Class 11 Biology Chapter 1 The Living World

Key Concept: Evolutionary Relationships, Taxonomic Category Challenges

c) Panthera leo and Panthera tigris

[Solution Description] To determine which organisms are more closely related, we need to compare their position within the taxonomic hierarchy and acknowledge the challenges of classifying at higher levels, where shared characteristics decrease. Panthera leo (lion) and Panthera tigris (tiger) belong to the same genus, indicating a closer relationship than organisms in different genera or families. The challenge arises in distinguishing species when evolutionary history is complex.

Key Concept: Class and Order

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description] The assertion states that a key characteristic of class Mammalia is the presence of mammary glands, which is true as it defines mammals. In the reason, it mentions that a class comprises one or more orders with shared attributes. This statement is also true but does not directly explain why mammary glands are a defining feature of Mammalia. Therefore, both statements are true, but the reason doesn’t directly justify the assertion’s specific point about mammary glands.

Key Concept: Real-world Application, Classification Challenges

c) It enables more precise identification of keystone species crucial for ecosystem balance.

[Solution Description] Taxonomic classification provides a structured framework for identifying species based on their relationships and characteristics. This helps in understanding which species are endangered or require protection. By classifying organisms accurately, conservationists can prioritize efforts to protect biodiversity hotspots and ensure genetic diversity is maintained. Additionally, it helps in monitoring ecosystem changes over time and evaluating the success of conservation strategies.

Key Concept: Class to Phylum

d) Amphibia – Chordata

[Solution Description] The classification of classes into their respective phyla requires understanding the defining characteristics of each phylum. For example, class Mammalia belongs to the phylum Chordata because mammals have a notochord at some stage in their development.

Key Concept: Common Features

c) Mammary glands

[Solution Description] All members of the class Mammalia possess mammary glands, which are used to nourish their young. This is a key characteristic of mammals.

Key Concept: Genus Characteristics

a) Retractable claws and ability to roar

[Solution Description] The genus Panthera includes large cats such as lions, tigers, leopards, and jaguars. These animals share characteristics like retractable claws, the ability to roar due to a specific larynx structure, and being carnivorous predators. The presence of a mane is not universal among them, although it is found in male lions.

Key Concept: Taxonomic Hierarchy Application

c) Arthropoda

[Solution Description] The classes Insecta and Arachnida are part of the phylum Arthropoda. Both these classes include organisms with jointed legs and an exoskeleton, which are defining characteristics of arthropods.

Key Concept: Species and Genus Relation

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description] Both the assertion and reason are true statements. The genus Panthera does include species like Panthera leo (lion) and Panthera pardus (leopard), indicating that these species share certain close similarities, justifying their placement within the same genus. Furthermore, the statement in the reason correctly defines the purpose of a genus by explaining that it groups species with shared traits. Thus, the reason provides a valid explanation for the assertion.

Key Concept: Taxonomic Hierarchy Application, Classification Complexity

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description] To determine correctness, let’s analyze both statements: – Assertion (A) claims that taxonomic studies simplify classification through unique characteristics at each hierarchical level. This statement is true as taxonomic studies involve systematic categorization based on distinct traits found at different levels, which aid in organizing biodiversity.

– Reason (R) suggests that moving up the taxonomic hierarchy from species to kingdom makes classification increasingly complex because shared characteristics decrease. This statement is also true; higher categories like kingdom encompass a broad diversity of organisms with fewer shared traits, thus making classification challenging.

Now consider if (R) correctly explains (A): While both statements are individually true, (R) does not directly explain (A). The complexity mentioned in (R) relates to understanding and systematizing broad categories, whereas (A) refers to simplification achieved through distinct traits at given taxonomic levels. Thus, while both statements are factual, the reason doesn’t justify the assertion.

Key Concept: Advanced Classification, Evolutionary Relationships

c) They belong to the same class

[Solution Description] Humans and dolphins both belong to the class Mammalia as they are warm-blooded vertebrates with the presence of mammary glands in females. However, they belong to different orders; humans are part of Primata and dolphins belong to Cetacea. Understanding this classification helps in recognizing shared characteristics like live birth and lactation while acknowledging their divergent evolutionary paths.

Key Concept: Language of Names

c) Latin

[Solution Description] Scientific names are typically in Latin because it is a “dead” language that does not change over time, providing consistency.

Key Concept: Philosophical Implications, Complex Classification

c) Does an organism’s classification affect its perceived value to humans?

[Solution Description] The philosophical exploration of what defines life often leads to questions about how and why organisms are classified in specific ways. This involves reflecting on the essence of living systems beyond mere biological criteria, questioning if our classifications reflect nature’s true order or human-imposed structures.

Key Concept: Order Identification

b) Carnivora

[Solution Description] Both the families Canidae, which includes dogs, and Ursidae, which includes bears, are part of the order Carnivora. This order consists of mammals that predominantly have a diet consisting of meat.

Key Concept: Taxonomic Hierarchy Application, Species

d) Species

[Solution Description] “Canis lupus familiaris” refers to the domestic dog, where “Canis” is the genus, “lupus” represents the species, and “familiaris” indicates the subspecies. At the species level, “Canis lupus” groups organisms that share key morphological and genetic similarities, distinguishing them from other species. Understanding these distinctions helps scientists identify evolutionary relationships and ecological niches within ecosystems. Therefore, the species level serves as a crucial point in the taxonomic hierarchy for recognizing unique biological characteristics and fostering biodiversity research.

Key Concept: Basic Concept

c) It considers evolutionary relationships between organisms.

[Solution Description] Systematic study involves the systematic arrangement of organisms based on evolutionary relationships.

Key Concept: International Codes

c) ICZN

[Solution Description] The International Code of Zoological Nomenclature (ICZN) is responsible for ensuring that animal names are given according to standard rules. Thus, option c) ICZN is correct.

Key Concept: Comparative Analysis

b) Families have more similarities than orders

[Solution Description] Orders include fewer similarities than genera within a family because orders encompass multiple families, which have broader characteristics compared to the more specific attributes shared within a genus.

Key Concept: Hierarchical Complexity

c) The number of shared characteristics decreases.

[Solution Description] When moving from the species level to higher taxonomic categories like kingdoms, the specificity decreases, leading to fewer shared characteristics. Species within the same genus have many shared traits, but as we move up to family, order, class, phylum, and then kingdom, the shared characteristics decrease because the groups become more inclusive.

Key Concept: Class and Order Relationship

c) Diptera

[Solution Description] In the taxonomic hierarchy, an order of insects such as Diptera does not belong under the class Mammalia. Orders in the class Mammalia include Carnivora, Primata, and Cetacea.

Key Concept: Complex Hierarchical Analysis, Philosophical Implications

a) The existence of hybrid species questions the rigidity of species definition.

[Solution Description] The philosophical implication of taxonomy not providing a clear boundary for what defines a species arises due to overlapping characteristics and hybridization events. This makes it difficult to fit all organisms neatly into distinct categories, challenging traditional concepts of species delineation.

Key Concept: Taxonomic Challenges, Evolutionary Relationships

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description] The assertion and reason delve into the complexity of classification at different levels in the taxonomic hierarchy. At the kingdom level, distinguishing features are broad and less specific, making it challenging to precisely classify organisms as they share fewer traits. In contrast, species classification uses detailed morphological differences which are more evident, helping in easier differentiation among closely related organisms. Both the assertion and reason statements are true; however, the reason explains why species classification is clearer, not directly explaining the complexity at the kingdom level.

Key Concept: Scientific Name Format

b) Genus

[Solution Description] In the binomial nomenclature system, the first part of the scientific name represents the genus. Therefore, in Mangifera indica, “Mangifera” is the genus.

Key Concept: Naming Rules

c) Canis lupus

[Solution Description] In scientific naming, the genus starts with a capital letter and the specific epithet starts with a small letter. Both are italicized or underlined if handwritten.

Key Concept: Classification Complexity

a) More organisms are included and fewer characteristics are shared

[Solution Description] As one moves from species to kingdom, the classification becomes more complex because more and varied organisms are included at each higher taxonomic level. Consequently, there are fewer shared characteristics among the organisms as they are grouped into broader categories.

Key Concept: Complex Hierarchy, Evolutionary Relationships

b) Convergent evolution leading to diversity.

[Solution Description] When organisms within the same class exhibit significant variation in an evolutionary trait, several explanations are possible. One likely explanation is convergent evolution, where unrelated species develop similar traits due to adapting to comparable environments or ecological niches. This means that despite being in the same class, they might have undergone separate evolutionary paths, leading to noticeable differences in certain traits even though they share some core similarities at a higher taxonomic level.

Key Concept: Basic Definition

d) Biology

[Solution Description] The science that studies life forms and their life processes is known as biology.

Key Concept: Conservation and Biodiversity, Application of Taxonomy

b) By identifying and classifying endangered and endemic species

[Solution Description] Effective conservation strategies require precise identification of species that are endangered or vulnerable within biodiversity hotspots. Taxonomy allows for accurate classification and identification of these species, enabling targeted conservation efforts. By understanding the taxonomic relationships, conservationists can prioritize species based on their evolutionary significance and ecological roles.

Key Concept: Basic Definition

c) Science of classification

[Solution Description] Taxonomy is the science of classification, involving identification, nomenclature, and classification of organisms.

Key Concept: Genus Classification

b) Solanum

[Solution Description] Potato belongs to the genus Solanum. This is a classification based on shared characteristics within this genus.

Key Concept: Binomial Nomenclature

b) The specific epithet

[Solution Description] In binomial nomenclature, the first part represents the genus and the second part is the specific epithet. Thus, ‘indica’ refers to the specific epithet.

Key Concept: Author Identification

d) Carl Linnaeus

[Solution Description] The species name “Rosa canina” follows the binomial nomenclature system. The abbreviation “L.” after the specific epithet indicates that the species was first described by Carl Linnaeus, whose botanical author abbreviation is “L.”

Key Concept: Classification Criteria

a) Genetic makeup

[Solution Description] In modern taxonomy, genetic information and evolutionary relationships are crucial criteria. However, among the given options regarding structure, external structure is not a primary focus compared to genetic information and internal structure.

Key Concept: Complex Hierarchical Relationships, Taxonomic Category Comparison

d) Kingdom, Phylum, Class, Order, Family, Genus, Species

[Solution Description] The correct hierarchy in descending order is: Kingdom > Phylum/Division > Class > Order > Family > Genus > Species. This follows the principle of decreasing number of common characteristics as one moves from higher to lower categories.

Key Concept: Phylum Characteristics, Hierarchical Analysis

c) Notochord

[Solution Description] All members of the phylum Chordata possess a notochord at some stage of their development. The notochord is a flexible rod that provides support. Vertebrates are a sub-group of Chordata, and while most vertebrates replace the notochord with a spinal column during development, the presence of a notochord remains a defining characteristic of the phylum Chordata.

Key Concept: Conservation Movements, Real-world Application

b) By fostering awareness of species extinction and habitat destruction

[Solution Description] Early taxonomic studies laid the groundwork for identifying and cataloging species. This systematic classification helped highlight the diversity of life and the need for maintaining ecological balance, leading to modern conservation movements focused on protecting endangered species and habitats.

Key Concept: Characteristic Features

b) Floral characters

[Solution Description] The family Solanaceae, part of the order Polymoniales, is distinguished by its unique floral characters among other features. This characteristic helps differentiate members of this family from others within the same order, such as Convolvulaceae, also part of Polymoniales.

Key Concept: Language of Names

d) Latin

[Solution Description] Scientific names are typically written in Latin. This is because Latin was the universal language of science during the time when many of these naming conventions were developed.

Key Concept: Classification Criteria

b) Morphological similarities

[Solution Description] Species are grouped into a genus based on more common characters than they share with other species of different genera, primarily focusing on morphological similarities and differences.

Key Concept: Genus Differentiation

c) Panthera

[Solution Description] The genus that includes both lions and tigers is characterized by large cats. Lions belong to the species Panthera leo, while tigers are Panthera tigris. Both of these species belong to the same genus.

Key Concept: Basic Nomenclature

b) Nomenclature

[Solution Description] The process of providing standardized names to living organisms, ensuring each organism has a unique and universally accepted name, is called nomenclature.

Key Concept: Family Hierarchy Understanding

c) Above genus, below order

[Solution Description] In the classification system, ‘family’ ranks above the genus level and below the order level. It groups together related genera based on shared characteristics. Therefore, it is positioned above genus but below order.

Key Concept: Kingdom Classification

b) Penicillium

[Solution Description] The kingdom Fungi consists of heterotrophic organisms that absorb nutrients from organic material. Yeasts, molds, and mushrooms are typical fungi. Based on this understanding, among the options given, Penicillium is a well-known genus of fungi.

Key Concept: Contribution of Linnaeus

b) Binomial nomenclature

[Solution Description] Carolus Linnaeus is renowned for introducing the system of binomial nomenclature, which standardizes the naming of living organisms using two terms – the genus and the specific epithet.

Key Concept: Taxonomic Category Challenges, Evolutionary Relationships

d) Fewer common characteristics at higher levels make relationships less clear.

[Solution Description] At the phylum level, organisms are grouped based on a few broad characteristics that can encompass a wide range of diversity. This makes it difficult to directly observe and quantify traits as compared to species level which has more distinct and specific similarities.

Key Concept: Order Features

d) Carnivorous diet

[Solution Description] The order Carnivora is defined by the presence of adaptations suitable for a carnivorous diet, such as specialized teeth for tearing meat. This is a defining trait of both the order and its member families, including Felidae.

Key Concept: Taxonomic Complexity, Systematics

d) Fewer shared characteristics make comparisons difficult.

[Solution Description] The complexity increases at higher taxonomic levels because there are fewer characteristics shared among organisms. At these levels, broader similarities must be evaluated across diverse groups, making it harder to establish definitive relationships compared to the more narrowly defined lower categories like genus or species.

Key Concept: Order Composition

c) Convolvulaceae and Solanaceae

[Solution Description] The order Polymoniales includes plant families that share similar floral characteristics. According to the information provided, Convolvulaceae and Solanaceae belong to this order due to their floral attributes.

Key Concept: Taxonomic Hierarchy

d) Species, Genus, Family, Order, Class, Phylum, Kingdom

[Solution Description] The correct sequence in the taxonomic hierarchy from lowest to highest is species, genus, family, order, class, phylum/division, kingdom. This organizes living things in increasing levels of inclusivity.

Key Concept: Comparative Analysis, Evolutionary Relationships

c) Kingdom level covers a wider range of organism types

[Solution Description] In the taxonomic hierarchy, the kingdom level encompasses a broader range of diversity compared to the family level. A kingdom includes various phyla that house numerous classes and orders, representing a wide array of organisms with diverse characteristics. On the contrary, a family groups more closely related genera and species, indicating lower diversity but higher similarity within its members in terms of structure and function.

Key Concept: Family Characteristics

c) Floral structure

[Solution Description] The classification of families within the order Solanaceae is generally based on floral structure, since it includes genera like Solanum and Petunia which have unique flower patterns.

Key Concept: Writing Rules

b) Genus capitalized, species lowercase

[Solution Description] According to the Linnaean system of binomial nomenclature, the genus name is always capitalized, and the species name is written in lowercase. Both are italicized or underlined if handwritten.

Key Concept: Family Differentiation

c) Muscidae

[Solution Description] The order Carnivora includes families like Felidae (cats) and Canidae (dogs). Muscidae is a family of flies, which are not carnivores, thus not part of Carnivora. Hominidae is the human family under Primates, also not in Carnivora.

Key Concept: Comparative Analysis

b) Tiger and Leopard

[Solution Description] The genus is a taxonomic category that includes species with common characteristics. For this question, both the lion and tiger belong to the genus Panthera, which is characterized by large cats capable of roaring.