Biology Class 11 NCERT Solutions: Chapter 2 Biological Classification Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q: 8. What do the terms phycobiont and mycobiont signify?

Q_8_Phycobiont and Mycobiont


Phycobiont refers to the algal component of the lichens and mycobiont refers to the fungal component. Algae contain chlorophyll and prepare food for fungi whereas the fungus provides shelter to algae and absorbs water and nutrients from the soil. This type of relationship is referred to as symbiotic.

Q: 9. Give a comparative account of the classes of Kingdom Fungi under the following:

(i) Mode of nutrition

(ii) Mode of reproduction


The Classes of Kingdom Fungi

(A) Phycomycetes- This group of fungi includes members such as Rhizopus, Albugo, etc.

(i) Mode of nutrition

They are obligate parasites on plants or are found on decaying matter such as wood.

(ii) Mode of reproduction

Asexual reproduction takes place through motile zoospores or non-motile aplanospores that are produced endogenously in sporangium.

Sexual reproduction may be of isogamous, anisogamous, and oogamous type. It results in the formation of thick-walled zygospore.

(B) Ascomycetes- This group of fungi includes members such as Penicillium, Aspergillus, Claviceps, and Neurospora.

(i) Mode of nutrition

They are sporophyte, decomposers, parasitic or coprophilous (growing on dung) .

(ii) Mode of reproduction

Asexual reproduction occurs through asexual spores produced exogenously, such as conidia produced on conidiophores.

Sexual reproduction takes place through ascospores produced endogenously in sac-like asci and arranged inside ascocarps.

(C) Basidiomycetes- This group of fungi includes members such as Ustilago, Agaricus and Puccinia.

(i) Mode of nutrition

They grow as decomposers in soil or on logs and tree stumps. They also occur as parasites in plants causing diseases such as rusts and smuts.

(ii) Mode of reproduction

Asexual reproduction takes place commonly through fragmentation. Asexual spores are absent.

Sex organs are absent but sexual reproduction takes place through plasmogamy. It involves fusion of two different strains of hyphae. The resulting dikaryon gives rise to a basidium. Four basidiospores are produced inside a basidium.

(D) Deuteromycetes - This group of fungi includes members such as Alternaria, Trichoderma, and Colletotrichum.

(i) Mode of nutrition some members are saprophytes while others are parasites. However, a large number act as decomposers of leaf litter.

(ii) Mode of reproduction

Asexual reproduction is the only way of reproduction in deuteromycetes. It occurs through asexual spores called conidia.

Sexual reproduction is absent in deuteromycetes.

Q: 10. What are the characteristic features of Euglenoids?


Some characteristic features of Euglenoids are as follows.

⇾ Euglenoids (such as Euglena) are unicellular protists commonly found in fresh water.

⇾ Instead of cell wall, a protein-rich cell membrane known as pellicle is present.

⇾ They bear two flagella on the anterior end of the body.

⇾ A small light sensitive eyespot is present.

⇾ They contain photosynthetic pigments such as chlorophyll and can thus prepare their own food. However, in absence of light, they behave similar to heterotrophs by capturing other small aquatic organisms.

⇾ They have both plant and animal-like features, which makes them difficult to classify.

Characteristic Features of Euglenoids

Q: 11. Give a brief account of viruses with respect to their structure and nature of genetic material. Also, name four common viral diseases.


The Structure of Viruses

Viruses are sub-microscopic infectious agents that can infect all living organisms. A virus consists of genetic material surrounded by a protein coat. The genetic material may be present in the form of DNA or RNA.

Most of the viruses, infecting plants, have single stranded RNA as genetic material. On the other hand, the viruses infecting animals have single or double stranded RNA or double stranded DNA.

Bacteriophages or viruses infecting bacteria mostly have double stranded DNA. Their protein coat called capsid is made up of capsomere subunits. These capsomeres are arranged in helical or polyhedral geometric forms.

A. I. D. S, small pox, mumps, and influenza are some common examples of viral diseases.

The Examples of Viral Diseases

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