Think It Over (Page No. 228)
1. What do you understand by biodiversity?
Answer: Biodiversity refers to the variety and variability of all living organisms on Earth. It includes diversity within species (genetic diversity), between species, and of ecosystems. For example, the wide range of plants, animals, fungi, and microorganisms living in different habitats — forests, oceans, deserts — all together represent biodiversity.
2. How does the grouping of organisms help us understand diversity?
Answer: Grouping or classification helps us organize the enormous variety of living organisms into manageable categories based on shared characteristics. This makes it easier to study, identify, and understand relationships between different organisms. Without classification, studying millions of species individually would be nearly impossible.
3. On what basis, are plants and animals classified?
Answer: Plants and animals are classified on the basis of: body structure and organization, presence or absence of a backbone, mode of nutrition, reproductive methods, cell structure (prokaryotic or eukaryotic), and evolutionary relationships.
4. How does classification help address problemsin farming?
Answer: Classification helps farmers identify: which plant varieties are high-yielding or disease-resistant, which organisms are pests or beneficial insects, which animals are suitable for domestication, and which species are closely related enough for hybridization to develop better crop varieties.
Pause and Ponder (Page No. 231)
1. If many organisms share common features, could they also share acommon ancestry?
Answer: Yes. If many organisms share common features, they can share a common ancestry.
When organisms have similar body structures, characteristics, and ways of life, it suggests that they may have evolved from the same ancestor in the past. Over many generations, small changes (variations) accumulate, and new types of organisms arise, but they still retain some basic similarities with their ancestors.
Thus, similarities among organisms are evidence that they are related through evolution and have originated from a common ancestral form.
Pause and Ponder (Page No. 236)
2. How can a single-celled organism carry out all its life processes when billions of cells are required to perform similar functions in multicellular organisms like us?
Answer: A single-celled organism can carry out all its life processes because one cell itself performs all the necessary functions such as nutrition, respiration, excretion, growth and reproduction.
In unicellular organisms, the single cell is fully capable and specialized to do every life activity within it. The cell membrane allows exchange of materials, and the cytoplasm and organelles perform different functions needed for survival.
In multicellular organisms like humans, different groups of cells are specialized to perform different functions. That is why billions of cells are required to do the work that a single cell can do in a unicellular organism.
Pause and Ponder (Page No. 238)
3. Which plant features reduce their dependence on water but still require moist conditions?
Answer: Plants like mosses and ferns have features such as cuticle, stomata, and simple vascular tissues that reduce water loss and make them less dependent on water than algae. However, they still require moist conditions for reproduction because their male gametes need water to reach the female gametes.
4. Why do taller plants need specialisedtransport tissues?
Answer: Taller plants need specialised transport tissues because water and food have to be carried to long distances from roots to leaves and from leaves to other parts. Special tissues like xylem (for water) and phloem (for food) help in efficient transport throughout the plant body.
5. How do seeds and fruits affect, where and how plants can survive?
Answer: Seeds and fruits help plants to spread to new places through dispersal by wind, water, and animals. Seeds have a protective covering and stored food, which allows them to survive harsh conditions and germinate when conditions become favourable. This helps plants survive in different environments and locations.
Pause and Ponder (Page No. 242)
6. An earthworm (annelida) and a beetle (arthropoda), both have segmented bodies but the beetle has a hard external skeleton. How does the beetle’s external skeleton help it survive?
Answer: The beetle, which belongs to Arthropoda, has a hard external skeleton called an exoskeleton.
This exoskeleton helps the beetle to:
- Protect its soft body from injury and predators.
- Prevent water loss, which allows it to live in dry environments.
- Provide support and shape to the body.
- Help in movement by providing attachment for muscles.
Thus, the hard external skeleton gives the beetle better protection and adaptability compared to the earthworm.
Pause and Ponder (Page No. 247)
7. Does the term ‘biodiversity’ relate only to the variety of organisms, or does it encompass other elements?
Answer: Biodiversity does not refer only to the variety of organisms. It also includes the genetic differences among organisms and the variety of ecosystems in which they live. Thus, biodiversity includes organisms, their genes, and their environment.
8. If you find a new organism in a pond, what features will you observe to classify it and why?
Answer: To classify a new organism, we would observe:
- Its body structure (unicellular or multicellular)
- Mode of nutrition (autotrophic or heterotrophic)
- Presence of cell wall, chlorophyll, or organs
- Movement and reproduction methods
These features help in placing the organism into the correct group based on similarities and differences.
9. Why do genetic studies provide deep information about living beings?
Answer: Genetic studies reveal the DNA and hereditary information of organisms. They help us understand how organisms are related to each other, their evolution, and the transfer of characteristics from parents to offspring.
10. How can changes in climate affect the biodiversity?
Answer: Changes in climate can alter habitats and living conditions. Some organisms may fail to adapt and may die or migrate, which reduces biodiversity. Climate change can disturb ecosystems and affect the balance among living organisms.
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