Thallophyta, Practice Problems and FAQs

We see a variety of plants around us. They provide food, medicines, shelter, oxygen etc. In addition to this they make this planet Earth beautiful. We know that plants possess roots, shoots and leaves. Some plants also possess beautiful flowers.

Fig: A typical plant

But do you think all plants possess roots, stems and leaves? No, because there are certain plants which possess the simplest structure and in them the plant body is not differentiated into roots, stems and leaves. Now tell me what you call them?

Fig: Thallophyta

Yes, they are called thallophytes. Examples include algae and fungi. So in this article we are going to discuss thallophytes in depth.

Table of contents

• Thallophyta
• Major characteristics of thallophytes
• Classification of Thallophyta
• Economic importance of thallophytes
• Practice Problems
• FAQs

Thallophyta

The plants present in this group are simple and their body is not differentiated into roots, stems and leaves. Hence this plant body is called thallus. ‘Thallos’ in Greek means undifferentiated and ‘phyton’ means plant. The plant body lacks a vascular system here and hence the transportation of materials occurs by diffusion. Common examples under division Thallophyta include algae, fungi, and lichens.

Fig: Members of division Thallophyta

Major characteristics of thallophytes

The various organisms present under the division Thallophyta possess the following features:

• They do not possess a definite body structure like other higher plants.
• The plant body is not differentiated into stems, leaves, and roots in them.
• They are normally present in wet regions as they lack a vascular system and true roots that can help in the transportation of minerals and water.
• They do not possess xylem and phloem.
• Autotrophic thallophytes possess chlorophyll and prepare their own food by photosynthesis.
• Starch is the main reserve food in autotrophic thallophytes like algae.
• Glycogen is the reserve food in the heterotrophic thallophytes.
• Heterotrophic thallophytes like fungi depend on other organisms for food.
• The reproductive organs are simple and single celled in them.
• Fungi possess chitin, glucans, and glycoproteins in their cell walls.
• Algae possess cellulose, mannans, galactans, and calcium carbonate in their cell walls.
• The process of embryo formation is absent in thallophytes.
• The life cycle of algae varies, it shows haplotic, haplodiplontic and diplontic conditions.

Classification of thallophyta

Thallophyta belongs to the Subkingdom Cryptogamae (non-flowering plants) under the Kingdom Plantae. Thallophytes are classified into two subdivisions such as Fungi and Algae.

Fungi

Fungi are achlorophyllous, spore bearing, non-vascular, eukaryotic and non-motile thallophytes. The cell wall of fungi is made up of chitin, glucans, and glycoproteins. As they lack chlorophyll, they are incapable of synthesising their own food. They depend on other organisms for their food and hence are called heterotrophs. They live as parasites, saprophytes or symbionts. They show symbiotic relationships with other organisms. Common examples include mycorrhizae and lichen. They store glycogen as reserve food. Their body is composed of finger-like projections called hyphae. A network of hyphae is called mycelium. Hyphae can septate or aseptate.

Fig: Hyphae

Classification of fungi

Kingdom Fungi is divided into the following groups based on the morphology of reproductive structures, life cycle, types of spores produced etc.

Lichen

It is a symbiotic association of algae and fungi. The fungal partner is called mycobiont and the algal partner is called phycobiont. The algal partner will provide food to the fungal partner. In return the fungal partner will give protection and moisture. Examples include Crustose lichen, Foliose lichen and Fruticose lichen.

Fig: Lichen

Mycorrhiza

It is the symbiotic association of fungi with roots of higher plants. The fungus gets shelter and food from the plants. In return the immense network of fungus increases supply of water and essential minerals from the soil. Examples include Rhizopogon on Pinus roots.

Fig: Mycorrhiza

Algae

Algae possess the green photosynthetic pigment called chlorophyll. They are autotrophic and are able to synthesise their own food. They are simple and largely aquatic (Freshwater or marine). They are found in a variety of habitats such as wood, moist stones, and soils. A few fungi live in association with animals. Examples include sloth bear (Melursus ursinus). The forms and sizes of algae vary. The size of algae ranges from microscopic structures (Chlamydomonas), filamentous (Spirogyra), massive (kelp) to colonial (Volvox) forms. Vascular tissues are absent. They possess flexible bodies which enable them to move with the tides. They are usually covered by mucilage. They possess sexual reproduction which involves the fusuon of gametes. It can be isogamy, anisogamy or oogamy. An embryo stage is absent in the life cycle.

Fig: Algae

Classification of algae

Subdivision Algae is divided into three classes as follows:

Economic importance of thallophytes

The following are the major economic importance of thallophytes:

• Lichens act as pollution indicators, as they cannot grow in polluted environments.
• Litmus is obtained from lichens.
• Lichens are the pioneer organisms in bare rocks.
• Algae increase the amount of dissolved oxygen in their surroundings by photosynthesis.
• Algae fixes at least ½ of the total CO₂ on the Earth.
• Algae produce high-energy compounds and form as part of the aquatic food chains.
• Agar obtained from the red algae like Gracilaria and Gelidium are widely used in the making of jellies, culture media, chocolates, and ice-creams.

Fig: Gracilaria

• Various species of algae like Sargassum and Porphyra are used as food materials.

Fig: Edible algae

• Spirulina and Chlorella are used as food supplements as they are rich in proteins.

Fig: Chlorella

• Saccharomyces cerevisiae used for the preparation of different types of alcoholic beverages like beer, wine, rum etc.
• It is also used in the baking industry.

Fig: Baking industry

• Some fungi are used for the preparation of antibiotics. Examples include Penicillium which produces penicillin.

Fig: Penicillium

• Neurospora is widely used in genetic studies.

Fig: Neurospora

• Some fungi are edible. Examples include mushrooms and truffles.

Fig: Mushroom

Practice Problems

1. Algae are placed in the division _________________.

(A) Embryophyta

(B) Thallophyta

(C) Spermatophyta

(D) Tracheophyta

Solution: Most primitive and simple plants are included under the division Thallophyta in the Subkingdom Cryptogamae of Kingdom Plantae. They possess a thallus-like body which may be unicellular or multicellular. Algae possess a thallus like structure where the body is not differentiated into roots, stems and leaves. Hence the correct option is ‘B’.

2. Read the following statements and find out the incorrect statement.

(A) The subdivision Algae are classified into three classes.

(B) Algae reproduce asexually by formation of different types of spores, vegetatively by fragmentation, and sexually by the formation of gametes.

(C) The plant body of algae is well differentiated compared to bryophytes.

(D) Algae are chlorophyll bearing simple, autotrophic, thalloid, and largely aquatic organisms.

Solution: Algae reproduces in many ways which includes vegetative reproduction by fragmentation, asexual reproduction by different types of spores like oospores, aplanospores and hygnospores and sexual reproduction by the fusion of haploid gametes results in formation of diploid zygote.

The subdivision Algae is classified into 3 classes such as Chlorophyceae (Green algae), Phaeophyceae (Brown algae) and Rhodophyceae (Red algae). The plant body of algae is thallus-like and simple. They are photoautotrophic. These are mostly aquatic but are found in other habitats like moist soils also. The plant body of bryophytes are well differentiated compared to the algal plant body. Hence the correct option is ‘C’.

Fig: Algae

3. Lichens are considered as the symbiotic association of algal and a fungal species. Which of the following will happen if algal and fungal partners are separated from each other?

(A) Both will survive and grow normally independently

(B) Only the fungal component will survive whereas the algal component will die

(C) Both the algal and fungal component will die

(D) Only the algal component will survive whereas the fungal component will die

Solution: Symbiosis is the interaction between two organisms that mutually benefit from one another. Lichen is a symbiotic association of the algal component (phycobiont) and the fungal component (mycobiont). Phycobiont is photoautotrophic and produces the nutrients while the mycobiont provides anchorage and absorbs water and essential minerals from the soil. The survival of both the components in this association depends on one another. If the two components are separated from each other then both of them will die. Hence the correct option is ‘C’.

Fig: Lichen

4. As per the classification of Whittaker, the organism with a eukaryotic cell structure, a unicellular to multicellular organisation with a cell wall and showing heterotrophic nutrition is placed under the Kingdom ________________.

(A) Monera

(B) Plantae

(C) Fungi

(D) Protista

Solution: R. H. Whittaker developed the phylogenetic mode of classification which divided all the organisms into five major Kingdoms such as Monera, Protista, Fungi (Mycota), Plantae (Metaphyta), and Animalia (Metazoa). Kingdom Fungi include eukaryotic, single celled or multicellular organisms that are found in every habitat such as in moist, dark, and warm conditions. They are heterotrophs. The cell wall is composed of chitin. It includes moulds, mildews, yeasts, rust-causing fungi, morels, mushrooms, puffballs, bracket fungi, etc. Hence the correct option is ‘C’.

Fig: Puffballs

FAQs

1. Explain the common structure of the members of division Thallophyta?

Answer: The plants present in this division Thallophyta are simple and their body is not differentiated into roots, stems and leaves. Hence this plant body is called thallus. ‘Thallos’ in Greek means undifferentiated and ‘phyton’ means plant. Examples include algae, fungi and lichens.

Fig: Plant body of Thallophyta

2. What is the main difference between Pteridophyta and Thallophyta?

Answer: The members of Thallophyta possess single celled sex organs and the plant body is thallus like. It is not differentiated into stems, roots or leaves. Examples include algae, fungi and lichen. The members of the Pteridophyta possess multi-celled sex organs and possess stem-like, root-like, and leaf-like structures in the plant body.

Fig: Pteridophyta and Thallophyta

3. Can we say mushroom is a member of the division Thallophyta?

Answer: Fungi belongs to the division Thallophyta as the body is not differentiated into stems, roots and leaves in them. This Kingdom includes mushrooms and moulds. Hence we can say mushroom is a member of the division Thallophyta.

Fig: Mushroom

4. Can we say algae is a plant?

Answer: Algae belonging to division Thallophyta under the Kingdom plantae. The subdivision Algae is classified into 3 classes such as Chlorophyceae (Green algae), Phaeophyceae (Brown algae) and Rhodophyceae (Red algae). The plant body of algae is thallus-like and simple. They are photoautotrophic. These are mostly aquatic but are found in other habitats like moist soils also.