Study Guide - Biological Classification

Study Guide: Biological Classification

Short-Answer Quiz

Answer the following questions in 2-3 complete sentences based on the source material.

1. What were the primary limitations of Linnaeus's Two Kingdom system of classification that led to it being considered inadequate?

Linnaeus's Two Kingdom system was found to be inadequate because it did not distinguish between eukaryotes and prokaryotes, unicellular and multicellular organisms, or photosynthetic (green algae) and non-photosynthetic (fungi) organisms. A large number of organisms did not fall into either the Plantae or Animalia kingdom.

2. Identify the five kingdoms proposed by R.H. Whittaker in 1969 and list the five main criteria he used for his classification system.

The five kingdoms proposed by R.H. Whittaker are Monera, Protista, Fungi, Plantae, and Animalia. The main criteria he used for classification were cell structure, body organisation, mode of nutrition, reproduction, and phylogenetic relationships.

3. Describe the members of Kingdom Monera, including their abundance, typical habitats, and primary categories based on shape.

Bacteria are the sole members of Kingdom Monera and are the most abundant microorganisms, found almost everywhere, including extreme habitats. Based on shape, they are grouped into four categories: spherical (Coccus), rod-shaped (Bacillus), comma-shaped (Vibrium), and spiral (Spirillum).

4. What distinguishes Archaebacteria from other bacteria, and what are the three main groups based on their extreme habitats?

Archaebacteria are distinguished by a different cell wall structure, which is responsible for their survival in extreme conditions. The three main groups are halophiles (extreme salty areas), thermoacidophiles (hot springs), and methanogens (marshy areas).

5. What are the defining characteristics of Kingdom Protista, and why are the boundaries of this kingdom considered "not well defined"?

Kingdom Protista includes all single-celled eukaryotes, which are primarily aquatic and have a well-defined nucleus and other membrane-bound organelles. Its boundaries are not well defined because an organism considered a 'photosynthetic protistan' by one biologist may be classified as 'a plant' by another.

6. Explain the unique structure of a diatom's cell wall and describe the economic significance of their accumulated deposits.

In diatoms, the cell walls form two thin, indestructible overlapping shells embedded with silica that fit together like a soap box. The accumulation of these cell wall deposits over billions of years forms 'diatomaceous earth,' which is gritty and used in polishing and the filtration of oils and syrups.

7. Describe the basic body structure of filamentous fungi and the composition of their cell walls.

With the exception of unicellular yeasts, the bodies of fungi are filamentous and consist of long, slender, thread-like structures called hyphae. The network of hyphae is known as mycelium, and their cell walls are composed of chitin and polysaccharides.

8. What is a "dikaryon" in the fungal life cycle, and in which classes of fungi does this stage occur?

A dikaryon is an intervening stage in some fungi where a cell contains two nuclei per cell (n + n) following the fusion of two haploid cells. This dikaryophase occurs in the ascomycetes and basidiomycetes classes of fungi.

9. Why were viruses, viroids, and prions not included in Whittaker's five-kingdom classification system?

These acellular organisms were not included in the classification because they are not considered truly 'living' in the sense of having a cell structure. Viruses have an inert crystalline structure outside a living cell and are obligate parasites.

10. Define the symbiotic relationship that forms a lichen, identifying the two components and their respective roles.

Lichens are symbiotic, mutually useful associations between algae and fungi. The algal component (phycobiont) is autotrophic and prepares food, while the fungal component (mycobiont) is heterotrophic, provides shelter, and absorbs nutrients.

Essay Questions

1. Evolution of Biological Classification

Trace the evolution of biological classification systems, discussing the contributions and limitations of Aristotle, Linnaeus, and R.H. Whittaker. Explain how Whittaker's system resolved the specific inadequacies of the two-kingdom system.

2. Comparative Analysis of Kingdom Fungi

Provide a detailed comparative analysis of Kingdom Fungi's four classes: Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes. Discuss their mycelium structure, mode of spore formation, and key examples for each.

3. Metabolic Diversity in Monera

Discuss the statement: "Bacteria as a group show the most extensive metabolic diversity." In your answer, describe the different modes of nutrition found in Kingdom Monera, including photosynthetic autotrophs, chemosynthetic autotrophs, and heterotrophs (saprophytic/parasitic).

4. Biological Nature of Viruses and Acellular Agents

Explain the biological and structural characteristics of viruses. Detail their composition, the nature of their genetic material in plant vs. animal viruses, and the process by which they replicate. Support an argument on whether viruses should be considered living or non-living.

5. Diversity within Kingdom Protista

Describe the diversity within Kingdom Protista by detailing the key features, habitats, and representative examples of Chrysophytes, Dinoflagellates, Euglenoids, Slime Moulds, and Protozoans.

Glossary of Key Terms

Alternation of Generations

A life cycle phenomenon in plants where diploid sporophytic and haploid gametophytic phases alternate.

Archaebacteria

Bacteria living in harsh habitats (halophiles, thermoacidophiles, methanogens) with a unique cell wall structure.

Ascomycetes

Commonly known as sac-fungi; produce sexual spores called ascospores endogenously in asci.

Autotrophic

Organisms synthesizing their own food from inorganic substrates via light or chemical energy.

Basidiomycetes

Fungi like mushrooms; produce sexual spores called basidiospores exogenously on a basidium.

Capsid

The protein coat of a virus made of subunits called capsomeres.

Chitin

The tough material composing the cell walls of fungi.

Chrysophytes

A group in Kingdom Protista including diatoms and golden algae (desmids).

Coenocytic Hyphae

Continuous fungal tubes filled with multinucleated cytoplasm, lacking cross walls.

Cyanobacteria

Blue-green algae; photosynthetic autotrophs that can often fix atmospheric nitrogen.

Deuteromycetes

Imperfect fungi where only asexual or vegetative phases are known.

Diatomaceous Earth

Gritty soil formed by silica-rich cell wall deposits of diatoms over billions of years.

Dikaryon

A stage in some fungi (ascomycetes/basidiomycetes) with two nuclei (n + n) per cell.

Dinoflagellates

Marine photosynthetic protists; their rapid multiplication can cause 'red tides.'

Euglenoids

Freshwater protists with a protein-rich pellicle; behave as heterotrophs in the absence of light.

Heterocysts

Specialized cells in cyanobacteria (e.g., Nostoc) used for nitrogen fixation.

Lichens

Symbiotic associations between algae (phycobiont) and fungi (mycobiont).

Mycoplasma

The smallest known living cells; they completely lack a cell wall and can survive without oxygen.

Phylogenetic

Classification based on evolutionary relationships.

Plasmogamy

The fusion of protoplasm between two gametes; the first step in fungal sexual reproduction.

Prions

Infectious agents consisting of abnormally folded proteins causing neurological diseases.

Saprophytes

Heterotrophs that absorb soluble organic matter from dead substrates.

Viroids

Infectious agents smaller than viruses; consist of free RNA and lack a protein coat.

Virus

Non-cellular organisms with an inert crystalline structure and a genetic core of RNA or DNA.