What is Biology?

• Biology studies life forms and processes.
• The living world has an amazing diversity of organisms.
• Early humans easily differentiated between living and non-living things.
• Early humans attributed god-like status to inanimate things like wind and fire.
• Early humans also deified plants and animals.
• Awe and fear were common reactions to both inanimate and animate objects.
• The description of living organisms, including humans, came later in history.
• Societies with an anthropocentric view saw limited progress in biology.
• Systematic description of life forms led to systems of identification, nomenclature, and classification.
• Recognition of similarities among organisms revealed relationships among them.
• Present-day organisms are related to each other and to those that lived on Earth.
• This realization humbled humanity and led to biodiversity conservation efforts.
• Later chapters describe and classify animals and plants from a taxonomist's perspective.

Ernst Mayr (1904 – 2004)

• Ernst Mayr, born July 5, 1904, in Kempten, Germany, was a Harvard evolutionary biologist.
• Mayr was called "The Darwin of the 20th century" and one of the 100 greatest scientists of all time.
• In 1953, Mayr joined Harvard's Faculty of Arts and Sciences, retiring in 1975.
• Mayr became Alexander Agassiz Professor of Zoology Emeritus upon retirement.
• His 80-year career included research in ornithology, taxonomy, zoogeography, evolution, systematics, and the history/philosophy of biology.
• Mayr highlighted the origin of species diversity as a central question in evolutionary biology.
• He pioneered the present-day definition of a biological species.
• Mayr won the Balzan Prize (1983), International Prize for Biology (1994), and Crafoord Prize (1999).
• These are considered the "triple crown of biology."
• Mayr died in 2004 at the age of 100.

The Living World

• The living world's vast array of living types is amazing.
• Habitats like mountains, forests, fresh water lakes, deserts, and hot springs are incredible.
• The beauty of nature evokes awe and wonder.
• Ecological interactions and molecular processes prompt reflection on the nature of life.
• There are two questions about life: 1) What distinguishes living from non-living? and 2) What is the purpose of life?
• Science addresses the first question rather than the second.

Diversity in the Living World

• Observing the surroundings reveals a variety of organisms including visible and invisible organisms.

• Increasing the observation area increases the diversity of observed organisms.

• Dense forests are home to a greater amount of different organisms.

• Each unique plant, animal, or organism represents a species.

• There are 1.7-1.8 million known and described species.

• This is biodiversity.

• New organisms are constantly being identified, even in explored areas.

• There are millions of plants and animals with local names that vary by region.

• Standardized naming, or nomenclature, is needed to discuss organisms universally.

• Nomenclature requires correct organism description and attachment of the name to the correct organism, which is identification.

• Procedures for assigning scientific names are established and accepted worldwide to help study organisms.

• The International Code for Botanical Nomenclature (ICBN) is used for plants' scientific names.

• The International Code of Zoological Nomenclature (ICZN) guides animal naming.

• Scientific names ensure each organism has a unique name.

• Organism descriptions should enable people everywhere to arrive at the same name.

• Scientific names have two components: a generic name and a specific epithet.

• This system is called Binomial nomenclature, created by Carolus Linnaeus.

• Mangifera indica (mango) is an example of binomial nomenclature, where Mangifera is the genus and indica is the species.

• Biological Names are generally in Latin and written in italics.

• They are Latinized, regardless of their origin.

• The genus is the first word which represents the biological name

• The second component denotes the specific epithet.

• When handwriting the words must be underlined separately

• When printing the words are formatted in italics, this is done to indicate their Latin origin.

• The genus starts with a capital letter, and the specific epithet starts with a small letter. Mangifera indica shows this

• The author's name appears in an abbreviated form after the specific epithet.

• Mangifera indica Linn. means Linnaeus first described the species.

• Classification groups organisms into convenient categories based on easily observable characters.

• Recognizing groups such as plants, animals, dogs, cats, and insects involves associating certain characters to them.

• The picture of a dog or an Alsatian is universally recognizable.

• Mammals are animals with external ears and body hair and wheat implies wheat plants.

• "Dogs," "Cats," "Mammals," "Wheat," etc., are categories used to study organisms.

• The scientific term for these categories is taxa.

• Taxa can indicate categories at different levels with 'plants' and 'wheat' both forming a taxa.

• "Animals", "mammals", and "dogs" are taxa but a dog is a mammal and mammals are animals.

• Living organisms are classified into different taxa based on characteristics.

• This process is called Taxonomy.

• External/internal structure, cell structure, development, and ecological information are essential for modern taxonomy.

• Characterization, identification, classification, and nomenclature are basic to taxonomy.

• Human interest in organisms for their own use isn't new.

• Early classifications were based on the 'uses' of various organisms for food, clothing, and shelter.

• Interest in organism diversity and relationships grew.

• Study of these relationships is called systematics.

• The word systematics comes from the Latin 'systema,' meaning systematic arrangement of organisms.

• Linnaeus used "Systema Naturae" for his publication.

• Systematics includes identification, nomenclature, classification, and evolutionary relationships.

Taxonomic Categories

• Classification is a hierarchical process with each step representing a rank.
• A taxonomic category is part of an overall taxonomic arrangement.
• All categories together form the taxonomic hierarchy.
• Each category represents a rank and is called a taxon.
• Insects are a group of organisms sharing features like three pairs of jointed legs.
• Being classifiable, insects have a rank or category.
• Groups are a category and a rank.
• Each rank, or taxon, is a classification unit.
• Taxonomic groups/categories are distinct biological entities.
• Common categories like kingdom, phylum/division, class, order, family, genus, and species have emerged via taxonomical investigation.
• All organisms in plant and animal kingdoms have species as the lowest category.
• Grouping organisms requires knowing the characters of the individual.
• This helps identify similarity and dissimilarity among like/unlike organisms.

Species

• Taxonomic studies consider a group of individual organisms with fundamental similarities.
• Species are distinguished by distinct morphological differences.
• Mangifera indica, Solanum tuberosum (potato), and Panthera leo (lion) share indica, tuberosum, and leo as specific epithets.
• Mangifera, Solanum, and Panthera are genera with a higher level of taxon or category.
• Each genus might include one or more specific epithets representing various organisms.
• Panthera* has tigris and Solanum includes nigrum and melongena.
• Humans are Homo sapiens, belonging to the Homo genus.

Genus

• A genus is a group of related species sharing common features.
• Genera are aggregates of closely related species.
• Potato and brinjal are different species in the genus Solanum.
• Lion (Panthera leo), leopard (P. pardus), and tiger (P. tigris) are species of the genus Panthera.
• Panthera differs from Felis, which includes cats.

Family

• A family is a group of related genera with some similarities.
• Families are characterized on vegetative and reproductive characteristics of plant species.
• Solanum, Petunia, and Datura are placed in Solanaceae.
• Panthera, including lion, tiger, and leopard, is grouped with Felis (cats) in Felidae.
• Cats and dogs share similarities and differences and are in Felidae and Canidae.

Order

• Categories like species, genus, and families rely on similar characters.
• Higher taxonomic categories are identified based on aggregates of characters.
• An order, as a higher category, is an assemblage of families with a few similar characters. Plant families like Convolvulaceae and Solanaceae are in the order Polymoniales due to floral characters.
• The animal order, Carnivora, includes families such as Felidae and Canidae.

Class

• The class is a category that features similar orders.
• The order Primata, including monkeys, gorillas, and gibbons, is placed in the class Mammalia.
• The order Carnivora, a part of the class Mammalia which also includes tigers, cats and dogs.
• The class Mammalia has multiple orders contained within it.

Phylum

• Classes made up of animals constituting fishes, amphibians, reptiles, birds along which mammals constitute the next higher category called Phylum.
• Organisms which share presence of notochord and dorsal hollow neural system are included in the phylum Chordata.
• Classes that share similar characters are assigned to the higher category division in plants.

Kingdom

• All animals assigned to the phylum are grouped together in the highest category called Kingdom Animalia in the classification system.
• On the other hand Kingdom Plantae is assigned to distinct plants from what it is assigned from animals, through various divisions.
• We will refer to groups like this as animal and plant kingdoms.
• Taxonomic categories range from species to kingdom in ascending order.
• Taxonomists have developed sub-categories to help and further facilitate the scientific placements of taxa.
• When going higher from species to a kingdom there is a decrease in the number of characteristics and vice versa when going lower.
• The greater the category, the complexity increases as it becomes harder to place due to level of relationships.
• Taxonomic categories to which common organisms belong like the housefly, mango, and wheat belong can be found in Table 1.1.

Summary

• The living world contains a variety of species.
• Millions of plants and animals are known and identified but many remain unknown.
• Organisms are classified based on their range of size, color, habitat, and physiological and morphological features.
• Biologists have developed rules and principles for identifying, naming, and classifying organisms.
• Taxonomy is the branch of knowledge dealing with these aspects.
• Studying plant and animal species through taxonomy is useful for agriculture, forestry, industry, and understanding bio-resources.
• Taxonomy is universally developed under international codes.
• A biological name is assigned based on resemblances and differences between organisms.
• The name comprises two words based on binomial nomenclature.
• An organism occupies a place in the classification system.
• Classifications have multiple categories such as taxonomic categories or taxa.
• All the categories make a taxonomic hierarchy.