IJMB 2025 BIOLOGY PAPER II QUESTIONS
IJMB 2025 BIOLOGY PAPER II QUESTIONS BELOW
SOLUTIONS BELOW
*.IJMB BIOLOGY.*
*NUMBER FOUR*
(.4a.)
(i) Carbohydrates: Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen, in a ratio of 1:2:1. They are the primary source of energy for cellular activities. Carbohydrates exist in three forms: monosaccharides (simple sugars like glucose), disaccharides such as sucrose and lactose, and polysaccharides (complex sugars like starch, glycogen, and cellulose). In cells, glucose is broken down during cellular respiration to release energy in the form of ATP. Structural carbohydrates such as cellulose provide rigidity to plant cell walls, while glycogen serves as energy storage in animal cells.
(ii.) Proteins: Proteins are large, complex molecules composed of amino acids linked by peptide bonds. They contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Proteins perform a vast array of functions in cells, including serving as enzymes that speed up biochemical reactions, structural components like keratin and collagen, transporters such as hemoglobin, and hormones like insulin. The function of a protein depends on its three-dimensional structure, which is determined by the sequence of amino acids.
(iii) Lipids: Lipids are a diverse group of hydrophobic molecules that include fats, oils, phospholipids, and steroids. They are composed mainly of carbon, hydrogen, and a small amount of oxygen. Lipids function as long-term energy storage molecules, insulators, and protective barriers. Phospholipids are a major component of cell membranes, forming a bilayer that separates the internal environment of the cell from the external environment. Steroids like cholesterol are also important in maintaining membrane fluidity and are precursors for the synthesis of certain hormones.
(i.v) Nucleic Acids: Nucleic acids are macromolecules that store and transmit genetic information. The two main types are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). They are composed of nucleotides, which consist of a nitrogenous base, a sugar (deoxyribose in DNA and ribose in RNA), and a phosphate group. DNA contains the instructions for the development, functioning, growth, and reproduction of all living organisms. RNA plays a crucial role in protein synthesis by translating the genetic code from DNA into functional proteins…
*IJMB BIOLOGY*
*NUMBER THREE.*
(3a)
Cytokinesis in cell division: Cytokinesis is the final stage of cell division where the cytoplasm of a parent cell is divided into two daughter cells. It usually occurs after the completion of mitosis or meiosis. In animal cells, cytokinesis involves the formation of a cleavage furrow, which is a constriction that gradually deepens until the cell is pinched into two separate cells. This process is driven by a contractile ring composed of actin and myosin filaments that tighten to split the cell. In plant cells, due to the presence of a rigid cell wall, cytokinesis occurs through the formation of a cell plate at the center of the cell, which eventually develops into a new cell wall separating the two daughter cells. Cytokinesis ensures that each daughter cell receives an appropriate amount of cytoplasm and organelles, completing the process of cell division.
(3.b)
Diploblastic organization in Hydra: Diploblastic organization refers to organisms that develop from two primary germ layers: the ectoderm and the endoderm. In Hydra, which is a simple aquatic animal belonging to the phylum Cnidaria, this structure is clearly observed. The ectoderm forms the outer layer of cells responsible for protection and interaction with the environment, while the endoderm lines the inner cavity and is involved in digestion. Between these two layers is a non-cellular jelly-like substance called mesoglea, which provides support and flexibility. The absence of a third germ layer, the mesoderm, limits Hydra’s complexity, but it allows for basic tissue differentiation and simple body functions such as movement, feeding, and reproduction.
(3.c)
Reproduction in reptiles: Reptiles reproduce primarily through sexual reproduction, involving internal fertilization. Most reptiles are oviparous, meaning they lay eggs with leathery or calcareous shells that protect the developing embryos from desiccation. Some species are ovoviviparous, where eggs develop and hatch inside the mother’s body, providing additional protection to the embryos. A few species are viviparous, giving birth to live young with some form of placental connection. Reptiles generally exhibit minimal parental care, although some species guard their eggs until they hatch. The reproductive process in reptiles is influenced by environmental factors such as temperature, which in some species can determine the sex of the offspring through temperature-dependent sex determination…
(6b)
Protozoa excrete waste products such as ammonia by diffusion through their cell membrane. Some protozoa, like Amoeba, use a contractile vacuole to collect and expel excess water and soluble wastes.
(6c)
(PICK ANY FIVE)
(i) No genetic variation
(ii) Low adaptability to environmental changes
(iii) High risk of disease spread
(iv) Slows evolutionary progress
(v) Accumulation of harmful mutations
(vi) Leads to overpopulation
(vii) Short-term survival strategy
(viii) No parental care
(ix) Poor colonization of new environments
(6d)
Divergent evolution is the process by which related species evolve different traits due to adaptation to different environments. It leads to homologous structures, similar in origin but different in function (e.g., human arm and bat wing).
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