1. Why do we classify organisms?
Ans: We classify organisms to make it easier and more convenient to study their characteristics. By grouping organisms based on similarities in their physical traits, behaviors, and genetic makeup, we can categorize them into specific classes, families, or species. This classification helps scientists understand relationships between different organisms, organize biological knowledge, and study groups of organisms in a more systematic and efficient way.
2. Give three examples of the range of variations that you see in life forms around you.
Ans: Here are three examples of the range of variations observed in life forms:
(a) Small frog to big whale – Differences in size and body structure between a small frog and a large whale.
(b) Creeper to the eucalyptus tree – Variations in plant types, from low-growing creepers to tall eucalyptus trees.
(c) Black cuckoo to colourful peacock – Variations in bird species, from the more subdued black cuckoo to the brightly coloured peacock.
3. Which of the following do you think is a more basic characteristic for classifying organisms?
(a) The place where they live.
(b) The kind of cells they are made of. Why?
Ans: The more basic characteristic for classifying organisms is (b) The kind of cells they are made of. This is because the type of cells (prokaryotic or eukaryotic) determines fundamental biological characteristics, such as structure, function, and reproduction. While habitat (where they live) can vary greatly, organisms with similar cellular structures will exhibit more fundamental similarities in their biology, making the type of cells a more foundational basis for classification.
4. What is the primary characteristic on which the broad division of organisms is made?
Ans:The primary characteristic on which organisms are broadly divided is the nature of cells. Organisms are classified into two main groups based on this characteristic: prokaryotic cells (lacking a nucleus) and eukaryotic cells (containing a nucleus). This division further leads to the classification of organisms into various subclasses.
5. On what basis are plants and animals put into different categories?
Ans: Plants and animals are classified into different categories based on the following criteria:
(a) Presence or absence of a cell wall: Plants have a cell wall, which provides structure and protection, whereas animals lack a cell wall.
(b) Mode of nutrition: Plants are autotrophic, meaning they produce their own food through photosynthesis, while animals are heterotrophic, meaning they rely on consuming other organisms for nutrition.
6. Which organisms are called primitive, and how are they different from the so-called advanced organisms?
Ans: Primitive organisms are those that have simple, basic cell structures and mechanisms, with no division of labor among cells. These organisms typically consist of a single cell or few cells performing all functions. Examples include bacteria and algae.
Advanced organisms, on the other hand, have a more complex structure with many specialized cells that are organized into tissues, organs, and systems, each performing specific functions. These organisms exhibit a higher degree of organization and complexity, such as mammals, birds, and plants.
7. Will advanced organisms be the same as complex organisms? Why?
Ans: Yes, advanced organisms are the same as complex organisms. Advancement in evolution leads to the development of multiple specialized cells that perform unique and specific functions, resulting in complexity.
8. What is the criterion for the classification of organisms as belonging to the kingdom Monera or Protista?
Ans: The primary criterion for classification is the presence or absence of a nuclear membrane. Organisms without a nuclear membrane belong to the kingdom Monera, whereas organisms with a well-defined nucleus belong to the kingdom Protista.
9. In which kingdom will you place an organism which is single-celled, eukaryotic, and photosynthetic?
Ans: A single-celled, eukaryotic, and photosynthetic organism will be placed in the kingdom Protista, as it has a well-defined nucleus and photosynthetic ability.
10. In the hierarchy of classification, which grouping will have the smallest number of organisms with maximum common characteristics and which will have the largest number of organisms?
Ans: (a) The grouping with the smallest number of organisms and maximum common characteristics is species.
(b) The grouping with the largest number of organisms is kingdom.
11. Which division among plants has the simplest organisms?
Ans: The division Thallophyta (or Algae) has the simplest organisms among plants.
12. How are pteridophytes different from phanerogams?
Ans: The following are the differences between pteridophytes and phanerogams:
13. How do gymnosperms and angiosperms differ from each other?
Ans: Gymnosperms have naked seeds that are not enclosed within a fruit, whereas angiosperms have covered seeds that are enclosed within a fruit.
14. How do poriferan animals differ from coelenterate animals?
Ans: Listed below are the differences between poriferan and coelenterate animals:
15. How do annelid animals differ from arthropods?
Ans: Listed below are the differences between annelid and arthropods:
16. What are the differences between amphibians and reptiles?
Ans: The differences between amphibians and reptiles are as follows:
Table
Q17. What are the differences between animals belonging to the Aves group and those in the mammalian group?
Ans: Listed below are the differences between animals belonging to the Aves group and the mammalian group:
Table
18. What are the advantages of classifying organisms?
Ans: The classification of organisms offers the following advantages:
It simplifies the study of organisms by grouping them based on common features.
It helps in understanding the interrelationship and dependence of humans with other living entities.
Scientific experiments and studies become more organized and systematic.
It facilitates the crossbreeding and genetic modification of organisms, leading to various commercial applications.
19. How would you choose between two characteristics to be used for developing a hierarchy in classification?
Ans: To develop a classification hierarchy:
Gross characteristics (broad, general features) are considered first to form the foundation of the hierarchy.
Fine characteristics (specific, detailed traits) are used for further levels of classification.
For example:
Humans are classified as vertebrates due to the presence of a vertebral column.
Within vertebrates, tetrapods are distinguished based on the presence of four limbs.
Mammals within tetrapods are identified by the presence of mammary glands.
20. Explain the basis for grouping organisms into five kingdoms.
Ans: The five-kingdom classification is based on the following criteria:
Number of cells: Whether the organism is unicellular or multicellular.
Cellular structure: The arrangement and number of cell layers present.
Cell wall presence: Whether the organism has a cell wall or not.
Mode of nutrition: Autotrophic (self-feeding) or heterotrophic (feeding on others).
Level of organisation: The complexity of the organism, ranging from simple cellular to complex tissue-level organization.
21. What are the major divisions in the Plantae? What is the basis of these divisions?
Ans: The following table depicts plant division and the basis of classification for each division.
table
22. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Ans: In plants, the criteria for classification are primarily based on morphological characteristics, such as:Basic cell structure: Thallophytes and Bryophytes differ in body structure.
Seed visibility: Gymnosperms and Angiosperms are classified based on the presence of naked or enclosed seeds.
In animals, classification considers more detailed features such as:Cytology: The study of cell layers and internal structures.
Morphology: Structural variations in body systems.
Presence or absence of specific features: For example, the existence of a backbone.
Thus, while plant classification relies on broad external structures, animal classification focuses on detailed internal features.
23. Explain how animals in Vertebrata are classified into further subgroups.
Ans: Vertebrata is divided into two main subclasses:
Pisces:
Streamlined body, tail, and fins for swimming.
Adapted for living in water.
Tetrapoda:
Have four limbs for movement.
Further divided into:Amphibia:Can live on land and in water.
Have specialised organs for breathing underwater.
Reptilia:Crawl with the help of their body.
Thick skin helps them withstand extreme temperatures.
Aves:Modified forelimbs for flight.
Body covered with feathers, beak present, and teeth absent.Mammalia:Have mammary glands for nurturing offspring.
Body covered with hair, most are viviparous (give birth to live young).
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