Question

Select the mismatched pair of organism and its mode of multiplication
(a) Organism - Agave, Oxalis; Mode of multiplication - Bulbils
(b) Organism - Amoeba, Paramecium; Mode of multiplication - Binary fission
(c) Organism - Chlamydomonas, Ulothrix; Mode of multiplication - Sporangiospores
(d) Organism - Adiantum; Mode of multiplication - Adventitious buds present at leaf tips

Answer 1

Hint: This is a freshwater alga growing on sub­stratum like sand particles, rocks etc. The plant body is unbranched, filamentous and differentiated into apex and base.The genus of green biflagellate single- celled organisms of disputed classification, placed botanically in the green algal order.

Complete step by step answer:
Zoospores are formed during favourable conditions with proper growth of the plant. Any cell except holdfast is capable of producing zoospores. The protoplast either develops into a single zoospore or undergoes division and forms 2, 4, 8, 16 or 32 units. Each unit contains a single nucleus and cytoplasm. These small units form zoospores.
The Chlamydomonas during sexual reproduction involves three stages. They are the;
- Gametogenesis:The process of gametogenesis occurs by repeated division of the protoplast giving rise to 16- 32 gametes from a single cell.
- Syngamy: It is the process of fusion of gametes as a result in the formation of zygote. These zygotes formed will then transform into zygospores.
- Zygospore formation: Zygospore are the spores which have thick walls to protect from the extreme environment. Under favourable conditions the zygospore germinates.
So, the correct answer is, ‘Organism - Chlamydomonas, Ulothrix; Mode of multiplication - Sporangiospores.’

Additional information:
Ulothrix
- All the cells except the basal holdfast can divide and their wall is composed of outer pectin and inner cellulose. Inner to the cell wall is the cell membrane.
- The cell membrane encloses the protoplast. It consists of cytoplasm, chloroplast and nucleus.
- The cytoplasm forms a lining layer or primordial utricle adjacent to the cell membrane and in which a single nucleus remains embed­ded inside the cytoplasm.
- The central region is occupied by the vacuole, which contains cell sap.
- Reproduction takes place by vegetative, asexual and sexual means.
- Vegetative reproduction takes place by fragmentation.
- Asexual reproduction by occurs bi- or quadriflagellate zoospores.
Chlamydomonas
- The cell nucleus and nucleolus are prominent in cross- sections of Chlamydomonas cells.
- The nuclear membrane is continuous with the endoplasmic reticulum, and one to four Golgi bodies are situated nearby.
- Chromosome cytology is poor, with only eight discrete chromosomes being consistently visible by light microscopy in metaphase cells.
- Vegetative cells are normally haploid, but stable diploids can be selected using auxotrophic markers.
- Mitochondria are dispersed throughout the cytosol and are sometimes seen in electron micrographs as elongated or branching structures.
- A single cup- shaped chloroplast occupies the basal two thirds of the cell and partially surrounds the nucleus.

Note:
- Aplanospores consist of a cell wall,which is different from the original parent cell wall, allowing the survival of the organism in harsh conditions.
- The nitrogen deprivation causes Haematococcus Pluvialis to form cell aggregates. These aggregates finally become aplanospores.