Final answer:
A haploid organism is one that contains a single copy of each chromosome rather than a pair. This is primarily found in an organism's reproductive structures i.e., the gametes or spores. Transition from haploid to diploid occurs during fertilization when two haploid gametes fuse.
Step-by-step explanation:
When we say an organ contains a single copy of each chromosome in its nucleus instead of a pair. This condition is primarily found within an organism's repnism and is haploid, which means the organism's productive structures (such as ovaries and testes) and the cells are typically either gametes (like eggs and sperm in animals) or spores. Most animals and plants are actually diploid, meaning that each cell contains a pair of each chromosome, one from each parent, which are called homologous chromosomes.
The transition from diploid to haploid occurs during a special form of cell division called meiosis, where diploid germ cells (a special cell line that only produces gametes) divide to produce haploid cells.
These haploid gametes lose their ability to divide once they are formed, and there's no multicellular haploid life stage. During fertilization, two gametes (each carrying a single set of chromosomes) fuse together, thus restoring the diploid state for the next generation. The entire process ensures a constant number of chromosomes from generation to generation.
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