Advanced biology chapter 14: classification NOTES

Introduction You can observe the diversity of life in among the species of organisms. One of the major goals in biology is to identify, characterize, and classify the organisms living on Earth. Grouping will make it easier to work with the information about features of organisms. Biological classification is the grouping of organisms into specific categories based on a set of criteria.

Classification systems

Classification systems Taxonomy is a branch of system biology that involves the identifying, describing, naming, and classification based on the natural relations of all other organisms. System biology involves study and modelling of biological components including molecules, cells, organisms or entire species.

Artificial System of Classification The artificial system of classification is the system that doesn’t make meaningful groups Ex. Putting all land animals in one group, all aquatic organisms in one group, or all green creatures in one group These groupings are not meaningful, for example sea weed and sharks are both aquatic organisms, but they have almost nothing in common.

Natural System of Classification The natural system of classification is the most useful system to the biologist. It takes into account certain relationships among all organisms, the important features shared as large groups as possible and places organisms into distinct groups. The Linnaean system of classification is the most widely accepted natural system of classification.

Naming system of organism

Naming system of organisms Organisms have different names in different languages, but each organism has one correct scientific name. This scientific name can be understood by anyone as the same organism, and there won’t be confusion in calling or naming organisms. The method of naming organism is the Binomial System of Nomenclature, or Binomial nomenclature. It is the formal system of naming species which each organism’s name has two parts. The first part is the genus name, and the second part is the species name.

Rules in writing the scientific names The first letter of the genus name is always capitalized, but the rest of the genus name and species name are lowercase. In printed form, the scientific name should be italicized. When handwritten, the scientific name should be underlined. When abbreviating the scientific name, the genus name is abbreviated to the first letter. Ex. H. sapiens for Homo sapiens.

HIERARCHICAL SYSTEM OF CLASSIFICATION

HIERARCHICAL SYSTEM OF CLASSIFICATION Today’s classification system arranges organisms into groups of a descending hierarchy. Hierarchy consist of different levels of organization called taxa. In lower taxa, there is more similarities between organisms of the same taxa. Hierarchy: Domain Kingdom Phylum Class Order Family Genus Species

HIERARCHICAL SYSTEM OF CLASSIFICATION Domain is the broadest taxa. Kingdom is composed of related phyla. Phyla is a group of similar classes. Class is a group of related orders. Order is a group of related families. Family is a group of apparently related genera. Genus is a group of similar closely related species/ Species is a group of organisms that can interbreed and produce a fertile offspring. Taxa can be expanded when necessary.

HIERARCHICAL SYSTEM OF CLASSIFICATION The example of the hierarchy for Grey Wolf.

CLASSIFYING ORGANIMS

Domain & kingdom Refined methods in classification led to the three-domain, six kingdom classification system. The three domains are Bacteria, Archaea, and Eukarya. The six kingdoms are Bacteria, Archaea, Protista, Fungi, Plantae, and Animalia. The previous classification system didn’t have the domain taxon, and there were only 5 kingdoms: Monera (Prokaryota), Protista (Protoctista), Fungi, Plantae and Animalia The organisms are classified into domains based on the cell type, and into the kingdoms based on the cell structure and method of nutrition.

Domain bacteria Bacteria are prokaryotic organisms which are members of the domain and kingdom bacteria. Characteristics: Prokaryotic (lack true nucleus and membrane-bound organelles) cell wall with peptidoglycan Unicellular Autotrophic or Heterotrophic Bacteria are very diverse and they can vary in nutrition and habitat environment Bacteria reproduce asexually Examples: E. coli, S. aureus, B. lactis Image from http://images.celebeat.com/data/images/full/10030/bacteria.jpg

Domain archaea Archaebacterial are prokaryotic organisms that are members of domain and kingdom Archaea. Characteristics: Prokaryotic Cell wall without peptidoglycan Unicellular Autotrophic or heterotrophic They are extremophiles, which means they live in extreme environment. They can be found in boiling hot springs, thermal vents, and salty water. Archaebacterial reproduce asexually by binary fission Examples: Halophiles, Thermophiles, Methanogens Image from https://upload.wikimedia.org/wikipedia/commons/0/08/Thermal_hot_spring.jpg

Domain eukarya Eukaryotes are organisms with cell that has true nucleus and membrane-bound organelles. They are member of domain Eukarya. Domain Eukarya consist of 4 kingdoms Protista Fungi Plantae Animalia

Domain eukarya: kingdom Protista Protista are eukaryotic organisms that are either unicellular, colonial (exist in colonies) or multicellular. Protists are extremely diverse from each but fits neither into plants or animals. 3 Categories of Protists Algae – plant-like protists Slime Molds or Mildews – fungus-like protists Protozoan – animal-like protists Characteristics Eukaryotic Cell wall of Cellulose (some have chloroplasts) Unicellular, Multicellular, or Colonial Autotrophic or Heterotrophic Protists reproduce asexually via meiosis Examples: Amoeba, Euglena, Green Algae, Slime molds Image from http://www.stgeorgeschool-hermann.com/eighth/p-protist.gif

Domain eukarya: kingdom Fungi Fungi (Fungus, singular) are eukaryotic organisms that are either unicellular or multicellular. Fungi obtain food nutrients from organic materials from the environment by absorption. Characteristics Eukaryotic Cell wall of Chitin Unicellular, Multicellular, or Colonial Heterotrophic Fungi can reproduce sexually or asexually Examples: Mushrooms, Yeasts, Mold Image from http://cf.lnwfile.com/_/cf/_raw/ne/xb/su.png

Domain eukarya: kingdom plantae Plants are eukaryotic organism that are multicellular autotrophs. Plants make their own food through the process of photosynthesis. Characteristics Eukaryotic Cell wall of Cellulose Have Chloroplast Multicellular Autotrophic Plants reproduce sexually or by mitosis Examples: Trees, grasses, gymnosperms, lily Image from http://www.officialpsds.com/images/thumbs/plant-psd79290.png

Domain eukarya: kingdom animalia Animals are eukaryotic organism that are multicellular, whose cells lack cell walls and chloroplasts. Most animals are motile, which means they can move by themselves. Characteristics Eukaryotic No cell wall No chloroplast Multicellular Heterotrophic Animals can reproduce sexually or asexually Examples: Cat, Duck, Fishes, Sponge Image from http://www.vetray.com/wp-content/uploads/2012/11/animals.png

Determining species It is complicated and intricate to classify organisms at the species taxa than in any other level in the hierarchy, because there are lots of similarities that the organisms in the same genus have in common. It is not always easy to define or describe a species, so there are several ways of classifying a species. 4 concepts: Biological Species Concept Morphological/ Topological Species Concept Ecological Species Concept Phylogenetic Species Concept

Biological Species Concept This concept determines and classifies species as a group of organisms that are able to interbreed and produce fertile offspring in a natural environment. This concept is most commonly used in classification. Limitations: Some different organisms that are not in the same species can interbreed and produce a fertile offspring, Dogs and wolves are good example, they are in the same genus but different species, and they still can interbreed and produce a fertile offspring. The species that are already extinct couldn’t be classified by this concept.

Morphological/topological Species Concept This concept determines and classifies species based on comparisons of physical characteristics or traits with the type sample or specimen. Limitation: The limitation of this concept is that in a species, there can be more than one trait for a character, organisms can have different appearance in some characteristics, but they could be from the same species. So this concept can be too subjective.

Ecological species concpet This concept determines and classifies species based on its role in ecosystem and its adaptation to specific functions in a community. Limitation: The limitation is that two organisms may come from the same species, but they could be different in the way they feed, live, and function in a community.

Phylogenetic Species Concept This concept determines and classifies species based on phylogeny. Phylogeny is the evolutionary history of organism. It defines species as a group of organisms that came from one single ancestral parent. It works well because it can account for the extinct species. Limitations: The limitation is that the history of some species may not be known or not enough to classify.

METHODS AND FEATURES USED IN CLASSIFICATION OF ORGANISMS

Key for identification Organisms can be classified be designing and following an key Identification. Dichotomous key is a key identification that consists of series of “yes” or “no” questions that will lead to the correct classification for an organism. It works by comparing the feature and characteristics of the unknown with the known organisms and follow yes” or “no” questions. Example of Dichotomous key: http://study.com/cimages/multimages/16/key_simple_example.png

Characteristics Used in Classification Many characteristics are used in the classification of organisms. Morphological Features – comparing the appearance of the organisms Biochemical and Physiological features – comparing of chemistry and biological molecules, and how the organisms function chemically in their bodies. Genomic features – comparing the DNA, RNA , and protein, also comparing the chromosome number, structure, and genomic sequence of the organism.

References advBIOLOGY_-_CHAPTER_14_CLASSIFICATION.pdf http://examples.yourdictionary.com/kingdom-examples.html