NCERT solutions for class 9 science
Chapter – 7
Diversity In Living Organisms
There are a variety of organisms that occurs on earth from giant organisms like the blue whale and redwood tree to microscopic bacteria of few micrometres. These organisms are classified into groups on the basis of similarities in characteristics to make study easy and more convenient.
7.1-What is the basis of classification?
•A/c to Aristotle- classification according to whether they live on land or in water or in the air. This classification was misleading
• Some basic characteristics of classification-
1- Nucleus
2- Body design
3- Production of food
4- Process of photosynthesis
5- Level of organisation of their body
7.2-Classification and evaluation-
Living organisms are categorised on the basis of the body design in a form and function. Features of living organisms changes with the evolution of time.
Charles Darwin was first to describe the idea of evolution in 1859 in his book,” The origin of species.”
7.3-The Hierarchy of classification groups-
• Biologists such as Ernst Haeckel, Robert Whittaker and Carl Woese has tried to classify the living organisms into categories which are kingdoms.
• Whittaker classified organisms into five kingdoms which are as follows:
7.3.1- Protista– It includes Unicellular eukaryotic organisms such as hair-like cilia or whip-like flagella for moving around.
They can be autotrophic or heterotrophic
7.3.2-Monera- Organism does not have a definite nucleus and neither they have a multicellular body design.
Mode of nutrition can be either autotrophic or heterotrophic.
7.3.3-Fungi– these are heterotrophic Eukaryotic organisms. Some of them use decaying organic material as food and are therefore called saprotrophs.
Example -yeast, mold
7.3.4-Plantae-Autotrophs and are multicellular eukaryotes with cell walls.
7.3.5-Animalia-Heterotrophs and are multicellular eukaryotes without cell walls.
7.4-Plantae-
7.4.1-THALLOPHYTA-
• Do not have a well-defined body.
• The plants in this group are called algae.
•Example-Ulva
7.4.2-BRYOPHYTA
• Amphibians of the plant kingdom.
• Leaf-like structures and have no specialist tissues for the conduction of water and food from one part of your body to the other part of the body.
•Example-Riccia.
7.4.3-PTERIDO7PHYTA
• The plant body is differentiated into roots, stem, and leaves and has special tissues used for the conduction of water and other substances from one part to the other part of the plant.
•Seeds are results of the reproduction process.
•It consists of an embryo along with stored food.
•Example-Fern
7.4.4-GYMNOSPERMS
• Bare naked seeds.
•Usually are evergreen and woody.
•Example-Pines.
7.4.5-ANGIOSPERMS
• These are also called flowering plants
• The seeds develop inside an ovary which later modified as a fruit.
• Angiosperms are divided into two groups on the basis of the number of cotyledons present in the seeds-
1- monocotyledons or monocots=Having single cotyledons
2- Dicots- Having two cotyledons.
7.5 Animalia-
An organism which are multicellular and heterotrophic.
They are classified into the following types:
7.5.1- Porifera-
•Non motile animals attached to some solid support.
•Holes in the whole body.
•These animals are covered with a hard outside layer.
•Example –Sycon,Spongilla
7.5.2-COELENTERATA-
• Cavity in the body.
•Body is made up of two layers of cells-One makes cell on the outside of the body and the other make the inner lining of the body.
•Example – Hydra
7.5.3-PLATYHELMINTHES-
•Bilateral symmetry.
• Three layers of the cell.
• The body is flattened that is why these animals are called flatworms.
• There are either free-living or parasites.
•Example –Planarians,Liver flukes
7.5.4-NEMATODES-
•` Bilateral symmetry and triploblastic.
•Body is cylindrical in a shape.
•Example – Ascaris
7.5.5-ANNELIDA-
• Bilateral symmetry and Triploblastic and have a true body cavity.
• Differentiation occurs in a segmental fashion with the segments lined up one after the other from head to tail.
•Example – Earthworm
7.5.6-ARTHROPODA-
• Bilateral symmetry and segmented.
• Open circulatory system and the blood does not flow in a very well defined blood vessels.
•They have jointed legs.
•Example –Butterflies, House flies
7.5.7-MOLLUSCA-
•Bilateral symmetry.
• Little segmentation.
• Open circulatory system and kidney like an organ for excretion.
•They uses food for moving.
•Example – Snails, Octopus.
7.5.8-ECHINODERMATA-
• Finest skinned organism free-living Marine animals.
• Triploblastic and have a coelomic cavity.
•Hard calcium carbonate structures that they use as a skeleton.
•Example –Antedon
7.5.9-PROTOCHORDATA-
•Bilateral symmetrical
•Triploblastic and have a coelom.
•The notochord is a long rod-like support structure that runs along the back of the animal separates nervous tissue from the gut.
•Example –Herdmania.
7.5.10-Vertebrata-
These animals have a true vertebral columns and internal skeleton.
-Bilateral symmetrical.
-Have notochord.
-Triploblastic.
-Have six classes which are as follow:
7.5.10 (i) Cyclostomata-
•Jawless vertebrates.
•Elongated eel-like body, circular mouth, slimy skin.
•Example –Petromyzon.
7.5.10(ii)PISCES-
•These are aquatic animals.
•Skin covered with scales
•Respiration through gills and have a streamlined body.
•Cold blooded and two heart chambers.
•Example –Angler fish,lionfish
7.5.10(iii)AMPHIBIA-
•Lack of scales and mucus glands in the skin.
•Three heart chambers.
•Respiration through gills or lungs.
•Example –Frogs, Toads
7.5 .10(iv)REPTILIA-
• Cold-blooded and breathe through lungs.
•Three chambered heart except for crocodile which has four heart chambers.
•Eg-Turtle, king cobra
7.5.10(v)AVES-
•Warm blooded animals and have a four-chambered heart and lay eggs.
•Outside covering of feathers and two forelimbs for flight.
•Breathe through lungs.
•Example –White stork, Ostrich.
7.5.10 (vi)-Mammalia-
• Warm-blooded animals with four-chambered hearts.
•Have mammary glands for production of milk
•Skin has hairs as well as sweat and oil glands.
•Example – Platypus ,Echidna,Cat,Human.
7.6 Nomenclature-
•Introduced by-Carolus Linnaeus in the 18th century.
•We should take care of certain points while writing the scientific names :
1- The name of the genus begins with a capital letter.
2- The name of the species begins with the small letter.
NCERT Solutions
Page 80
Q1. Why do we classify organisms?
Answer:
We classify organisms so that study of their characteristics become easy and convenient.
Q2. Give three examples of the range of variations that you see in life-forms around you.
Answer:
1-Whale to small bacteria.
2-Transparent warms to bright flowers.
3-Pine trees to insects.
Page 82
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. Why?
Answer: The most basic classification of organisms according to kind of cells they are made up of. This is
because it has more accuracy and least complexity..
2-What is the primary characteristic on which the broad division of organisms is made?
Answer:The primary characteristic on which organisms are primarily divided is the nature of cells I.e. prokaryotic cells or eukaryotic cells..
3- On what basis are plants and animals put into different categories?
Answer: The following is the basis for categorization of plants and animals:
1- Nucleus
2- Body design
3- Production of food
4- Process of photosynthesis
5- Level of organisation of their body
Page 83
1- Which organisms are called primitive and how are they different from the so-called advanced organisms?
Answer: Primitive organisms have simple cell arrangements.These are different from advanced
organisms on the basis of division of cell. As primitive organisms has no division of cells.
2-Will advanced organisms be the same as complex organisms? Why?
Answer: Yes because they have similar complex cell arrangement.
Page 85
1-What is the criterion for classification of organisms as belonging to kingdom Monera or Protista?
Answer:
Monera- organism should not have definite nucleus and neither they have multicellular body
design .
Mode of nutrition should can be either autotrophic or heterotrophic.
Protista-it include Unicellular eukaryotic organisms such as hair- like cilia or whip -like flagella
for moving around .
They should be autotrophic or heterotrophic.
2- In which kingdom will you place an organism which is single-celled, eukaryotic and photosynthetic?
Answer:
Protista 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:
Kingdom Monera will have the smallest number of organisms and Kingdom Animalia will have the largest number of organisms.
Page 88
1- Which division among plants has the simplest organisms?
Answer:
Thallophyta has the simplest organisms .
2. How are pteridophytes different from the phanerogams?
Answer:
•Pteridophytes possess a naked embryo while phanerogams possess a covered embryo.
•Unclear reproductive organ in pteridophytes while well defined reproductive organ in
phanerogams
3. How do gymnosperms and angiosperms differ from each other?
Aswer:
Gymnosperms have naked seeds while in angiosperms have covered seeds.
Page 94
1. How do poriferan animals differ from coelenterate animals?
Answer: In peripheral Colin is absent as well as there is no division of labour while in coelenterate Colin is present and there are division of labour.
2. How do annelid animals differ from arthropods?
Answer:
•Skeleton is absent in Annelida while in arthropods skeleton is present.
•Hermaphrodites are present while in arthropods different sexes are present.
3. What are the differences between amphibians and reptiles?
Answer:
Amphibia has moist and soft skin whereas in water they breathe through skin. While in
reptilia skin is hardened and come to land to inhale oxygen.
4. What are the differences between animals belonging to the Aves group and those in the mammalian group?
Answer:
1-Aves have feathers in their body while mammalia have hairs in their body.
2-Aves body is streamlined while mammaila body is not streamlined.
Exercise
Q1. What are the advantages of classifying organisms?
Answer: The advantages of classifying organisms are-
* It makes the study of irganisms easier.
* It tells abiut the inter-relationship among irganisms.
* It also gives the knowledge if evolution of species.
* It helps to develop methods of preservation and conservation of plant ans animal species.
Q2. How would you choose between two characteristics to be used for developing a hierarchy in classification?
Answer: On the basis of characteristics (gross and fine characters) of various organisms,we can develop a hierarchy in classification
Q3. Explain the basis for grouping organisms into five kingdoms.
Answer: The basis if grouping organisns into 5 kingdoms are-
* cell structure(eukaryotic,prokaryotic)
*cell no. (uni and multicellular)
* nutrition mode (heterotrophs,autotrophs)
*Cell wall (plant and animal cell)
Q4. What are the major divisions in the Plantae? What is the basis of these divisions?
Answer:Major divisions in plantae are -Thallophyta ,Bryophyta,pteridophyta,phanerogams.
Basis of divisions are differentiated parts and vascular tissues.
Q5. How are the criteria for deciding divisions in plants different from the criteria for deciding
the subgroups among animals?
Answer: In plants division in plants are based on parameter of visibility of seeds as well as
bryophytes while in animals division is based on type of skin, and respiratory organs as well as
number of heart chambers.
Q6. Explain how animals in Vertebrata are classified into further subgroups.
Answer:
1-Cyclostomata-Jawless vertebrates, Elongated eel-like body ,circular mouth ,slimy skin .
•Example-Petromyzon.
2-PISCES-These are acquatic animals.Skin covered with scales Respiration through gills and have
streamlined body. Cold blooded and two heart chambers.
•Example-Angler fish,Lion fish
3-AMPHIBIA-Lack of scales and mucus glands in the skin.Three heart chambers. Respiration
through gills or lungs.
•Example-Frogs,Toads
4-REPTILIA-Cold blooded and breathe through lungs.Three chambered heart except crocodile
which have four heart chambers.
•Example-Turtle,King cobra
5-AVES-Warm blooded animals and have a four chambered heart and lay eggs. Outside
covering of feathers and two forelimbs for flight. Breathe through lungs.
•Example-White stork,Ostrich.
6-Mammalia- Warm blooded animals with four chambered hearts. Have mammary glands for
production of milk Skin has hairs as well as sweat and oil glands.
•Example-Platypus ,Echidna,Cat,Human.