? 3. Could you think of other organisms or organ systems that also have similar folded structures? a. What advantages does folding provide for these organisms? ______________________________________________________________________________ Task 2: Differentiating between acoelomate and coelomate organisms A major developmental event in bilaterally symmetrical organisms (see Task 3) was the development of a fluid filled cavity (coelom) between the outer body wall and the gut (Fig. 14.46 in your dissection atlas). The coelom created a tube-within-tube arrangement allowing space for visceral organs and an increase in overall body size (Why?). This structure also provides support and aids in movement/burrowing in some animals. However, not all organisms are coelomates; some lack a coelom altogether and are called acoelomate (a = without, see Fig. 14.22-14.24 in your dissection atlas), while others are characterized by a pseudocoelom (pseudo = false, see Fig. 14.36 and 14.37 in your dissection atlas). All three types of body cavities are illustrated below in Figure 4. Figure 4. Types of body cavities
  6. 6. 6 Examine the organisms listed in Table 2 and complete the missing sections. Table 2 Sample Organism Acoelomate Pseudocoelomate Coelomate Phylum Platyhelminthes Nematoda Annelida Genus Dugesia Ascaris Lumbricus Common name Flatworms, planaria Roundworms Segmented worms, Earthworms Drawing of Cross section (slide) If specimens are available, dissect them longitudinally. Sketch your observations in the space provided. Questions: 1. Looking at the three representative specimens, what is the main difference between coelomate, pseudocoelomate and acoelomate organisms?
  7. 7. 7 2. How are the organs and tissues organized differently in coelomates and acoelomates? ______________________________________________________________________________ Task 3: Body plans and symmetry While the diversity of animal forms is great, the basic body plans can be categorized by the presence and type of body symmetry (Fig. 5). Symmetry refers to the correspondence in size and shape between opposite sides of an organism’s body. Sponges, which lack body symmetry, are considered asymmetrical whereas animals whose bodies are arranged around a central axis and can be divided by more than two planes along the longitudinal axis exhibit radial symmetry. This primitive type of symmetry evolved amongst members of phylum Cnidaria (sea anemones, box jellies, jellyfish and hydra, see Fig 14.7 and 14.16 in your dissection atlas) and Ctenophora (comb jellies, see Fig. 14.21 in your dissecting atlas). The bodies of the more evolutionarily advanced bilaterians, in contrast, can be divided into right and left halves along a sagittal plane. Make sure you understand the basic differences between the three types of symmetry. Figure 5. Types of symmetry Compare and contrast the different types of symmetry by examining the animals listed for each type in Table 3. Answer the questions that follow.
  8. 8. 8 Table 3 Symmetry type Description Example Phyla/Species Spherical This symmetry is found in protozoa. Any plane passing through the center divides the body into equivalent/mirrored halves. Best suited for floating and rolling. Radiolaria (amoeboid protozoa) WE WILL NOT EXAMINE THIS TYPE OF SYMMETRY IN THIS LAB Asymmetrical Sponge Radial Sea anemone Bilateral Perch Questions: 1. In what kind of environment would each type of body symmetry would be most efficient?
  9. 9. 9 2. What is the advantage of having bilateral symmetry? Can any particular task be achieved more efficiently? a. Why would this type of symmetry lead to cephalization? 3. Out of all the organisms you examined, is there a particular pattern between the organisms that have bilateral symmetry? Radial symmetry? Make sure to consider morphology. ______________________________________________________________________________ Task 4: Developmental patterns in bilateral animals: Protostomes vs. Deuterostomes Bilateral animals follow two major patterns of embryonic development. Based on these patterns, they are classified as either deuterostomes or protostomes. In deuterostomes, the blastopore (first embryonic opening) becomes the anus, while in protostomes the blastopore becomes the mouth. Also, cleavage, the initial process of cell division after a zygote is formed, differs in the two lineages; in protostomes, cleavage is spiral while in deuterostomes, it is radial (Fig 6). The separation of the metazoans (multicellular animals) into two separate lineages, suggests an evolutionary divergence of the bilateral body plan. This suggests that deuterostomes and protostomes are separate, monophyletic lineages (See Fig 2).
  10. 10. 10 Figure 6. Comparison of protostomes and deuterostomes Examine the animals noted under the “Example species” row in Table 4. Answer the questions that follow. PROTOSTOMES Spiral Mouth Mouth Anus Coelom Mesoderm GutDeterminate DEUTEROSTOMES Radial Anus Gut Mesoderm Mouth AnusCoelom
  11. 11. 11 Table 4 Protostomes Deuterostomes Cleavage type Spiral Radial Blastopore becomes Mouth Anus Representative Phyla Platyhelminthes, Arthropoda, Annelida, Mollusca, Nematoda, and smaller phyla Chordata, Echinodermata, and smaller phyla Example species Nematoda - Ascaris Sea star – Asterias Drawing ______________________________________________________________________________ Task 5: Describing positions in bilaterally symmetrical animals For a large portion of this course you will be examining bilaterally symmetrical animals from various phyla. To be able to locate and refer to specific regions of animal bodies, we will use terminology listed in Table 5. Table 5 Term Meaning dorsal toward the upper surface (back) ventral toward the lower surface (belly) anterior; cranial toward the head posterior; caudal toward the tail medial toward the midline of the body proximal toward the end of the appendage nearest the body lateral toward the side; away from the midline of the body distal toward the end of the appendage farthest away from the body frontal plane divides the body into dorsal and ventral halves transverse plane divides the body into anterior and posterior halves sagittal plane divides the body into left and right halves
  12. 12. 12 Figure 7. Planes of sections in a crayfish In addition to the terms listed in Table 5, different terminology is used to describe radially symmetrical vs. bilaterally symmetrical animals. These terms are listed in Table 6. Table 6 As a group, practice using these directional terms to refer to a particular part/portion of the body. Make sure to use available specimens to practice and to include both radially and bilaterally symmetrical animals during this exercise. ______________________________________________________________________________ Radial Bilateral Direction Synonyms Direction Synonyms oral apical anterior rostral, cranial, cephalic aboral basal posterior caudal peripheral — dorsal — peripheral — ventral — peripheral — left (lateral) sinister peripheral — right (lateral) dexter medial medial proximal proximal distal distal sagittal plane frontal plane transverse plane
  13. 13. 13 Task 6: Body axes charades – Run by your TA To practice using the correct terminology when referring to different locations on the body, you will play a game of charades. Your TA will divide the whole class into two groups, each of which will be given a list of organs/body parts. Each group’s list will be different therefore make sure that you do not to share your list with members from the other group. Your group will choose a student from another group to describe one of the words on your list to his/her group. The student will have 2 minutes to describe the word, using only the words from the bilateral body axes (see Tables 5 and 6). Note that you cannot use words that describe the function of the organ/body part. For example, if the organ to be described is the heart, you are not allowed to say that it pumps blood. Instead, you can say that it is posterior to the head and is anterior to the belly button. If his/her group can guess the right answer, then that team gets a point but if they don’t guess correctly, then your team gets the point. Make sure to alternate the order of the teams guessing. ______________________________________________________________________________ LOOK AHEAD: Before coming to lab next week, make sure to read the Development task sheet.