CBSE Class 9 Science Chapter 12 Patterns In Life Diversity And Classification MCQs Set 02

Answer: (B) Diverse animal hosts prevent the virus from replicating effectively inside their bodies

Explanation:
According to the chapter's 'Bridging Science and Society' section on forests with rich biodiversity, the Western Ghats' forest diversity acts as a biological barrier because many animals serve as hosts where the virus cannot replicate inside their bodies, thereby interrupting transmission.

Answer: (B) It separated unicellular microscopic organisms from both plants and animals, addressing the problem of organisms like Amoeba and Paramecium that showed mixed characteristics

Explanation:
• Amoeba and Paramecium moved like animals but were unicellular and heterotrophic
• The two kingdom system couldn't accommodate organisms that had characteristics of both kingdoms
• Protista provided a dedicated kingdom for these unicellular eukaryotic organisms, solving the classification dilemma.

Answer: (B) It would be classified as an invertebrate animal, as the absence of a notochord is a defining characteristic

Explanation:
The chapter clearly establishes that the presence or absence of a notochord is a major criterion for classifying animals into chordata and non-chordata groups. Organisms without a notochord but with organ system organisation belong to invertebrates, which include diverse phyla from cnidarians to molluscs and arthropods.

Answer: (B) They have root-like structures (rhizoids) and may possess stem-like and leaf-like structures, representing an important evolutionary transition from aquatic to terrestrial life

Explanation:
Bryophytes like mosses and liverworts show an important shift from water to land. Although they lack true roots, stems, and leaves, they possess rhizoids and leaf-like structures. This intermediate level of differentiation places them between the simple thallophytes and the complex pteridophytes, reflecting their role as the plant kingdom's 'amphibians.'

Answer: (B) The binomial nomenclature system's capacity to incorporate geographical information and aid biodiversity conservation

Explanation:
The chapter's discussion of the Purple Frog notes that the species name 'sahyadrensis' reflects its place of discovery—the Sahyadri Hills. This demonstrates how the binomial system not only names organisms but can also incorporate geographical context. The discovery itself highlighted the need for biodiversity conservation in the Western Ghats, showing classification's practical conservation role.

Answer: (B) Both lack chlorophyll and obtain nutrients by absorption, with cell walls made of chitin

Explanation:
Although yeast is unicellular and mushrooms are multicellular, the chapter explains they share fundamental fungal characteristics: heterotrophic nutrition through absorption and cell walls composed of chitin. This shared cellular structure and mode of nutrition outweigh the difference in organism complexity, making cell wall composition a more fundamental criterion for kingdom placement than organisation level alone.

Answer: (B) Both belong to the genus Panthera, yet each has a distinct species name, showing how similar organisms can be grouped at higher levels while remaining distinct at lower levels

Explanation:
The chapter uses Tiger (Panthera tigris) and Lion (Panthera leo) to illustrate how the hierarchical system works. At the genus level (Panthera), they are grouped together because they share common features like the ability to roar and similar skull structure. At the species level, they are distinguished as separate entities. This exemplifies the nested hierarchy where broader groups contain organisms that become increasingly similar at lower levels.

Answer: (B) Protochordates possess a notochord at least once during their life and help explain how animals with notochords may have arisen from simpler invertebrate forms

Explanation:
The chapter describes protochordates as primitive types of chordates that possess a notochord at least once during their life. This structure provides internal support without restricting movement, representing a crucial change in body organisation. Their existence helps scientists understand the evolutionary transition from invertebrates to vertebrates, showing how a notochord-bearing structure could have evolved from simpler forms.

Answer: (B) Dead organic matter would accumulate, soil fertility would decrease, and nutrient cycling would be severely disrupted, affecting all organisms dependent on fertile soil

Explanation:
The chapter explicitly states that fungi break down complex organic matter into simpler substances, making them readily available in soil as minerals. Without fungal decomposition, dead plants and animals would decay slowly, soil fertility would decline, and the entire nutrient cycling process would be compromised, ultimately affecting food production and ecosystem health.

Answer: (B) Organisms with similar body structures and evolutionary relationships would be separated into different groups, while unrelated organisms might be grouped together, obscuring their true biological relationships

Explanation:
The chapter notes that Aristotle's system had limitations because it relied on easily observable external characteristics like habitat. This approach would incorrectly group organisms—for example, both whales (aquatic mammals) and fish would be water-dwellers despite their different evolutionary origins. Modern classification relies on structural, cellular, and genetic similarities that better reflect evolutionary relationships, which habitat alone cannot indicate.

Answer: (B) All protists are unicellular eukaryotes with a membrane-bound nucleus, though they may lack or possess a cell wall and vary in their mode of nutrition

Explanation:
The chapter describes Kingdom Protista as containing single-celled eukaryotes with a well-defined, membrane-bound nucleus. While individual protists vary considerably—some are autotrophic (like Chlamydomonas), others heterotrophic (like Amoeba and Paramecium), and some show both characteristics (like Euglena)—they all share the fundamental eukaryotic cell structure with a true nucleus, distinguishing them from prokaryotic Monera.

Answer: (B) Diverse habitats with different soil types, climatic conditions, and topography support varied ecological niches, allowing a greater variety of species to coexist with minimal competition

Explanation:
The chapter explains that India's diverse natural landscape—with mountains, deserts, rainforests, plateaus, and coastlines—each having distinct soil types and climatic conditions, supports wide species variety. The Western Ghats, Indo-Burma region, and Himalayas exemplify how environmental heterogeneity creates multiple ecological niches, enabling more species to thrive than would be possible in uniform habitats.

Answer: (B) Segmentation allows greater flexibility and more precise control of movements through muscles in each segment, plus the presence of a nerve cord for coordination, enabling more sophisticated locomotion and behaviour

Explanation:
The chapter explains that annelids, such as earthworms, possess cylindrical bodies divided into segments with muscles and a nerve cord. This segmentation allows greater flexibility and more precise control of movements compared to the simpler body plans of earlier invertebrate groups. The body cavity also provides space for organ development, representing a significant advancement in animal organisation.

Answer: (B) Cell type—specifically whether cells are prokaryotic or eukaryotic—is a fundamental criterion for classification that reflects deep evolutionary differences, not just superficial structural variations

Explanation:
The chapter details how the discovery of this key difference prompted scientists to create Kingdom Monera. This decision reflects the fundamental principle that cell type (prokaryote versus eukaryote) represents a major evolutionary divide. This criterion proved more reliable than simply grouping all microscopic organisms together, demonstrating how classification criteria should reflect genuine biological relationships rather than convenience.

Answer: (B) Plants needed transport tissues, seeds, and flowers to overcome challenges of drying air, gravity, and dispersal

Explanation:
The chapter traces how plant groups evolved increasingly sophisticated structures to address the demands of terrestrial life. Early algae absorbed water and nutrients directly; bryophytes developed some differentiation but still needed moisture; pteridophytes gained vascular tissues for water and food transport; gymnosperms developed seeds and needle-like leaves for dry conditions; angiosperms added flowers and fruits for efficient pollination and seed dispersal. Each innovation allowed plants to expand their range and reduce dependence on water.

Answer: (B) Monera lacks a membrane-bound nucleus whereas Protista possesses a true nucleus

Explanation:
• Bacteria and cyanobacteria in Monera have a primitive nucleus without a membrane
• Amoeba and Paramecium in Protista have membrane-bound nuclei
• This structural difference in nuclear organization became the key reason for separating these kingdoms when microscopy improved and revealed this critical distinction.

Answer: (B) It fails to capture evolutionary relationships and can group unrelated organisms together

Explanation:
A habitat-based system groups organisms by where they live rather than by their shared ancestry or structural similarities. This means a flying insect and a flying bird would be grouped together despite being distantly related, while aquatic dolphins and terrestrial whales would be separated even though they share a common ancestor. The chapter emphasises that modern classification reveals evolutionary relationships and deeper connections that simple habitat grouping cannot show.

Answer: (B) Cell wall material reflects evolutionary relationships and shared biochemical pathways in nutrition and reproduction

Explanation:
Both yeast and mushrooms share the trait of absorbing nutrients from dead or decaying organic matter and possessing chitin cell walls. These characteristics indicate a common evolutionary origin and similar biochemical strategies for obtaining and processing food, placing them together in Kingdom Fungi despite differences in multicellularity. This demonstrates how structural and biochemical features unite organisms more meaningfully than organisational complexity alone.

Answer: (B) Bryophytes thrive in moist and shady places and appear as green mats especially during monsoons

Explanation:
The need for water to enable reproductive cell movement means bryophytes cannot occupy dry environments. Their distribution reflects this constraint—they grow as lush green mats on damp rocks, soil, and old buildings, particularly during monsoon seasons when moisture is abundant. This geographic and seasonal pattern directly results from their reproductive mechanism requiring external water, earning them the title 'amphibians of the plant kingdom' since they bridge water and land but remain moisture-dependent.

Answer: (B) They show evolution toward internal support without developing the notochord-to-vertebral column pathway

Explanation:
Echinoderms represent an evolutionary trajectory toward internal skeletal support that diverges from the vertebrate lineage. While vertebrates evolved from notochords that became vertebral columns, echinoderms developed a different internal support system using calcium carbonate. This shows that multiple solutions evolved for similar structural challenges—the chapter emphasises that animal body structures reflect environmental demands and evolutionary pathways, not a single ladder of complexity.

Answer: (B) Loss of these regions threatens irreplaceable biodiversity that cannot be recovered elsewhere

Explanation:
Endemic species exist only in specific regions; if those habitats are destroyed, the species disappear forever and cannot be found or reintroduced anywhere else. The chapter identifies Western Ghats, Indo-Burma, and other regions as global biodiversity hotspots precisely because they contain unique species found nowhere else. Habitat loss in these areas results in permanent extinction, making their protection critical for maintaining global biological diversity.

Answer: (B) Each segment can move somewhat independently, enabling more complex locomotion than unsegmented bodies

Explanation:
Body segmentation means different sections can contract and relax independently or in coordinated sequences, enabling more sophisticated movement patterns than simple, whole-body contraction. An earthworm can perform peristaltic waves along its body to burrow through soil efficiently. Segmented arthropods like insects use their segments for even more diverse movements. This structural feature opened new ecological niches and survival strategies, representing a genuine advance in animal organisation over simpler, non-segmented invertebrates.

Answer: (B) Scientific names can embed historical and geographical information about discovery while serving classification

Explanation:
While Carolus Linnaeus's binomial system fundamentally provides a standardised, universal naming method, scientific names often contain embedded information. The species name 'sahyadrensis' honours the Sahyadri Hills where this frog was discovered, creating a connection between the organism's scientific identity and its habitat. This practice serves dual purposes: maintaining the systematic precision required for global scientific communication while incorporating meaningful context about the organism's origin and significance.

Answer: (B) Oxygen accumulation in the atmosphere made Earth suitable for diverse aerobic life forms

Explanation:
Cyanobacteria were among the first organisms capable of photosynthetic oxygen production. When oxygen accumulated in the atmosphere over millions of years, it transformed Earth's chemistry and enabled the evolution of aerobic organisms that require oxygen for respiration. This single microbial innovation fundamentally altered planetary conditions and made possible the tremendous diversity of complex life forms—plants, animals, and fungi—that depend on oxygen. The chapter emphasises this as evidence of how even microscopic organisms reshape global environments.

Answer: (B) They demonstrate an intermediate stage between invertebrates lacking notochords and vertebrates with vertebral columns

Explanation:
Protochordates occupy a crucial position in animal evolution. The notochord provides internal support without restricting movement, representing a structural innovation that enabled the vertebral column to evolve. By studying protochordates, scientists understand how simpler invertebrate body plans could have given rise to the first vertebrates. The chapter presents this as evidence of gradual evolutionary change, where new structures built on previous innovations rather than appearing suddenly. This demonstrates how classification systems reflect actual evolutionary history and relationships.