Lab 4 Cell Structure of Prokaryotes and Eukaryotic Protists, Plants and Animals

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1 Lab 4: Cell Structure of Prokaryotes and Eukaryotic Protists, Plants and Animals Week of October 4, 2021 PreLab- to be done before you meet with your lab section. • To prepare for the PreLab quiz, read over the whole lab. • You may want to refer to Chapters 6, 27, and 28 of your eText for more information. • Watch this video that describes how prokaryotic cells differ from eukaryotic cells. https://www.youtube.com/watch?v=Pxujitlv8wc&t • Protists are eukaryotic organisms. They are often discussed in terms of their methods and structures involved in locomotion. For each of the following organisms that you will be observing in lab, list the organelle(s) that it uses for its primary form of locomotion. eText sections 28.1.3, 28.2.2, and 28.3.2 may be helpful Euglena Paramecium Amoeba Volvox • When you have finished, complete the PreLab quiz in Blackboard. You may use the lab and your eText while you are working on the quiz. The quiz is due before you meet with your lab section. Preparation • Read through the entire set of exercises before lab and mark anything you will need to ask about. This will prepare you to work more efficiently in lab because you might not have to read through all the background information while you could be doing the activities. • Know what is meant by the following terms: prokaryotic, eukaryotic, protists, • Bring your Biology text or eBook (laptop or tablet—not phone) to lab this week. Chapters 6, 27 and 28.

2 Introduction: This week you will be combining many concepts you have learned and skills you have acquired to make observations of cells. You will be practicing techniques in microscopy; identifying cell structures you’ve learned about through your textbook and in lecture, and becoming familiar with the types of cells found in the organisms we’ll study as we move through the course. Objectives: 1. Know the difference between prokaryotic and eukaryotic cells. 2. Be able to identify bacilli, spirilli and cocci bacterial shapes. 3. Be able to identify vegetative cells and heterocysts in Anabaena. 4. Be able to identify the representative protist organisms observed in lab. 5. Name the characteristic structures and their function of a plant cell. 6. Name the characteristic structures and their function of an animal cell. 7. Know the difference between the red blood cells of the frog and human. PROKARYOTIC CELLS: Bacteria and Cyanobacteria Exercise 1: Bacterial Cell Types Bacteria are prokaryotic organisms. That is, they lack membrane-bound organelles (like mitochondria, chloroplasts, Golgi complex, endoplasmic reticulum, nuclei, lysosomes, etc.). Also, they are much smaller than most eukaryotic cells, so we won’t be able to see much, if any, of their internal structure. However, bacteria come in a variety of shapes, which we can see at 400x. Three especially common shapes are rod, spiral, and spherical. Rod-shaped bacteria are known as bacilli (singular, bacillus ); spiral forms are known as spirilla (singular, spirillum ); and spherical bacteria are called cocci (singular, coccus ). Materials: Prepared slides of: Staphylococcus aureus Bacillus megaterium Spirillum volutans Procedure: 1. (Look at the slide before putting it on the microscope. NOTE the stained area of the slide and make sure that it is centered under the objective) 2. Examine the slide of bacterial shapes under high power (focus with the 4X, then 10X objective and then switch to 40x objective). 3. In the spaces provided, draw each type of bacteria.

3 4. Record whether these different types of bacteria occur in pairs, chains, clusters, or as individual, unattached cells. Exercise 2: Observation of Anabaena , a filamentous cyanobacterium Anabaena is a prokaryotic organism like bacteria. Anabaena is a filamentous, photosynthetic, cyanobacterium comprised mostly of photosynthetic cells. Sporadically interspersed along the chain of photosynthetic cells are cells known as heterocysts . Heterocysts have the unique ability to convert nitrogen (N 2 ) into ammonia (NH 3 ), a process known as nitrogen fixation. This conversion is important because most plants depend on nitrogen for growth but are unable to use it unless it is converted to NH 3 . Soil bacteria are another type of prokaryote that can fix nitrogen. It is not surprising that soil bacteria have mutualistic relationships with plants. Materials: Clean microscope slide and coverslip Living culture of Anabaena Procedure: 1. Make a wet mount of Anabaena from the living culture on the side bench. 2. Observe the organism under 100x (using the 10x objective) and 400x and record your observations. You will need to reduce light and close the iris diaphragm to improve the contrast to see the organism. Figure 27.14 of your text. Label: • Photosynthetic (vegetative) cells • Heterocysts Anabaena (100 X) Anabaena (400 X) Bacillus megaterium Bacilli (400X) Staphylococcus aureus Cocci (400X) Spirillum volutan s Spirilla (400X)

4 EUKARYOTIC CELLS: Protists, Animals and Plants Exercise 3: Observation of Protists During this lab session, you will begin to appreciate the enormous diversity of eukaryotic organisms. We’ll begin with single celled eukaryotes called protists. You’ll also look at some multicellular algae exhibiting interdependence among individual cells. For each taxonomic group and representative organism, consider its relationship to other taxa (see figure 28.5), how they live (Where do they live? How do they acquire food?) and consider their structure (What do their cells look like? Are they unicellular, multicellular, colonial?) Located on the side bench, you will find several cultures or specimens of representative protists. They are: The Protists you will observe and the eText references: Euglena , a flagellate (Excavata) ( Figure 28.10 ) Paramecium , a ciliate (SAR, Alveolate) ( Figure 28.19) Diatoms (SAR, Stramenopile) ( Figure 28.5 and 28.12 ) Laminaria , a brown alga (SAR, Stramenopile) ( Figure 28.14 ) Chaos or Amoeba (Unikonta, Amoebozoan) ( Figure 28.5 ) Volvox , a multicellular green alga, (Archaeplastida) ( Figure 28.5 ) Procedures: For Paramecium and Euglena : Paramecia are heterotrophic protists that that move using cilia. Euglena are photosynthetic protists that move with a flagellum. Euglena can be both autotrophic and heterotrophic depending on the availability of light. The internal structure of cilia and flagella is the same. Cilia are generally shorter and more numerous compared with flagella. Materials: Microscope slides and coverslips Protoslo or Detain Living cultures of Paramecium, Euglena 1. Prepare wet mount slides of the living cultures using a small amount of Detain or Protoslo to slow the organisms. Place a drop of cells and a drop of slowing agent on the slide. Mix them together with a toothpick (your instructor will demonstrate this procedure).

5 2. Using your microscope focus with the 4X objective first, then 10X objective and then switch to 40X objective. Observe the organism under high power. Use the iris diaphragm to adjust the light. Having trouble viewing, you can watch the following videos: Euglena swimming : https://www.youtube.com/watch?v=4MlR3dKfXmc Paramecium swimming at 100X: https://www.youtube.com/watch?v=MPCQb6HL3Ow&feature=youtu.be Paramecium 400X: https://www.youtube.com/watch?v=P6oHxbXKILw For Diatoms: Diatoms are ecologically important photosynthetic protists found in aquatic and marine environments. They have a cell wall made of silica consisting of two halves. Euglena 400X Label: flagellum, eyespot, nucleus, chloroplast Paramecium 100 or 400X Label: cilia, contractile vacuole, nucleus, oral groove, food vacuoles

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