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Session 7 - Body wall organization of organisms

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1 Biology 125 Name __________________________ Session 7 - Body wall organization of organisms Objectives At the completion of this session, each student should be able to: 1. list and briefly describe each of the major structural and functional tissue types in plants and animals. 2. describe the typical basic body architecture typical of each of the major groups of modern organisms. 3. recognize cross sections of representative organisms from each of the major groups of modern organisms. Session 7 - Background information Use this information plus the information in Chapters 21 - 26, 29, and 33 in Starr and Taggart to answer the questions on the worksheets. You will also find chapter 4 useful for comparison of prokaryotic and eukaryotic cells. The organizational patterns you are studying today are the products of reproduction in these organisms, and usually develop from either a single cell (fertilized egg) or from a fragment of an existing organism. I. Kingdom Eubacteria A. Eubacteria (bacteria and cyanobacteria, also called Eubacteria) are unicellular. These organisms consist of single cells or of colonies containing one or two types of cells. Most cells appear to be capable of functioning independently in a natural environment, so Eubacteria are called unicellular. B. Eubacterial cells have no nuclear membrane between their DNA and their cytoplasm and are therefore called prokaryotic (see Figures 4.11 and 21.2 in Starr and Taggart). These cells also lack large visible structures in the cells, so the cell contents appear fairly uniform when viewed with a light microscope. The prokaryotic cellular organization allows the cells to respond to their environment very quickly and to reproduce themselves very quickly, but the mechanics of separating the replicated DNA during cell replication limits the DNA content (and therefore the information content) of each cell which in turn restricts the maximum size of the cell. C. Eubacterial cells usually have cell walls which give the cells a spherical, rod, or spiral shape (see page 334 in Starr and Taggart). D. Eubacterial cells may occur as free individuals, as clusters, or as filaments. These may in turn be free in the environment or may be embedded in a gelatinous mass to form a large colony.2 II. Kingdom Protista A. Most protistans are considered unicellular. These organisms consist of individual cells or of colonies with one or two cell types (at least one of which can survive independently in a natural environment). B. Protistan cells have a nuclear envelope (nuclear memberanes) between their DNA and their cytoplasm and are therefore called eukaryotic (see Figures 4.14 - 4.16 in Starr and Taggart). We will look at the nuclear structure in more detail when we study cellular reproduction. C. Photosynthetic protistans usually have a rigid cell wall around each cell outside of its cell membrane. Once formed, the cell wall determines the shape of the cells of these organisms. Heterotrophic protistans may have protective shells outside of the cell, but usually are supported primarily by internal structures in the cytoplasm of the cell. Cell shapes in protistans can be extremely complex. D. Protistan cells may exist as isolated individuals or may be part of a colony consisting of a cluster or a filament of cells. Photosynthetic protistans usually consist of single cells or filamentous colonies. Most heterotrophic protistans exist as isolated single cells, but some of the heterotrophic protistans form complex highly branched colonies. III. Kingdom Fungi A. Some fungi are unicellular, but most fungi form multiple interdependent cell types in the process of developing fruiting bodies and are therefore considered multicellular. The feeding structure of most hyphal fungi is really more like a colony of filaments (hyphae) than it is like a multicellular structure (see Figures 24.4 and 24.5 in Starr and Taggart). B. Fungal cells are eukaryotic. C. Fungal cells usually have cell walls containing chitin for at least part of their life cycle. D. In the hyphal fungi, the feeding body contains one cell type joined end-to-end to form long filaments (hyphae) which branch and interconnect (see Figures 24.4 and 24.5 in Starr and Taggart). The cells in a filament may be partly or completely fused together. E. The "fruiting bodies" of fungi may consist of a hyphal filament with a cluster of spores on the end (as in bread molds - see Figure 24.6 in Starr and Taggart) or may be a complex three dimensional structure formed from millions of cells of several different types (as in sac fungi, mushrooms, and bracket fungi - see Figures 24.3 and 24.7 in Starr and Taggart). Surface covering tissue, spore producing tissue, and support/transport tissues can be distinguished in many complex fruiting bodies. 1. Molds typically form simple sporangia on the ends of aerial hyphae. This gives mold colonies a fuzzy surface. The morphology of the sporangia differs among groups. 2. Sac fungi produce spores in asci or sacs. The sacs are usually on the upper surfaces of a cup-like complex fruiting body. Lichens usually have a sac fungus as the fungal component but also have algal cells among the hyphae. 3. Gill fungi bud basidiospores from the lateral and lower surfaces of gill-like structures on a complex fruiting body.3 IV. Kingdom Plantae A. Most plants are multicellular with multiple interdependent cell types. B. Plant cells are eukaryotic. C. Almost all plant cells have cell walls containing cellulose (see Figures 4.13, 4.15 and 4.21 in Starr and Taggart). D. Organization of plant cells and tissues differs among the groups in the kingdom. 1. Some green algae are unicellular (see Figure 22.20 in Starr and Taggart). 2. Many green algae are organized as filaments or clumped colonies (see Figure 22.19c in Starr and Taggart). 3. Some complex green algae, most brown algae, many red algae, and all bryophytes (mosses) have multicellular bodies which can form complex shapes, especially in brown algae and mosses (see Figures 22.13, 22.17, 22.18, 22.19, and 23.8 in Starr and Taggart). Organization of cells into distinct tissues is usually not present, but partially formed covering tissue, supporting tissue, and "ground" tissue (fills in spaces, serves storage and photosynthesis functions) are recognizable in some species. Fully formed vascular tissue is not present. 4.


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