1. Construct and use dichotomous keys to identify organisms. 2. Define scientific name and the binomial system of nomenclature.

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1 OBJECTIVE SHEET TAXONOMY 1. Construct and use dichotomous keys to identify organisms. 2. Define scientific name and the binomial system of nomenclature. 3. Name and describe the general characteristics of each of the five most common Kingdoms. 4. Describe how biologists group organisms based on Phylogeny (lines of evolutionary descent). 5. Construct a cladogram based on derived characteristics. 6. Discus how similarities in DNA and RNA as well as the use of Molecular Clocks aids in the development of more accurate Phylogenies. 7. Explain the Modern classification of Organisms by identifying the characteristics of the Three-Domain System. 8. Classify a human being using Taxons 1

2 Above is a cladogram showing the evolutionary relationships of dinosaurs leading to modern day birds. Constructing a cladogram helps biologists organize the fossil record to show their evolutionary relationships to modern day organisms. 2

3 Reference pgs A scientific discipline known as allows scientists to classify organisms and assign them a universally accepted name. Advantages of Classification By organizing life into groups, biologists can communicate with each other around the world. The advantages of classification include: 1. Biologists can study the diversity of life with Biological meaning. 2. A name can be recognized by all scientists regardless of language barriers. 3. Newly discovered organisms can be understood better by making comparisons to existing groups. These comparisons can shed light on the evolutionary ancestory of the organism. 4. Classification allows biologists to get a more complete picture of how life evolved on the planet and how this affects the current trends of life on the today s planet. LINNAEUS S HIERARCHIAL CLASSIFICATION Carolus Linnaeus ( ) devised a system to put into the diversity of life. He started the science of taxonomy. First he assigned each species a scientific name composed of two names = binomial nomenclature. Each name is made up of the genus and species name in Latin. Sometimes a third name is included to give credit to the discoverer. Secondly, he adopted a filing system for grouping species into a hierarchy of increasingly general categories. Although, he used only three categories (one in bold), we commonly use all the ones below: KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES 3

4 The purpose of taxonomy (the identification and classification of species) is to: Sort out closely related organisms and assign them to separate species, describing the characteristics that distinguish one species from another. Each taxonomic category from Kingdom all the way to species is called a TAXON The Kingdom taxon contains the greatest number of organisms as it is the least specific while the species taxon is the most specific. The Species designation is the only taxon that occurs naturally. Organisms decide for themselves whom they want to reproduce to make offspring with under natural conditions. 4

5 The Old Five Kingdom System A five kingdom classification system was introduced in which all living things can fit into, based on their complexity and the methods by which their nutritional needs are met. KINGDOM CHARACTERISTICS Monera Protista Fungi Plantae Animalia Bacteria and Cyanobacteria- All monerans are single-celled. Unlike other cells, the monerans lack a nucleus, and other organelles. They are all prokaryotic. Ameba, Euglena, Paramecia Protists are mainly unicellular organisms that have a membrane-bound nucleus and many other organelles. Some are colonial and multicellular. All protists are eukaryotic. Mushrooms, water mole, bread mold fungi are non-motile and cannot photosynthesize. They are heterotrophic as they absorb nutrients from a living or non-living source. Fungi differ from plants in the way the cell wall is made, in their method of reproduction, and even in their body structure. Includes the mosses, ferns, grasses, shrubs, flowering plants and trees most photosynthesize and contain chloroplasts. All plant cells have a membrane-enclosed nucleus and cell walls that contain a substance called cellulose. All members of the animal kingdom are multicellular. The cells have a discrete nucleus that contains chromosomes. Most animals can move and depend on organic materials for food. Excluding the very simple species, most animals reproduce by means of gametes called egg and sperm cells. Archetista Viruses although not living and acellular, the structure of viruses can evolve to produce drastic changes. Viruses have a protein coat surrounding either DNA or RNA. This sixth kingdom is sometimes used for convenience. Linnaeus s system is still used today but it has its limitations. Using Linnaeus s system of taxons, taxonomists have always tried to group organisms according to biologically important characteristics. But which similarities and differences are most important? Linnaeus s system has limitations and problems although it is still widely used in biology today. 5

6 Phylogeny By using Darwin s ideas about descent with modification, taxonomists can now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities. A phylogeny is a description of the history of descent of a group of organisms from their common ancestor. Groups of evolutionarily related species are represented as related branches in a phylogenetic tree, or a cladogram. A group of species that consists of all the evolutionary descendants of a common ancestor is called a clade. Named clades and species are called taxa. 6

7 How do biologists use phylogenetic trees? A derived trait is one that differs from its form in the common ancestor of a lineage. A node on a tree indicates a derived feature. Biologists can use phylogenetic trees to reconstruct ancestral states. Phylogenetic trees may include estimates of times of divergence of lineages, as determined by a molecular clock analysis. Phylogenetic trees are used to reconstruct the past and understand the origin of traits. Phylogenetic trees are used to make appropriate evolutionary comparisons among living organisms. They can sometimes be used to even predict future evolution. A phylogenetic tree is divided into the following types of groups: 7

8 The cladogram below shows the phylogenetic relationships among 6 species labeled (A-F). Use the three groups to match its position on the cladogram. Well known Paraphyletic Groups: The class Reptilia as traditionally defined, are paraphyletic because it excludes birds (class Aves) and mammals (class Mammalia). Using Linneaus system, the three taxa are classes of equal rank. However, mammals hail from the mammallike reptiles and birds are descended from the dinosaurs (a group of Diapsida), both of which are classified as reptiles. Reptiles would be monophyletic if they were defined to include Mammalia and Aves. The prokaryotes (single-celled life forms without cell nuclei), are paraphyletic because they exclude the eukaryotes, a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria. 8

9 Read page 452 in your text. List the ways that barnacles and limpets are different from each other. List several reasons why we think that barnacles and crabs share a more recent common ancestor than the ancestor that barnacles share with limpets? The table below right shows the ancestral and derived states of 5 traits (a through e) for 6 species. For each box in the cladogram, write in a number (1-6) to indicate where that species should be positioned in the cladogram. Note: circles in the cladogram show where specific derived traits appeared. (-) = ancestral state, (+) = derived state 9

10 Found within the genetic code of all organisms is DNA. This provides us with an excellent way of comparing organisms at their most basic level their genes. Scientists can sequence or read the information coded in DNA and can compare the genetic similarities amongst organisms to trace the history of their genes over millions of years. The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more they are related in evolutionary terms. A cladogram helps biologists understand how one lineage branched from another in the course of evolution. Molecular Clocks Molecular clocks allow biologists to make more accurate phylogenetic trees. Simple mutations occur all the time causing slight changes in the DNA structure. Some mutations have positive or negative effects on the phenotype of an organism. Many mutations have no effect at all. These neutral mutations accumulate in the DNA of different species at about the same rate. Comparing such DNA sequences in two species can reveal how dissimilar the genes are and thus provide an indication of how long ago the two species shared a common ancestor. Some genes accumulate mutations faster than others so biologists can time different kinds of evolutionary events, each of which ticks at a different rate. What evidence indicates that Species C is more closely related to Species B than to Species A? 10

11 Reference pgs The Three-Domain System Using the molecular clock model, scientists have grouped modern organisms according to how long they have been evolving independently. The modern day method of classification includes a new taxon called a domain. The three domains are the domain Bacteria, domain Archaea, and domain Eukarya. List the characteristics that distinguish members of the domain Bacteria from members of the domain Archaea. Fill in the missing parts of the chart below as you study the features of each domain: 11

12 Complete the summary of Living Things below: Use the colour diagram in your text pg to indicate the name of each Domain in the diagram. You may want to use colour to hi-lite each domain. 12

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15 ACROSS 1. eventually exposes recessive genes to the environment for 3. red hair, blue eyes, etc. 4. kingdom with prokaryotic members 8. many different phyla are grouped into one 10. individuals that can interbreed belong to the same 11. an alternate form of a gene, (B or b) 12. to change with time 13. similar looking structure, but suggest evolution along different lineage. 14. according to Lamarck, these can be passed on. 19. wing of a bird and the arm of a person are said to be 21. tried to support Oparin s hypothesis 22. kingdom characterized by being non photosynthetic and getting nutrition by absorption 23. many different genus may belong to the same 24. traits that are present before they are useful. DOWN 2. believed that variations are the raw material for evolution 3 a random change in DNA that turns out to be helpful 5 type of evolution that results in birds and bats having wings (put N and V in the same box) 7 governs one trait 9 appendix, coccyx, dentin in chickens are said to be 15 Bbtt x BBTt 16 a questionable scientific name 17 a trait that must be present in a homozygous condition to show up 18 the science of classification 20 kingdom characterized by nutrition by ingestion, multicellular and eukaryotic 15

16 Why You Are Homo sapiens 1. At present there are six generally recognized kingdoms of organisms and three domains. Since human cells have discrete nuclei surrounded by a nuclear membrane, you belong to the domain Eukarya. Your cells lack chloroplasts and cell walls, and you are a multicellular heterotroph, with highly differentiated tissues and organ systems. That makes you a member of the kingdom Animalia. 2. What kind of animal are you? You possess a spinal column composed of bony vertebrae that has largely replaced a cartilaginous rod you had as an embryo, the notochord. At that time you also had structures that had you been a fish would have developed into gill slits. You have a dorsal nerve cord and brain. These traits mark you out as a chordate and a vertebrate that is, you belong to the phylum Chordata (because you either have or have had a notochord) and to the subphylum Vertebrata (because you have vertebrae that replaced the softer notochord) 3. Among the vertebrates there are several classes: cartilaginous fish, bony fish, jawless fish, amphibia, reptiles, mammals and birds. You are homeothermic (warm blooded) and so must be either a bird or a mammal. Lacking feathers and having teeth and (if you are female) the potential for nursing your young you are of the class Mammalia. If you are male, do not be concerned; even if you cannot nurse, having hair is enough. 4. A number of orders exist within the classes. The Insectivores, for instance, include the moles and shrews, the Chiroptera are the bats, and the Carnivora include dogs, cats, and ferrets among others. Your opposablethumbs, frontally directed eyes, flat fingernails, and other characteristics identify you as the order Primate, along with monkeys, apes and tarsiers. 5. Primates include a number of families. You and the New World monkeys (Western hemisphere) are obviously very different they have prehensile tails, for instance, which you and all Old World monkeys (Eastern hemisphere) and apes lack: indeed, you and the apes lack tails altogether. Your posture is upright, you have long legs and short arms, and not much body hair. You are blessed with your very own family with no other occupants: family Hominidae. 6. Within the Hominidae, anthropologists distinguish several species, all but one of which are known only as fossils. Australopithecus is one of these. If you are alive, you do not belong to any of those extinct genera, but to the genus Homo. 7. Again, the genus Homo has only one living species called sapiens. Since many taxonomists insist that the species name always includes the genus name, (binomial nomenclature) please think of yourself as Homo sapiens. 16

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