Introduction to Biology and Ernst Mayr

• Biology is the study of life forms and processes
• Early humans easily recognized the difference between living and non-living things
• Early humans revered inanimate objects like wind and fire, as well as certain plants and animals
• Societies that focused on an anthropocentric perspective in biology achieved limited progress in biological knowledge
• The detailed description of life forms led to systems of identification, nomenclature, and classification
• Studies revealed shared similarities among living organisms, both horizontally and vertically
• The understanding of the relationship between all living organisms, past and present, led to cultural movements focused on biodiversity conservation
• Subsequent chapters include descriptions and classification of animals and plants from a taxonomist's viewpoint

Ernst Mayr (1904-2004)

• Ernst Mayr was an evolutionary biologist at Harvard University
• He was called "The Darwin of the 20th century"
• Mayr joined Harvard's Faculty of Arts and Sciences in 1953 and retired in 1975
• His research covered ornithology, taxonomy, zoogeography, evolution, systematics, and the history/philosophy of biology
• Mayr established species diversity origin as a central evolutionary biology question
• He pioneered the modern definition of a biological species.
• Mayr received the Balzan Prize in 1983, the International Prize for Biology in 1994, and the Crafoord Prize in 1999
• These prizes are widely known as biology's triple crown
• Mayr passed away in 2004 at age 100

The Living World

• Habitats with living organisms include cold mountains, deciduous forests, oceans, fresh water lakes, deserts, and hot springs
• The beauty of nature and ecological interactions evoke awe
• Consideration of life leads to questions about the difference between living and non-living, and the purpose of life

Diversity in the Living World

• Includes a variety of living organisms, from visible plants and animals to unseen microorganisms
• Increased observation area results in a wider range and variety of organisms
• Each unique plant, animal, or organism represents a species
• The number of known and described species ranges from 1.7 to 1.8 million
• This range refers to biodiversity, which is the number and types of organisms on Earth

Nomenclature

• New organisms are continuously identified from exploring new and old areas
• There are millions of plants and animals worldwide known by local names that vary by region
• Standardizing the naming of living organisms is needed so each organism has a universal name, this process is called nomenclature
• Nomenclature depends on correct organism description for proper identification and to know what organism the name applies to
• Scientists have developed procedures for assigning a scientific name to each known organism
• Scientific names are based on agreed principles and criteria, as provided in the International Code for Botanical Nomenclature (ICBN) for plants
• Animal taxonomists follow the International Code of Zoological Nomenclature (ICZN)
• Scientific names ensure each organism has a unique name
• An organism's description enables people anywhere to identify it by the same name
• These names also ensure that a name has not been previously used for another known organism

Binomial nomenclature

• Biologists use universal principles for scientific names of known organisms
• Each name contains two components: a generic name and a specific epithet
• This system of providing names with two components is called binomial nomenclature
• Binomial nomenclature was introduced by Carolus Linnaeus
• Mangifera indica is an example of binomial nomenclature, where Mangifera is the genus and indica is the specific epithet

Universal rules

• Biological names are generally in Latin and written in italics, either Latinized or derived from Latin
• A biological name's first word represents the genus, the second word represents the specific epithet
• In a biological name, the genus starts with a capital letter, and the specific epithet starts with a small letter, illustrated by Mangifera indica
• The author's name appears after the specific epithet in abbreviated form to denote that the species was first described by that person, i.e., Mangifera indica Linn.

Classifying Organisms

• Classifying living organisms involves grouping them into categories using easily observable characteristics
• The process of classification is necessary to ease the study of organisms since it is nearly impossible to study all of them
• A group can also be called a taxa
• Taxa can indicate categories at various levels
• Taxonomy is classifying all living organisms into different taxa based on characteristics
• External and internal structure, plus cell structure, development, and ecological information are essential for classification
• Key processes: characterization, identification, classification, and nomenclature are basic to taxonomy
• Taxonomy is an age-old practice, and humans have always been interested in classifying organisms, mainly those useful to their own
• Early classifications were based on the uses of various organisms for basic needs
• Systematics is the study of different organisms, their diversities, and relationships
• The word 'systematics' comes from the Latin word 'systema', for the systematic arrangement of organisms
• Linnaeus used 'Systema Naturae' as his publication title, indicating the importance he placed on systematic arrangement
• Systematics now includes Identification, Nomenclature, Classification and Evolutionary relationships between organisms

Taxonomic Categories

• Classification is hierarchical, with each step representing a rank or category
• A taxonomic category is part of the overall taxonomic arrangement
• All taxonomic categories together form the taxonomic hierarchy
• Each category is a unit of classification and is called a taxon (plural: taxa)
• An illustration of taxonomic categories: insects grouped by three pairs of jointed legs, giving insects rank and category
• Groups represent category
• A category denotes rank
• Ranks/taxa are units of classification
• Taxonomic groups/categories are biological entities, not just morphological aggregates

Taxonomic Studies

• Taxonomic studies led to developing common categories like kingdom, phylum/division, class, order, family, genus, and species
• Species is the lowest category for all organisms in the plant and animal kingdoms
• Placing an organism in categories requires knowledge of individual/group characters
• This aids in identifying similarities and differences among the same/different organisms

Species

• Taxonomic studies consider species as a group of individual organisms with fundamental similarities
• Species can be distinguished from related species by distinct morphological differences
• In Mangifera indica, Solanum tuberosum, and Panthera leo, "indica", "tuberosum", and "leo" are specific epithets
• Mangifera, Solanum, and Panthera are genera and represent a higher taxonomic category
• A genus can have multiple specific epithets for different organisms with morphological similarities
• Panthera includes tigris, and Solanum includes nigrum and melongena
• Humans belong to Homo sapiens

Genus

• Genus has a group of related species having more common characteristics than species of other genera
• Genera consist of closely related species
• Potato and brinjal are different species within the genus Solanum
• Lion (Panthera leo), leopard (P. pardus), and tiger (P. tigris) share common features as species of the genus Panthera
• Panthera differs from Felis, the genus of cats

Family

• A family contains related genera with fewer similarities than genus and species
• Families are characterized through both vegetative/reproductive characters
• Solanum, Petunia, and Datura are genera in the Solanaceae family
• Panthera (lion, tiger, leopard) and Felis (cats) are in the Felidae family
• Cats and dogs have similarities and differences, placing them in the Felidae and Canidae families

Order

• Species, genus, and families are based on similar features
• Order is a higher taxonomic category that is identified based on aggregate characters
• Orders are assemblages of families that exhibit a few similar characteristics
• Plant families like Convolvulaceae and Solanaceae are included in the order Polymoniales, based on floral characters
• Animal order Carnivora includes Felidae and Canidae families

Class

• Class includes related orders
• Primata (monkey, gorilla, gibbon) is placed in Mammalia along with Carnivora (tiger, cat, dog)
• Class Mammalia includes other orders as well

Phylum

• Phylum is a higher category which includes classes comprising animals like fishes, amphibians, reptiles, birds, and mammals
• Presence of a notochord and dorsal hollow neural system are common characteristics for the members of the Phylum Chordata
• Divisions perform the same function, but for plants

Kingdoms

• Kingdom Animalia is highest category for animals which consists of phyla
• Kingdom Plantae is distinct from plants and consists of divisions

Taxonomic Categories

• Taxonomic categories from species to kingdom show how characteristics decrease
• Lower taxa share more characteristics, while higher categories have greater difficulty relating to other taxa at the same level
• Table 1.1 illustrates the taxonomic categories of organisms like housefly, man, mango, and wheat