The Living World Overview

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Questions and Answers

What is the primary basis for the artificial system of classification?

Morphological characters (correct)

Genetic similarities

Evolutionary relationships

Ecological roles

Which classification system uses a number of characters to illustrate natural relationships among organisms?

Artificial system

Phylogenetic system

Natural system (correct)

Cytological system

Who is known as the father of taxonomy and proposed the two kingdom system of classification?

Ernst Haeckel

R.H. Whittaker

Aristotle

Carl Linnaeus (correct)

In the five kingdom system, which kingdom includes all prokaryotes?

Monera Signup and view all the answers

What distinguishes the three kingdom classification system from the two kingdom system?

Presence of the kingdom Protista Signup and view all the answers

Which classification system is based on the evolutionary relationship of organisms?

Phylogenetic system Signup and view all the answers

Which of the following classifications was NOT proposed by R.H. Whittaker?

Three kingdom system Signup and view all the answers

What is the main characteristic used to separate organisms into the two kingdom classification system?

Presence or absence of cell wall Signup and view all the answers

What characteristic is NOT true about bacteria?

They have a well-organized nucleus. Signup and view all the answers

Which type of bacteria is known for its ability to thrive in extreme conditions?

Methanogens Signup and view all the answers

What is a defining feature of mycoplasma?

They can live without oxygen. Signup and view all the answers

Which of the following bacteria are known for being autotrophic and photosynthetic?

Cyanobacteria Signup and view all the answers

Which group of bacteria is least likely to cause diseases in humans or animals?

Chemosynthetic bacteria Signup and view all the answers

What type of reproduction is primarily observed in bacteria?

Asexual reproduction Signup and view all the answers

Which of the following is NOT a characteristic of eubacteria?

Absence of flagella Signup and view all the answers

What is the role of heterotrophic bacteria in ecosystems?

Decomposition Signup and view all the answers

Which of the following statements accurately describes diatoms?

Diatoms are a significant contributor to marine primary production. Signup and view all the answers

What is the mode of nutrition of most protozoans?

Saprophytic and parasitic Signup and view all the answers

Which of the following is a characteristic of slime moulds?

They form a plasmodium under favorable conditions. Signup and view all the answers

What distinguishes Euglena from other unicellular flagellates?

Euglena can photosynthesize in sunlight but acts as a predator without it. Signup and view all the answers

What is the primary composition of the cell wall in fungi?

Chitin or fungal cellulose Signup and view all the answers

What color is most commonly associated with diatoms?

Golden brown Signup and view all the answers

Which of the following organisms is a sporozoan?

Plasmodium Signup and view all the answers

Which group includes organisms that primarily live in aquatic environments and use cilia for movement?

Ciliated protozoans Signup and view all the answers

What is the process that involves the fusion of male and female gametes?

Plasmogamy Signup and view all the answers

Which type of mycelium is characteristic of Phycomycetes?

Aseptate and coenocytic Signup and view all the answers

What type of spores do Ascomycetes produce asexually?

Conidia Signup and view all the answers

Which of the following is NOT a characteristic of Basidiomycetes?

Asexual spores are commonly found Signup and view all the answers

Which type of fungi includes species that grow on dung?

Ascomycetes Signup and view all the answers

What is the main mode of nutrition for organisms in the Kingdom Animalia?

Holozoic Signup and view all the answers

Which of the following accurately describes Deuteromycetes?

They are considered fungi imperfecti. Signup and view all the answers

Viruses are characterized by which of the following traits?

Inert crystalline structure outside of living cells Signup and view all the answers

Study Notes

Biological Classification

Biological classification is the scientific process of organizing organisms into groups and subgroups based on similarities and differences, placing them in a hierarchical structure.
Classification is essential because it's impossible to study every organism. Studying a few representative organisms within a group reveals key characteristics of the entire group.
Classification facilitates the identification of new organisms by providing a framework for recognizing their similarities to known groups.
Classification helps understand the relationships between different groups of organisms.
Understanding past organisms is only possible with a comprehensive classification system.

Types of Classification Systems

Artificial Classification: Organisms are grouped based on one or two easily observable physical traits, avoiding evolutionary relationships. Examples include grouping plants as flowering or non-flowering, or animals as vertebrates and invertebrates. (e.g., Aristotle).
Natural Classification: This approach considers numerous characteristics to reveal natural similarities and differences, and hence natural relationships among organisms. This system aims to depict evolutionary relationships accurately. (e.g., Bentham and Hooker).
Phylogenetic Classification: Groups organisms based on their evolutionary relationships. Organisms are classified based on how they evolved from earlier forms on Earth, from primitive to highly evolved. (e.g., Engler and Prantl, Hutchinson).

Kingdom System

Two Kingdom System (Plantae and Animalia): Organisms categorized based on presence or absence of cell walls. Linnaeus proposed this system.
Three Kingdom System (Plantae, Protista, and Animalia): Separates unicellular organisms (algae, fungi, and some animals) as a separate category. Haeckel developed the system.
Five Kingdom System (Monera, Protista, Fungi, Plantae, Animalia): Organisms divided by characteristics like cell structure (prokaryotic or eukaryotic), mode of nutrition, and other features. Recognizes and distinguishes different groups. R.H. Whittaker developed the system.

Monera

Includes all prokaryotes.
Unicellular, prokaryotic organisms, the most ancient.
Lack membrane-bound organelles (e.g., nucleus).
Genetic material (DNA) is not in a nucleus.
Reproduction typically asexual.
Includes mycoplasma, bacteria, actinomycetes, and cyanobacteria.

Eubacteria

True bacteria; rigid cell walls.
May be motile if they possess flagella.
Includes Photosynthetic bacteria; some are photosynthetic (Cyanobacteria).
Some are heterotrophic (acquire food by consuming organic matter) and others perform chemosynthesis (oxidize inorganic substances to produce energy).

Protista

Mostly unicellular; some colonial eukaryotes—eukaryotic life forms.
Mode of nutrition is diverse (photosynthetic, saprophytic, parasitic, or holozoic).
Includes diatoms, dinoflagellates, euglenoids, slime molds, and protozoa.
Many protists are responsible for photosynthesis in aquatic environments.

Fungi

Achlorophyllous (lacking green pigments) organisms; heterotrophic- obtain food from other organisms.
Cell walls contain chitin or fungal cellulose; reserves are in glycogen.
Modes of nutrition include saprophytic, parasitic, and symbiotic.
Reproduction occurs vegetatively, asexually, or sexually. Important groups are phycomycetes, ascomycetes, basidiomycetes, and deuteromycetes.

Phycomycetes

Found in moist, aquatic, or decaying-wood habitats; mycelium (vegetative body) is aseptate and coenocytic.
Reproduce asexually (zoospores and aplanospores). Example: Rhizopus (bread mold).

Ascomycetes

Saprophytes, decomposers, parasites, and coprophilous organisms.
Mycelium is branched and septate; asexual spores are conidia; sexual spores are ascospores produced within ascocarps. Example: Neurospora, Penicillium, Saccharomyces.

Basidiomycetes

Saprophytic, decomposers, or coprophilous; mycelium is branched and septate; asexual spores are not found; sexual reproduction via basidiospores in basidiocarps (fruiting body). Example: Agaricus (mushroom).

Deuteromycetes ("Imperfect Fungi")

Only vegetative and asexual phases observed; mycelium is septate and branched. Example: Alternaria and Penicillium.

Plantae (Plants)

Eukaryotic organisms; photosynthetic mode of nutrition; cell wall composed of cellulose.
Life cycle involves both diploid (sporophytic) and haploid (gametophytic) phases.
Includes algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.

Animalia (Animals)

Multicellular, eukaryotic organisms; heterotrophic mode of nutrition; no cell wall.
Reproduce sexually; mode of nutrition: holozoic (ingesting whole food).
Includes several phyla (e.g., Chordata, Arthropoda, Mollusca).

Viruses, Viroids, and Lichens

Not included in the five-kingdom system.
Viruses are non-cellular; consist of a protein coat and nucleic acids (DNA or RNA); replicate within a host cell; cause many plant and animal diseases
Viroids are smaller than viruses; consist of only RNA; cause plant diseases.
Lichens are symbiotic associations between algae (phycobiont) and fungi (mycobiont); indicator species for pollution.

Additional Details

DNA Viruses: The protein coat (capsid) made of subunits called capsomeres is used to protect nucleic acid. Capsomers arranged structurally (for example, in helical or polyhedral geometric forms).
Viroids: Discoverd by T.O. Diener, infectious agents smaller than viruses; contain only RNA, no protein coat. Potato spindle tuber disease is an example.

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Description

Explore the essential concepts of biological classification, the hierarchical organization of organisms, and the significance of various classification systems. Learn about artificial classification and its role in understanding the relationships among organisms.