so i gotta write a 3775 word essay today is my last day i haven't even started gimme some info on sexual reproduction
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Answer:
Reproduction (or procreation) is the biological process by which new “offspring” are produced from their “parents”.
Asexual reproduction yields genetically-identical organisms because an individual reproduces without another.
In sexual reproduction, the genetic material of two individuals from the same species combines to produce genetically-different offspring; this ensures mixing of the gene pool of the species.
Organisms that reproduce through asexual reproduction tend to grow exponentially and rely on mutations for DNA variation, while those that reproduce sexually yield a smaller number of offspring, but have larger genetic variation.
Explanation:
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Answer:
Explanation:
Plants are eukaryotic organisms that evolved over billions of years. There is enormous diversity in reproductive strategy in plants. Eukaryotes have nuclei in each cell that contain DNA coiled into chromosomes. Chromosomes are the organism’s reproductive functional unit and occur in single (haploid), double (diploid) or multiple copies (polyploid) in each cell.
Genetic material is replicated by enzymes and other classes of molecules that act on the chromosomes. Over evolutionary time, plants have evolved myriad reproductive strategies. Researchers have shown that different reproductive modes can be experimentally induced in plants, suggesting that gene expression interacting with the environment facilitates which reproductive strategy the plant selects.
Sexual reproduction involves a specialised division process in highly differentiated cells called meiosis. Meiosis includes a reduction step in these cells which halves their ploidy, for example reducing them from diploid to haploid, and produces male and female gametes. The gametes may be spores, as in the pteridophyte, which includes the medicinal plant Equisetum arvense, or in seeds. Seeds evolved in Gymnospermae, a group that contains the medicinal tree Ginkgo biloba where they are referred to as naked seeds, and in Angiospermae that produce seeds from flowers (Heinrich et al. 2012). The gametes later fuse and the resulting zygote retains the parent plant’s original ploidy. Sexual reproduction may occur between gametes of different individuals of the same species or between gametes of the same individual in a process known as selfing. Plant ploidy is a factor in a plant’s phenotype and reproductive strategy. For example, researchers found that a diploid form of the medicinal herb Taraxacum officinale reproduced sexually while a triploid form of the same herb tended to reproduce asexually by apomixis (Verduijn et al. 2003). Asexual reproduction involves clonally reproducing offspring such that they are genetically identical to the parent plant, except for differences caused by random genetic mutations (Glémin & Galtier 2012). There is little or no evidence of strict asexual plants (Birky 2010). Most plant species either engage in both sexual and asexual reproduction or contain populations that have adopted asexual reproduction, such as in Taraxacum officinale (Glémin & Glatier 2012). Another form of asexuality is selfing. Selfing plants have ovules that are fertilised by pollen grains from the same individual. Plants with both selfing and asexual reproductive strategies tend to have sexual out-crossing progenitors. Asexual and selfing lineages tend to be shorter lived in evolutionary terms. This is because genetic diversity is reduced by non-out-crossing reproductive strategies (Holsinger 2000).