NCERT Class 9 Science Chapter 7 Diversity in Living Organisms

Chapter 7 Diversity in Living Organisms

Intext Questions
Question 1: Why do we classify organisms?
Answer: We classify organisms because it is easier and more convenient to study their characteristics. Similarities exhibited by various organisms allow us to categorise different entities into a class.

Question 2: Give three examples of the range of variations that you see in lifeforms around you.
Answer:
• small fish to big whale
• pine trees to insects
• colourless insects to brightly coloured flowers

Question 3: 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. Why?
Answer: The most basic classification of organisms is the kind of cells they are made up of because species with different characteristics can live in a particular habitat, whereas the organisms with similar cell arrangements will show same characteristics.

Question 4: What is the primary characteristic on which the broad division of organisms is made?
Answer: The primary characteristic on which the broad division of organisms is made are prokaryotes (made up of one cell) and eukaryotes (made up of more than one cell).

Question 5: On what bases are plants and animals put into different categories?
Answer: Plants are animals are put into different categories on the following bases:
• Presence or absence of a cell wall.
• The mode of nutrition.

Question 6: Which organisms are called primitive and how are they different from the so-called advanced organisms?
Answer: Primitive organisms are the organisms that exhibit a very simple and basic cell arrangement, mechanism and structure and no division of labour is observed whereas advanced organisms are organisms possessing many cells that are grouped into various tissues performing different functions.

Question 7: Will advanced organisms be the same as complex organisms? Why?
Answer: Yes, advanced organisms will be the same as complex organisms. The result of advancement shows the multiple cell arrangements that operate independently.

Question 8: What is the criterion for classification of organisms as belonging to kingdom Monera or Protista?
Answer:
• Monera: These organisms do not have a defined nucleus or organelles, nor show multi-cellular body designs. The mode of nutrition of organisms can be either autotrophic or heterotrophic. Example: bacteria, blue-green algae or cyanobacteria, and mycoplasma.
• Protista: This group consists of many kinds of unicellular eukaryotic organisms. These organisms have a defined nucleus. Some of these organisms use appendages for moving around. Their mode of nutrition can be autotrophic or heterotrophic. Example: unicellular algae, diatoms and protozoans.

Question 9: In which kingdom will you place an organism which is single celled, eukaryotic and photosynthetic?
Answer: In Protista, the organism is single-celled, eukaryotic and photosynthetic.

Question 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?
Answer: The organisms that belong to the Monera will have the smallest number of organisms and with maximum characteristics in common whereas the organisms that belong to the Animalia will have the largest number of organisms.

Question 11: Which division among plants has the simplest organisms?
Answer: Algae or Thallophyta has the simplest organism among plants.

Question 12: How are pteridophytes different from the phanerogams?
Answer:
• Pteridophytes
→ They have a naked embryo.
→ Exhibit unclear reproductive organ.
• Phanerogams
→ They have a covered embryo.
→ Exhibit well defined reproductive organ.

Question 13: How do gymnosperms and angiosperms differ from each other?
Answer: In gymnosperms, the seeds are naked, whereas in angiosperms, the seeds are covered.

Question 14: How do poriferan animals differ from coelenterate animals?
Answer:
• Porifera
→ Division of labour is not noticed.
→ The cellular level of the organisation exhibited.
→ Coelom absent.
→ Example: Spongilla, Sycon etc.
• Coelenterate
→ Division of labour is observed.
→ The tissue level of the organisation exhibited.
→ Coelom present.
→ Example: Hydra, Sea anemone etc.

Question 15: How do annelid animals differ from arthropods?
Answer:
• Annelida
→ The entire body is segmented into rings.
→ Skeleton is absent.
→ Hermaphrodites.
→ Example: Earthworm, Leech etc.
• Arthropoda
→ Segmentation of the body into the head, abdomen and the thorax region.
→ Presence of exoskeleton.
→ Presence of different sexes, bisexuals present.
→ Example: Prawn, Spider etc.

Question 16: What are the differences between amphibians and reptiles?
Answer:
• Amphibian
→ Skin is moist and soft.
→ When in water, they breathe through their skin.
→ Respire through lungs or gills.
→ Indirect development is noticed.
→ Example: Toad, Salamander etc.
• Reptiles
→ Skin is hardened.
→ They can exist in water. They come to land to intake oxygen.
→ Respire through lungs.
→ Direct development observed.
→ Example: Turtle, Snakes etc.

Question 17: What are the differences between animals belonging to the Aves group and those in the mammalia group?
Answer:
• Aves
→ Body is covered with feathers.
→ Teeth absent.
→ Possess a beak.
→ Forelimbs are present and modified to take a flight.
→ Bones are hollow and body is streamlined.
• Mammalia
→ Body is covered with hairs
→ Teeth present.
→ Do not possess a beak.
→ Forelimbs are present and used for multiple activities.
→ Bones are solid and body is not streamlined (except for whales).

Exercise Questions
Question 1: What are the advantages of classifying organisms?
Answer: Advantages of classifying organisms:
• Better categorization of living beings based on common characters.
• Easier study for scientific research.
• Better understanding of human relations and dependency on other organisms.
• It helps in-cross breeding and genetic engineering for commercial purposes.

Question 2: How would you choose between two characteristics to be used for developing a hierarchy in classification?
Answer: For classifying an organism in a hierarchy, the most fundamental and visible character is first taken into consideration. For example, plants differ from animals in chloroplast, locomotion, and cell wall. But, only locomotion is considered as the most basic characteristic of classification. After choosing the fundamental, basic characteristic one can further classify the organism on the basis of the first feature chosen.

Question 3: Explain the basis for grouping organisms into five kingdoms.
Answer: The basis of grouping organisms into five kingdoms was given by Whittaker. They are as follows:
• Whether the cell is prokaryotic or eukaryotic.
• Whether the cell is unicellular or multicellular.
• Whether the cell wall is present or absent.
• Whether the cell prepares its own food or obtains its food from outside.

Question 4: What are the major divisions in the Plantae? What is the basis for these divisions?
Answer: The kingdom Plantae is divided into five major divisions.
• Thallophyta or Algae: Like body.
• Bryophyta: The body is divided into leaf and stem.
• Pteridophyta: The body is separated into root, stem and leaf.
• Gymnosperm: Seed-bearing, naked seeds.
• Angiosperm: Seed bearings covered seeds.

Question 5: How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Answer: Classification of plant is different than the classification of animals. In plants, classification is based on the morphology of the plants (i.e., differentiated or undifferentiated plant body, with or without seeds, naked seeds or seeds inside fruits, etc.) whereas in animals, classification is mainly on the basis body design of an animal (i.e., presence or absence of a notochord).

Question 6: Explain how animals in Vertebrata are classified into further subgroups.
Answer: Vertebrates are classified further into 5 sub-groups on the basis of simple to complex forms of structures and their functions.
• Pisces: They are aquatic, cold blooded animals. Their heart has two chambers. Their body is covered by scales or plates. They lay eggs and perform respiration through gills. Their endoskeleton is made up of cartilage. Example: Fishes
• Amphibians: They are cold blooded animals and live in both water and land. Respiration is through gills, lungs, skin. They have three chambered heart. Example: Frogs
• Reptiles: They are cold blooded animals. They have three chambered heart and they breathe through lungs. Example: Snakes
• Aves: They are warm blooded animal, oviparous vertebrates covered with feathers. They have a four chambered heart and perform respiration by lungs. Example: Birds
• Mammals: They are warm blooded animal with four chambered heart. They are viviparous and possess characteristics like pinna and hair on skin and canine. Example: Humans.