Chapter 2: Biodiversity for 9th Class students provides a comprehensive understanding of the diversity of life on Earth. This updated guide, based on the Lahore Board and all Punjab Boards’ new syllabus, covers key topics, including taxonomic ranks, kingdoms, and ecological importance. Perfect for students preparing for exams.
1. Which of the following taxonomic ranks represents the broadest rank of classification?
- a) Species
- b) Genus
- c) Kingdom
- d) Domain
Answer: d) Domain
Explanation: The taxonomic hierarchy is arranged in increasing specificity as follows: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species. “Domain” is the broadest category, encompassing the largest diversity of organisms.
Tip: Remember the hierarchy using the mnemonic “Dear King Philip Came Over For Good Soup.”
2. Which characteristic is unique to organisms in the domain Archaea?
- a) Cell walls made of peptidoglycan
- b) Presence of a nucleus
- c) Ability to live in extreme environments
- d) Lack of ribosomes
Answer: c) Ability to live in extreme environments
Explanation: Archaea are unique due to their ability to thrive in extreme environments (e.g., high temperatures, high salinity). Their cell walls lack peptidoglycan (found in bacteria).
Tip: Associate Archaea with “extremophiles” to remember this unique trait.
3. Which of these statements is NOT related to bacteria?
- a) Do not have a nucleus
- b) Cell wall made of peptidoglycan
- c) Most are heterotrophic
- d) Have chlorophyll in their chloroplasts
Answer: d) Have chlorophyll in their chloroplasts
Explanation: Bacteria do not have chloroplasts; photosynthetic bacteria, such as cyanobacteria, have chlorophyll but not in chloroplasts. Chloroplasts are unique to eukaryotic cells.
Tip: If you see “chloroplasts,” think “eukaryotes,” not bacteria.
4. Which of these organisms belong to the domain Eukarya?
- a) Escherichia coli
- b) Yeast
- c) Coronavirus
- d) None of these
Answer: b) Yeast
Explanation: Yeast is a eukaryotic organism (a type of fungus) with a true nucleus. Escherichia coli is a bacterium, and Coronavirus is a virus, which is non-cellular and does not belong to any domain.
Tip: Eukaryotes have a nucleus, while bacteria and viruses do not.
5. Which of the following is a key characteristic that distinguishes eukaryotic cells from prokaryotic cells?
- a) Lack of a cell wall
- b) Presence of a nucleus
- c) Absence of ribosomes
- d) Smaller size
Answer: b) Presence of a nucleus
Explanation: Eukaryotic cells are defined by having a true nucleus enclosed in a membrane, whereas prokaryotic cells lack a nucleus.
Tip: The “eu” in “eukaryote” means “true,” referring to the true nucleus.
6. Which kingdom includes organisms that are primarily unicellular, eukaryotic, and often heterotrophic?
- a) Archaea
- b) Protista
- c) Fungi
- d) Plantae
Answer: b) Protista
Explanation: Protists are primarily unicellular eukaryotic organisms. They can be heterotrophic (e.g., amoebas) or autotrophic (e.g., algae).
Tip: Think of protists as the “miscellaneous” category of eukaryotes.
7. Why are fungi classified as heterotrophs?
- a) Have chitin in the cell wall
- b) Absorb nutrients
- c) Reproduce by spores
- d) Form symbiotic relationships with plants
Answer: b) Absorb nutrients
Explanation: Fungi are heterotrophic because they obtain their nutrients by absorbing organic material from their environment, often by secreting enzymes.
Tip: Fungi are like nature’s recyclers, breaking down dead organic matter.
8. Why are viruses challenging to classify within traditional biological kingdoms?
- a) They lack cellular structure and organelles.
- b) They can perform photosynthesis.
- c) They are larger than most bacteria.
- d) They have a complex nervous system.
Answer: a) They lack cellular structure and organelles.
Explanation: Viruses are non-cellular entities that lack organelles, metabolism, and the ability to reproduce independently, making them hard to classify under the traditional biological kingdoms.
Tip: Viruses are considered “obligate intracellular parasites.”
9. Which of the following is the correct way for writing the scientific name of humans?
- a) Homo sapiens
- b) Homo sapiens
- c) Homo Sapiens
- d) homo sapiens
Answer: a) Homo sapiens
Explanation: The correct format for scientific names follows binomial nomenclature, with the genus (Homo) capitalized, the species (sapiens) lowercase, and both italicized.
Tip: Remember the rule: Genus capitalized, species lowercase, both italicized.
10. Which information can you get if you know the scientific name of an organism?
- a) Kingdom and phylum
- b) Phylum and genus
- c) Genus and species
- d) Class and species
Answer: c) Genus and species
Explanation: The scientific name of an organism follows the binomial nomenclature system, which consists of the genus name (capitalized) and species name (lowercase).
Tip: Genus is the first word, and species is the second word in a scientific name.
B. Short Answer Questions
1. What is the term used to describe the variety of life on Earth?
Answer: Biodiversity.
2. How is biodiversity crucial for humans and for the planet Earth?
Answer: Biodiversity provides essential resources like food, medicine, and raw materials, maintains ecological balance, supports ecosystem services like pollination, and ensures resilience against environmental changes.
3. What are the seven taxonomic ranks used in the Linnaean system?
Answer: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
4. Can you provide the taxonomic classification for lions and corn?
Answer:
- Lion:
Domain: Eukarya, Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Carnivora, Family: Felidae, Genus: Panthera, Species: Panthera leo. - Corn:
Domain: Eukarya, Kingdom: Plantae, Phylum: Magnoliophyta, Class: Liliopsida, Order: Poales, Family: Poaceae, Genus: Zea, Species: Zea mays.
5. What are the basic differences between archaea and bacteria?
Answer:
- Archaea: Cell walls lack peptidoglycan, thrive in extreme environments, and have unique genetic and metabolic pathways.
- Bacteria: Cell walls contain peptidoglycan, found in diverse environments, and have simpler genetic structures.
6. What were the shortcomings of the three-kingdom classification system?
Answer: It did not account for the differences between prokaryotes and eukaryotes, placed unicellular and multicellular organisms together, and failed to categorize viruses.
7. Which kingdom includes organisms that are multicellular, heterotrophic, and lack cell walls?
Answer: Kingdom Animalia.
8. Enlist the distinguishing characteristics of fungi.
Answer:
- Eukaryotic organisms
- Cell walls made of chitin
- Heterotrophic, absorbing nutrients from their environment
- Reproduce by spores
- Lack chlorophyll.
9. List the three main domains that encompass all living organisms.
Answer: Bacteria, Archaea, Eukarya.
10. Why cannot we classify viruses in any kingdom?
Answer: Viruses lack cellular structure, cannot perform metabolism, and require a host cell for reproduction, making them non-living outside a host.
11. How does binomial nomenclature facilitate clear communication about organisms across different languages?
Answer: Binomial nomenclature provides a universal, standardized naming system that avoids confusion caused by local names and ensures accurate identification and classification.
C. Detailed Answer Questions
1. Discuss the concept of biodiversity and its significance in maintaining the health of ecosystems.
Answer:
Biodiversity refers to the variety of life forms on Earth, including genetic diversity, species diversity, and ecosystem diversity. It plays a crucial role in maintaining ecosystem health by providing resilience to environmental changes, ensuring the stability of food webs, supporting ecosystem services like pollination, water purification, and climate regulation, and offering resources like food, medicine, and raw materials.
2. Explain the importance of classification in biology and how it helps us understand the relationships between different organisms.
Answer:
Classification organizes organisms into hierarchical categories based on shared traits, enabling scientists to identify, study, and understand organisms systematically. It reveals evolutionary relationships, aids in predicting characteristics of organisms, and facilitates communication among researchers.
3. Describe the Linnaean system of taxonomic hierarchy in detail, outlining the seven major taxonomic ranks and their relationships.
Answer:
The Linnaean system classifies organisms into a hierarchical structure with the following ranks:
- Domain: Broadest category (e.g., Eukarya).
- Kingdom: Groups organisms with basic similarities (e.g., Animalia).
- Phylum: Organizes kingdoms into more specific groups (e.g., Chordata).
- Class: Subdivides phyla (e.g., Mammalia).
- Order: Groups classes with shared traits (e.g., Carnivora).
- Family: Groups related genera (e.g., Felidae).
- Genus and Species: Identify specific organisms (e.g., Homo sapiens).
4. Compare and contrast the domains Archaea and Eubacteria, focusing on their key characteristics.
Answer:
- Archaea:
- Cell walls lack peptidoglycan.
- Adapted to extreme environments (e.g., high temperatures, salinity).
- Unique RNA sequences and membrane lipids.
- Eubacteria:
- Cell walls contain peptidoglycan.
- Found in diverse habitats.
- Include both beneficial and pathogenic species.
5. Describe the distinguishing characteristics of the four kingdoms within the domain Eukarya.
Answer:
- Protista: Mostly unicellular, autotrophic or heterotrophic, e.g., amoebas.
- Fungi: Cell walls of chitin, absorb nutrients, e.g., mushrooms.
- Plantae: Multicellular, autotrophic, cell walls of cellulose, e.g., trees.
- Animalia: Multicellular, heterotrophic, no cell walls, e.g., humans.
6. Discuss the challenges of classifying viruses within the traditional three domains of life.
Answer:
Viruses are acellular, lack metabolic processes, and depend on host cells for reproduction, making them distinct from living organisms. This prevents their inclusion in the three domains of life.
7. Explain the rules and guidelines for suggesting scientific names to organisms.
Answer:
- Use Latin or Latinized words.
- Write in italics or underline when handwritten.
- Capitalize the genus name; use lowercase for the species name.
- Avoid duplication within a genus.
