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BiologySecondary Education

This lesson contains 18 slides, with interactive quizzes and text slides.

Items in this lesson

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Expected Learning Outcomes

1. Know about different types and structures of algae .
2.  Understand different modes of nutrition and reproduction of algae.
3. Learn about the beneficial and harmful microbes that exist.
4. Answer the questions based on the same.

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A Microorganism can be defined as a organism that requires a microscope to be seen and cannot be seen by the naked human eye.
There are 5 types of microorganisms: Bacteria, Viruses Protozoa, Algae and Fungi. 

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Algae is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. The oceans cover about 71% of the Earth’s surface, yet algae produce more than 71% of the Earth’s oxygen; in fact, some scientists believe that algae produce 87% of the world’s oxygen.

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Unicellular or Multicellular
  • Multicellular marine algae, or seaweeds, are plant-like organisms that generally live attached to rocks or other hard substrata in coastal areas. They belong to three different groups, recognized since the mid-nineteenth century on the basis of thallus color: red algae , brown algae , and green algae.

  • Chlamydomonas is a genus of green algae consisting of about 150 species all unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae".

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Presence/ Absence of Cell Wall and Chlorophyll 
Algae possess cell walls made up of agar, cellulose, glycoproteins, polysaccharides and pectin. The composition of the Algal cell wall completely differs from the plants and bacterial cell walls. Algae also possess chlorophyll, but there are very rare cases where algae doesn't contain chlorophyll. Instead they contain other accessory pigments that help the algae absorb light. 

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Fun Facts! 
1. Kelps are the largest algae. They can grow up to more than 200 feet. 

2. Fossilized algae are used in making dynamite. 

3. Algae are vital in many food chains acting as the primary producer of organic matter.

 4. Algae produce about 80% of all organic substances created on the planet.

 5. Scientists know more than about 100,000 species of algae, but there are probably more of              them on the planet.

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Mode of Nutrition
The mode of nutrition in algae is primarily of three types, namely photoautotrophic, heterotrophic and mixotrophic. Algae show some properties similar to plants due to the presence of chloroplasts and eukaryotic cellular construction. Also, they share some features similar to animals in having flagella and centriole.

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Modes of Reproduction

 Vegetative reproduction:
This may be of several types.
(i) By cell division:
The mother cells divide and the daughter cells are produced, which become new plants. This is exclusive type of reproduction in some Desmids, Diatoms, Euglena, etc.
(ii) Fragmentation:
The plant body breaks into several parts or fragments and each such fragment develops into an individual. This type of vegetative reproduction is commonly met within filamentous forms, e.g., Ulothrix, Spirogyra, etc.

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Beneficial and Harmful Algae 
  • Beneficial algae: Brown Algae- It can be used for weight loss and  to cure diseases like cancer, arthritis, stress etc. 

  • Harmful algae: Parasitic Algae-The well known disease ‘red rust of tea’ is not caused by any parasitic fungus but an algal form Cephaleuros virescens.

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Which of the following is the correct name of the algae and its shape?
Chlamydomonas- Oval
Chlamidomonous- Oval
None of these

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Select the odd one out.
Cell Membrane
Cell wall

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Also, algae share some features similar to animals in having flaglella and ______.

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Which of the following materials is NOT found inside the cell wall of an algae?

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