CBSE Class 9 Science, Diversity in Living Organisms: Chapter notes (Part-II)

This article brings you the CBSE Class 9 Science, Diversity in Living Organisms: Chapter Notes (Part-II). This part is a continuation of the Diversity in Living Organisms: Chapter Notes (Part-I). In this part you will learn about the classification of different kingdoms and binomial nomenclature of organisms.

CBSE Class 9 Science Chapter Notes on Diversity in Living Organisms
CBSE Class 9 Science Chapter Notes on Diversity in Living Organisms

This article brings you the CBSE Class 9 Science notes on chapter 7 ‘Diversity in Living Organisms’ (Part-II). These chapter notes are prepared by the subject experts and cover every important topic from the chapter. At the end of the notes, you can try the questions asked from the discussed set of topics. These questions will help you to track your preparation level and get a hold on the subject.

In the previous part, i.e., CBSE Class 9 Science notes on chapter 7 ‘Diversity in Living Organisms’ (Part-I), the main topics discussed were: Biodiversity, Classification, Rober H. Whittaker’s five kingdom classification. Further topics are discussed here.

Also Read: CBSE Class 9 Science, Diversity in Living Organisms: Chapter notes (Part-I)

Main topics covered in this part of CBSE Class 9 Science,  Diversity in Living Organisms: Chapter Notes, are:

  • Classification of Kingdom Planate
  • Classification of Kingdom Planate
  • Binomial Nomenclature
  • Conventions for Writing the Scientific Name

Also Read: CBSE Class 9 Complete Study Material for 2020-2021

Key notes for Chapter-Diversity in Living Organisms, are:

Classification of Kingdom Plantae:

Kingdom Plantae can be further classified into five divisions. Their key characteristics are given below:

1. Thallophyta: 

  • Basic and elementary plants with undifferentiated body parts (thallus type).
  • Reproduce through spores.
  • Commonly known as algae.
  • Examples: Spirogyra, Chara, Ulva, Ulothtrix, etc.

2. Bryophyta:

  • Plant body is differentiated into stem and leaf like structure.
  • Vascular system is absent, which means there is no specialized tissue for transportation of water, minerals and food.
  • Found on both land and water therefore known as ‘Amphibians of Plantae kingdom’.
  •  Examples: Moss, Liverwort, Hornwort, etc.

CBSE Class 9 Science Syllabus 2020-2021

3. Pteridophyta:

  • Plant body is differentiated into root, stem and leaf.
  • Vascular system is present.
  • Plants do not bear seeds and hence are called cryptogams.
  • Examples: Marsilea, Fern, horsetails, etc.

Note: Plants of rest of the divisions bear seeds and hence are called phanerogams.

4. Gymnosperms:

  • Plants have naked seeds without fruits or flowers
  •  The word ‘gymnos’ means naked and ‘sperma’ means seed.
  • They are perennial, evergreen and woody plants.
  • Examples: Pine, Cycas, Deodar, etc.

5. Angiosperms:

  • The seeds are covered. The word ‘angios’ means covered.
  • They are also known as flower-bearing or flowering plants.
  • Plant embryos in seeds have structures called cotyledons.
  • Cotyledons: Cotyledons are called ‘seed leaves’ because in many instances they emerge and become green when the seed germinates.
    On the basis of the number of cotyledons present in the seed, angiosperms are divided into two groups
    (a) Monocotyledonous: Seeds have a single cotyledon. For examples: wheat, rice, maize, etc.

(b) Dicotyledonous: Seeds have two cotyledons. For example: Mustard, gram, mango, etc.

Try the following questions:

Q1. Write names of few thallophytes. 

Q2. What are Phanerogams? 

Q3. Differentiate between Gymnosperms and Angiosperms on the basis of fruits.
Q4. Give three points of difference between monocot and dicot plants.

Q5. How are Pteridophytes different from Phanerogams?

Classification of Kingdom Animalia

Kingdom Animalia is further classified into different phylum. Their key characteristics are given below:

1. Porifera: 

  • Cellular level of organization.
  • These animals have pores all over which led to a canal system for circulation of water and food.
  • The body is covered with a hard outer layer called skeleton.
  • Commonly known as sponges.
  • They are aquatic animals.
  • Examples: Sycon, Spongilla, Euplectelia, etc.

2. Coelenterata: 

  • Cellular level of organization.
  • There is a cavity in the body hence the name Coelenterate (coelom means cavity).
  • The body wall is made up of two layers of cells (diploblastic).
  • They are also aquatic animals.
  • Examples: Hydra, Jelly fish, Sea anemone, etc.

3. Platyhelminthes: 

  • The body is flattened from top to bottom and hence they are also named as flatworms.
  • The body wall is composed of three layers of cells (triploblastic).
  • A true internal body cavity or coelom is absent, hence lacks proper organs.
  • They are free-living or parasitic animals.
  • Examples: Planaria, liver fluke, tapeworm, etc.

4. Nematohelminthes: 

  • The body is bilaterally symmetric and triploblastic.
  • Body is cylindrical in shape.
  • A pseudocoelom is present.
  • Examples: Roundworms, Pinworms, Wuchereria, etc.

5. Annelida: 

  • These are bilaterally symmetrical and triploblastic.
  • True body cavity is present.
  • The body is divided into segments and hence the name annelida.
  • Extensive Organ differentiation.
  • Examples: Earthworm, leech, etc.

6. Arthropoda: 

  • Animals have jointed appendages which gives the name arthropoda (the word ‘arthropod’ means jointed legs’).
  • Tough exoskeleton made of chitin, is present.
  • This is the largest group of animals; in terms of number of species.
  • They are bilaterally symmetrical and triploblastic
  •  Examples: Cockroach, housefly, spider, prawn, scorpion, etc.

7. Mollusca: 

  • Body is bilaterally symmetrical.
  • The soft body is covered with a hard shell made of calcium carbonate.
  • Circulatory system is open and kidney like organ is present for excretion.
  • The body has well developed muscular feet for locomotion.
  • Examples: Snail, mussels, octopus, etc.

8. Echinodermata: 

  • The body is covered with spines, which gives the name echinodermata (In Greek, echino means hedgehog, and derma means skin).
  • Body is radially symmetrical, Triploblastic with coelom.
  • The animals have well developed water canal system, which is used for locomotion.
  • Skeleton is made of calcium carbonate.
  • Examples: Starfish, sea urchins, etc.

9. Chordata: 

  • Animals have notochord, pharyngeal gill slits and post anal tail; for at least some stages of life.
  • They have segmented muscles in an unsegmented trunk.
  • Exhibit a complete digestive system.

Chrodata is further divided into two groups as explained below:

A. Protochordata: 

  • Animals are bilaterally symmetrical, triploblastic and ceolomate.
  • Body is bilaterally symmetrical, triploblastic with coelom.
  • Notochord, a long rod-like structure which runs along the back of the animal, is present at least at some stages of life.
  • This provides attachment points for muscles.
  • It also separates the nervous tissues from the gut.
  • Examples: Balanoglossus, herdmania, amphioxus, etc.

B. Vertebrata:

  • Notochord is replaced by spinal column.
  • Dorsal nerve chord is present.
  • Animals are triploblastic and coelomate.
  • Animals have paired gill pouches.

Vertebrates are further divided into two main classes, viz. pisces and tetrapoda.

(a) Pisces: 

  • They are commonly known as fish.
  • The body is streamlined.
  • Muscular tail is present which assists in locomotion.
  • Streamlined body covered with scales.
  • They are cold-blooded animals.
  • Paired gills are present as respiratory organs.
  • The heart is two chambered.
  • They lay eggs.
  • Fishes can be bony (Rohu and Katla) or cartilaginous (Shark).

(b) Tetrapoda: 

  • Animals have four limbs for locomotion and hence the name tetrapoda.

Tetrapoda is again divided into four classes, that are explained below:

(i) Amphibia: 

  • They are adapted to live both in water and land.
  • Mucus glands on skin keep the skin moist.
  • Respiration is through gills when in water and through lungs when on land.
  • Three-chambered heart is present.
  • They are cold blooded animals.
  • Examples: Frog, toad, salamander, etc.

(ii) Reptilia: 

  • These are crawling animals.
  • Skin is covered wth scales.
  • Most of the reptilians have three chambered heart but crocodile has four-chambered heart.
  • They don’t need water to lay eggs, rather eggs are covered with hard shells and laid on land.
  • They are cold blooded animals.
  • Examples: Snakes, lizards, crocodile, turtle, etc.

(iii) Aves: 

  • The body is covered with feathers.
  • Forelimbs are modified into wings.
  • Respiratory organs are gills.
  • These are warm-blooded animals.
  •  Four-chambered heart is present.
  • Bones are hollow (pneumatic) to assists in flying.
  • All the birds belong to this class.

(iii) Mammalia: 

  • Mammary glands are present in females to nurture their young ones.
  • The body is covered with hairs.
  • Skin has sweat glands and sebaceous glands.
  • Most animals are viviparous (giving birth to live young ones), some are oviparous (producing eggs).
  • Examples: Human, horse, chimpanzee, lion, etc.

Binomial Nomenclature of Organisms:

Binomial nomenclature system was given by Carolus Linnaeus  (1707 – 1778). He suggested a scientific name to each organism to prevent the confusion over different names in different languages.

Conventions for writing the scientific name:

  • The biological name is composed of two terms. The first term is called genus name and the second term is called species name.
  • The genus name always begins with a capital letter, while the species name begins with a small letter.
  • In print, the scientific name is written in italics.
  • When handwritten, the genus name and species name have to be underlined separately.

Try the following questions:

Q1. Why does tapeworm not have digestive trait?

Q2. Why do we keep both snake and turtle in the same class?

Q3. Write the important characteristics of sponges.

Q4. Name the following:
(a) An egg laying mammal.
(b) A reptile with four chambered heart.
(c) A mammal which can fly.
(d) An aquatic mammal.

Q5. What is the difference between cold-blooded and warm-blooded animals?

Q6. List two distinguishing features between annelids and arthropods.

Also Read: CBSE Class 9 Science Chapter Notes - All Chapters

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