Classification and Taxonomy

Introduction to Classification and Taxonomy

• Definition: The science of classifying life according to shared characteristics.

Carolus Linnaeus and Binomial Nomenclature

• Linnaeus' Contribution: Developed the system of binomial nomenclature.

  • This system assigns every organism two names.

  • Example: Humans are named Homo sapiens.

• Structure of Names:

  • The first word (Genus) is broader (e.g., Homo).

  • The second word (Species) is specific (e.g., sapiens).

• Examples:

  • Humans: Homo sapiens

  • Homo erectus: same Genus as humans, different Species.

Formatting Binomial Names

• Typographical Rules:

  • Genus is capitalized; species is lowercase.

  • Written in italics if typed, underlined if handwritten.

  • Examples:

    • Cow: Bos taurus

    • Gray Wolf: Canis lupus

Common Names vs. Scientific Names

• Issues with Common Names: Can be misleading as they suggest incorrect affiliations.

  • Example:

    • Jellyfish: Not a fish, not made of jelly.

    • Seahorse: A fish, despite its name.

    • Starfish: Not a fish.

    • Prairie Dog: More closely related to rodents than to dogs.

• Example of Confusion:

  • Puma, Cougar, and Mountain Lion are all the same species: Puma concolor.

Historical Classification Issues

• Early Classification: Based on physical features; led to errors.

  • Example: Sharks (fish) and dolphins (mammals) were thought closely related based on appearance.

  • Mushrooms were grouped with plants due to their growth characteristics.

Modern Classification: Utilization of DNA

• DNA Analysis:

  • A method for determining relatedness among species.

  • Differences in DNA sequences can reveal how closely organisms are related.

• Example: Comparing DNA sequences of flowers to ascertain the closest relatives.

Levels of Taxonomy (Classification)

• Definition: Each level of classification is called a taxon.

  • Begins with very broad categories and becomes more specific.

    • Levels Include: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Mnemonic Device: "Dear King Philip Came Over for Good Spaghetti" to remember the order of taxonomy levels.

Example of Taxonomy Levels: Leopard

• Domain: Eukarya (organisms with cells that have nuclei).

• Kingdom: Animalia (all animals).

• Phylum: Chordata (animals with backbones).

• Class: Mammalia (mammals).

• Order: Carnivora (meat-eaters).

• Family: Felidae (cat family).

• Genus: Panthera (big cats).

• Species: Panthera pardus (leopard).

Comparing Taxonomy Levels of Leopard, Lion, and Rabbit

• Common Levels: Domain (Eukarya), Kingdom (Animalia), Phylum (Chordata), Class (Mammalia).

• Differences:

  • Order: Leopards & Lions (Carnivora) vs. Rabbits (Lagomorpha).

  • Family: Leopards & Lions (Felidae) vs. Rabbits (Leporidae).

  • Genus: Leopards & Lions (Panthera) vs. Rabbits (different genus).

• Conclusion: The closer the species in levels, the more closely related they are.

Domains and Kingdoms Overview

• Domains: Three major domains of life.

  • Bacteria: Prokaryotes with peptidoglycan in cell walls.

  • Archaea: Prokaryotes without peptidoglycan; can live in extreme conditions.

  • Eukarya: Eukaryotic organisms with nuclei and organelles.

• Kingdoms: Six recognized kingdoms, subject to change:

  • Domain Bacteria: Kingdom Eubacteria (common bacteria).

  • Domain Archaea: Kingdom Archaea (extremophiles).

  • Domain Eukarya: Include kingdoms Protista, Fungi, Plants, Animals.

  • Protista: Simple, single-celled organisms (e.g., amoebas).

Conclusion and Review

• Assess understanding of classification and taxonomy principles.

Introduction to Classification and Taxonomy

Definition

The science of classifying life according to shared characteristics, which allows scientists to organize and categorize organisms in a structured framework.

Carolus Linnaeus and Binomial Nomenclature

Linnaeus' Contribution

Carolus Linnaeus, a Swedish botanist, is often referred to as the father of modern taxonomy. He developed the system of binomial nomenclature, which assigns every organism a unique two-part name.

• Example: Humans are named Homo sapiens.

Structure of Names

The binomial name consists of two parts:

1. Genus: The first word is the genus, which is broader and indicates a group of closely related species (e.g., Homo).

2. Species: The second word is the specific name, indicating an individual species within the genus (e.g., sapiens).

• Examples:

  • Humans: Homo sapiens

  • Homo erectus: shares the same Genus as humans, but represents a different species within that genus.

Formatting Binomial Names

Typographical Rules

When writing binomial names, certain typographical rules must be followed:

• The genus name is always capitalized; the species name is written in lowercase.

• If typed, both names should be in italics; if handwritten, both names should be underlined.

• Examples:

  • Cow: Bos taurus

  • Gray Wolf: Canis lupus

Common Names vs. Scientific Names

Issues with Common Names

Common names can often be misleading as they imply incorrect biological affiliations. This can create confusion in scientific literature and discussions.

• Examples:

  • Jellyfish: Not actually a fish and is not made of jelly, it's a gelatinous zooplankton.

  • Seahorse: While it has "horse" in its name, it is indeed a fish.

  • Starfish: Not a true fish; scientifically referred to as sea stars.

  • Prairie Dog: More closely related to rodents than to canines, despite its name.

Example of Confusion

Different names often refer to the same species, leading to further confusion:

• Puma, Cougar, and Mountain Lion are all the same species, scientifically known as Puma concolor.

Historical Classification Issues

Early Classification

Earlier classification systems relied heavily on observable physical features, which led to numerous errors in categorization:

• Example: Sharks (classified as fish) and dolphins (classified as mammals) were once thought to be closely related based on their similar body shapes.

• Mushrooms were incorrectly grouped with plants due to superficial growth characteristics, despite significant biological differences.

Modern Classification: Utilization of DNA

With advancements in technology, the modern classification of organisms utilizes DNA analysis:

• DNA Analysis: A method of examining the genetic material to determine relatedness among species.

• Differences in DNA sequences among organisms can reveal their evolutionary relationships.

• Example: Scientists may compare DNA sequences of flowering plants to ascertain their closest relatives and reclassify them accurately.

Levels of Taxonomy (Classification)

Definition

Each level of classification is referred to as a taxon. This hierarchy begins with broad categories and becomes progressively more specific.

Levels Include:

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Mnemonic Device

To remember the order of taxonomy levels, the phrase: "Dear King Philip Came Over for Good Spaghetti" is commonly used.

Example of Taxonomy Levels: Leopard

• Domain: Eukarya (organisms with cells that contain nuclei).

• Kingdom: Animalia (all animals).

• Phylum: Chordata (animals with backbones).

• Class: Mammalia (mammals).

• Order: Carnivora (meat-eaters).

• Family: Felidae (cat family).

• Genus: Panthera (big cats).

• Species: Panthera pardus (leopard).

Comparing Taxonomy Levels of Leopard, Lion, and Rabbit

Common Levels

Leopard, lion, and rabbit share some common classification levels:

• Domain: Eukarya

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

Differences

• Order:

  • Leopards & Lions: Carnivora (meat-eating mammals)

  • Rabbits: Lagomorpha (herbivorous mammals).

• Family:

  • Leopards & Lions: Felidae (cat family)

  • Rabbits: Leporidae (rabbit family).

• Genus:

  • Leopards & Lions: Panthera (big cats)

  • Rabbits: Different genus (e.g., Oryctolagus for the European rabbit).

Conclusion

The closer the species are in the classification levels, the more closely related they are likely to be in evolutionary terms.

Domains and Kingdoms Overview

Domains

There are three major domains of life:

1. Bacteria: Comprises prokaryotes with peptidoglycan in their cell walls.

2. Archaea: Consists of prokaryotes that lack peptidoglycan and can survive in extreme conditions.

3. Eukarya: Includes eukaryotic organisms characterized by the presence of nuclei and organelles.

Kingdoms

Currently, six kingdoms are recognized, and this classification is subject to change as new discoveries are made:

• Domain Bacteria: Kingdom Eubacteria (includes common bacteria).

• Domain Archaea: Kingdom Archaea (extremophiles that thrive in harsh environments).

• Domain Eukarya: Comprises kingdoms Protista (simple, single-celled organisms, e.g., amoebas), Fungi, Plants, and Animals.

Conclusion and Review

Encourage students to assess their understanding of classification and taxonomy principles by reviewing the hierarchical levels and the significance of accurately naming organisms.