TAXONOMY: The Science of Naming Organisms

I. Why Classify? Classification of Living Things A. Biological classification names and orders organisms in a logical manner. B. 2 Important features: 1. Assign a universally accepted name 2. Place organisms into groups that share important traits and follow accepted roles

II. BIOLOGICAL CLASSIFICATION The Greek philosopher, Aristotle (384-322 BC) developed the first system of biological classification.

He classified all the organisms he knew into two groups: Plants and Animals

He subdivided plants into 3 groups, Herbs, Shrubs, and Trees, depending on their size and structure of a plant.

He grouped animals according to various characteristics, including their habitat and physical differences.

According to his system, birds, bats, and flying insects are classified together even though they have little in common besides the ability to fly.

A. 18th Century Europeans established classification system rules for naming organisms Used Latin or ancient Greek words recognized by scientists all over the world (universal language) Described physical characteristics of species (sometimes 20 words long)

In the late 18th century, a Swedish botanist, Carolus Linnaeus (1707-1778), developed a method of grouping that is still used today. Linnaeus’s system was based on Phylogeny – evolutionary relationships, shared body structures.

B. Carolus Linnaeus developed the modern classification system known as binomial nomenclature (2-part scientific name consisting of Genus and species names.)

1. Genus refers to relatively small groups of organisms to which a particular type of organism belongs. * (The genus name is always capitalized & underlined)

Example of scientific name: Homo sapiens Species refers to individuals that can breed and produce fertile young. It is the Latin description of some important characteristic of the organism. *(The species name is not capitalized. , but it is underlined) Example of scientific name: Homo sapiens

The first letter of the genus name is uppercase, but the first letter of the specific epithet is lowercase. Ex: Canis familiaris

Dichotomous key - useful to identify many organisms Dichotomous key - useful to identify many organisms. A key is made up of sets of numbered statements.

3. Today, an international committee determines if a scientific name for a new species is acceptable, and not already given to some other species. Preserved specimens are kept of every known species of organism on earth

C. The classification system of Linnaeus was further grouped according to shared body structures. Later, with the acceptance of Darwin’s theory of evolution, biologists began classifying organisms according to an organism’s common ancestor.

Linnaeus called the different classification categories, classification groups or taxa (plural of taxon). Taxonomy is the science of naming organisms. A taxonomist is a scientist who classifies organisms.

3. The smallest taxon is the species, then the genus

Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family TAXON Kingdom Phylum Class Order Family Genus Species EXAMPLE Animalia Chordata Mammalia Carnivora Felidae Lynx Lynx rufus (bobcat)

4. The family includes groups of genera (plural of genus). Ex: All catlike organisms are in the family Felidae.

5. An order consists of groups of families 5. An order consists of groups of families. Ex: Dogs and cats are in the order Carnivora. (Carnivores are meat eaters.)

6. A class consists of groups of orders 6. A class consists of groups of orders. Ex: Carnivores and primates (including humans and chimpanzees) are in the class Mammalia. Mammals have body hair, are worm blooded, & produce milk for their young.

7. A phylum consists of groups of classes 7. A phylum consists of groups of classes. Ex: fishes, birds, reptiles, andmammal are in phylum Chordata. Chordates usually have a backbone or notochord (spinal chord) sometime in their lives.

8. Linnaeus only had 2 kingdoms: Plants & Animals 8. Linnaeus only had 2 kingdoms: Plants & Animals. Ex: Kingdom Plantae and Kingdom Animalia

Section 17.1 Summary – pages 443-449 Scientific and common names Many organisms have common names. However, a common name can be misleading. For example, a sea horse is a fish, not a horse. In addition, it is confusing when a species has more than one common name. Section 17.1 Summary – pages 443-449

Section 17.1 Summary – pages 443-449 Taxonomy: A framework Taxonomists group similar organisms, both living and extinct. Classification provides a framework in which to study the relationships among living and extinct species. For example, biologists study the relationship between birds and dinosaurs within the framework of classification. Archaeopteryx Section 17.1 Summary – pages 443-449

Section 17.1 Summary – pages 443-449 Taxonomic rankings Compare the appearance of a lynx, Lynx rufus, a bobcat, Lynx canadensis, and a mountain lion, Panthera concolor. Lynx Mountain lion Bobcat Section 17.1 Summary – pages 443-449

Section 17.1 Summary – pages 443-449 Domain Eukarya Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Felidae Genus Lynx Species Lynx rufus Lynx canadensis Bobcat Lynx Section 17.1 Summary – pages 443-449

III. TAXONOMY TODAY Species is the only taxon that has a clear biological identity 1. Species share a common gene pool because they breed with one another. 2. The members of a species determine which individuals belong to the species by their willingness and ability to breed. (finding a mate and producing offspring)

B. The taxa above species (i. e. genus, family, etc B. The taxa above species (i.e. genus, family, etc.) do not have clear biological identity because taxonomists do not always agree on how to group them.

C. Evolutionary theory states that living species evolved from an earlier species referred to as a common ancestor.

Evolutionary Relationships Based on Similarities Structure- homologous Geographic Distribution Chromosome Comparisons Breeding Behavior Biochemistry These similarities, as Darwin stated, indicate common ancestry.

Section 17.2 Summary – pages 450-459 Structural similarities For example, plant taxonomists use structural evidence to classify dandelions and sunflowers in the same family, Asteraceae, because they have similar flower and fruit structures. Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Structural similarities Taxonomists observe and compare features among members of different taxa and use this information to infer their evolutionary history. Section 17.2 Summary – pages 450-459

Geographical Distribution

Section 17.2 Summary – pages 450-459 Geographical distribution Probing Bills Grasping Bills Crushing Bills Feeders Cactus Insect Feeders Seed Feeders Fruit Feeders Parrot Bills Ancestral Species Section 17.2 Summary – pages 450-459

This provides the purpose and guiding philosophy to modern classification systems. Taxonomists group organisms that show evolutionary relationships by identifying and studying homologous structures in adults, developing embryos, and in well preserved fossils.

Homologous structures – a similar structure or characteristic in different species that may have a different function but shows common ancestry. Ex: flipper of whale and human arm. Analogous structures – structures in different species that may be used for the same function, but are anatomically very different. Ex: wings of bird & wings of butterfly

Homologous Structures

D. Biochemical taxonomy is based on all forms of life sharing organic molecules that are almost identical from species to species. (organic molecules include carbohydrates, lipids, proteins, and nucleic acids)

Section 17.2 Summary – pages 450-459 Chromosome comparisons For example, cauliflower, cabbage, kale, and broccoli look different but have chromosomes that are almost identical in structure. Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Chromosome comparisons Therefore, biologists propose that these plants are related. Section 17.2 Summary – pages 450-459

These similarities and differences are used to help classify organisms. All organisms have DNA and RNA. DNA and RNA are most similar in organisms which are most closely related.

A diagram, called a phylogenetic tree, shows the evolutionary relationships among organisms. It illustrates relationships among species – not individuals based on structural and molecular comparisons.

Section 17.2 Summary – pages 450-459 Cladistics Velociraptor Robin Allosaurus Archaeopteryx Sinornis Theropods Feathers with shaft, veins, and barbs Flight feathers; arms as long as legs Light bones 3-toed foot; wishbone Down feathers Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Life’s Six Kingdoms Section 17.2 Summary – pages 450-459

IV. THE FIVE KINGDOM SYSTEM Microscopes were discovered after Linnaeus’ time, thus the discovery of microorganisms made it necessary to expand classification from 2 to 5 kingdoms.

B. The 5 kingdoms include: 1. Kindgom Monera – All prokaryotes. (Prokaryotes are one-celled organisms that lack nulei, mitochondria, and chloroplasts, and reproduce by binary fission (asexual, simple cell division). Bacteria are the only members.

2. Kingdom Protista – All single-celled eukaryotes and some multicelled photosynthetic eukaryotes. Eukaryotes possess a nucleus and membrane bound organelles. Some have chloroplasts. Protists are divided into 3 groups: plant-like, animal-like, and fungus-like protists.

Section 17.2 Summary – pages 450-459 A Paramecium Protists: A diverse group Anal pore Cilia Kingdom Protista contains diverse species that share some characteristics. Oral groove A protist is a eukaryote that lacks complex organ systems and lives in moist environments. Gullet Contractile vacuole Micronucleus and macronucleus Section 17.2 Summary – pages 450-459

                                                                                                                                                                                          

3. Kingdom Fungi – Plant-like organisms that do not carry on photosynthesis (heterotrophs – obtain food from other organisms) . Have cell walls with no cellulose and some have multiple nuclei in their cells.

Section 17.2 Summary – pages 450-459 Fungi: Earth’s decomposers Organisms in Kingdom Fungi are heterotrophs that do not move from place to place. A fungus is either a unicellular or multicellular eukaryote that absorbs nutrients from organic materials in the environment. Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Fungi: Earth’s decomposers There are more than 50,000 known species of fungi. Section 17.2 Summary – pages 450-459

4. Kingdom Plantae – Multicellular organisms with cell walls having cellulose. Carry on photosynthesis (autotrophs – able to make their own food). Includes plants, mosses, & ferns).

All autotrophs make their own food by photosynthesis while absorbing nutrients and water. Heterotrophs cannot make their own food, so they must either absorb food or ingest their food by eating.

Section 17.2 Summary – pages 450-459 Plants: Multicellular oxygen producers All of the organisms in Kingdom Plantae are multicellular, photosynthetic eukaryotes. None moves from place to place. Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Plants: Multicellular oxygen producers A plant’s cells usually contain chloroplasts and have cell walls composed of cellulose. Plant cells are organized into tissue that, in turn, are organized into organs and organ systems. Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Plants: Multicellular oxygen producers The oldest plant fossils are more than 400 million years old. However, some scientists propose that plants existed on Earth’s landmasses much earlier than these fossils indicate. Section 17.2 Summary – pages 450-459

Section 17.2 Summary – pages 450-459 Plants: Multicellular oxygen producers There are more than 250,000 known species of plants. Although you may be most familiar with flowering plants, there are many other types of plants, including mosses, ferns, and evergreens. Section 17.2 Summary – pages 450-459

5. Kingdom Animalia – multicellular organisms without cell walls but have cell membranes, ingest their food (heterotrophs).

The Kingdom Animalia Animals are multicellular heterotrophs Nearly all are able to move from place to place Animal cells do not have cell walls Their cells are organized into tissues that, in turn, are organized into organs and complex organ systems

Section 17.2 Summary – pages 450-459 Animals: Multicellular consumers Animals are multicellular heterotrophs. Nearly all are able to move from place to place. Animal cells do not have cell walls. Section 17.2 Summary – pages 450-459

THE END The Diversity of Life