2013
Science MAGAZINE
Reproduction reproduction
Is the biologist process by which now “of spring� individual organisms are procedure from their parents. Reproduction is a fundamental feative of all know life, each individual organism exists as the result or reproduction. The known methods of reproduction are brealdly grouped into two main types.
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SEXUAL REPRODUCTION Is a biological process by which organisms create descendentes that havae a combination of gentic material conhibuted from two differents of members of species of gametes. In this especies the two sexes are reffered to as male (reproducing species a microspore) and female (producing eggs and 3 microspores).
ASEXUAL REPRODUCTION Is the process by which an organism creates a genetically similar or identical copy of itself without a contribution of genetic material from another individual. Bacteria divide asexually via binary fission; viruses take control of host cells to produce more viruses. These organisms often do not posses different sexes, they are capable of splitting themselves into two or more indivuduals. Most plants can reproduce b spores asexually. 4
Most animals (including humans) and plants reproduce sexually. Sexually reproducing organisms have different sets of genes for every trait( called alleles). Offspring inherit one allele for each trait from each parent, thereby ensuring that offspring have a combination of the parents genes. Diploid having two copies of every gene within an organism, it is believed that the masking of deleterious alleles favors the evolution of a dominant diploid 5
phase in organisms that alternate between haploid an diploid phases where recombination accurs freely.
Bryophyte reproduces sexually but its commonly seen life forms are all haploid, which produce gametes. The zygotes of the gametes develop into sporangium which produces haploid spores. The diploid stage is relatively short compared with that of haploid stage. The advantage of diploid only takes place in diploid life stage, bryophyte still maintains the sexual reproduction during its 6
evolution despite the fact that the haploid stage does not benefit from heterosis at all. This may be an example that the sexual reproduction has a bigger advantage by itself, since it allows gene shuffling among different members of the species, that permits natural selection of the fit over these new hybrids or recombination that are haploid forms.
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ALLOGAMY
Allogamy is a term used in the field of biological reproduction describing the fertilization of an ovum from one individual with the spermatoz oa of another.
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AUTOGAMY Self-fertilization (also known as autogamy) occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual. They are bound and all the cells merge to form one new gamete.
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MITOSIS 10
MEIOSIS
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