Introductory Biology

7.2 Sexual Reproduction

The type of reproduction can be determined by the similarity between the daughter cells to the parents.  Asexual reproduction produces two clones that are genetically identical to a single parent. It is advantageous in stable environments and requires little time/ energy. Its Disadvantageous in a changing environment and cannot get rid of any  of their mutations. There are various types of asexual reproduction like: binary fission, fragmentation, budding, and re-growth of lost parts. Budding is when a part of the body buds new offsprings. Re-growth of lost parts is where parents like coral polyp and sea stars splits  in half and grows the lost parts of that half producing a clone. It divides in the middle and get a whole bunch of clones.

Sexual reproduction produces one diploid offspring from two haploid gametes and the daughter cells only get half of the genes from the parents. Advantageous in a changing environment and has so much more diversity that the parasites can be escaped. Its disadvantages are that it requires more time, more energy, more costly, and produces relatively fewer offspring. Other disadvantages are: the risk of disease transmission, risky recombinations, competition between same gender for the opposite sex, and sexual cannibalism. Sexual reproduction may have evolved as a mechanism to repair damaged DNA when homologous chromosomes pair up and exchange genetic materials during crossing over.

Eukaryotes have three different kinds of sexual life cycles: haploid life cycle, diploid lie cycle, and the alternation of generations. The haploid life cycle is most common in many protists and is the simplest sexual life cycle. The only diploid cell is the zygote and it immediately goes through meiosis, producing 4 haploid cells. The diploid life cycle is very typical for animals, which include humans as well. Haploid gametes are produced by muticellular diploid individuals from meiosis. *The gametes produced by meiosis  are the only haploid cells. The gametes immediately unite during fertilization to produce diploid zygotes. In order to produce mulitellular diploid organism, the diploid zygote divides by mitosis. The alternation of generations is common to plants and some protists. There is an alternation between muticellular diploid and haploid individuals during this cycle. The diploid sporophyte divide by meiosis producing haploid spores. These haploid spores divide by mitosis producing multicellular gametophytes. The gametophytes divide by mitosis to produce haploid gametes and unite during fertilization to produce diploid zygote. The zygote divides by mitosis in order to produce multicellular diploid sporophyte. Depending on the organism, they undergo different types of life cycles.

Smell is only in your brain..and not in the molecules.


One thought on “7.2 Sexual Reproduction

  1. Yurika,

    Good job of summarizing 7.2 on sexual reproduction. You’ve thoroughly described asexual and sexual methods and the various life cycles involving sexual reproduction.

    Mr. F.

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