Posted on: 03:58 Tue, 17 Jun 2025

BIOLOGY PAPER I QUESTIONS:-







BIOLOGY THEORY ANSWER:-

(1)




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(2)
i. ferns
ii. amyloplast
iii. aestivation
iv. isogamy
v. ascospores
vi. bacilli
vii. rhizoids
viii. psilophyta
ix. prokaryotes
x. mycelium

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(3)
(i) Symbiosis: A close and long-term interaction between two different biological species, where at least one benefits (e.g., mutualism, commensalism, parasitism).

(ii) Halophytes: Plants adapted to grow in high-salinity environments, such as salt marshes, by tolerating or excluding salt.

(iii) Biological control: The use of natural enemies (e.g., predators, parasites) to manage pest populations, reducing the need for chemical pesticides.

(iv) Pollution: The introduction of harmful substances or energy (e.g., chemicals, noise) into the environment, causing adverse effects on ecosystems

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(4)


(4b)
Types of Lichens
(i) Crustose: Grow flat and tightly attached to surfaces (e.g., rocks).
(ii) Foliose: Leaf-like, loosely attached with a lobed structure (e.g., on tree bark).
(iii) Fruticose: Shrubby or hair-like, three-dimensional growth (e.g., reindeer moss).

- Range Forms
Lichens thrive in diverse habitats, from arid deserts to arctic tundra, indicating a wide ecological tolerance, often ranging from 0°C to 30°C and varying humidity levels

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(5a)
Photosynthesis is the biochemical process by which green plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose. It occurs in the chloroplasts of plant cells, which contain the green pigment chlorophyll. During the process, plants absorb carbon dioxide (CO?) from the air and water (H?O) from the soil. In the presence of sunlight, these react to form glucose (C?H??O?) and release oxygen (O?) as a byproduct. The general equation for photosynthesis is:
6CO? + 6H?O <===> C?H??O? + 6O?

This process is essential for the survival of most life forms on Earth as it provides oxygen for respiration and organic food for heterotrophic organisms.

(5b)
Vascular tissues are specialized conducting tissues in higher plants (vascular plants) that are responsible for the transport of water, minerals, and organic substances. They form the plant’s vascular system and are composed mainly of xylem and phloem. These tissues are vital for the plant’s survival, support, and growth.

=MAIN TYPES OF VASCULAR TISSUES=
(a) Xylem
(i) Function: Transports water and dissolved minerals unidirectionally from the roots to the aerial parts of the plant (stems and leaves).

(ii) Structure: Composed mainly of dead cells including tracheids and vessel elements, which form hollow tubes for water conduction. It also contains xylem parenchyma (living cells for storage) and xylem fibers (for support).

(iii) Location: Found in the center or inner part of the vascular bundle.

(iv) Characteristics:
-Cells have thick, lignified walls providing mechanical strength to the plant.
-Transport occurs passively, driven by transpiration pull and cohesion of water molecules.
-Xylem tissue is generally more abundant than phloem in vascular bundles.

(b) Phloem
(i) Function: Transports organic nutrients, mainly sugars (like sucrose), amino acids, proteins, and some plant hormones bidirectionally from leaves to growing parts and storage organs (roots, fruits, seeds).

(ii) Structure: Made up of living cells including sieve tube elements (which lack nuclei but have cytoplasm), companion cells (which assist sieve tubes), phloem fibers, and phloem parenchyma.

(iii) Location: Located on the outer side of the vascular bundle.

(iv) Characteristics:
-Cells have thin, non-lignified walls and are permeable to organic substances.
-Transport is an active process requiring energy (ATP).
-Phloem fibers provide some support but phloem overall does not contribute significantly to mechanical strength.
-Phloem tissue is less abundant than xylem in vascular bundles

=Arrangement and Importance=
(i) Xylem and phloem are arranged together in vascular bundles, connecting roots, stems, and leaves to facilitate efficient transport.
(ii) Xylem occupies the inner part, while phloem is positioned towards the outer part of the vascular bundle.
(iii) This arrangement supports both transport and mechanical stability of the plant.

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(6a)
Angiosperms, commonly known as flowering plants, represent the most diverse and widespread group of land plants, comprising over 300,000 species, including crops like rice, wheat, and ornamentals like roses. They are distinguished by their reproductive structures, flowers, which contain male stamens and female pistils, facilitating pollination by insects, wind, or other agents. A unique feature is double fertilization, where one sperm fertilizes the egg to form the embryo, while another fuses with polar nuclei to create the endosperm, a nutrient-rich tissue for the developing seed. This process occurs within an ovary, which develops into a fruit enclosing the seed, enhancing seed dispersal and protection. Angiosperms possess advanced vascular tissues—xylem for water and mineral transport, and phloem for nutrient distribution—allowing them to grow into large trees, shrubs, or herbs. Their evolutionary success is attributed to efficient reproduction, adaptability to various climates, and symbiotic relationships with pollinators. Economically, they are vital, providing food, timber, medicines (e.g., aspirin from willow), and textiles, making them foundational to human civilization and ecosystems worldwide.

(6b)
Alternation of generation is a life cycle characteristic of plants and some algae, involving a regular alternation between two distinct multicellular phases: the diploid sporophyte and the haploid gametophyte. The sporophyte, which produces spores through meiosis, is the dominant phase in vascular plants like angiosperms, where it forms the familiar plant body (e.g., stem, leaves, flowers). These spores germinate into the gametophyte, a smaller haploid phase that produces gametes (sperm and eggs) via mitosis. Fertilization of gametes restores the diploid sporophyte, completing the cycle. In bryophytes (e.g., mosses), the gametophyte is dominant, with the sporophyte dependent on it, while in angiosperms, the gametophyte is reduced to structures like pollen and the embryo sac within the flower. This alternation ensures genetic diversity by separating spore and gamete production, adapting plants to terrestrial environments by balancing reproductive and vegetative phases. The cycle’s complexity, especially in seed plants, supports their evolutionary success and ecological dominance.


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