20 Questions
What is the structure that attaches to the oogonial wall or a nearby cell and germinates into a small filament?
Dwarf male plant
How does the zygote develop after liberation from the oogonial wall?
It undergoes a resting period before germinating by producing zoospores
What type of reproduction is characterized by the fusion of identical motile gametes?
Isogamous reproduction
What is the term for a small, filamentous structure that develops from an androspore?
Dwarf male plant
What is the term for the process by which an organism breaks into smaller pieces that can grow into new individuals?
Vegetative fragmentation
What is the term for a spore that is motile and capable of moving towards a fertilization site?
Zoospore
What is the outcome of zygote germination in certain algae?
Four polyhedral cells that produce a mother colony
What is the primary method of asexual reproduction in certain algae?
Formation of autocoenobia
What type of reproduction occurs in certain algae, resulting in the fusion of gametes?
Isogamous reproduction
What is a characteristic of zoospores in certain algae?
They can be biflagellate or quadriflagellate
How do certain algae reproduce vegetatively?
Through fragmentation
What is the shape of the chloroplast in certain algae?
Ring- or girdle-shaped
What is the characteristic of the zygote in the life cycle of Ulothrix?
It is the only diploid phase
What is the characteristic of the zoospores produced by the zygote in Ulothrix?
They are quadriflagellate
What is the term for the gametes in isogamous reproduction?
Isogametes
What is the term for the aplanospores that acquire thick walls and dark pigments in unfavorable environmental conditions?
Hypnospores
What is the mode of vegetative reproduction in Oedogonium?
Fragmentation
What is the characteristic of the filaments in Oedogonium?
They are unbranched and uniseriate
What is the function of the holdfast in Oedogonium?
It attaches the filament to a substratum
What is the term for the residual portions of cells that divide to bring about intercalary growth in Oedogonium?
Caps
Study Notes
Oogonium Formation
- Formed by enlargement of a cap cell, becoming spherical and bright orange
Antheridium Formation
- Can occur in two ways:
- In macrandrous species, small flattened antheridia are formed by successive rapid divisions of cap cells
- In nannandrous species, antheridia are formed from an antheridial-like cell, releasing swarmer (androspores) that do not fuse with the oogonium
Androspores and Dwarf Male Plant
- Androspores are released from an androsporangium and swim towards the oogonium, but do not fuse with it
- Instead, they become attached to the oogonial wall or a nearby cell and germinate into small two- or three-celled filaments
- The distal end of the filament functions as the antheridium
Zygote Development
- Develops a two- or three-layered wall
- After liberation, undergoes a resting period before germinating by producing zoospores
Cell Structure
- Cells are cylindrical with many nuclei in the peripheral cytoplasm
- Chloroplasts are reticulate with pyrenoids
Ulothricales
- Order III: Ulothricales
- Family: Ulothricaceae
- Members found in freshwater, marine, and soil habitats
- Algae reproduce vegetatively by fragmentation, asexually by zoospores, aplanospores, or sexually by isogametes or anisogametes
Ulothrix
- Unbranched, uniseriate cylindrical filament that grows attached to solid objects
- Cells have single chloroplasts that may be ring- or girdle-shaped with one or many pyrenoids
- Reproduction:
- Vegetatively through fragmentation
- Asexually by zoospores, aplanospores, or hypnospores
- Sexually by isogametes
- Zoospores are either biflagellate or quadriflagellate
Oedogoniales
- Order IV: Oedogoniales
- Family: Oedogoniaceae
- Only family in this order, comprising three genera: Oedogonium, Bulbochaete, and Oedocladium
Oedogonium
- Unbranched, uniseriate filament with uninucleate cells
- Occurs in freshwater, attached by means of a basal holdfast as an epilithic or epiphytic alga
- Chloroplasts possess many pyrenoids
- Nucleus lies in the periphery of the cell
- Filaments are polar due to the presence of a holdfast
- Reproduction:
- Vegetative: through fragmentation
- Asexual: by zoospores, akinetes, or aplanospores
- Sexual: by oogamy
- Oogonia and antheridia may be on separate filaments (heterothallic) or on the same filament (homothallic)
This quiz tests your understanding of the formation of oogonium and antheridium in certain species. Learn about the different ways antheridia can occur and the different species that exhibit distinct characteristics.
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