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What is the primary method of multiplication among algae under favourable conditions?
What is the primary method of multiplication among algae under favourable conditions?
What is the outcome of cell division in unicellular forms?
What is the outcome of cell division in unicellular forms?
What is the condition necessary for each akinete to grow into a new filament?
What is the condition necessary for each akinete to grow into a new filament?
What is the result of the vegetative cells drying up or decaying?
What is the result of the vegetative cells drying up or decaying?
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What is the outcome of fragmentation in multicellular forms?
What is the outcome of fragmentation in multicellular forms?
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What is the function of akinetes?
What is the function of akinetes?
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What is the characteristic of the parent cell wall in an akinete?
What is the characteristic of the parent cell wall in an akinete?
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Under what conditions does cell division take place?
Under what conditions does cell division take place?
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What is the characteristic of isogamous reproduction?
What is the characteristic of isogamous reproduction?
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What is the characteristic of anisogamous reproduction?
What is the characteristic of anisogamous reproduction?
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What is the characteristic of oogamous reproduction?
What is the characteristic of oogamous reproduction?
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In which type of reproduction are male gametes produced in the antheridium?
In which type of reproduction are male gametes produced in the antheridium?
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What is the name of the female reproductive body in Rhodophyceae?
What is the name of the female reproductive body in Rhodophyceae?
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What is the characteristic of heterogamous reproduction?
What is the characteristic of heterogamous reproduction?
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What is the name of the male reproductive body in Rhodophyceae?
What is the name of the male reproductive body in Rhodophyceae?
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What is the type of sexual reproduction common in unicellular algae?
What is the type of sexual reproduction common in unicellular algae?
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What is the characteristic of the family Chlorococcaceae in the order Chlorococcales?
What is the characteristic of the family Chlorococcaceae in the order Chlorococcales?
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What is the term for the asexual reproductive structures formed by certain cells in Pediastrum?
What is the term for the asexual reproductive structures formed by certain cells in Pediastrum?
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What is the characteristic of the chloroplast in Hydrodictyon?
What is the characteristic of the chloroplast in Hydrodictyon?
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What is the type of sexual reproduction in Pediastrum?
What is the type of sexual reproduction in Pediastrum?
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What is the term for the type of colony formed by Pediastrum?
What is the term for the type of colony formed by Pediastrum?
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What is the characteristic of the cells in Hydrodictyon?
What is the characteristic of the cells in Hydrodictyon?
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What is the fate of the zygote in Pediastrum after a period of dormancy?
What is the fate of the zygote in Pediastrum after a period of dormancy?
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What is the characteristic of the sexual reproduction in Hydrodictyon?
What is the characteristic of the sexual reproduction in Hydrodictyon?
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Study Notes
Asexual Reproduction
- Asexual reproduction occurs in unicellular forms, resulting in reproduction, and in multicellular forms, leading to growth.
- It takes place under favorable conditions.
- There are three types of asexual reproduction: mitosis, fragmentation, and akinetes.
Mitosis
- Mitosis results in two daughter cells, which usually separate immediately.
- Each daughter cell grows into a new individual.
Fragmentation
- Fragmentation occurs in multicellular forms with a filamentous thallus.
- It involves breaking of the filament into small portions of living cells called fragments.
- Each fragment grows into a new individual under favorable conditions.
Akinetes
- Akinetes are single-celled resting fragments, specially modified to function as a means of perennation and multiplication.
- They are formed either singly or in chains in the vegetative filament.
- Akinetes are gorged with reserve food materials and have a highly resistant cell wall.
- Each akinete grows into a new filament under suitable conditions.
Sexual Reproduction
- Sexual reproduction is oogamous.
- When zygotes are formed, meiosis occurs, followed by ordinary mitosis.
- Three of the resulting nuclei diminish, and the remaining one gives a motile cell that emerges from the zygote wall and swims for a short time.
- This cell ceases to move and undergoes successive divisions to form a new colony.
Order II: Chlorococcales
- This order is represented by three families: Chlorococcaceae, Protosiphonaceae, and Hydrodictyaceae.
- Hydrodictyaceae includes Pediastrum and Hydrodictyon.
Pediastrum
- Pediastrum is a planktonic, flat colony whose peripheral cells are provided with one or two protrusions.
- Asexual reproduction is accomplished by the formation of autocoenobia.
- Certain cells of the coenobium divide, forming zoospores that swim for a time and then aggregate and arrange themselves in a manner similar to that of the mother colony.
Sexual Reproduction in Pediastrum
- Sexual reproduction in Pediastrum is isogamous.
- Isogametes are produced in certain cells and fuse to produce a diploid zygote.
- The zygote germinates, producing zygospores that swim shortly, rest, and each give rise to a polyhedral cell that is responsible for the production of autocoenobium.
Hydrodictyon
- Hydrodictyon has a net-like structure, with cylindrical cells that have many nuclei.
- The chloroplast is reticulate and has a number of pyrenoids.
- Asexual reproduction is mainly through autocoenobia formation, as in Pediastrum.
Types of Sexual Reproduction
- Isogamous: both male and female gametes are morphologically similar but differ physiologically; it is considered primitive.
- Heterogamous: both male and female gametes differ morphologically and physiologically.
- Anisogamous: both fusing gametes are motile, but the male gametes are smaller in size.
- Oogamous: the most advanced type of sexual reproduction, common among higher algae; male gametes are motile and numerous, while female gametes are non-motile and larger in size.
Life Cycles in Algae
- There are three different types of life cycles, depending on when meiosis occurs, the type of cells produced, and if there is more than one free-living stage present in the life-cycle.
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Description
This quiz covers cell division methods, including mitosis, and how they result in reproduction or growth in unicellular and multicellular forms.
