Life Cycles (Mitosis and Meiosis). Mitosis Cell replication The segregation of identical chromosomes...
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Transcript of Life Cycles (Mitosis and Meiosis). Mitosis Cell replication The segregation of identical chromosomes...
![Page 1: Life Cycles (Mitosis and Meiosis). Mitosis Cell replication The segregation of identical chromosomes into 2 new cells, each containing exact copies of.](https://reader036.fdocuments.in/reader036/viewer/2022081520/56649e255503460f94b13cb9/html5/thumbnails/1.jpg)
Life Cycles(Mitosis and Meiosis)
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Mitosis
• Cell replication
• The segregation of identical chromosomes into 2 new cells, each containing exact copies of the DNA in the original cell.
• Function?
– Growth
– Repair
– Asexual Reproduction
• Haploid cells have only one copy of each chromosome (N) or cells without paris of homologous chromosomes.
• Diploid cells have two copies of each somatic chromosome (non-sex chromosomes), usually one from the mother and one from the father (2N).
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Meiosis
• Separates homologous chromosomes
• Formation of gametes (sex cells)• 4 cells with ½ the number of chromosomes as the parent cell.
– e.g. sperm and egg cells• Function?
– Sexual Reproduction
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Life cycles – general rules
• In biology, a life cycle includes the major sexual stages of a species, especially in regard to its ploidy.
• There are three types of cycles:
– zygotic meiosis (fungi, some green algae, protozoa)
– gametic meiosis (animals, some brown algae)
– sporic meiosis (plants, many algae)
• All sexual cycles feature the alternating haploid and diploid phases.
• The haploid organism becomes diploid through fertilizations of gametes, resulting in a zygote. To return to the haploid stage, meiosis occurs.
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Stages of Life
• Haploid or Diploid
• Produce cells either by meiosis or mitosis
• Cells produced by mitosis are always identical
• Cells produced by meiosis – dividing cells must be diploid and produced cells are haploid
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Gametic Cycle: Diploid life cycle• No multicellular stage is
haploid
• Unicellular stage is haploid and produced by meiosis
• Organism - Animals
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Put these in the correct position: 1. mitosis and growth2. multicellular diploid adults3. gametes4. fusion of gametes5. zygote6. ploidy (n or 2n)
diploid cycle diploid cycle
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Zygotic Cycle: Haploid life cycle
• Unicellular diploid stage
• Multicellular haploid stage
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haploid cyclehaploid cycle
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Sporic Cycle: Diploid/Haploid life cycle• Spore – gametes of higher vascular
plants
• Multicellular diploid stage
• Multicellular haploid stage
• Mitosis occurs in both diploid and haploid phase
• A sporophyte is the diploid structure or phase of life of a sexually reproducing plant
• A gametophyte is the haploid structure or phase of life of a sexually reproducing plant
• Alternation of generations: This life cycle is characterized by there being two separate free-living plants, the gametophyte (haploid plant) and the sporophyte (diploid plant) in each generation.
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Alternation of generations - ferns
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Alternation of generations - Flowering plants
Diploid = 2 N
Meiosis Haploid = 1 N
Mitosis
Diploid = 2 NFertilization
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Life Cycle Summary
Diploid Life cycle
Haploid Life cycle
Alternation of Generations
Mitosis?
Meiosis?
Fertilization
Mitosis after meiosis?
Mitosis after fertilization?
Multicellular diploid stage?
Multicellular haploid stage?
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What you should be able to do:• Identify the main functions of meiosis and mitosis.
• Use the terms haploid and diploid correctly in regard to meiosis and life cycle diagrams.
• Identify the products of mitosis and meiosis: In terms of number of cells, and the relative amount of the DNA in each of the cells produced as well as the relationship between the offspring cells.
• Identify the appropriate life cycle diagram for an animal, plant or fungus.
• Explain how each of the life cycles results from alternating haploid and diploid forms.
• Identify the "ploidy" level (haploid vs diploid) of each stage in a life cycle diagram, given the locations of mitosis and meiosis in the life cycle, and vice-versa.
• Identify the stages in the butterfly and mouse life cycles; order them in the proper sequence.