Question

LAB: Phylum Chlorophyta: Green Algae

The Chlorophyta are a diverse group of microalgae and macroalgae, that are most common in freshwater with a significant number of marine representatives. The green algae show a wide range of sexual reproduction and range from unicellular to truly multicellular varieties. They share most of their characteristics with members of the kingdom Plantae and are considered the primary ancestors of terrestrial plants. Observe prepared slides and living specimens of Chlamydomonas, Volvox, Oedogonium and Spirogyra. Chlamydomonas. Chlamydomonas and Ulva are described in your lab manual.

Describe the appearance of Chlamydomonas.________________________________________
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Describe the structure of the Volvox colony, daughter colonies and zygotes. ________________
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Identify the function of the holdfast, oogonium and antheridial cells of Oedogonium. _________
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Describe the process of conjugation in Spirogyra. ______________________________________
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What is the role of the pyrenoid? ___________________________________________________

Answer 1

1. Chlamydomonas is a microscopic, unicellular fresh water algae. They are spherical in shape with a cell wall surrounding the cytoplasm. They have large chloroplast and a central nucleus. Two flagella arise from the basal granule in the cytoplasm.

2. Volvox is a photosynthetic spherical colonial alga. Each little alga within the colony bears two flagella, whip-like hairs. The individual alga are connected to each other by thin strands of cytoplasm that enable the whole colony to swim in a coordinated fashion. The individual alga also have small red eye spots.

During asexual reproduction cells enlarge and undergo a series of cell divisions until they form a small sphere referred to as daughter colony inside the parent colony.

During sexual reproduction male and female gametes undergo fertilization to form a zygote.

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3. A holdfast is a root-like structure that anchors aquatic sessile organisms such as seaweed, algae sponges etc.

Oogonium refers to female sex organ with undifferentiated germ cells which produces oocytes in certain algae.

Antheridial cells refers to male reproductive organs in Oedogonium.

4. Conjugation is a means of sexual reproduction in Spirogyra. Two filaments of Spirogyra form conjugation tubes. The contents of one cell passes through the tube an fuses with a cell from the other filament. The cytoplasm of the cell acting as the male travels through this tube and fuses with the female cytoplasm, and the gametes fuse to form a zygospore on fertilization.

2 Male gametes fuse with female gametes Passages form between adjacent cells Zygotes form in alternate cells OD

5. Pyrenoids are sub-cellular micro-compartments found in chloroplasts of many algae. They are associated with the operation of a carbon-concentrating mechanism (CCM).