Moving Beyond Plants and Animals

Why did we come up with the five kingdoms? Classification of organisms into plants and animals was easily done and understood, but a large number of organisms did not fall into either category. Hence the two kingdom classification used for a long time was found inadequate. Besides, gross morphology a need was also felt for including other characteristics like cell structure, nature of cell wall, mode of nutrition, habitat, methods of reproduction, evolutionary relationships, etc. Whittaker (1969) proposed a five kingdom classification to solve the pitfalls of the two kingdom system of classification. The main criteria for classification used by him include cell structure, body organization, mode of nutrition, reproduction and phylogenetic relationships. Whittaker’s five-kingdom scheme consists of animals, plants, fungi, monera and protists(Fig.2.4). It is still not easy to fit all 28 Unit Two: Characteristics and Classification of Organisms organisms into the five-kingdom scheme. For example, many protista with chlorophyll (the protophyta) show important resemblances to some members of the algae, but the algae are classified into the plant kingdom. Figure 2. 4. The five kingdoms of life Self Assessment 2.6 1. Do you agree or disagree with the classification of algae as a plant? Explain. 2. Do you suggest an alternative category or group for organisms’ such as algae and the likes? Attention Viruses are not included in any kingdom – they are not considered to be living organisms because they lack key characteristics of living things. Viruses are particles that are not alive. They cause diseases and infections. Viruses are made up of nucleic acids, either DNA or RNA, surrounded by a protein coat. They are smaller than the tiniest bacterium. Most biologists agree that viruses are not alive because they don’t grow, develop, or carry out respiration. All viruses replicate, or make copies of themselves. However, viruses need the help of living cells to copy themselves. In order to copy itself, a virus must enter a living cell. The cell in which a virus replicates is called the host cell. Activity 2.10: Debate Debate on why it is difficult for biologists to develop a rigid classification scheme? Do you think the Whittaker’s five-kingdom scheme has solved the classification problems biologists are trying to answer for generations? Procedure: 1. Divide members of your classmates into three groups. 2. Members of group 1 support the idea that Whittaker’s five-kingdom scheme has solved the classification problems. 3. Members of group 2 are against the idea that Whittaker’s fivekingdom scheme has solved the classification problems. 4. The third group will be the audience. 5. Let members of group 1 and 2 present their position each in five minutes, and 6. Let students from group three ask questions both groups. 29 29 Grade 9 Biology Unit Two: Characteristics and Classification of Organisms Activity 2.11: Collaborative Learning What do you think about when you hear the word bacteria? You probably think about germs or something that is bad for you. Did you know that some bacteria are actually helpful? For example, some bacteria help with human digestion, while other bacteria help produce cheese, yogurt, and sourdough bread. However, other bacteria cause diseases in humans, for example Mycobacterium tuberculosis, causes tuberculosis, and Haemophilus ducreyi, chancroid. Discuss the major distinguishing features of kingdom Monera Key Terms Archaebacteria: a group of microorganisms considered to be an ancient form of life that evolved separately from the bacteria Chemosynthetic: synthesis food using chemical reaction. Eubacteria: true bacteria 30 Grade 9 Biology 2.6.1. Kingdom Monera Objectives At the end of this section, the student will be able to: • describe the kingdom Monera and give example of organisms • describe importance of Monera What are Monera? Monera includes eubacteria and archaebacteria. Eubacteria (true bacteria) have strong cell walls. They exist in various shapes and forms (Figs 2.5 and2.6). Some eubacteria are heterotrophs; otherscan make their food (autotrophs). Some autotrophic bacteria make their own food the way plants do; they are photosynthetic. Others make energy by chemical reactions; chemosynthetic. The eubacteria live in most habitats, except the most extreme. Some eubacteria cause diseases, like strep throat and pneumonia. Most eubacteria, however, are harmless and helpful. Figure 2.5. Examples major groups of Monera Archaebacteria (Archaea) have very different cell walls than bacteria, but like bacteria, archaebacteria make their own food. They are chemosynthetic and photosynthetic. Archaebacteria live in extreme environments. They live in such places as swamps, deep-ocean hot water vents and seawater evaporating ponds. The environments in which the archaebacteria live often have no oxygen (Fig 2.5). Figure 2.6. Some representative of taxa of kingdom monera 30 Unit Two: Characteristics and Classification of Organisms Attention Most people tend to think of bacteria in terms of illness and disease. However, there are actually only a few disease-causing bacteria compared to the number of harmless and beneficial bacteria. In fact, we could not survive without bacteria. Bacteria cause diseases in plants, animals, and humans. Disease causing bacteria enter the human body through openings such as the mouth. Bacteria are carried in air, food, and water. Sometimes bacteria enter the body through skin wounds. There are two ways bacterial diseases harm people. First, the growth of bacteria can interfere with the normal function of body tissues. Second, the bacteria can release a toxin that directly attacks the host. Important characteristics of monera: • Simple prokaryotic unicellular organisms • Lack a well-defined nucleus or any membrane bound organelles • Most have a rigid cell wall • Have various modes of nutrition. Could autotrophs or heterotrophs • Known as decomposers and mineralizers in the biosphere 2.6.2. Kingdom Protista Objectives At the end of this section, the student will be able to: • describe the kingdom Protista and give examples of organisms • describe importance of Protista What are protists? There is no such thing as a typical protist. Kingdom protista contains the most diverse organisms of all the kingdoms (Figs. 2.7 and 2.8). There are single-celled (unicellular) protists as well as many-celled (multicellular) protists. Some are microscopic, others are very large. Some can make their own food, some cannot. Protists have only one thing in common—they are all eukaryotes. That means most of their metabolic processes (chemical reactions) take place inside their membrane-bound organelles. Other than that, organisms classified as protists are quite different from each other. Some protists, called protozoans, seem to be like animals except that they only have one cell. Others, called algae, seem to be like plants except they do not have roots, stems, or leaves. Algae are photosynthetic and autotrophic. Unicellular algae are the basis of aquatic food chains and produce much of the oxygen in Earth’s atmosphere. Still, other protists seem to be like fungi except that they do not have the same kind of cell walls that fungi have. Activity 2.12: Collaborative Learning Classify the following statements into useful versus harmful relating to the importance of bacteria: endospores germinate in human lungs, cause infection in humans, provide nitrogen in a usable form for plants, f lavor food, oxygen is a byproduct of making food and Create toxins. Self Assessment 2.7 If someone tells you that bacteria are bad, how would you respond? Activity 2.13: Collaborative Learning You have learned that all life is organized into five kingdoms. Without using your notes, name all five kingdoms. Some of the organisms you will learn about in this section are plantlike, and some are animal-like. Still others have characteristics like fungi. Some of them were placed in different kingdoms before they were finally classified as Kingdom Protista. As you read this sub-section keep in mind how much variety there is in the world of Protista. 31 31 Grade 9 Biology Unit Two: Characteristics and Classification of Organisms Figure 2.7. Examples major groups of protists Figure 2.8. Some representative taxa of kingdom Protista Self Assessment 2.8 1. What are the characteristic features of protists? 2. Write the single common feature to all protists. 32 Grade 9 Biology Activity 2.14: Reflective discussion You probably come into contact with algae every day. Diatoms are a type of algae whose remains become a powdery, porous rock called diatomite. Diatomite is highly absorbent. It is used in pet litter and to clean up chemical spills. It also is used as an abrasive in household cleaners. It is even added to paint to add sparkle. Now that you know that diatomite is absorbent, sparkling, and abrasive, see if you can imagine some additional uses for it. Discuss the additional application and present to your classmate. 32 2.6.3. Kingdom Fungi Unit Two: Characteristics and Classification of Organisms Objectives At the end of this section, the student will be able to: • describe the kingdom fungi and give example of organisms • describe the importance of fungi What are fungi? Fungi are eukaryotic organisms that include micro-organisms such as yeasts, moulds and mushrooms. Except for unicellular yeasts, fungi are filamentous multicellular organisms. Their bodies consist of long, slender thread-like structures called hyphae. Hyphae play an important role in how they obtain food. Fungi possess a cell wall that is made up of chitin and polysaccharides. Like animals, fungi are heterotrophic in nutrition. But unlike animals, fungi do not ingest (eat) their food. Instead, a fungus absorbs nutrients from the environment outside of its body. Many fungi accomplish this task by secreting powerful enzymes into their surroundings, digest compounds from a wide range of sources, living or dead. These enzymes break down complex molecules into smaller organic compounds that the fungi can absorb into their bodies and use (Figs 2.9 and 2.10). Figure 2.9. Examples of fungi Most fungi absorb soluble organic matter from dead substrates and hence are called saprophytes (decomposers). Decomposer fungi break down and absorb nutrients from non-living organic material, such as fallen logs, animal corpses, and the wastes of living organisms. Activity 2.15: Peer conferencing So far, you have studied bacteria, and protists. In this section, you will learn about the kingdom Fungi. Fungus is the singular of fungi. Mushrooms are types of fungi. Think about places you have seen mushrooms growing. What do those places have in common? Were they hot, dry, cool, or damp? Did the mushrooms appear suddenly or grow slowly over time? 33 33 Grade 9 Biology Unit Two: Characteristics and Classification of Organisms Key Terms Mutualism: symbiotic relationship in which both species benefit. Parasitism: symbiotic relationship in which one organism benefits at the expense of another. Symbiosis: permanent, close association between two or more organisms of different species. Attention Some fungi cause food to spoil, others cause diseases, and some are even poisonous. However, fungi are important and beneficial. Without fungi, the world would be overrun with huge amounts of waste, dead organisms, and dead plants. Thanks to many fungi, some bacteria, and protists, the organic material is broken down and recycled into the raw materials that other living organisms need. Self Assessment 2.9 1. What are the characteristic features of fungi? Fungi cannot make their own food. They are heterotrophs. Fungi use a process called extracellular digestion to obtain nutrients. This means food is digested outside a fungus’s cells and then the digested food is absorbed. For example, some hyphae of a fungus will grow into an orange. They release digestive enzymes into the orange that break down the large organic molecules into smaller molecules. These small molecules are absorbed into the hyphae and move into the flowing cytoplasm. Fungi can also live with different living as parasites or mutualists. Parasitic fungi absorb nutrients from the cells of living hosts. Some parasitic fungi are pathogenic, causing diseases in humans (Example: Candida albicans cause rush and Tinea pedis cause athlete’s foot), animals and plants. Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate with actions that benefit the host. For example, mutualistic fungi that live inside certain termite species use their enzymes to break down wood, making food available for termites. Fungi can also live as symbionts in association with algae as lichens and with roots of higher plants as mycorrhiza. Fungi can reproduce either asexually by vegetative means (fragmentation, fission and budding), asexual reproduction through spores formation and sexually. The various spores are produced in distinct structures called fruiting bodies. Yeast (saccharomyces service) is a very important fungus used for making injera rise and allows us to make alcohol (Tej, Tella, Beer etc.). Figure 2.10. Some repressive taxa of kingdom fungi 34 Grade 9 Biology 34 2.6.4. Kingdom Plantae Unit Two: Characteristics and Classification of Organisms Objectives At the end of this section, the student will be able to: • describe the kingdom Plantae and give example of organisms • describe characteristic features of major divisions of plants • give examples of flowering plants What are plants? Kingdom Plantae includes all eukaryotic, and multicellular autotrophic organisms. Plants make their own food through the process of photosynthesis. Plants have chloroplast and chlorophyll pigment, which is required for photosynthesis. Photosynthesis also provides oxygen in the atmosphere. • Some parasitic. • Nearly all live on land. • Sexual reproduction predominates. • They do not move from place to place; they are stationary. • Their cells contain a rigid cell wall made up of cellulose. • They reproduce asexually by vegetative propagation or sexually. • There are over 250 000 species of plants. These include flowering plants, mosses, ferns, and coniferous plants (see figs 2.11 and 2.12). Figure2.11. Examples of major groups of plants Self Assessment 2.10 1. What are the characteristic features of plants? Activity 2.16: Reflective Discussion Think of all the things that plants provide for us. They are an important source of food. They also provide oxygen through photosynthesis. Some plants are valuable sources of medicine. What are some other things that plants provide? Activity 2.17: Inquiring and Researching Name or think of at least f ive different plants. You might think of flowers, bushes, shrubs, ferns, trees, and grasses to name a few. They are all plants, yet they look different from each other. As in the other kingdoms you have studied, the plant kingdom has divisions based on shared characteristics. If you were to place plants in divisions, what characteristics would you use? Hint: Look at figure 2.12 to find useful features to classify plants. 35 35 Grade 9 Biology Unit Two: Characteristics and Classification of Organisms Activity 2.18: Interviewing Ask a botanist about the economic, medicinal and ecological uses of plants (e.g., food, medicinal, ornamental, horticultural, cultural, spiritual, aesthetic, music and arts etc.). Activity 2.19: Investigating Think about all the animals you are familiar with. They may be pets, animals in nature, or captive animals such as in a circus or zoo. This section explains what all animals have in common. List the characteristics you know about that all animals share. 36 Grade 9 Biology Key Terms Angiosperms: Most diverse seed plant group. Only group that makes flowers and fruits. Bryophyte: is the common name for three lineages of plants: mosses, liverworts, and horn-worts. Dicots: Most diverse groups of angiosperms; members have two seed leaves, branching leaf veins. Embryophyta: land plants; photosynthetic species that protect and nourish the embryo on the parental body Gymnosperm: Seed plant that does not make flowers or fruits; for example, a conifer. Monocots: Highly diverse angiosperm group; includes plants such as grasses that have one seed leaf and parallel veins. Seed plant (spermatophyte): Plant that produces seeds and pollen; an angiosperm or gymnosperm. Vascular plant: Plant having specialized tissues (xylem and phloem) that transport water and sugar within the plant body. 2.6.5 Kingdom Animalia Objectives At the end of this section, the student will be able to: • list the characteristic feature of the animal kingdom, • describe characteristic features of invertebrates and vertebrates • list the common class of animals What is an Animal? Kingdom Animalia includes all multicellular, heterotrophic, eukaryotic organisms. Constructing a good definition of an animal 36 Unit Two: Characteristics and Classification of Organisms is not straightforward, as there are exceptions to nearly every criterion for distinguishing animals from other life forms. However, several characteristics of animals, when taken together, sufficiently define them. Animals differ from both plants and fungi in their mode of nutrition. Unlike plants, animals are not photosynthetic. Animals consume food obtained from other organisms (i.e. they are heterotrophs). But unlike fungi, most animals do not feed by absorption; instead, animals ingest their food and then use enzymes to digest it within their bodies. In contrast to plants and fungi, however, animals lack the structural support of cell walls. Instead, animal cells are held together by structural proteins, the most abundant being collagen, which is found only in animals. Many animals have two types of specialized cells not seen in other multicellular organisms: muscle cells and nerve cells. In most animals, these cells are organized into muscle tissue and nervous tissue, respectively, and are responsible for moving the body and conducting nerve impulses. The ability to move and conduct nerve impulses underlies many of the adaptations that differentiate animals from plants and fungi, making muscle and nerve cells central to what it means to be an animal. Most animals reproduce sexually. Animals are very diverse. They are generally classified into two groups based on the presence or absence of backbone as invertebrates (animals with no backbone) and vertebrates (animals with a backbone(Fig. 2.13 -2.15). Figure 2.13. Major groups of animals 37 37 Grade 9 Biology Unit Two: Characteristics and Classification of Organisms Activity 2.20: Collaborative Learning Groups Figure 2.13. Major groups of animals What are the two largest groups of animals recognized by biologists/ zoologists? Make a field visit in your school compound or village and try to classify the animals you see/know into invertebrates or vertebrates. (Hint: you could use a dichotomous key) Figure 2.14. Major groups of invertebrates Key Terms Anatomy: the study of internal structure, as revealed by dissection. Invertebrates: are animals without a backbone. Morphology: is the study of the form or outward appearance of organisms. Vertebrates: are animals with a backbone. Self Assessment 2.11 1. What are the characteristic features of animals? 2. What are the differences between invertebrates and vertebrates? 38 Grade 9 Biology Activity 2.21: Interviewing Make internet search or ask a biologist about medically or agriculturally important insects (e.g., grasshopper, tsetse fly, mosquito, honey bee, etc.) and list their importance (Hint: economic, pollination, pest, aesthetic, music and arts, cultural, spiritual, vector, etc.). 38 Unit Two: Characteristics and Classification of Organisms Figure 2.15. Major groups of vertebrates 2.7 Renowned Taxonomists in Ethiopia Objectives At the end of this section, the student will be able to: • Appreciate the works of renowned taxonomists in Ethiopia. As stated in section 2.5 of this textbook, Ethiopia is known for high degree speciesdiversity and endemcity. However, only few studies have been done to identify, name and classify the biodiversity at different levels (e.g., gene, species, and ecosystem).. Among the factors that led to inadequate level of studies done in Ethiopia in the field of biodiversity could be due to the few number of scientists educated and trained in taxonomy despite the country’s rich biodiversity. Yet, as the result of efforts made over the past six decades, our country has trained and educated a couple of renowned taxonomists that contributed the publication of volumes of books on the Flora of Ethiopia, for example. Among these scientists are Dr. Mesfin Taddese, Professor Sebsebe Demissew, Professor Ensermu Kelbessa and Professor Silesh Nemomissa to mention a few of them. In addition, there are few other zoologists like Professor Abebe Getahun; who contributed to the field of animal taxonomy. Below, we will discuss briefly the contributions made by some distinguished Ethiopian taxonomists to the scientific community in general and Ethiopian society in particular. Activity 2.22: Collaborative Learning Read a book or search on Internet about important fish species, mammals, and birds. Then list their economic, medicinal, aesthetic, cultural, spiritual, and/or ecological importance. Activity 2.23: Collaborative Learning Do you know any renowned Ethiopian taxonomist? If you know one, please write the name and the contribution of the renowned Ethiopian taxonomist. 39 39 Grade 9 Biology Unit Two: Characteristics and Classification of Organisms Professor Sebsebe Demissew Professor Sebsebe Demissew has participated in several successful research projects universities in Europe and Africa. He has published books and articles on the vegetation and plants of Ethiopia and Africa. He is a member of national and international professional organizations and has served as Chair of the Biological Society of Ethiopia, Secretary-General of the Association for the Taxonomic Study of the Flora Tropical Africa (AETFAT) in addition to being a Council member of the International Association for Plant Taxonomy. He has also served as a director of Flora of Ethiopia and Gulelle botanical Garden.