Chapter 7: Diversity in Living Organisms (Questions and Answer)

Questions and Answer 

1. Why do we classify organisms?
We classify organisms to organize the vast diversity of life into meaningful groups based on similarities and differences. This helps in:

• Studying organisms more efficiently instead of examining each one individually.
• Understanding evolutionary relationships between different species.
• Identifying and naming organisms systematically.

2. Give three examples of the range of variations that you see in life forms around you.

Example 1: Size Variation

• Microscopic bacteria are only a few micrometers in size.
• The blue whale, the largest animal, can grow up to 30 meters.
• Redwood trees can reach heights of about 100 meters.

Example 2: Lifespan Variation

• Mosquitoes live only for a few days.
• Humans have an average lifespan of about 70-80 years.
• Some pine trees can survive for thousands of years.

Example 3: Color and Appearance Variation

• Some worms are colorless or even transparent.
• Birds like parrots and peacocks have vibrant colors.
• Flowers come in a wide range of colors, from white to bright red, yellow, and blue.

Basis of Classification

1. Which 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.

Answer:
(b) The kind of cells they are made of is a more basic characteristic.

• The place where organisms live (habitat) is not reliable for classification because vastly different organisms can live in the same environment (e.g., corals, whales, and sharks all live in water but are very different).
• The type of cell (prokaryotic or eukaryotic) is more fundamental because it influences the structure, function, and complexity of an organism.

2. What is the primary characteristic on which the broad division of organisms is made?
Answer:

• The most fundamental characteristic for classifying organisms is the type of cell they have.
• Prokaryotic organisms (without a nucleus, like bacteria) are fundamentally different from eukaryotic organisms (with a nucleus, like plants and animals).
• This distinction affects cellular processes, organization, and the ability to form multicellular organisms.

3. On what bases are plants and animals put into different categories?
Answer:

• Plants and animals are classified separately based on mode of nutrition and body structure.
  • Plants are autotrophic (they make their own food through photosynthesis) and have cell walls.
  • Animals are heterotrophic (they consume food from external sources) and do not have cell walls.
• Additionally, plants have a simpler, less specialized body structure, while animals have specialized organs for movement, digestion, and other functions.

Classification and Evolution 

Answers

1. Which organisms are called primitive, and how are they different from the so-called advanced organisms?

Answer:

• Primitive organisms are those with ancient body designs that have remained unchanged over long periods of time.
• Advanced organisms have newer body designs that have undergone modifications and adaptations over time.
• Differences:
  • Primitive organisms usually have simpler structures (e.g., bacteria, algae).
  • Advanced organisms tend to have more specialized and complex body structures (e.g., mammals, flowering plants).

2. Will advanced organisms be the same as complex organisms? Why?

Answer:

• Not always. While most advanced organisms tend to be complex, some advanced organisms can still be simple if they have evolved in a way that does not require complexity.
• Reason:
• Evolution does not always lead to more complexity; sometimes, organisms evolve by simplifying their structures to adapt better (e.g., some parasites lose complex organs because they rely on a host).
• However, in most cases, newer organisms tend to have more specialized structures, making them both advanced and complex.

The Hierarchy of Classification

Answers

1. What is the criterion for classification of organisms as belonging to kingdom Monera or Protista?
Answer:

• The main criterion for classifying an organism into Monera or Protista is the cell structure:
  • Monera: Organisms are unicellular prokaryotes (no defined nucleus or membrane-bound organelles).
  • Protista: Organisms are unicellular eukaryotes (have a defined nucleus and membrane-bound organelles).

2. In which kingdom will you place an organism that is single-celled, eukaryotic, and photosynthetic?
Answer:

• An organism that is single-celled, eukaryotic, and photosynthetic would belong to the kingdom Protista. Many unicellular algae, which are eukaryotic and photosynthetic, are classified under this kingdom.

3. 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?
Answer:

• The grouping with the smallest number of organisms and maximum common characteristics is the species.
• The grouping with the largest number of organisms and least common characteristics is the kingdom.

Plantae 

1. Which division among plants has the simplest organisms?

   • Thallophyta (Algae) have the simplest organisms among plants. They lack well-differentiated structures and are predominantly aquatic.

2. How are pteridophytes different from the phanerogams?

   • Pteridophytes (ferns, horsetails, etc.) are cryptogams (plants with hidden reproductive organs), meaning their reproductive organs are inconspicuous. They reproduce via spores and do not produce seeds.
   • Phanerogams, on the other hand, are seed-producing plants with well-differentiated reproductive organs. They include gymnosperms (which produce naked seeds) and angiosperms (which produce seeds enclosed in fruits).

3. How do gymnosperms and angiosperms differ from each other?

• Gymnosperms produce naked seeds (seeds are not enclosed in fruits). Examples include pine and deodar.
• Angiosperms produce covered seeds, where the seeds are enclosed within a fruit formed from the ovary. They are also classified into monocots and dicots based on the number of cotyledons in their seeds. Examples include wheat (monocot) and pea (dicot).

Animalia 

Answers:

1. How do poriferan animals differ from coelenterate animals?

   • Poriferans (Sponges):
     • Have a simple body structure with pores (Ostia) for water circulation.
     • Lack true tissues, organs, and a body cavity.
     • Sessile (attached to surfaces) and mostly marine.
     • Example: Sponges (Sycon, Spongilla).
   • Coelenterates (Cnidarians):
     • Have a body cavity (gastrovascular cavity) for digestion.
     • Possess stinging cells (cnidocytes) for defense and capturing prey.
     • Can exist as free-swimming (Medusa) or attached (Polyp).
     • Example: Jellyfish, Hydra, Coral.

2. How do annelid animals differ from arthropods?

   • Annelida (Segmented Worms):
     • Bilaterally symmetrical, soft-bodied organisms with true segmentation.
     • Have a closed circulatory system.
     • Possess a true coelom (body cavity).
     • Example: Earthworm, Leech.
   • Arthropoda (Jointed-legged animals):
     • Have an exoskeleton made of chitin.
     • Open circulatory system with a hemocoel.
     • Body divided into head, thorax, and abdomen with jointed appendages.
     • Example: Insects (Butterfly, Cockroach), Crustaceans (Crabs, Prawns).

3. What are the differences between amphibians and reptiles?

   • Amphibians:
     • Can live both on land and in water.
     • Moist, glandular skin (no scales).
     • Lay eggs in water; larvae undergo metamorphosis (e.g., tadpoles).
     • Respiration through lungs, gills, and skin.
     • Example: Frog, Toad, Salamander.
   • Reptiles:
     • Completely terrestrial (though some live in water).
     • Dry, scaly skin to prevent water loss.
     • Lay eggs with tough shells on land.
     • Respiration only through lungs.
     • Example: Snake, Lizard, Crocodile.

4. What are the differences between animals belonging to the Aves group and those in the Mammalia group?

• Aves (Birds):
  • Body covered with feathers.
  • Forelimbs modified into wings for flight.
  • Lay eggs (oviparous).
  • Beak present, no teeth.
  • Example: Pigeon, Sparrow, Eagle.
• Mammalia (Mammals):
• Body covered with hair/fur.
• Give birth to live young (except monotremes like platypus, which lay eggs).
• Possess mammary glands to nourish young.
• Have external ears (pinna) and different types of teeth.
• Example: Human, Dog, Whale, Bat.

Exercises

1. What are the advantages of classifying organisms?

Ans: 

Classifying organisms provides several advantages:

• Simplifies Study: Organisms are grouped based on similarities, making them easier to study.
• Universal Identification: Scientific names ensure that organisms are identified globally without confusion.
• Understanding Evolutionary Relationships: Helps trace the evolutionary lineage and common ancestors of species.
• Predicting Characteristics: Organisms within a group share traits, allowing scientists to predict unknown characteristics.
• Ecosystem Conservation: Helps in biodiversity conservation by identifying endangered species and their ecological roles.

2. How would you choose between two characteristics to be used for developing a hierarchy in classification?

Ans: 

When choosing between two characteristics:

• Fundamental vs. Superficial: More basic structural and functional traits are preferred over external appearances.
• Evolutionary Significance: Traits that indicate evolutionary lineage are prioritized over temporary or adaptive traits.
• Broad vs. Specific Traits: Broader characteristics (e.g., presence of a backbone) help in higher-level classification, while finer details (e.g., fur type) help in subclassification.

3. Explain the basis for grouping organisms into five kingdoms.

Ans: 

The five-kingdom classification proposed by R.H. Whittaker is based on:

• Cell Type: Prokaryotic (Monera) or Eukaryotic (other kingdoms).
• Cell Structure: Presence or absence of a cell wall.
• Mode of Nutrition: Autotrophic (Plantae) vs. Heterotrophic (Animalia, Fungi).
• Body Organization: Unicellular (Monera, Protista) vs. Multicellular (Fungi, Plantae, Animalia).
• Reproduction: Asexual or sexual reproduction modes.

4. What are the major divisions in the Plantae? What is the basis for these divisions?

The major divisions in the Plantae kingdom are:

1. Thallophyta (Algae): Simple, body without roots, stems, or leaves.
2. Bryophyta (Mosses & Liverworts): Non-vascular plants, live in moist environments.
3. Pteridophyta (Ferns): First vascular plants, reproduce via spores.
4. Gymnosperms: Seed-producing plants with uncovered (naked) seeds.
5. Angiosperms: Flowering plants with seeds enclosed in fruit.

Basis of Division:

• Presence or absence of vascular tissue.
• Ability to produce seeds.
• Presence of flowers.

5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

Ans: 

• Plants: Classified based on structure, presence of vascular tissues, seeds, and flowers.
• Animals: Classified based on body symmetry, presence of a notochord, type of skeleton, and reproduction methods.

Plants are mainly classified by their reproductive structures and complexity, while animals are grouped based on body organization and evolutionary lineage.

6. Explain how animals in Vertebrata are classified into further subgroups.

Ans: Vertebrates are classified based on skeletal structure, mode of reproduction, and habitat adaptation into the following groups:

1. Cyclostomata: Jawless, eel-like, circular mouth, scaleless, slimy skin (e.g., Lampreys).
2. Pisces (Fishes): Aquatic, gills for respiration, exoskeleton of scales, cold-blooded.
3. Amphibia: Can live in water and on land, gills in larvae, lungs in adults (e.g., Frogs).
4. Reptilia: Dry scaly skin, lay eggs on land, cold-blooded (e.g., Snakes, Lizards).
5. Aves (Birds): Feathers, flight adaptation, lay eggs, warm-blooded (e.g., Eagles, Pigeons).
6. Mammalia: Body covered with hair, give birth to young ones, warm-blooded (e.g., Humans, Tigers).

Each group has unique characteristics that help them adapt to their environment effectively.