Algae are autotrophic organisms which contain a variety of pigments. They are one of the major producers in the marine environment.
Did you know which algae is used as a super food in the International Space Station?
Yes, it is Chlorella, the unicellular green algae which is rich in proteins. It is also used for the production of oxygen there. Let’s dive deep into the details of green algae.
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Like all members of the plant kingdom, the life cycle of algae shows alternation of generation. The haploid gametophyte generation that develops from haploid spores gives rise to gametes by mitosis. Then the zygote is formed by the fusion of haploid gametes. The diploid sporophytic generation develops from the diploid zygote. The sporophyte produces haploid spores by meiotic division.
Depending on the prevalence of the haploid and diploid generations, the life cycle of algae can be of three types as follows:
Algae is divided into three classes based on the nature of pigments, storage material and complexity of structure. These classes are - Chlorophyceae, Phaeophyceae and Rhodophyceae.
These algae are green in colour due to the predominance of green pigments. They are of different types based on the complexity of the thallus as follows:
They have a cell wall with the outer layer made up of pectose and the inner layer made up of cellulose. Their reserve food material is starch but some algae also store food in the form of oil droplets. Photosynthetic pigments include chlorophyll a and chlorophyll b which are present within chloroplasts. Pyrenoids are non-membrane bound organelles in the chloroplasts which store proteins and starch. Chloroplasts can be of various shapes such as:
They reproduce by vegetative, asexual and sexual methods.
Green algae shows all three types of life cycle:
Question 1. In Ulothrix, meiosis occurs in which part of the body?
(A) hold fast
(D) Filament cells
Solution : Ulothrix belongs to the class Chlorophyceae. It is a filamentous algae found attached to some solid objects. They reproduce normally by vegetative reproduction and spore formation. During sexual reproduction mainly isogametes are formed. Fusion of gametes results in the formation of zygotes. Zygote later develops into a thick walled zygospore. Zygospore undergoes meiotic division and forms meiospores which germinate to form new filaments. Hence in Ulothrix, meiotic division takes place through the zygote.
Thus, the correct option is B.
Question 2. An algal species reproduces with the help of fusion between a small motile gamete and large immotile gamete. What type of reproduction do you think occurs in this algae?
(D) Reproduction by asexual flagellated zoospores.
Solution : In algae, reproduction by fusion of gametes is known as sexual reproduction. The type of reproduction in which a smaller motile male gamete fuses with a larger immotile female gamete is known as oogamy.
Thus, the correct option is A.
Question 3. Read the following statements (A - D) and find out the incorrect statement.
(A) Algae usually reproduce vegetatively by fragmentation,
(B) Algae reproduce asexually by the formation of different types of spores.
(C) Algae are divided into four classes.
(D) Algae are chlorophyll bearing simple, thalloid, autotrophic organisms.
Solution : Algae are simple chlorophyll-bearing, eukaryotic, autotrophic organisms in which the plant body is a thalloid. Algae reproduce vegetatively by fragmentation and asexually with the help of spores. Algae is divided into 3 classes as follows:
Thus, the correct option is C.
Question 4. Identify the odd one from the options given below.
Solution : Chlamydomonas, Chlorella and Ulothrix belong to the class Chlorophyceae or green algae whereas Porphyra belong to the class Rhodophyceae or red algae.
Thus, the correct option is D.
Question 1. What is the basis of classification in Algae?
Solution: Algae are classified based on the nature of pigments, storage materials and complexity of structure.
Question 2. Give one example for unicellular, colonial and filamentous green algae.
Question 3.Write down the life cycle exhibited by the following green algae:
Chlamydomonas, Cladophora, Spirogyra, Ulothrix
Question 4. Define pyrenoids.
Solution: Storage bodies called pyrenoids are present in the green algae. They store starch and proteins.
|The Living World||Biological Classification||Plant Kingdom|
|Animal Kingdom||Morphology of Flowering Plants||Anatomy of Flowering Plants|
|Structural Organization in Animals||Cells: The Unit of Life||Biomolecules|
|Cell Cycle and Division||Transport in Plants||Mineral Nutrition|
|Photosynthesis in Higher Plants||Respiration in Plants||Plant Growth and Development|
|Digestion and Absorption||Breathing and Exchange of Gases||Body Fluids and Circulation|
|Excretory Products and their Elimination||Locomotion and Movement||Neural Control and Coordination|
|Chemical Coordination and Integration|