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9th Class Biology · Punjab Board · Chapter 2

Chapter 2: BiodiversityLong Questions with Answers

10 long (comprehensive) questions of 9th Class Biology Chapter 2, Biodiversity, answered in full with headings, diagrams and tables, including important board-paper questions beyond the book. Punjab Board new syllabus.

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Chapter 2· Biodiversity

Long Questions with Answers

Long answers, explained in full with headings. Learn the structure: definition, explanation, diagram or table, example.

Set A: Textbook comprehensive questions 7 questions

The long questions at the end of the chapter in your book.

Long Q 2.1

Discuss biodiversity and its significance in maintaining the health of ecosystems.

Answer

Biodiversity

Biodiversity means the variety of organisms in a particular area, measured by the number of kinds of organisms and the variation within each kind. It is not evenly spread out: it depends on climate, altitude and soil; tropical regions have more than polar regions.

Significance

  • Ecosystem stability: biodiversity maintains the balance of ecosystems and plays an important role in biogeochemical cycles such as the carbon and nitrogen cycles.
  • Climate regulation: plants and algae absorb carbon dioxide and keep the climate balanced.
  • Natural resources: food, medicine, building materials and fuel.
  • Economic benefits: agriculture, tourism and pharmaceutical industries depend on it.

More kinds of organisms mean more links in food webs, so an ecosystem recovers better if one species is lost. The UN marks 22 May as International Biodiversity Day to promote its protection.

Long Q 2.2

Explain the importance of classification in biology and how it helps us understand the relationships between different organisms.

Answer

Classification

The process in which organisms are divided into groups and subgroups on the basis of similarities and differences. About 2 million kinds are known, so they must be grouped to be studied.

Aims

  • To determine similarities and differences so that organisms can be studied easily.
  • To find the evolutionary relationships among organisms.

Importance

  • Groups similar organisms, making it easier to identify and understand them.
  • A framework for studying and comparing species.
  • Explains the inter-relationships among organisms: members of one genus are closer than members of one family.
  • Helps identify new species and understand their evolution.
  • Provides a common language for biologists.

Understanding relationships

The ranks show how close organisms are: the human and the fruit fly share only domain and kingdom; the human and lion share domain to class (Mammalia). In recent times, genetics is used to confirm these relationships.

Long Q 2.3

Describe the Linnaean system of classification in detail, stating the seven taxonomic ranks and their relationships.

Answer

The Swedish botanist Carl Linnaeus devised the Linnaean system in 1735 with seven taxonomic ranks: kingdom, phylum (division), class, order, family, genus and species. In 1977 the rank of domain was added.

DomainKingdomPhylumClassOrderFamilyGenusSpeciesbroadestnarrowestmore similar members ↓
The ranks nest inside one another.
  1. Kingdom: a domain is divided into kingdoms (Eukarya: Animalia, Plantae, Fungi, Protista).
  2. Phylum (division for plants and fungi): each kingdom divided into related phyla.
  3. Class: each phylum divided into related classes.
  4. Order: each class into related orders.
  5. Family: each order into related families.
  6. Genus: each family into related genera.
  7. Species: the lowest level; organisms that interbreed and produce fertile offspring.

Relationship between ranks

Each rank contains one or more ranks below it. Moving down, the groups get smaller and their members share more characteristics. Example: Human — Eukarya, Animalia, Chordata, Mammalia, Primates, Hominidae, Homo, Homo sapiens.

Long Q 2.4

Compare and contrast the domains Archaea and Bacteria, focusing on their key characteristics.

Answer

Similarities

  • Both are prokaryotes: no nucleus or membrane-bound organelles.
  • Mostly unicellular, with a cell wall.
  • Some of both can photosynthesise.

Differences

FeatureArchaeaBacteria
Cell wallno peptidoglycan; polypeptides and proteinspeptidoglycan
rRNAresembles eukaryotesbacterial
Membrane lipidsunique; allow life in extremesordinary
Habitathot springs, salt lakes, acid/alkaline waters; also soil, oceansall environments, including bodies of organisms
Energysome from sulphur or ammonia; photosynthesis without oxygenmostly heterotrophic; some photosynthetic (cyanobacteria)
KingdomArchaebacteriaEubacteria
Examplesmethanogens, halophiles, thermophiles, acidophilesE. coli, cyanobacteria, decomposers
Bacteriaprokaryotic, no nucleuswall: peptidoglycaneverywhereArchaeaprokaryotic, no nucleuswall: no peptidoglycanextreme environmentsEukaryaeukaryotic: nucleus +membrane-bound organellesProtista, Fungi, Plantae, AnimaliaBacterial and archaeal cells are smaller than eukaryotic cells
The three domains.
Long Q 2.5

Describe the distinctive characteristics of the four kingdoms within the domain Eukarya.

Answer

Kingdom Protista

Unicellular, colonial, filamentous or simple multicellular eukaryotes. Plant-like (algae: Euglena, diatoms), animal-like (protozoa: Amoeba, Paramecium), fungus-like (slime and water molds).

Kingdom Fungi

Eukaryotic heterotrophs that absorb food from decaying matter; cell walls of chitin; mostly multicellular (mushrooms, rusts, smuts, molds), some unicellular (yeast).

Kingdom Plantae

Multicellular, cellulose walls, autotrophic by photosynthesis, multicellular sex organs, form embryos. Mosses, ferns, conifers, flowering plants.

Kingdom Animalia

Multicellular heterotrophs without cell walls; develop from embryos; ingest food and digest it within their bodies. Vertebrates and invertebrates.

Euglenaplant-like (alga)Amoebaanimal-like (protozoan)Parameciumanimal-like, ciliaSlime moldfungus-likeProtista: eukaryotes, unicellular, colonial, filamentous or simple multicellular
Examples of protists.
Long Q 2.6

Discuss the challenges of classifying viruses within the traditional three domains of life.

Answer

What a virus is

Viruses are ultramicroscopic and at the borderline of living and non-living. A virus is nucleic acid (DNA or RNA) in a protein coat.

protein head(DNA inside)tailtail fibresBacteriophage (attacks bacteria)spikes on envelope · RNA insideInfluenza virus
A bacteriophage and an influenza virus.

Challenges

  • Acellular: the three domains are defined by cell type (prokaryotic or eukaryotic), but viruses have no cells.
  • No organelles, no metabolism: they cannot make proteins or energy on their own.
  • Obligate parasites: they reproduce only inside host cells (plants, animals, bacteria), using the host's machinery.
  • Not clearly alive: outside a host they behave like chemical particles.

Therefore viruses are not included in the classification system, because they lack any of the characteristics of the three domains of life. Prions (protein only) and viroids (RNA only) are likewise unclassified.

Long Q 2.7

Explain the rules and guidelines for suggesting scientific names to organisms.

Answer

The scientific naming of organisms (binomial nomenclature) follows international rules:

  1. For scientific naming, words are taken from the Latin language.
  2. Every scientific name has two parts: genus name first, followed by the species name.
  3. Every scientific name has to be unique; the same name cannot be used for two organisms.
  4. Genus name begins with a capital letter; species name with a small letter.
  5. At the time of printing, it is typed in italics.
  6. When handwritten, the two parts are underlined separately.
Printed (italics):Homo sapiensHandwritten:Homo sapienseach part underlined separatelyGenus: capital first letterspecies: small first letterLatin words · genus first, species second · unique for each organism
Writing the name correctly.

Examples: Allium cepa (onion), Solanum tuberosum (potato), Homo sapiens (human).

Set B: More important long questions 3 questions

Long questions often set in board papers from this chapter, answered in the same full style.

Imp. LQ 1

Describe the history of classification from the two-kingdom to the three-domain system.

Answer
(a) 2-Kingdom (earliest)PlantaeAnimalia(b) 3-Kingdom (Haeckel, 1866)ProtistaPlantaeAnimalia(c) 5-Kingdom (Whittaker, 1969)MoneraProtistaPlantaeFungiAnimalia(d) 3-Domain (Woese, 1977)ArchaebacteriaEubacteriaProtistaPlantaeFungiAnimaliaArchaeaBacteriaEukarya
Classification systems compared.

Early workers

Aristotle (plants and animals), Al-Jahiz (350 animals), Caesalpinio (15 plant genera), Tournefort (class and species), Linnaeus (seven ranks, 1735).

Two kingdoms

Plantae (autotrophs, including bacteria and fungi) and Animalia (heterotrophs). Failed with Euglena and did not separate prokaryotes.

Three kingdoms (Haeckel, 1866)

Protista added for Euglena-like organisms and prokaryotes. Fungi still wrongly in Plantae.

Five kingdoms (Whittaker, 1969)

Monera, Protista, Fungi, Plantae, Animalia, on cellular organization and mode of nutrition; modified by Margulis and Schwartz (1988) using genetics.

Three domains (Woese, 1977)

Archaea, Bacteria, Eukarya: prokaryotes split into two domains; six kingdoms in all.

Imp. LQ 2

Write a note on the significance of binomial nomenclature over common names.

Answer
  • Uniqueness: two organisms cannot have the same scientific name.
  • Universal: Latin is spoken by no country, so the name is the same everywhere: a standard way of communication.
  • Common names vary by region: onion is piyaz, ganda, bassal or vassal.
  • One common name, many organisms: "blue bell" for dozens of plants; "black bird" for crow and raven.
  • Common names are unscientific: silver fish, cray fish, jellyfish and star fish are not fish (a fish has a backbone, fins and gills).
Printed (italics):Homo sapiensHandwritten:Homo sapienseach part underlined separatelyGenus: capital first letterspecies: small first letterLatin words · genus first, species second · unique for each organism
Scientific names.
Imp. LQ 3

Describe the domain Archaea and its kingdom.

Answer

Archaea are the most primitive organisms. They are prokaryotes whose cell wall lacks peptidoglycan and is made of polypeptides and proteins. Their rRNA resembles eukaryotes. Unique membrane lipids let them live in extreme environments (hot springs, salt lakes, acidic or alkaline waters), though some live in soil and oceans. Some obtain energy from sulphur or ammonia; others photosynthesise without producing oxygen.

Kingdom ArchaebacteriaFeature
Methanogensproduce methane
Halophilesextremely salty places
Thermophileshot springs
Acidophilesextremely acidic places
End of Chapter 2 Long QuestionsNext: Chapter 2 MCQs →

The rest of Chapter 2

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Full guide: Biodiversity (notes, diagrams, all questions, self-test)
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