Biology MCQs
Topic Notes: Biology
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
51
To which biological group does the parasitic organism Puccinia belong?
Answer:
Fungus
Puccinia is a genus of fungi, specifically known as rust fungi, which are obligate plant parasites. These fungi cause significant agricultural damage by infecting various crops, including wheat and other cereals. They complete their complex life cycles on different host plants, forming characteristic rust-colored spores on the surfaces of infected leaves and stems.
52
Which category of lichen is characterized by a thallus that adheres firmly to rocky substrates?
Answer:
Crustose
Crustose lichens possess a crust-like thallus that is tightly appressed to the substrate, such as rocks or concrete. This growth form makes them extremely difficult to detach without damaging the underlying surface, distinguishing them from foliose or fruticose forms.
53
Within the historical two-kingdom classification system, how were fungi classified?
Answer:
Kingdom Plantae
In the traditional two-kingdom classification system established by Linnaeus, all living organisms were divided into Plantae and Animalia. Because fungi are sessile and possess cell walls, they were historically grouped within the Kingdom Plantae, despite their heterotrophic mode of nutrition which distinguishes them from true plants.
54
Which of the following organisms is classified as a non-hyphal, unicellular fungus?
Answer:
Yeast
Yeasts are distinct among fungi because they exist primarily as single-celled organisms rather than forming the filamentous hyphal networks characteristic of molds and mushrooms. This unicellular growth habit is a key diagnostic feature of yeast species.
55
What is the biological classification of the pathogen responsible for ringworm?
Answer:
Fungi
Ringworm is a common skin infection caused by dermatophytes, which are a group of fungi that thrive on keratin found in the skin, hair, and nails. Despite the name, it is not caused by a worm.
56
Approximately what percentage of Ascomycota species are involved in lichen symbiotic associations?
Answer:
50%
Lichens are composite organisms consisting of a fungal partner (the mycobiont) and a photosynthetic partner (the photobiont). Research indicates that roughly half of all known Ascomycota species have evolved to exist in this mutualistic relationship, demonstrating the ecological success and evolutionary significance of the lichenized lifestyle.
57
Which of the following organisms possesses a cell wall that is not composed of cellulose?
Answer:
fungi
While plants, algae, and mosses have cell walls primarily composed of cellulose, fungi are distinct because their cell walls are composed of chitin. Chitin is a long-chain polymer of N-acetylglucosamine, which provides structural rigidity and protection to fungal cells, differentiating them from the cellulose-based cell walls found in the plant kingdom.
58
In which fungal phylum do dikaryotic hyphae persist for an extended period during the life cycle?
Answer:
Basidiomycota
In Basidiomycota, the dikaryotic phase, where each cell contains two genetically distinct nuclei, represents the dominant and long-lived stage of the life cycle. This phase is essential for the development of the basidiocarp, or fruiting body.
59
What is the characteristic morphology of a foliose lichen?
Answer:
Leaf like
Lichens are categorized by their growth forms. Foliose lichens are defined by their flat, leaf-like thallus structure that is loosely attached to the substrate. This morphology allows for distinct upper and lower surfaces, differentiating them from crustose (crust-like) or fruticose (shrubby or branching) forms.
60
Which fungal species is commonly referred to as 'black bread mold'?
Answer:
Rhizopus
Rhizopus stolonifer is widely known as the black bread mold. It is a common zygomycete fungus that grows rapidly on starchy foods, producing dark-colored sporangia that give the mold its characteristic black, fuzzy appearance on the surface of bread.