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Plant Kingdom: Algae (Detailed Notes, Comparison Table & 35+ MCQs) for NEET

 


Introduction-

  • The algae belong to the sub phylum Thallophyta because it's body is not differentiated into root, stem and leaves.

Doston, pichle lecture mein humne  ek aise group ki  baat ki thi  jinka kabhi koi  group nahin banaya gaya : virus , prions viroids ki.
  • Algae are chlorophyll-bearing, simple, thalloid, autotrophic eukaryotic organisms. 
  • During photosynthesis, they produce oxygen with help of light energy from the sun and form carbohydrates.

Table of content 

  • Introduction to Algae (General Characteristics)
  • ​Habitat and Morphology
  • ​Reproduction in Algae (Vegetative, Asexual, and Sexual)
  • ​Classification of Algae:
    • ​Chlorophyceae (Green Algae)
    • ​Phaeophyceae (Brown Algae)
    • ​Rhodophyceae (Red Algae)
  • ​Comparison Table: Pigments, Food, and Cell Wall
  • ​Economic Importance of Algae
  • ​Practice MCQs for NEET Biology

🚀 "Sirf Notes hi nahi, is chapter ke Full Video Lectures aur MCQs ke liye hamara [NEET Biology Master Hub] visit karein — Jahan milega NEET 2026 ka complete study material ek hi jagah!"


Economic importance of Algae-

  • Algae are chief producers in the marine ecosystem. They fix almost half of atmospheric carbon di oxide through the photosynthesis.
  • Some algae like spirulina and Chlorella is used by space traveller as food. Porphyra, Laminaria, sargassum and 70 species of marine algae used as source of food.
  • In fishes, Algae plays a very important role because it helps in the production process. Fish used plankton and zooplankton as food.
  • It helps in maintaining the health of the marine ecosystem because algae are naturally absorbent of carbon dioxide and also provide oxygen to the water.
  • Some algae like Gelidium and Gracilaria produce Agar that are used in making ice cream, jellies and growth of microbes .
  • Some algae produces hydrocolloids algin and carrageen , water holding substances.

Extra Shot of Economic importance of Algae:

  • Algae are very sensitive. If there is a slight change in the environment their pigments change or might get died. 
  • Water pollution is checked with the help of Algae like Euglena and Chlorella.
  • Algae are rich in minerals and vitamins. So they are also used as Biofertilizer which helps in increasing soil quality .
  • Algae are good source of carbohydrates, fats, proteins, and vitamins A, B, C, and E as well as the minerals like iron, potassium, magnesium etc. Therefore they are used as source of food.

General features of Algae- 

  • They are found in both freshwater and marine water.
  • They are found in a variety of habitats like moist stones, soils and wood. 
  • Some of them make symbiotic association with fungi in the form of lichen. 
  • Algae are also reported to be found in association with the animals like sloth bears. 
  • They are unicellular and microscopic like Chlamydomonas to colonial forms like Volvox and to the filamentous forms like Ulothrix and Spirogyra.
  • Some of the marine alga  form the kelp. Kelp may be hundred meter long.
  • The algae reproduce by vegetative, asexual and sexual methods.
  • Vegetative reproduction is by fragmentation. Each fragment develops into a thallus. 
  • Asexual reproduction is by the production of different types of spores, the most common being the zoo spores. Zoospores are flagellated and motile and on germination give rise to new plants.
  • Sexual reproduction takes place through fusion of two gametes. In Spirogyra The gametes can be flagellated and similar in size  or non-flagellated or non-motile.  Such reproduction is called isogamous. 
  • Fusion of two gametes dissimilar in size, as in some species of Chlamydomonas and Eudorina is termed as anisogamous. 
  • If Fusion takes place between one large and non-motile female gamete and smaller motile male gamete is termed oogamous like  Volvox, Fucus.

Classification of algae – 

  • Algae are classified in to main three groups – Chlorophyceae, Phaeophyceae and Rhodophyceae

Chlorophyceae

  • They are green algae and are found in salt, fresh or brackish water.
  • They are usually  green due to the presence  of pigments chlorophyll a and b. In Algae, the shape of of chloroplast may vary from species to species.
  • The chloroplasts shows various shape ie. Spiral shape in Spirogyra, cup shaped in Chlamydomonas, star shaped in Zygnema, girdle shaped in Ulothrix .

🟢 Chlorophyceae (Green Algae) - Video Guide

Lecture ke mukhya bhago par jaane ke liye samay (time) par click karein:⏱ 00:00 - Chlorophyceae Introduction⏱ 00:57 - Pigments: Chlorophyll a & b⏱ 01:46 - Shapes of Chloroplast
⏱ 02:58 - Pyrenoids (Storage Bodies)⏱ 03:45 - Cell Wall: Cellulose & Pectose
⏱ 05:33 - Habitat & Occurrence⏱ 07:19 - Zoospores & Asexual Reproduction
⏱ 09:08 - Sexual Reproduction in Green Algae
⏱ 09:44 - Examples: Volvox, Spirogyra, Chara
  • Most of Most of the members have one or more storage bodies called pyrenoids located in the chloroplasts. Pyrenoids contain protein besides starch. 
  • Green algae usually have a rigid cell wall made of cellulose and pectose. 
  • They store their food in form of starch and some members also store in form of oil droplet.
  • Vegetative reproduction usually takes place by fragmentation or by formation of different types of spores. 
  • Asexual reproduction is by flagellated zoospores produced in zoosporangia. 
Volvox : Colonial Algae
  • The sexual reproduction shows considerable variation in the type and formation of sex cells and it may be isogamous, anisogamous or oogamous. 
  • The number of flagella in green algae is 2 to 8 which are equal and located apically. For Ex- Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara Oedogonium

Extra Shot of Chlorophyceae :
  • It is the largest group in Algae.
  • They also have little amount of β-carotenoids.
  • The pigments are present in chloroplasts.
Phaeophyeae-
  • Algae  are commonly known as brown algae  and found primarily in marine habitats but rarely found in fresh water.
  • They show great variation in size. Their size varies  from simple branched, filamentous forms like Ectocarpus and are   profusely branched  to form the  kelps. 
  • They possess chlorophyll a, c, carotenoids and xanthophylls. 
  • They are also found  in various  colours from olive green to brown depending upon the amount of the xanthophyll pigment, fucoxanthin present in them. 
  • Food is stored in the form of  complex carbohydrates, like laminarin or mannitol. 
  • The vegetative cells have a cellulosic wall usually covered on the outside by a gelatinous coating of algin. 
  • The plant body is usually attached to the substratum by a holdfast. They also have  stalks and stipes. They bear a  leaf-like photosynthetic organ called the frond.
Laminarin
  • Vegetative reproduction takes place by fragmentation.
  • Asexual reproduction in most brown algae is by biflagellate zoospores .
  • Sexual reproduction may be isogamous, anisogamous or oogamous.
  • Union of gametes may take place in water or within the oogonium.
  • The gametes are pyriform  or pear-shaped with  two laterally flagella. For Ex- Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus

👌👌Remember - In this group, there are no unicellular and colonial brown algae reported so far.


Rhodophyceae-

  • The members of Rhodophyceae are commonly known as Red algae.
  • They have red colored photosynthetic pigments like  r phycocyanin and r phycoerythrin along with chlorophyll a, d, xanthophyll and β-carotenoid.
Polysiphonia 
  • They are aquatic and  marine  but like Batrachospermum some  are freshwater algae are also reported.
  • They store reserve food in the form of Floridean starch. 
  • They reproduce Vegetatively by fragmentation.
  • The sexual reproduction is accompanied by complex post fertilization development. 

For Example -Porphyridium, Gelidium, Gracilaria Batrachospermum , Polysiphonia.


Comparison table of Green, Brown and Red Algae: 

Features Chlorophyceae (Green) Phaeophyceae (Brown) Rhodophyceae (Red)
Major Pigments Chlorophyll a, b Chlorophyll a, c, Fucoxanthin Chlorophyll a, d, Phycoerythrin
Stored Food Starch Mannitol, Laminarin Floridean Starch
Cell Wall Cellulose Cellulose and Algin Cellulose, Pectin and Polysulphate esters
Flagella 2-8, Equal, Apical 2, Unequal, Lateral Absent

Extra Shot of Rhodophyceae :

  • Some species like Batrachospermum , Polysiphonia exhibit Alternation of generations in their life cycle.
  • The  sexual reproduction is only of the Oogamous type and involve the fusion of non motile gamete.
  • Akinete, aplanospore, Azygospore are non motile spore involved in asexual reproduction.
  • They are unicellular like Porphyridium or multicellular like  Geotrichum. 
Algae ke baad, Plant Kingdom ka agla mahatvapurna topic Bryophytes hai. Bryophytes ke detailed notes yahan padhein: Bryophytes: Detailed Notes & MCQs


NEET MULTIPLE CHOICE  QUESTIONS 
100 % Challenge 
Questions yahi se aayaga

1.How many statement is /are correct .
1. Body of algae is generally is thalloid but some algae are filament ous.
2. Chlamydomonas is Colonial algae. 
3. Volvox is Microscopic form of algae.
4.  Algae are found in both fresh and marine water. Some marine algae form kelps up to 100 meters.

A. Two         B. Four 
C. Three       D. One 
Answer: A 

2.Match the list: 
A. Colonial       1.Volvox
B. Kelps             2. Ectocarpus
C.Filamentous 3.Spirogyra
D.Microscopic   4. Chlamydomonas 
       A    B   C   D
A.    1    2    3   4
B.    2    3    1   4
C.    3    1    2   4
D.   1     3    2   4
Answer: A  

3. Which of the following statement is not correct. 
A. Some of algae are found in moist stone, soils and wood.
B. Some of algae are found in symbiotic association with fungi in form of lichen.
C. Vegetative mode of reproduction is absent. They reproduce only by means of asexually and sexually.
D.  Flagellated Zoospores is most common method of asexual reproduction.
Answer : C  

4. Algae make association with which of the following animals.
A. Lemur       
B. Thylacine
C. Sloth Bear 
D. Gecko lizard
Answer : C  

5. Which one of the method of vegetative reproduction in Algae.
A. Fission 
B.fragmentation 
C. Binary fision
D.None of the above.
Answer : B  

6. Sexual reproduction take place by the fusion of flagellated and motile gamete in :
A. Spirogyra 
B. Ulothrix 
C. Volvox 
D. Chara 
Answer : A  

7. Sexual reproduction take place by the fusion of non flagellated and non motile gamete in :
A. Spirogyra 
B. Ulothrix 
C. Volvox 
D. Chara 
Answer: B  

8. Anisogamous  sexual reproduction take place between two gamete of dissimilar size in 
A. Fucus
B.Eudorina
C.Laminaria
D. Volvox
Answer: B  

9. Which one the following statement is correct for the oogamous type of sexual reproduction. 
A . Fusion take place between non motile and motile gamete.
B. Female gamete is non flagellated and large in size  and male gamete is flagellated and small.
C. Oogamous type of reproduction can be seen in Volvox and Fucus.
D. All of the above 
Answer: D  

10. Which of the following statement is not correct for the  Chlorophyceae.
A. These are green in color due to presence of pigment of chlorophyll a and Chlorophyll b.
B. Chlorophyll pigment are organised in various shape of chloroplast.
C. Most of the member of chlorophyceae have one or more storage bodies called pyrenoids.
D. Some of the members store food in form of Floridean starch.
Answer: D  

11. Members of Chlorophyceae have rigid cell wall and made up of 
A.Cellulose and lactose
B.Cellulose and algin
C. Cellulose and Pectose
D. Lactose and Pectose
Answer : C  

12. Consider the following statement and select the correct code:
1. Body of members of green algae are unicellular, colonial or filamentous.
2. Members of chlorophyceae are found in Fresh, Brackish or salt water. 
A. Only 1   B.only 2 
C. Both 1 and 2 
D. Neither 1 nor 2 
Answer: C  

13. Green algae have storage bodies called pyrenoids which contain
A. Starch and Protein
B. Starch and cellulose
C. Protein and cellulose
D.Starch and cellulose
Answer: A  

14. In members of chlorophyceae, vegetative reproduction takes place by the 
A. Fragmentation and  spores 
B. Fission and spores. 
C. Fragmentation and fission
D. Spores only.
Answer: A  

15. Which of the following are not member of Chlorophyceae. 
A. Volvox and chara.
B. Ulothrix and Spitogyra
C. Dictyota and Fucus
D.Chlamydomonas and Oedogonium
Answer: C  

16. Which of the following is correct for the number,  and position of flagella with respect to Chlorophyceae. 
     Number      Position
A.     2          equal & apical
B.    2 to 8   equal & apical
C.     2     unequal & apical 
D.  2 to 8  unequal & apical
Answer : B  

17. Consider the following statement and select the correct code 
1. Green algae reproduce asexually by  zoospore.
2. Zoospore are flagellated and produced in zoosporangium.
A. Only  1      B. Only 2 
C. Both 1 and 2 
D. Neither 1 nor 2 
Answer : C  

18. Identify the following algae given in diagram.





















A.Ulothrix 
B.Chara
C. Volvox
D. Fucus
Answer: A

19. Consider the following statement with  respect to Pheophyceae and select the correct code ;
1. Members show great variation in size and form
2. They are primarily found in brackish and marine water.
3. They are  rarely found  in fresh water.
4. They are commonly called as brown algae.
A. 1, 2   3 and 4
B. 2, 3 and 4
C. 1, 2, and 3
D. 1, 2   and 4 
Answer : A  

20. Which member of Pheophyceae is filamentous  form and form kelp up to 100 meters.
A. Ectocarpus
B. Dictyota
C. Laminaria
D. Sargassum 
Answer : A 

21. Which one of the following pigment is not found in Brown algae.
A. Chlorophyll a and b
B. Chlorophyll a and c
C. Xanthophyll
D. Fucoxanthin.
Answer : A  

22. In Pheophyceaen,  food is stored in form of 
A. Allolactose
B. Floridean starch
C. Starch 
D. Mannitol and Laminarin
Answer : D  

23. Cell wall of brown algae is made up of :
A. Cellulose and algin
B. Cellulose and  pectose
C. Algin and Pectose
D. Cellulose, Algin and Pectose
Answer : A  

24. Which of the following statement is not correct about the Pheophyceaen. 
A. They are present in well light region and in deep sea where no light penetrates.
B. They are various in color from olive green to various type of  brown in color depend on pigments.
C. The vegetative cell has cellulosic wall and covered by gelatinous algin.
D.  The protoplast has plastids , vacuole and nucleus.
Answer : A  

25. In Brown algae, vegetative reproduction takes place by 
A. Fission     B. Spores
C.Fragmentation
D. Budding 
Answer : C  

26. Asexual reproduction in Pheophyceae takes place by the zoospores. Which of the following is not a feature of zoospore.
A. Biflagellate
B. Pear shaped
C. Unequal flagella 
D. Apical located flagella
Answer : D  

27. Which of the body structure of brown algae is leaf like photosynthetic organ
A. Holdfast 
B. Stipe 
C. Frond
D. All of the above
Answer : C  

28. Which  one of the following is not member of Pheophyceae. 
A. Ectocarpus and Laminaria
B. Dictyota and Fucus
C. Sargassum  and Fucus
D. Gracilaria and Gelidium
Answer : D  

29. Consider the following statement and select the correct code:
1. During sexual reproduction,  fusion of gamete takes place in water.
2. In oogamous species, fusion of gamete takes place within oogonium.
3. The gamete bear two  unequal flagella located laterally.
4. The gametes are pyriform or pear shaped. 
A. 1 2 and 3   B. 2 3 and 4
C. 1 2 and 4   D. 123 and 4
Answer : D  

30. Body of Brown algae is devided into Frond, stipe and holdfast. Identify the "A" in given Diagram.

A. Holdfast    
B. Branch
C. Air bladder 
D. Chlorophyll 
Answer : C

31. How many statement is/are correct.
1. Most of the red algae are found in salt or marine water.
2. Red algae prefer warm area to live.
3. Red algae are not found in fresh or brackish water.
4. Red algae occur in both well lighted region and in great depth where light not penetrate. 
A. One              B. Two
C. Three           D. Four
Answer  : C  

32. Which of the following statement is not correct.
A. The thallus  of red algae is multicellular but some complex body organisation can exist.
B.  Body of red algae is red due to presence of r - phycoeryhtin.
C. Food is stored in form of Laminarin or mannitol 
D. Flagella are absent in red algae.
Answer: C  

33. Consider the following algae in which vegetative reproduction takes place by the fragmentation.
A. Red algae
B.Green algae
C. Brown algae
D. All of the above.
Answer : D  

34. Which of the following pigment is absent in Members of Rodophyceae. 
A. Chlorophyll  b
B. Phycoerythrin
C. Chlorophyll  a
D. Chlorophyll  d
Answer : A  

35. Consider the following constituents  which are present in cell wall of Rhodophyceae and select the correct  code.
1. Pectin   2. Algin
3. Cellulose 
4. Polysulphate ester
A. 1 3 and 4   B. 2 3 and 4
C. 1 2 and 4   D. 123 and 4
Answer : A  

36. Which one of the following food reserve of algae is similar to amylopactin and glycogen.
A. Starch
B. Laminarin
C. Mannitol
D. Floridean starch
Answer : D  

37. Consider the following statements and select the 
correct code :
1. Red algae reproduce asexually by motile spores.
2. Red algae reproduce sexually by motile gamete.
3. In Red algae, sexual reproduction is oogamous and accompanied by complex post fertilization development. 
A.  only 3    B. 1 and 2
C. 1 and 3   D. 2 and 3
Answer:  A  

38. Identity the letter ' A' in given diagram of Porphyra, red algae.

A. Stipe   B. Frond
C. Holdfast D. Air bladder
Answer : B

39.What number of marine algal species used as food.
A. 40   B. 50   C.60      D. 70
Answer: D  

40. Which of the following group of algae used as source of food.
A. Porphyra, Sargassum,  Laminaria
B.Chara, Fucus , Volvox
C.Dictyota, Polysiphonia, Gelidium
D. Ulothrix, Spirogyra, Gracilaria 
Answer: A  

41. Algin is hydrocolloids having water holding capacity obtained from member of
A. Red algae 
B. Brown algae
C. Green algae
D. All of the above
Answer: B  

42. Carrageen is hydrocolloids having water holding capacity obtained from member of
A. Red algae 
B. Brown algae
C. Green algae
D. All of the above
Answer:  A  

43. Which of the following statement is not  correct about the agar.
A. It is used to grow microbes.
B. It is used to prepare the ice cream and  jelly. 
C. Agar is not used commercially due to some restriction.
D.  It is obtained from Gelidium and Gracilaria.
Answer: C  

44. A unicellular algae rich in protein is used as source of food by space traveller.
A. Clamydomonsas
B. Volvox 
C. Chara
D. Chlorella 
Answer: D  

45. Which of the following statement is correct.
A. Algae are primary producers of energy in all aquatic animals.
B. Algae increase level of dissolved oxygen in environment. 
C. At least half of the carbon dioxide is fixed by the algae on earth.
D. All of the above.
Answer : D  

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