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Sexual Reproduction. Section 7-2. Similarity to Parents is Determined by the Type of Reproduction . The type of reproduction that produces an organism determines how similar the organism is to its parents and siblings Reproduction – process of producing offspring – can be sexual or asexual

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similarity to parents is determined by the type of reproduction
Similarity to Parents is Determined by the Type of Reproduction
  • The type of reproduction that produces an organism determines how similar the organism is to its parents and siblings
  • Reproduction – process of producing offspring – can be sexual or asexual
  • Asexual Reproduction – a single parent passes copies of all of its genes to each of its offspring. No fusion of haploid cells
slide3
An individual produced by asexual reproduction is a clone.
  • Prokaryotes reproduce by a type of asexual reproduction – binary fission
  • Sexual Reproduction – two parents each form haploid reproductive cells which join to form offspring. Occurs in eukaryotic organisms.
types of asexual reproduction
Types of Asexual Reproduction
  • Fission – the separation of a parent into 2 or more individuals of about the same size
  • Fragmentation – the body breaks into several pieces. Some or all of fragments later develop into complete adults when missing parts are regrown
  • Budding – new individuals split off from existing ones
advantages and disadvantages of each type of reproduction
Advantages and Disadvantages of Each Type of Reproduction
  • Asexual Reproduction
    • simplest and most primitive method of reproduction
    • allows organisms to produce many offspring in a short period of time without using energy to produce gametes or to find a mate
    • DISADVANTAGE – DNA does not vary much between individuals
advantages and disadvantages of each type of reproduction6
Advantages and Disadvantages of Each Type of Reproduction
  • Sexual Reproduction
    • provides a powerful means of quickly making different combinations of genes among individuals
    • genetic diversity
how sexual reproduction evolved
How sexual reproduction evolved
  • Many protists are haploid most of the time – reproduce asexually
  • Protists only form diploid individuals when under stress in the environment
  • Biologists think this is because only diploid cells can repair damaged DNA
  • As organisms became larger, it was necessary to be able to repair the damaged DNA.
slide8
Pairing of homologous chromosomes during meiosis may have been original way to repair DNA damage. In fact, many enzymes involved in DNA repair also involved in meiosis.
eukaryotes have three kinds of sexual life cycles
Eukaryotes Have Three Kinds of Sexual Life Cycles
  • Life Cycle – the entire life span in the life of an organism from one generation to the next
  • Life cycle of sexually reproducing organisms follows a basic pattern of alternation between the diploid and haploid chromosome numbers. The type of cell that undergoes meiosis and when meiosis occurs determines the type of sexual life cycle an organism undergoes.
eukaryotes will experience one of three types of life cycles
Eukaryotes will experience one of three types of life cycles
  • Haploid Life Cycle
    • simplest of sexual life cycles
    • Haploid cells occupy the major portion of the life cycle
    • zygote is the only diploid cell and will undergo meiosis immediately after formed to go back to haploid state.
    • Haploid cell gives rise to haploid multicellular individuals that produce gametes by mitosis NOT meiosis.
    • Gametes fuse to produce diploid zygote – cycle continues.
    • when diploid zygote undergoes meiosis, opportunity arises for the cell to correct any genetic damage.
eukaryotes will experience one of three types of life cycles11
Eukaryotes will experience one of three types of life cycles
  • Diploid Life Cycle
  • adult individuals are diploid, each individual inheriting chromosomes from two parents
  • diploid reproductive cells undergo meiosis to produce gametes
  • Gametes will join in a process called fertilization
  • After fertilization, resulting zygote will divide by mitosis.
  • Diploid zygote will give rise to all cells of the adult. All adult cells are diploid.
  • Diploid individual that develops from zygote – occupies major portion of diploid life cycle.
  • gametes are the only haploid cells.
eukaryotes will experience one of three types of life cycles12
Eukaryotes will experience one of three types of life cycles
  • Alternation of Generation
  • Plants, algae and some protists
  • alternates between haploid and diploid phases
  • diploid phase that produces spores – called sporophyte
  • spore forming cells in sporophyte undergo meiosis to produce spores – haploid reproductive cells produced by meiosis that are capable of developing into an adult without fusing with another cell.
  • Gives rise to a multicellular individual called a gametophyte (haploid phase that produces gametes by mitosis).
  • gametophytes produce gametes that fuse and give rise to the sporophyte
  • gametophyte and sporophyte phases alternate or take turns