Learn How Animals Are Classified

Learn How Animals Are Classified For centuries, the practice of naming and classifying living organisms into groups has been an integral part of the study of nature.  Aristotle (384BC-322BC) developed the first known method of classifying organisms, grouping organisms by their means of transport such as air, land, and water. A number of other naturalists followed with other classification systems. But it was Swedish botanist, Carolus (Carl) Linnaeus (1707-1778) that is considered to be the pioneer of modern taxonomy. In his book Systema Naturae, first published in 1735, Carl Linnaeus introduced a rather clever way to classify and name organisms. This system, now referred to as Linnaean taxonomy, has been used to varying extents, ever since. About Linnaean Taxonomy Linnaean taxonomy categorizes organisms into a hierarchy of kingdoms, classes, orders, families, genera, and species based on shared physical characteristics. The category of phylum was added to the classification scheme later, as a hierarchical level just beneath kingdom. Groups at the top of the hierarchy (kingdom, phylum, class) are more broad in definition and contain a greater number of organisms than the more specific groups that are lower in the hierarchy (families, genera, species). By assigning each group of organisms to a kingdom, phylum, class, family, genus, and species, they can then be uniquely characterized. Their membership in a group tells us about the traits they share with other members of the group, or the traits that make them unique when compared to organisms in groups to which they do not belong. Many scientists still use the Linnaean classification system to some extent today, but it is no longer the only method for grouping and characterizing organisms. Scientists now have many different ways of identifying organisms and describing how they relate to each other. To best understand the science of classification, it will help to first examine a few basic terms: classification - the systematic grouping and naming of organisms based on shared structural similarities, functional similarities, or evolutionary historytaxonomy - the science of classifying organisms (describing, naming, and categorizing organisms)systematics - the study of the diversity of life and the relationships between organisms Types of Classification Systems With an understanding of classification, taxonomy, and systematics, we can now examine the different types of classifications systems that are available. For instance, you can classify organisms according to their structure, placing organisms that look similar in the same group. Alternatively, you can classify organisms according to their evolutionary history, placing organisms that have a shared ancestry in the same group. These two approaches are referred to as phenetics and cladistics and are defined as follows: phenetics  - a method of classifying organisms that is based on their overall similarity in physical characteristics or other observable traits (it does not take phylogeny into account)cladistics  - a method of analysis (genetic analysis, biochemical analysis, morphological analysis) that determines relationships between organisms that are based solely on their evolutionary history In general, Linnaean taxonomy uses  phenetics  to classify organisms. This means it relies on physical characteristics or other observable traits to classify organisms and does consider the evolutionary history of those organisms. But keep in mind that similar physical characteristics are often the product of shared evolutionary history, so Linnaean taxonomy (or phenetics) sometimes reflects the evolutionary background of a group of organisms. Cladistics  (also called phylogenetics or phylogenetic systematics) looks to the evolutionary history of organisms to form the underlying framework for their classification. Cladistics, therefore, differs from phenetics in that it is based on  phylogeny  (the evolutionary history of a group or lineage), not on the observation of physical similarities. Cladograms When characterizing the evolutionary history of a group of organisms, scientists develop tree-like diagrams called cladograms. These diagrams consist of a series of branches and leaves that represent the evolution of groups of organisms through time. When a group splits into two groups, the cladogram displays a node, after which the branch then proceeds in different directions. Organisms are located as leaves (at the ends of the branches).   Biological Classification Biological classification is in a continual state of flux. As our knowledge of organisms expands, we gain a better understanding of the similarities and differences among various groups of organisms. In turn, those similarities and differences shape how we assign animals to the various groups (taxa). taxon  (pl. taxa) - taxonomic unit, a group of organisms that has been named Factors That Shaped High-Order Taxonomy The invention of the microscope in the mid-sixteenth century revealed a minute world filled with countless new organisms that had previously escaped classification because they were too tiny to see with the naked eye. Throughout the past century, rapid advances in evolution and genetics (as well as a host of related fields such as cell biology, molecular biology, molecular genetics, and biochemistry, to name just a few) constantly reshape our understanding of how organisms relate to one another and shed new light on previous classifications. Science is constantly reorganizing the branches and leaves of the tree of life. The vast changes to a classification that have occurred throughout the history of taxonomy can best be understood by examining how the highest level taxa (domain, kingdom, phylum) have changed throughout history. The history of taxonomy stretches back to the 4th century BC, to the times of Aristotle and before. Since the first classification systems emerged, dividing the world of life into various groups with various relationships, scientists have grappled with the task of keeping classification in sync with scientific evidence. The sections that follow provide a summary of the changes that have taken place at the highest level of biological classification over the history of taxonomy. Two Kingdoms (Aristotle, during 4th century BC) Classification system based on:  Observation (phenetics) Aristotle was among the first to document the division of life forms into animals and plants. Aristotle classified animals according to observation, for example, he defined high-level groups of animals by whether or not they had red blood (this roughly reflects the division between vertebrates and invertebrates used today). Plantae  - plantsAnimalia  - animals Three Kingdoms (Ernst Haeckel, 1894) Classification system based on:  Observation (phenetics) The three kingdom system, introduced by Ernst Haeckel in 1894, reflected the long-standing two kingdoms (Plantae and Animalia) that can be attributed to Aristotle (perhaps before) and added third kingdom, Protista that included single-celled eukaryotes and bacteria (prokaryotes). Plantae  - plants (mostly autotrophic, multi-cellular eukaryotes, reproduction by spores)Animalia  - animals (heterotrophic, multi-cellular eukaryotes)Protista  - single-celled eukaryotes and bacteria (prokaryotes) Four Kingdoms (Herbert Copeland, 1956) Classification system based on:  Observation (phenetics) The important change introduced by this classification scheme was the introduction of the Kingdom Bacteria. This reflected the growing understanding that bacteria (single-celled prokaryotes) were very much different from single-celled eukaryotes. Previously, single-celled eukaryotes and bacteria (single-celled prokaryotes) were grouped together in the Kingdom Protista. But Copeland elevated Haeckels two Protista phyla to the level of kingdom. Plantae  - plants (mostly autotrophic, multi-cellular eukaryotes, reproduction by spores)Animalia  - animals (heterotrophic, multi-cellular eukaryotes)Protista  - single-celled eukaryotes (lack tissues or extensive cellular differentiation)Bacteria  - bacteria (single-celled prokaryotes) Five Kingdoms (Robert Whittaker, 1959) Classification system based on:  Observation (phenetics) Robert Whittakers 1959 classification scheme added the fifth kingdom to Copelands four kingdoms, the Kingdom Fungi (single and multi-cellular osmotrophic eukaryotes) Plantae  - plants (mostly autotrophic, multi-cellular eukaryotes, reproduction by spores)Animalia  - animals (heterotrophic, multi-cellular eukaryotes)Protista  - single-celled eukaryotes (lack tissues or extensive cellular differentiation)Monera  - bacteria (single-celled prokaryotes)Fungi  (single and multi-cellular osmotrophic eukaryotes) Six Kingdoms (Carl Woese, 1977) Classification system based on:  Evolution and molecular genetics (Cladistics/Phylogeny) In 1977, Carl Woese extended Robert Whittakers Five Kingdoms to replace Kingdom bacteria with two kingdoms, Eubacteria and Archaebacteria. Archaebacteria differ from Eubacteria in their genetic transcription and translation processes (in Archaebacteria, transcription, and translation more closely resembled eukaryotes). These distinguishing characteristics were shown by molecular genetic analysis. Plantae  - plants (mostly autotrophic, multi-cellular eukaryotes, reproduction by spores)Animalia  - animals (heterotrophic, multi-cellular eukaryotes)Eubacteria  - bacteria (single-celled prokaryotes)Archaebacteria  - prokaryotes (differ from bacteria in their genetic transcription and translation, more similar to eukaryotes)Protista  - single-celled eukaryotes (lack tissues or extensive cellular differentiation)Fungi  - single and multi-cellular osmotrophic eukaryotes Three Domains (Carl Woese, 1990) Classification system based on:  Evolution and molecular genetics (Cladistics/Phylogeny) In 1990, Carl Woese put forth a classification scheme that greatly overhauled previous classification schemes. The three-domain system he proposed is based on molecular biology studies and resulted in the placement of organisms into three domains. BacteriaArchaeaEukarya

An Overview of the Animal Welfare Act

An Overview of the Animal Welfare Act The Animal Welfare Act (AWA) is a federal law that was passed in 1966 and has been amended several times since then, notably in 2006. It empowers the Animal Care program of the USDA’s Animal and Plant Health Inspection Service (APHIS) to issue licenses and adopt and enforce regulations meant to protect the basic welfare of creatures kept in captivity. The law can be found at the official United States Government Publishing Office under its proper bill title: 7 U.S.C.  §2131. The Animal Welfare Act protects certain animals in certain  facilities but is not as effective as animal advocates would like. Many complain about its limited scope, and some even argue that animals are entitled to rights and freedoms equal to humans and should not be owned or used in any regard. Which Facilities Are Covered by the AWA? The AWA applies to facilities that breed animals for commercial sale, use animals in research, transport animal commercially, or publicly exhibit animals. This includes zoos, aquariums, research facilities, puppy mills, animal dealers, and circuses. The regulations adopted under the AWA establish minimum care standards for animals in these facilities, including adequate housing, handling, sanitation, nutrition, water, veterinary care, and protection from extreme weather and temperatures. Facilities that are not covered include farms, pet stores, hobby breeders, and places that commonly hold pets as well as quasi-commercial animals like milk cows and bure-pred dogs. Without the protection guaranteed to animals in other facilities and industries, these animals sometimes suffer harsh treatment- though animal rights groups often step in to defend these creatures. The AWA requires that the facilities  are  licensed and registered or their AWA-covered activities will be shut down. Once a facility is licensed or registered, it is subject to unannounced inspections. Failures to comply with AWA standards can lead to fines, confiscation of the animals, license and registration revocation, or cease and desist orders. Which Animals Are and Are Not Covered? The legal definition of the word â€Å"animal† under the AWA is â€Å"any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other  warm-blooded  animal, as the Secretary may determine is being used, or is intended for use, for research, testing, experimentation, or exhibition purposes, or as a pet.† Not every animal kept by these facilities is covered. The AWA has exclusions for birds, rats or mice used in research, livestock used for food or fiber, and reptiles, amphibians, fish, and invertebrates. Because 95 percent of the animals used in research are mice and rats and because the nine billion land animals slaughtered for food in the U.S every year are exempted, the vast majority of animals used by humans are excluded from the AWA’s protection. What Are the AWA Regulations? The AWA is a general law that does not specify the standards for animal care. The standards can be found in the regulations that are adopted by APHIS under the authority granted by the AWA. Federal regulations are adopted by government agencies with specific knowledge and expertise so they can set their own rules and standards without getting Congress bogged down in small details. The AWA regulations can be found in Title 9, Chapter 1 of the Code of Federal Regulations. Some of these regulations include those for the indoor housing of animals, which specify minimum and maximum temperatures, lighting, and ventilation. Regulations for animals kept outdoors maintain that the creature must be sheltered from the elements and offered food and clean water regularly. Also, for facilities with marine mammals, the water must be tested weekly and animals must be kept with a compatible animal of the same or similar species. In addition, a minimum tank size is required, depending on the size and types of animals housed. Participants in â€Å"swim with the dolphins† programs must agree in writing to the rules of the program. Circuses, which have been under constant fire since animal rights activism increased in the 1960s, must not use deprivation of food and water or any kind of physical abuse for training purposes, and animals must be given a rest period between performances. Research facilities are also required to establish Institutional Animal Care and Use Committees (IACUC) that must inspect the animal facilities, investigate reports of AWA violations, and review research proposals to â€Å"minimize discomfort, distress, and pain to the animals.​ Criticisms of the Animal Welfare Act One of the biggest criticisms of the AWA is the exclusion of rats and mice, which make up the majority of the animals used in research. Similarly, since livestock is also excluded, the AWA does nothing to protect farmed animals. There are currently no federal laws or regulations for the care of animals raised for food. Although there are general criticisms that the housing requirements are insufficient, some animal rights advocates claim that the regulations for marine mammals are especially inadequate. Marine mammals in the wild swim for miles each day and dive hundreds of feet deep in the open ocean, while tanks for porpoises and dolphins can be as small as 24 feet long and only 6 feet deep. Many of the criticisms of the AWA are directed against the IACUCs. Since IACUCs tend to include people who are affiliated with the institution or are animal researchers themselves, many advocates question whether these committees can objectively evaluate research proposals or complaints of AWA violations.