Question

Discuss with your teacher the following topics
i. Haploid insects and lower plant cell division occur in which part of the body?
ii. Some haploid cells in higher plants where cell division does not occur.
iii. Some diploid cells in animals where cell division does not occur.

Answer 1

Organisms vary in terms of pairs of chromosomes present in the DNA. Haploid organisms have a single set of chromosomes whereas diploid organisms have two sets of chromosomes.

Complete answer:
i. Haploid insects and lower plants have a haplontic life cycle. During the haplontic life cycle, fertilization occurs, and then the zygotic meiosis happens to form the haploid organisms. The gametes in a haplontic life cycle are produced through mitosis. These kinds of cell divisions are seen in lower plants like algae and fungi which reproduce sexually from the haploid cells of the gametangia. It is also seen in insects like bees, wasps, and ants where the haploid gametes fuse to form the haploid organisms through zygotic meiosis.
ii. Some haploid cells in higher plants where cell division does not occur are the polyploidy cells. The polyploidy is defined as a condition in which the cells consist of several pairs of chromosomes than the original set or the two sets of chromosomes. Due to this, the original ploidy level of the plant gets altered. Polyploidy occurs when cytokinesis fails. This happens after the telophase stage of cell division.
iii. Diploid cells are the cells that have two sets of chromosomes in the cells. Diploid cells are produced by the process of mitosis of cell division. This is because during mitosis the diploid chromosome number is preserved as the chromosomes are replicated and identical copies are made which are distributed equally amongst the daughter cells. Animals like frogs, mosquitoes, humans have diploid cells in which cell division does not occur. These cells are known as somatic cells.

Note: Polyploidy is a feature of higher plants only. It is not observed in the lower plants or animals usually. This is because in the case of animals polyploidy causes sterility. Polyploidy is artificially introduced in higher plants by treating the cell culture with colchicine.