Biological Classification Flashcards

Summary flashcards covering the biological classification systems, kingdom characteristics (Monera, Protista, Fungi, Plantae, Animalia), and acellular agents (Viruses, Viroids, Prions, Lichens) based on lecture notes.

Aristotle

The earliest scientist to attempt a more scientific basis for classification, using simple morphological characters to classify plants into trees, shrubs, and herbs.

Two Kingdom system

Classification system developed in Linnaeus' time that divided organisms into Kingdom Plantae and Kingdom Animalia.

R.H. Whittaker ($1969$)

The scientist who proposed the Five Kingdom Classification, consisting of Monera, Protista, Fungi, Plantae, and Animalia.

Five Kingdom Classification Criteria

The main criteria used include cell structure, body organisation, mode of nutrition, reproduction, and phylogenetic relationships.

Three-domain system

A system that divides Kingdom Monera into two domains and places remaining eukaryotic kingdoms in a third domain, resulting in a six-kingdom classification.

Kingdom Monera

The kingdom whose sole members are bacteria, comprising all prokaryotic organisms.

Coccus ($pl.: cocci$)

Spherical-shaped bacteria.

Bacillus ($pl.: bacilli$)

Rod-shaped bacteria.

Vibrium ($pl.: vibrio$)

Comma-shaped bacteria.

Spirillum ($pl.: spirilla$)

Spiral-shaped bacteria.

Archaebacteria

Special bacteria that live in harsh habitats, including halophiles (salty areas), thermoacidophiles (hot springs), and methanogens (marshy areas).

Methanogens

Bacteria present in the gut of ruminant animals like cows and buffaloes, responsible for producing methane ($\text{biogas}$) from dung.

Eubacteria

Known as 'true bacteria,' characterized by a rigid cell wall and, if motile, a flagellum.

Cyanobacteria

Also known as blue-green algae, these are photosynthetic autotrophs containing chlorophyll $a$, often forming blooms in polluted water bodies.

Heterocysts

Specialised cells in organisms like Nostoc and Anabaena used to fix atmospheric nitrogen.

Chemosynthetic autotrophic bacteria

Bacteria that oxidise inorganic substances like nitrates and ammonia to produced energy for $ATP$ production, playing a role in nutrient recycling.

Mycoplasma

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

Kingdom Protista

Kingdom that includes all single-celled eukaryotes, such as Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds, and Protozoans.

Chrysophytes

A group in Protista including diatoms and golden algae (desmids), found in fresh water and marine environments.

Diatomaceous earth

Accumulated cell wall deposits of diatoms over billions of years, which are gritty and used in polishing and filtration.

Gonyaulax

A red dinoflagellate that undergoes rapid multiplication, causing the sea to appear red, known as 'red tides.'

Pellicle

A protein-rich layer in euglenoids that makes their body flexible in the absence of a cell wall.

Plasmodium ($\text{Slime Moulds}$)

An aggregation formed by slime moulds under suitable conditions that may grow several feet.

Pseudopodia

'False feet' used by amoeboid protozoans, such as Amoeba, to move and capture prey.

Kingdom Fungi

A unique kingdom of heterotrophic organisms showing great diversity in morphology and habitat, including mushrooms and yeast.

Hyphae

Long, slender thread-like structures that make up the bodies of multicellular fungi.

Mycelium

The network of hyphae in a fungus.

Coenocytic hyphae

Continuous tubes of hyphae filled with multinucleated cytoplasm.

Saprophytes

Organisms that absorb soluble organic matter from dead substrates.

Plasmogamy

The fusion of protoplasms between two motile or non-motile gametes during the fungal sexual cycle.

Karyogamy

The fusion of two nuclei during the sexual cycle of fungi.

Dikaryon

A condition in some fungi where two nuclei ($n + n$) exist per cell following plasmogamy but before karyogamy.

Phycomycetes

A class of fungi with aseptate and coenocytic mycelium, including Mucor, Rhizopus, and Albugo.

Ascomycetes

Commonly known as sac-fungi, these are mostly multicellular (e.g., Penicillium) or rarely unicellular (e.g., Yeast or $Saccharomyces$).

Basidiomycetes

Commonly known as mushrooms, bracket fungi, or puffballs, characterized by the production of basidiospores on a basidium.

Deuteromycetes

Commonly known as imperfect fungi because only their asexual or vegetative phases are known.

Alternation of generations

The life cycle phenomenon in plants featuring alternating diploid sporophytic and haploid gametophytic phases.

Holozoic

The mode of nutrition in Kingdom Animalia characterized by the ingestion of food.

Dmitri Ivanowsky ($1892$)

The scientist who recognized microbes smaller than bacteria as the cause of the mosaic disease of tobacco.

Contagium vivum fluidum

A term meaning 'infectious living fluid,' used by M.W. Beijerinck ($1898$) to describe the pathogen called a virus.

W.M. Stanley ($1935$)

The scientist who demonstrated that viruses could be crystallised and consist largely of proteins.

Capsid

The protein coat of a virus that protects the nucleic acid, made of small subunits called capsomeres.

Bacteriophages

Viruses that infect bacteria, usually containing double-stranded $DNA$.

Viroids

Infectious agents smaller than viruses, discovered by T.O. Diener ($1971$), consisting of free $RNA$ of low molecular weight and lacking a protein coat.

Prions

Infectious agents consisting of abnormally folded protein that cause neurological diseases like Mad Cow disease (BSE).

Lichens

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