Chlorophyceae, Definition, Characteristics, and Reproduction

Chlorophyceae, commonly known as green algae, are an essential group of green plants that contribute significantly to aquatic ecosystems and play a vital role in photosynthesis. These organisms are especially important for the NEET exam and the biology syllabus , as understanding them can help students secure a good score in the examination.

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Definition of Chlorophyceae

Characteristics of Chlorophyceae

• Members of Chlorophyceae possess chlorophyll a and b in the same proportions as higher plants, giving them a green color.
• In addition to chlorophyll, they contain beta-carotene (a yellow pigment) and various xanthophylls (yellowish or brownish pigments), contributing to their characteristic color spectrum.
• Chlorophyceae store food primarily as starch, similar to higher plants. They may also store fats or oils, which serve as additional energy reserves, especially during unfavorable conditions.
• Green algae in Chlorophyceae can be unicellular (single-celled), multicellular (many cells), colonial (living as a loose group of cells), or coenocytic (a large cell without cross-walls that may contain one or multiple nuclei).
• Their cells have membrane-bound chloroplasts and nuclei, which facilitate photosynthesis and cell function.
• Chlorophyceae are found mostly in freshwater habitats (such as ponds, lakes, and rivers) where charophytes are common, and in marine habitats, where chlorophytes dominate.
• Some green algae are terrestrial, growing on soil, rocks, and tree bark. Terrestrial varieties are mostly from the Trebouxiophyceae class, which includes species with unique adaptive features.
• Some green algae exist in symbiotic relationships; for instance, certain algae form lichens by associating with fungi, while others live symbiotically within animals such as Hydra and Paramecium bursaria.
• Green algae are thought to be the ancestors of higher green plants, although there is ongoing debate regarding their exact evolutionary lineage.

Reproduction in Chlorophyceae

Vegetative Reproduction

Asexual Reproduction

Sexual Reproduction

• Isogamous reproduction, where similar-sized gametes fuse.
• Anisogamous reproduction, where gametes of different sizes merge.
• Oogamous reproduction, where a large, non-motile egg cell fuses with a smaller, motile sperm cell.

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MCQs of Chlorophyceae

Q1. The shape of chloroplasts in green algae may be:

1. Discoid
2. Reticulate
3. Spiral
4. All of these

Q2. Statement I: Most members of green algae have one or more storage bodies called pyrenoids located outside the chloroplasts.

Statement II: Green algae usually have a rigid cell wall made of an inner layer of cellulose and an outer layer of pectose.

1. Both Statement I and Statement II are correct.
2. Both Statement I and Statement II are incorrect.
3. Statement I is correct and Statement II is incorrect.
4. Statement I is incorrect and Statement II is correct.

Q3. Pyrenoid consists of;

1. protein besides starch.
2. protein around starch.
3. starch around protein.
4. Both (1) and (3)

Answers of MCQs of Chlorophyceae