Biological Classification and Five Kingdoms

Earliest attempt at a scientific classification of organisms, grouping unicellular and multicellular organisms together.

Organisms classified into two kingdoms: Plantae and Animalia. Plants and animals with cell walls were grouped together (a major flaw).

System proposed by Whittaker including Monera, Protista, Fungi, Plantae, Animalia. Categorized by cell structure and lifestyle.

Included very different organisms in a single group, like bacteria and fungi.

More accurate classification due to consideration of cell structure, mode of nutrition, and evolutionary relationships.

A cell lacking a true nucleus and membrane-bound organelles. Instead of a nucleus, their genetic material (DNA) is present in a region called the nucleoid.

A cell with a true nucleus and membrane-bound organelles, providing compartments for specialized functions.

A rigid outer layer that provides structural support and protection to the cell. It is made of different materials depending on the organism.

Cellulose, a complex carbohydrate that gives plants their rigidity and structure.

Chitin, a strong and flexible polysaccharide also found in the exoskeletons of insects.

Organisms that can produce their own food through processes like photosynthesis or chemosynthesis.

Organisms that obtain their food from other organisms, either by consuming them directly or by absorbing nutrients from decaying matter.

An organism that obtains nutrients from dead organic matter.

Unicellular, colonial, or filamentous algae that contain chlorophyll a, similar to green plants. They often form blooms in polluted water bodies and can fix atmospheric nitrogen in specialized cells called heterocysts.

Organisms that cannot synthesize their own food and rely on other organisms or dead organic matter for nutrition.

Organisms that can synthesize their own food from inorganic substrates, such as sunlight and carbon dioxide.

Unicellular prokaryotic organisms that thrive in extreme environments like hot springs, salty areas, and marshy areas. They have a different cell wall structure than bacteria, allowing them to survive in harsh conditions.

Archaebacteria that produce methane gas as a byproduct of their metabolism. They are found in the guts of ruminant animals like cows and buffaloes.

Bacteria reproduce primarily through binary fission, a process where a single cell divides into two identical daughter cells.

Organisms without a cell wall that are the smallest living cells. They can survive without oxygen.

Under unfavorable conditions, some bacteria produce spores, which are dormant, resistant forms that can survive harsh environments.

Euglenoids are a group of single-celled organisms with unique characteristics. They have a flexible body due to a protein-rich layer called a pellicle, and they can photosynthesize like plants, but they are not plants.

Dinoflagellates are single-celled organisms that often have two flagella for movement. Some of them, like the red dinoflagellates, can cause red tides, which are harmful algal blooms that release toxins.

A pellicle is a thin, flexible layer made of protein that provides structural support for the cell membrane in Euglenoids.

Flagellated protozoans are single-celled organisms that use flagella for movement. They can be free-living or parasitic, and some cause diseases.

Ciliated protozoans have thousands of tiny hair-like structures called cilia that help them move and collect food.

Sporozoans are parasitic protozoans that have a spore-like stage in their life cycle. They are known for causing diseases like malaria.

A hypha is a long, thread-like structure that makes up the body of a fungus. They are often branched and interconnected to form a network called mycelium.

Mycelium is a network of interconnected hyphae that makes up the body of a fungus. It allows the fungus to spread and absorb nutrients.

A stage in fungal life cycles where cells contain two distinct nuclei from different parental sources (n + n). This stage precedes karyogamy (nuclear fusion).

The fusion of two haploid nuclei from different parental sources, forming a diploid nucleus (2n). This occurs after the dikaryotic stage in fungi.

A specialized club-shaped cell in basidiomycete fungi that produces four haploid basidiospores through meiosis.

A haploid spore produced by meiosis within a basidium in basidiomycetes. These spores can germinate and develop into new fungal mycelia.

A reproductive structure of a basidiomycete fungus, such as a mushroom or bracket fungus, where basidia are formed and basidiospores are released.

A group of fungi characterized by aseptate (non-compartmentalized) mycelium, production of motile zoospores or aplanospores, and sexual reproduction via zygospores.

A diverse group of fungi characterized by the formation of asci (sac-like structures) that contain ascospores (haploid spores) produced through sexual reproduction.

A group of fungi that reproduce only asexually. Often referred to as 'imperfect fungi' because their sexual stages were not initially observed.

The kingdom Plantae encompasses all eukaryotic organisms with cell walls made of cellulose. They are mostly autotrophic, using photosynthesis to produce their own food. Examples include algae, mosses, ferns, and flowering plants.

A life cycle in plants that alternates between a diploid (2n) sporophyte phase and a haploid (n) gametophyte phase. The sporophyte produces spores, which develop into the gametophyte, which produces gametes (sperm and egg) that fuse to form a diploid zygote, initiating the sporophyte phase again.

Animals are multicellular, heterotrophic, eukaryotic organisms lacking cell walls. They display complex development, sensory systems, and locomotion, often with specialized tissues and organs.

A non-cellular, obligate parasite containing genetic material (DNA or RNA) enclosed within a protein coat. Viruses cannot reproduce on their own and require a host cell to replicate.

An infectious agent consisting of a small, circular RNA molecule without a protein coat. They are smaller than viruses and can cause diseases in plants.

An infectious protein that can cause fatal neurodegenerative diseases. Prions are misfolded proteins that can induce other proteins to misfold, leading to damage in the brain.

A symbiotic association between a fungus and an alga (sometimes a cyanobacterium). The fungus provides structure and protection, while the alga provides food through photosynthesis.

A mode of nutrition where organisms ingest solid food, digest it internally, and absorb the nutrients. This is characteristic of animals.