9th Class Biology Chapter 3 Notes English Medium

Important Notes of 9th Class Biology Chapter 3 Notes English Medium written by Honorable Sir Adnan Haider Suib. These notes are very helpful in the preparation of Biodiversity Class 9th for students of the 9th class Biology English Medium and these are according to the paper patterns of all Punjab boards.

Summary and Contents:
Topics which are discussed in the notes are given below:
  • Here are the detailed biodiversity 9th class to help you prepare for your exams.
  • Very Important Multiple Choice Questions (MCQs) of Chapter No.3 Biodiversity English Medium.
  • Taxonomic Hierarchy: The groups into which organisms are classified are known as taxonomic categories or taxa (singular “taxon”). The taxa form a ladder, called taxonomic hierarchy. All organisms are divided into five kingdoms. So kingdom is the largest taxon. On the basis of similarities, each kingdom is further divided into smaller taxa in the following way:
  • 1. Phylum (Division: for plants and fungi): A phylum is a group of related classes.
  • 2.  Class: A class is a group of related orders.
  • 3. Order: An order is a group of related families.
  • 4. Family: A family is a group of related genera.
  • 5. Genus: A genus is a group of related species.
  • 6. Species: A species consists of similar organisms.
  •  You can also download the biology notes for class 9th chapter 3 biodiversity for free.
  • Species - The Basic Unit of Classification: Species is the basic unit of classification. “A species is a group of organisms which can interbreed freely among them and produce fertile offspring, but are reproductively isolated from all other such groups in nature.” Each species possesses its own distinct structural, ecological and behavioural characteristics. 
  • In the definition of species we must emphasize “in nature” because two organisms related to two different but closely related species can cross-breed under artificial conditions. In such unnatural crosses they produce infertile offspring. For example, a cross between a male donkey and a female horse produces an infertile offspring i.e. mule.
  • If you're looking for comprehensive biodiversity notes class 9th, you've come to the right place.
  • History Of Classification Systems: The earliest known system of classification of organisms comes from the Greek philosopher Aristotle. He classified all living organisms known at that time as either in the group ‘plantae’ or in ‘animalia’. In 700s, Abu-Usman Umer Aljahiz described the characteristics of 350 species of animals in his book. He wrote a lot about the life of ants. In 1172, Ibn Rushd (Averroes) translated Aristotle’s book “de Anima (On the Soul)” in Arabic. In the end of 15th century, many biologists had started work on classification methods e.g.
  • Carolus Linnaeus divided nature into three kingdoms: mineral, vegetable and animal. Linnaeus used five ranks in classification: class, order, genus, species, and variety. Linnaeus is best known for his introduction of the method still used to formulate the scientific name of every species. 
  • Biologists prefer such a system that can provide maximum information about the basic differences and similarities among different organisms. According to earlier classification system, organisms were classified into two kingdoms but now taxonomists agree on five-kingdom classification system. We will see the basis of these classification systems and the drawbacks in the two-kingdom and three-kingdom classification systems.
  • Two-Kingdom Classification System: It is the oldest system and classifies all organisms into two kingdoms i.e. Plantae and Animalia. According to it, all organisms that can prepare food from simple inorganic materials and thus can store energy, are autotrophs and are included in kingdom plantae. On the other hand, the organisms that cannot synthesize their food and depend on autotrophs or others are heterotrophs and are included in kingdom animalia. According to this system, bacteria, fungi and algae were included in kingdom plantae. 
  • Some taxonomists found this system unworkable because; many unicellular organisms like Euglena have both plant-like (presence of chlorophyll) and animal-like (heterotrophic mode of nutrition in darkness and lack of cell wall) characters. So there should be a separate kingdom for such organisms. This system also ignores the difference between organisms having prokaryotic and those having eukaryotic cells.

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