The Living World Lecture Notes

Ernst Mayr: The Darwin of the 20th Century\n\n* Birth and Life Span: Ernst Mayr was born on 5 July 1904, in Kempten, Germany. He passed away in 2004 at the age of 100.\n* Academic Career: He was a Harvard University evolutionary biologist. He joined Harvard's Faculty of Arts and Sciences in 1953 and retired in 1975 with the title Alexander Agassiz Professor of Zoology Emeritus.\n* Research Areas: His 80-year career included ornithology, taxonomy, zoogeography, evolution, systematics, and the history and philosophy of biology.\n* Legacy:\n * Mayr is considered one of the 100 greatest scientists of all time.\n * He defined the biological species, which is the currently accepted definition.\n * He established the origin of species diversity as a central question of evolutionary biology.\n* Awards (The Triple Crown of Biology):\n * Balzan Prize in 1983\n * International Prize for Biology in 1994\n * Crafoord Prize in 1999\n\n# Characteristics of Living Organisms\n\nBiology is defined as the science of life forms and living processes. Living organisms are characterized as self-replicating, evolving, and self-regulating interactive systems capable of responding to external stimuli.\n\n* Growth:\n * Defined as the increase in mass and increase in number of individuals (twin characteristics).\n * In multicellular organisms (plants and animals), growth occurs by cell division.\n * Plants grow continuously throughout their life span, while animals grow only to a certain age. Cell division still occurs in animals in specific tissues to replace lost cells.\n * In non-living objects (mountains, boulders, sand mounds), growth is by accumulation of material on the surface (extrinsic). Living organisms grow from inside (intrinsic).\n * Growth is not a defining property of life because non-living objects can grow by mass increase.\n* Reproduction:\n * Production of progeny possessing features similar to parents. This includes sexual and asexual means.\n * Examples: Fungi produce millions of asexual spores; Yeast and Hydra use budding; Planaria (flat worms) exhibit true regeneration; Fungi, filamentous algae, and protonema of mosses multiply by fragmentation.\n * In unicellular organisms (bacteria, Amoeba), reproduction is synonymous with growth (increase in cell number).\n * Reproduction is not an all-inclusive defining characteristic because some living organisms do not reproduce (e.g., mules, sterile worker bees, infertile human couples).\n* Metabolism:\n * The sum total of all chemical reactions occurring in the body. All living organisms (unicellular or multicellular) exhibit metabolism.\n * Isolated metabolic reactions in vitro (in a test tube) are not living things but are living reactions. Metabolism is a defining feature of life forms.\n* Consciousness and Response to Stimuli:\n * The ability to sense surroundings and respond to environmental stimuli (physical, chemical, or biological).\n * Plants respond to light, water, temperature, pollutants, and other organisms. Photoperiod affects reproduction in seasonal breeders (plants and animals).\n * Human beings are unique for having self-consciousness (awareness of self).\n * Consciousness is the defining property of living organisms.\n\n# Diversity, Identification, and Nomenclature\n\n* Biodiversity: The number and types of organisms on Earth. Currently, approximately $1.7-1.8 \text{ million}$ species are known and described.\n* Nomenclature: The process of standardizing the naming of living organisms so they are known by the same name globally. This requires Identification (describing the organism correctly to attach a name).\n* International Codes:\n * ICBN: International Code for Botanical Nomenclature (for plants).\n * ICZN: International Code of Zoological Nomenclature (for animals).\n* Binomial Nomenclature:\n * Proposed by Carolus Linnaeus.\n * Each scientific name has two components: Generic name and Specific epithet.\n* Universal Rules of Nomenclature:\n 1. Names are usually in Latin and written in italics.\n 2. The first word is the Genus (starts with a capital letter), and the second is the Specific epithet (starts with a small letter).\n 3. When handwritten, words are separately underlined. When printed, they are in italics.\n 4. The author's name appears at the end in abbreviated form (e.g., Mangifera indica Linn., indicating Linnaeus). \n\n# Taxonomy and Systematics\n\n* Taxonomy: The process of classification based on characteristics (characterization, identification, classification, and nomenclature). It considers external/internal structure, cell structure, development, and ecological information.\n* Systematics: Derived from the Latin word systema (meaning systematic arrangement). It includes identification, nomenclature, classification, and accounts for evolutionary relationships. Linnaeus titled his publication Systema Naturae.\n* Taxon: The scientific term for a category or rank. Plural: taxa.\n\n# The Taxonomic Hierarchy\n\nClassification involves a hierarchy of steps where each step represents a rank or category, known as a taxon. The categories in ascending order are:\n\n1. Species: A group of individual organisms with fundamental similarities. Species can be distinguished by distinct morphological differences (e.g., indica, tuberosum, leo).\n2. Genus: Aggregates of closely related species. For example, Solanum includes potato, tomato, and brinjal. Panthera includes lion (P. leo), leopard (P. pardus), and tiger (P. tigris).\n3. Family: A group of related genera with fewer similarities. Plants: Solanum, Petunia, and Datura are in Solanaceae. Animals: Panthera and Felis (cats) are in Felidae. Dogs are in Cancidae.\n4. Order: Assemblage of families with few similar characters. Plant families Convolvulaceae and Solanaceae are in order Polymoniales (based on floral characters). Animal order Carnivora includes Felidae and Cancidae.\n5. Class: Includes related orders. For example, Class Mammalia includes Order Primata (monkey, gorilla, gibbon) and Order Carnivora.\n6. Phylum or Division: Classes with common features like a notochord and dorsal hollow neural system (Phylum Chordata). \"Division\" is used for plants.\n7. Kingdom: The highest category. All animals are in Kingdom Animalia; all plants are in Kingdom Plantae.\n\nKey Rule: As one goes higher from species to kingdom, the number of common characteristics decreases.\n\n# Table 1.1: Organisms and Taxonomic Categories\n\n* Man: Homo sapiens | Genus: Homo | Family: Hominidae | Order: Primata | Class: Mammalia | Phylum: Chordata\n* Housefly: Musca domestica | Genus: Musca | Family: Muscidae | Order: Diptera | Class: Insecta | Phylum: Arthropoda\n* Mango: Mangifera indica | Genus: Mangifera | Family: Anacardiaceae | Order: Sapindales | Class: Dicotyledonae | Division: Angiospermae\n* Wheat: Triticum aestivum | Genus: Triticum | Family: Poaceae | Order: Poales | Class: Monocotyledonae | Division: Angiospermae\n\n# Taxonomical Aids\n\nTaxonomical aids are procedures, techniques, and stored information used for identification and classification.\n\n* Herbarium: A storehouse of collected plant specimens that are dried, pressed, and preserved on sheets. Sheets contain labels with date/place of collection, English, local, and botanical names, family, and collector's name.\n* Botanical Gardens: Collections of living plants for reference. Each plant is labeled with its botanical name and family. \n * Famous Gardens: Kew (England), Indian Botanical Garden (Howrah, India), National Botanical Research Institute (Lucknow, India).\n* Museums: Set up in educational institutes. Specimens are preserved in containers with preservative solutions, as dry specimens, or stuffed (birds/mammals). Insects are kept in boxes after collecting, killing, and pinnin. Skeletons are also kept.\n* Zoological Parks (Zoos): Wild animals kept in protected environments under human care. This helps in learning about food habits and behavior. Conditions mimic natural habitats.\n* Taxonomic Key: Used for identification based on similarities and dissimilarities. \n * Couplet: Based on contrasting characters in a pair.\n * Lead: Each statement in the key.\n * Keys are analytical and separate keys are needed for each category (family, genus, species).\n* Recording Descriptions: \n * Flora: Contains the account of habitat and distribution of plants of a given area (an index).\n * Manuals: Provide info for identification of names of species in an area.\n * Monographs: Contain information on any one taxon.\n * Catalogues: Another means of recording descriptions for identification.