Class 9th Biology Chapter 3 Biodiversity Notes
This chapter focuses on biodiversity and the classification of organisms. Biodiversity refers to the variety of organisms present in different ecosystems. There are over 10 million kinds of organisms on Earth, but only a third of these have been studied and cataloged by biologists. Despite the vast diversity, all organisms share many biological characteristics.
The five principal groups of organisms are prokaryotes, protists, fungi, plants, and animals. Biodiversity is not evenly distributed on Earth, with the richest biodiversity found in the tropics. Biodiversity plays a crucial role in providing food, drugs, industrial materials, and maintaining ecosystems by regulating the chemistry of the atmosphere and water supply.
Classification is a method by which biologists divide organisms into groups and subgroups based on their similarities in characteristics. The aims of classification are to determine similarities and differences among organisms and find their evolutionary relationships. The taxonomic hierarchy includes five main groups: kingdom, phylum (or division for plants and fungi), class, order, family, genus, and species.
Exercise and MCQ’s
Long Questions Answers
Short Answer Questions
The history of classification systems dates back to Aristotle, who classified organisms as either plants or animals. Over time, various biologists proposed different classification systems, with Carolus Linnaeus introducing the system of scientific names still used today. The two-kingdom classification system divided organisms into Plantae and Animalia, but it was found to be inadequate due to the complexity of some organisms and the differences between prokaryotic and eukaryotic cells.
As a result, the modern consensus is to use the five-kingdom classification system, which includes Plantae, Animalia, Fungi, Protista, and Monera (for prokaryotes). This system allows for a more accurate representation of the diversity and relationships among organisms.
Important Conceptual Questions
- How many kinds of organisms inhabit the Earth, and how many of them have been studied and cataloged by biologists?
- What are the five principal groups of organisms mentioned in the chapter?
- What does biodiversity refer to, and what factors influence the diversity of flora and fauna in a region?
- Why is biodiversity richest in the tropics, and what is the estimated age of Earth’s biodiversity?
- What are some important roles of biodiversity, including its significance in human life and industrial materials?
- What is the purpose of biological classification, and why is it necessary to divide organisms into groups and subgroups?
- Describe the taxonomic hierarchy and its different levels, from kingdom to species.
- What is the basic unit of classification, and how is a species defined in this context?
- Who was Carolus Linnaeus, and what were his contributions to the field of biological classification?
- What are the aims of classification, and how do biologists determine the similarities and differences among organisms for classification purposes?
- Describe the two-kingdom classification system, including its basis for dividing organisms into Plantae and Animalia.
- Why did some taxonomists find the two-kingdom classification system unworkable, and what are some of its drawbacks?