Sara AustinConcept: Microorganism Reproduction
OUTLINE: CONCEPT PRESENTATION:
Microorganism Reproduction
Background Information (Handout):
BACTERIAL REPRODUCTION:
Binary Fission: the single strand of DNA replicates, resulting in identical genetic material being transferred to each new cell. Following replication of the genetic material, the bacterium produces a cross wall, dividing the cell in to two identical bacteria, which may separate or remain attached.
Bacterial Conjugation:
1- Donor cell produces pilus (cytoplasmic projection)
2- Pilus attaches to recipient cell, brings the two cells together
3- The mobile plasmid is nicked and a single strand of DNA is then transferred to the recipient cell
4- Both cells recircularize their plasmids, synthesize second strands, and reproduce pili. Both cells are now viable donors.
VIRAL REPRODUCTION:
LYTIC CYCLE:
Viral genetic material injected into host cell and takes over machinery to produce parts of future viruses. Parts are assembled and the cell explodes (lysis), releasing more harmful viruses. “Virulent” viruses undergo a lytic cycle.
LYSOGENIC CYCLE:
Viral genetic material remains dormant, replicated with the host cell DNA each time the cell divides.
“Temperate” viruses undergo a lysogenic cycle. At some point, the lytic cycle is triggered.
RETROVIRUSES contain RNA as their genetic material. The virus contains reverse transcriptase, which it the directions in the new DNA code, and the lytic cycle is triggered.
Fungal Reproduction:
Fungi reproduce both asexually and sexually but always produce spores as reproductive cells. Spores are usually dispersed by air currents, and germinate in suitable conditions.
•Haploid hyphae, found below the soil, fuse to begin reproduction.
•The hyphae enlarge, break through the soil as white spheres called buttons
•Buttons grow and mature, forming a stalk and a spherical cap
•Within the cap, gills form, consisting of many tangled, modified hyphae.
•Specialized extensions from gills containing two haploid nuclei of different parents fuse, then undergo meiosis to produce four haploid spores, which are released over several days
Advance Preparations:
Teachers should prepare in advance any demonstrations (bread mold and dung chamber – start dung chamber 4 days in advance of use), handouts with web links for research, worksheets, and microscopes and slides for examination of prepared specimens. Teachers should generate quiz questions, exit diagram blanks, whole-class wall diagram (fungal reproduction), materials for mushroom lab.
Special Materials:
Need to collect herbivore dung (try rabbit owners?)
Buy mushrooms for dissection
Bread for mould study
Specimen slides of various microorganisms
Curriculum Emphasis:
This concept is part of the SBI3C course, within the Microbiology strand
Three types of microorganisms are examined: bacteria, viruses, and fungi
These microorganisms have different types of reproduction - diagrams and life cycle graphics are essential
Specific Expectation:
C3.4 By the end of the course, students will be able to explain the different methods of reproduction in various types of bacteria, viruses, and fungi
Lesson Sequence Outline:
Subject / Activities / Assessment / FOR/AS/OFLesson 1 / Bacterial Reproduction / Lecture with animations, photos, Yeast Demo, microscope slides / Exit diagram,
True/false quiz / FOR
AS
Lesson 2 / Viral
Replication / Lecture with animations, Gizmo: Virus Lytic Cycle / Gizmo worksheet, online assessment / FOR
AS
Lesson 3 / Fungal Reproduction / Dung Chamber demo, Brief lecture with animations, microscope slides, mushroom lab / Whole-class Wall diagram, lab work sheets / FOR
AS
Lesson 4 / Comparison Activity / Class discussion for rubric design Research, work on products / Completed product (DI) / OF
Lesson 5 / Applications: STSE connections / Lecture with videos, animations, photos / Begin research projects: RAFT activities / AS/OF
Student Difficulties/Misconceptions:
Students will have some basic concepts about microorganisms from previous grades: the role of microorganisms in food chains and ecosystems, the immune system; the exchange of genetic information; bacteria, plant-like and animal-like protists, fungi, and viruses.
Skills: Students should have some basic microscope skills and be able to recognize eukaryotic cells (plant and animal) by their organelles.
Students may think there were no effective treatments for diseases because they were undiagnosed in the past – but anti-infective agents been used for thousands of years. The Chinese recognized that mouldy soybean curd was effective against skin infections. Scabies was treated with sulfur. Mercury was used to treat syphilis.
Viruses represent an example of the “which came first” riddle. Viruses seem to be a stage between abiotic and biotic organisms, yet they must have appeared after cells, as viruses cannot reproduce on their own. A decimal numbering system is also used for viral classification (e.g., H1N1). It was decided years ago that viruses would not use Latinized binomial terms.
Students may think that mushrooms growing on trees only benefit nutritionally – but in fact, mushrooms can use trees to gain a better, sunnier position in a shady environment like a rain forest. Sometimes fungi climb tress and vines to release their spores from as high a position as possible.
Pathogenic organisms and the diseases they cause do not remain static. The incidence of new of changing diseases caused by bacteria, viruses, and protozoa are increasing.
If moulds are so ubiquitous, why are we not affected by all of them? Moulds are opportunistic organisms: they infect humans at sites of lesions, or when immunodeficient, or during serious diseases such as cancer or diabetes.
Gene therapy diagrams look straightforward and reliable, but gene therapy is still experimental and controversial. Some stunning success stories, and some devastating failures.
Teaching Ideas/Strategies:
Build interest using the many available animations, photographs, video clips and real microscope slides.
Demonstration:Build a dung chamber as an attention grabber for the content about Fungi:
•Go for a hike and find some dung from a vegetarian animal (rabbit or deer pellets)
•Put the dung in a petrie dish with a damp paper towel or sprinkle with water
•Start about four days before this lesson so that students can see some real-life examples of the fungi as they proceed through the section content
Student Exploration: Virus Lytic Cycle Gizmo (explorelearning.com)
Release a lytic virus in a group of cells and observe how cells are infected over time and eventually destroyed. Data related to the number of healthy cells, infected cells, and viruses can be recorded over time to determine the time required for the virus to mature within a cell. Student exploration sheets and online assessment provided, along with teaching notes and vocabulary pages.
Evaluation Procedures:
Assessment for and as learning proceeds with student tasks in Lessons 1 to 3:
Lesson 1: True/False Quiz – Bacterial Reproduction
Exit Diagram – Bacterial Reproduction
Lesson 2:Gizmo worksheet and online assessment – Viral Reproduction
Lesson 3:Whole-class Wall Diagram – Fungal Reproduction
Lab Worksheet – Fungal Reproduction
Assessment of learning in Lessons 4 and 5:
Lesson 4: Reproduction Comparison using DI Products - Students create a comparison of reproductive strategies of bacteria (binary fission), fungi (spores, nuclear fusion), and viruses (lysogenic and lytic cycles). Students develop this by examining teacher-provided charts/posters/diagrams/videos (and do online research as needed) illustrating the life cycle and reproductive strategy of a representative from each of bacteria, fungi, and viruses. Students choose the form of this comparison, as long as critical information is present: a song, a poem, a letter, a set of resumes, a business plan, a poster, an advertisement, a graphic organizer, a commentated video/podcast, a script. The rubric for all products is the same: students are being evaluated on their ability to explain the different methods of reproduction in various types of bacteria, viruses, and fungi. Students and teachers can together develop a rubric to evaluate the products.
Lesson 5: Applications: RAFT Activity – Students create authentic products demonstrating their ability to relate the reproduction of bacteria, viruses and fungi to STSE.
Role / Audience / Format / TopicAnaerobic Bacteria / Other anaerobic bacteria / Travel Guide / Journey through the waste treatment plant
Insulin Biotechnology Technician / His parents / Letter / My job: What it is and why it matters
Crop Disease Forecasting Expert / Farmer / E-mail / How to prevent potato blight
World Anti-Doping Agency (WADA) / International Olympic Committee (IOC) / Recommendation Report / Olympic Policy on Gene Doping
Genetically-Modified food / The Public / Complaint / People don’t trust me – why?
Applications and Societal Issues:
Microorganisms and Human Disease - Harmful microorganisms are the cause of disease and decay that is not due to structural problems or mutations in humans. Many microorganisms also cause disease and decay in crops and farm animals.Biotechnology: bacterial vectors are used extensively for gene transfer, viral vectors are being studies as means for medical therapies, and microorganisms themselves are being used as probiotics to replenish gastrointestinal tract and compete with other dangerous microorganisms to reduce their effects. The extensive use of antibiotics in soaps and other products as well as in treatment has led to concerns about their overuse and the resultant antibiotic-resistant strains.
Biotechnology in Industries – Emphasis is on both preventing microorganism growth in food handling facilities (Maple Leaf meats - contamination), and on the use of microorganisms to manufacture products (Hormone production - insulin, Food production – yogurt, beer, breads). Microorganisms are also used to process waste in waste management facilities.
Selected Annotated References:
Di Giuseppe et al., Nelson Biology 11: College Preparation (2003) Nelson, Toronto.
Student Text, Teacher’s Resource and website:
Communicable disease surveillance site
Canadian Public Health Agency
Viral Geometry and Structural Diversity film
The geometric structures of viruses are beautiful and can be used, along with genomic information, to identify them.
(3 minutes 22 seconds)
Gizmo: Viral Lytic Cycle
Animation of Binary Fission:
Actual film of bacteria dividing by binary fission:
Disease Outbreak News – World Health Organization
A nice overview and summary of bacteria, viruses and fungi. The website is for pet diseases, but human diseases are also mentioned.
Biology4kids: A simple, whimsically-written website that explains the various types of micro-organisms in simple language, but does include terminology appropriate for high school students. Quizzes available. Advertising is a bit distracting