Diversity in the Living World: Biology

Diversity in the Living World

• Biology focuses on life forms and processes
• The living world has an incredible variety of organisms
• Humans first distinguished between living and non-living things
• Early humans admired certain inanimate objects, animals, and plants
• These entities inspired awe and fear
• Later, humans described living organisms, including themselves
• Societies with a human-centered view had limited biological advances
• A systematic description of life forms led to systems for identification, naming and classifying organisms
• This recognition occurred by observing similarities among living organisms, both vertically and horizontally
• All living organisms, past and present, are related
• It led to cultural movements to conserve biodiversity which humbled humanity

Ernst Mayr (1904-2004)

• Ernst Mayr, born in Germany in 1904, was a Harvard University evolutionary biologist
• He was known as "The Darwin of the 20th century"
• Mayr joined Harvard in 1953 and retired in 1975 as Alexander Agassiz Professor of Zoology Emeritus
• Mayr's research spanned ornithology, taxonomy, zoogeography, evolution, systematics, the history and philosophy of biology over his 80-year career.
• He made the origin of species diversity a central question in evolutionary biology
• Mayr pioneered the accepted definition of a biological species
• He received the Balzan Prize (1983), the International Prize for Biology (1994), and the Crafoord Prize (1999)
• These awards are known as the "triple crown of biology"

The Living World

• The living world is amazing because of the range of living things
• Habitats include cold mountains, forests, oceans, lakes, deserts or hot springs
• Awe-inspiring aspects include galloping horses, migrating birds, valleys of flowers, attacking sharks
• Ecological interactions and molecular processes prompt reflection on the nature of life
• The concept of life has two parts; the technical, distinguishing the non-living, and the philosophical meaning of life
• Science does not address the philosophical

Diversity in the Living World

• There is a wide range of living organisms all around
• Both visible and microscopic organisms exist in diversity
• More observation area leads to greater organism variety
• Dense forests contain higher numbers and kinds of living organisms
• Species refer to different types of plant, animal, or organism
• 1.7-1.8 million species are known and described so far
• This is referred to as biodiversity

Nomenclature, Identification and Classification

• There are countless plants and animals worldwide with local names
• Local names for organisms vary by region
• If we didn't find ways to identify organisms, confusion would arise
• Nomenclature is needed to standardize the naming of living things to a single universal name.
• Nomenclature depends on correct organism description and identification
• Protocols for assigning scientific names have been created by scientists
• Biologists worldwide accept scientific names
• The International Code for Botanical Nomenclature (ICBN) provides guidelines for plant scientific names
• Animals are named by the International Code of Zoological Nomenclature (ICZN)
• Scientific names ensure organisms have one unique name, and enable accurate identification worldwide
• It also makes sure that names are unique
• A scientific name has a generic name and a specific epithet
• Binomial nomenclature uses these two components
• Biologists worldwide use the binomial nomenclature system by Carolus Linnaeus
• This two-word naming approach is convenient

Nomenclature Rules

• Biological names are typically in Latin and written in italics
• Biological names are either Latinized or derived from Latin regardless of origin
• The genus is represented by the first word in a biological name, while the specific epithet is the second
• Biological names that are handwritten must be underlined separately; printed names must be italicized to indicate their Latin origin
• Genera starts with a capital letter. Specific epithet starts with a small letter
• Mangifera indica shows this convention
• After the specific epithet, the name of the author appears in an abbreviated form
• Mangifera indica Linn is an example
• It refers to Linnaeus who first described the species
• Classification is vital to organize the study of living things due to its impossibility
• Grouping anything into relevant categories depending on easily observable characteristics is referred to as classification
• Familiar groups are plants, animals, dogs, cats and insects
• These terms link certain characteristics to the creature inside the group
• Dogs evoke the image of dogs and not cats
• Alsatians evoke the image of a specific type, while mammals evoke a general image
• Wheat evokes the image of wheat and not other crops
• Dogs, cats, mammals, wheat, etc are referred to as taxa
• Taxa classify categories at different levels
• Plants, wheat, animals, mammals. and dogs all indicate taxa
• Organisms are classified into different taxa according to their characteristcs
• External/internal structure, cell structure, development process and ecology form the basis of modern taxonomic studies
• Taxonomy relies on characterization, identification, classification and nomenclature.
• Humans have had long-standing interests in organisms
• Early classifications of various organisms was based on identifying basic needs of food, clothing and shelte
• The study of organismal diversity and interrelationships is called systematics
• Latin word Systema means systematic arrangement of organisms
• Linnaeus used the term "Systema Naturae" for his publication

Taxonomic Categories

• Systematics includes identification, nomenclature and classification
• It considers evolutionary relationships.
• Classification is a multi-step process with hierarchical ranks/categories
• Taxonomic category is a component of the taxonomic arrangement
• All categories make up the taxonomic hierarchy
• Taxon (taxa pl.) is a category, a level of classification
• An example of taxonomic categories and hierarchy is insects.
• Insects possess three pairs of jointed legs, making them a distinct group
• Insects, which can be classified and given a rank/category
• Remember that groups and categories denote the rank
• Each rank/taxon is a unit of classification
• Taxa are distinct biological units rather than morphological aggregates
• Taxonomic investigations have resulted in categories; kingdom, phylum/division, class, order, family, genus, species
• Species is the lowest category for plants and animals
• Placing an organism into various categories depends on its knowledge or characteristics
• This facilitates identifying similarities and dissimilarities in various species.

Species, Genus, Family, Order, Class and Phylum

• Species is a group of individual organisms with fundamental similarities
• One can distinguish closely related species by distinct morphological differences
• Mangifera indica, Solanum tuberosum and Panthera leo all utilize indica, tuberosum, and leo as the specific epithets
• The genera are different from the specific epithet
• Genera may have one or more specific epithets representing organisms of morphological similarities
• Panthera tigris for example
• Solanum includes species like nigrum and melongena
• Humans belong to the the species sapiens and the genus Homo
• The scientific name for humans is Homo sapiens
• The genus is composed of connected species with common attributes
• Genera are seen as collections of related species
• Potato and brinjal belong to Solanum
• Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) share features as species of the genus Panthera
• The genus differs from Felis which includes cats
• Family contains related genera with less similarities than genus/species
• Vegetative and reproductive characteristics are taken into account with families
• Three plant genera – Solanum, Petunia, Datura are in the Solanaceae family
• Genera Panthera and Felis (cats) are grouped into the Felidae family for animals
• Dogs and cats are in different families as well; Felidae and Canidae
• Categories like species, genus, and families are founded upon the number of common features
• Orders and other higher taxonomic groups are identified based on the collection of characters
• Order is an assemblage of related families, with limited attributes
• Plant families such as Convolvulaceae and Solanaceae are categorized into the order Polymoniales as determined by their floral characteristics
• Animal order Carnivora includes Felidae and Canidae
• Class contains related orders
• Primata (monkey, gorilla, gibbon) and Carnivora (tiger, cat, dog) are put in Mammalia
• Other orders can also be found in this class
• Phylum is the next level
• Classes of animalia combine to form phylum
• Examples are amphibians, reptiles, birds and mammals
• Chordata includes presence of notochord and dorsal hollow neural system
• In plants, classes are assigned to divisions

Kingdom

• Kingdom Animalia contains animal phyla
• Plantae contains plant divisions
• Animal and plant kingdoms are the two recognized groups
• Figure 1.1 shows taxonomic categories in ascending order from species to kingdom
• Developed taxa facilitate sound placement
• As you move to higher categories, common characteristics decrease
• Lower taxa have more shared traits
• Higher categories make it more difficult to determine relationships, rendering classification more complex
• Table 1.1 refers the taxonomic categories of common organisms

Organisms with their Taxonomic Categories as Examples

Summary of The Living World

• The living world is diverse, with many identified species
• More species remain unknown
• Range of size, color, habitat, physiology, and morphology defines living organisms
• Biologists use rules and principles for identification, nomenclature, and classification of organisms
• Taxonomy is the knowledge branch dealing with these aspects
• Taxonomic studies aid agriculture, forestry, industry and knowing bio-resources and diversity
• International codes universally evolved identification, naming, and classification
• Organisms are identified using resemblance, differences, and binomial names
• In the classification system, organisms occupy ranks
• Taxa are taxonomic categories that constitute a taxonomic hierarchy