lab2_plant life cycles_2007

lab2_plant life cycles_2007 - Laboratory 2 Plant Life...

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Plant Life Cycles Laboratory 2
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32 Laboratory 2: Plant Life Cycles OBJECTIVES After completing this lab you will be able to: 1. Note differences between the human and plant life cycles. 2. Observe the alternation of generations in plants 3. Discuss the trends in the evolution of terrestrial plants 4. Understand the similarities and differences in the life cycles of mosses, ferns and angiosperms LAB PREPARATION You should do the following in preparation for this laboratory: 1. Read and study the laboratory experiments. 2. Read Chapters 29, 30, & 38 in Campbell (7th Ed.). 3. Bring to lab a flower with mature (pollen-bearing) anthers from at least 3 different species. 4. Bring your Photo Atlas for Biology to lab. INTRODUCTION This lab is an introduction to plant life cycles. When you review the diagrams of the moss, fern and angiosperm life cycles, understand that no matter how simple or complex the plant, their life cycles do not change. Only the structures that represent each stage of the life cycle differ. The life cycle stages themselves remain the same. Keep this in mind as you read and prepare for this lab. A. The Human Life Cycle To help you understand the plant life cycle, this lab begins with a review of the human life cycle, which is illustrated in Figure 2-1a. For comparison purposes the plant life cycle is illustrated in Figure 2- 1b. Note that the two diagrams differ in the lower half of the circle. The human life cycle starts with a diploid individual. Each somatic cell has two sets of chromosomes, one inherited from the mother and one inherited from the father. Recall that a somatic cell in a multicellular organism is any cell except the sperm or egg cell. Meiosis is the process of producing haploid cells in the reproductive structures of an individual. Haploid cells have only one copy of each chromosome pair. These haploid cells are called gametes . The word gamete comes from the Greek gamos and means marriage. The gametes ultimate purpose is to marry (or fuse with) another gamete, to produce a zygote which, in turn, is diploid. Syngamy refers to the period of time when two gametes come together. ( Syn means together and gamos means marriage.) When
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Laboratory 2: Plant Life Cycles 33 this happens, the resulting cell is diploid, for it will have two sets of chromosomes, one from each of the gametes. Therefore, syngamy marks the transition from a haploid stage to a diploid stage, just as meiosis marks the transition from diploid to haploid. B. The Plant Life Cycle In the plant life cycle (Figure 1-1b), there are two types of individuals (i.e., diploid and haploid) involved in the cycle, instead of only one type (diploid) as in the human cycle. In plants, the diploid individual is called the sporophyte ( spore = spore and phyte = plant) and the haploid individual is called the gametophyte ( gameto =gamete and phyte = plant). The diploid sporophyte and haploid gametophyte take turns producing one another.
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This note was uploaded on 04/10/2008 for the course BIO 172L taught by Professor Gerald during the Spring '08 term at Hawaii.

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lab2_plant life cycles_2007 - Laboratory 2 Plant Life...

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