Characteristics of living organisms

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Cambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore informationUnit 1Characteristics andclassification ofliving organismsWelcome to the exciting and amazing world of living things.Go outside and look around you. Look at the sky, the soil, trees,plants, people, animals. Nature is all around you if you have theeyes to see it. Count how many living things you can see.What is it that makes living things different from things thatare not alive?Biology is the study of living things. It deals with what all livingthings can do, how they do it and why they do it. In biology, there isalways a relationship between the structure of an organism, itsfunction, and its adaptation to its function or environment. Biologyalso tackles the important topics such as population, environmen-tal issues as well as health issues.In this course, you will learn to identify different kinds of livingthings and how to classify them. Most of the six activities in thisunit will take you only five to ten minutes to complete.This unit is divided into five sections:ACharacteristics of living organismsBClassification of living organismsCThe hierarchical classification systemDBinomial system of naming speciesESimple dichotomous keyWhen you have studied this unit, you should be able to:• list and describe the characteristics of organisms• define the terms nutrition, excretion, respiration, sensitivity, reproduction,growth and movement• outline the use of a hierarchical classification system for living organisms • classify living organisms into kingdoms, orders, classes, families, generaand species• define and describe the binomial system of naming species• construct dichotomous keys• use simple dichotomous keys based on easily identifiable features.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore information2NSSC BiologyA Characteristics of living organismsActivity 1 will help you think about what makes living things dif-ferent from non-living things.ACTIVITY 1This activity should take you about five to ten minutes.What makes living things different from non-living things?Look at Figure 1. Look at the living and non-living things whichyou can see in the picture.Figure 1Answer these questions in your notebook.1 List three different living things which you can see in Figure 1.2 List five different non-living things which you can see inFigure 1.It is obvious that people are living things. Most of us realise thatplants are living too, but what about a car? Cars need fuel, and cando many of the things that animals and plants can do.An individual living thing, such as an animal or a plant , is calledan organism. The term ‘living organism’ is usually used to describesomething which displays all the characteristics of living things.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore informationModule 1 Unit 13Characteristics of living thingsThere are seven activities which make organisms different fromnon-living things. These are the seven characteristics of livingorganisms.1 NutritionLiving things take in materials from their surroundings that theyuse for growth or to provide energy. Nutrition is the process bywhich organisms obtain energy and raw materials from nutrientssuch as proteins, carbohydrates and fats.2 RespirationRespiration is the release of energy from food substances in all living cells. Living things break down food within their cells torelease energy for carrying out the following processes.3 MovementAll living things move. It is very obvious that a leopard moves butwhat about the thorn tree it sits in? Plants too move in variousdifferent ways. The movement may be so slow that it is verydifficult to see.4 ExcretionAll living things excrete. As a result of the many chemical reactions occurring in cells, they have to get rid of waste productswhich might poison the cells. Excretion is defined as the removal oftoxic materials, the waste products of metabolism and substancesin excess from the body of an organism.5 GrowthGrowth is seen in all living things. It involves using food toproduce new cells. The permanent increase in cell number and sizeis called growth.6 ReproductionAll living organisms have the ability to produce offspring.7 Sensitivity All living things are able to sense and respond to stimuli aroundthem such as light, temperature, water, gravity and chemical substances.Learn these seven characteristics of living organisms. They formthe basis of the study of Biology. Each one of these characteristicswill be studied in detail during the course. Whilst many otherthings carry out one or more of the above processes, only livingorganisms possess all of these characteristics.ACTIVITY 2This activity should take about five minutes.A motor car needs petrol and air in order to move. It produceswaste gases.a Which characteristics of living organisms are similar to thoseof a motor car?b Why is a car not a living organism?© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore information4NSSC BiologyACTIVITY 3Spend about ten minutes on this activity.1 Some yeast, sugar and water are mixed in a test-tube. Thediagrams show the test-tube at the start and after one hour.Figure 2a Which process causes this change?AgrowthBirritabilityCreproductionD respirationb Excretion, irritability and reproduction are characteristicsof:Aall animals and plantsBanimals onlyCplants onlyD some animals and some plants onlyc Which one of the following functions is carried out bygreen plants but not by animals?AexcretionBgrowthCphotosynthesisD respirationd Figure 3 shows how fish react when the glass on one sideof an aquarium tank is tapped with a finger.Figure 3What characteristics of living organisms does this demonstrate?A excretion and movementB excretion and nutritionC growth and irritabilityD irritability and movement2 Complete the passage below by choosing the words from thislist:excretion growth irritability movement nutritionorganisms reproduction respirationA Living things are often called ______________.B All living things release energy from their food in a processcalled ______________, which happens inside their cells.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore informationModule 1 Unit 15C Some of the energy is used for ________________, whichusually happens more quickly in animals than in plants.D The food from which the energy is released is taken intothe body in a process called ________________.E All living things get bigger as they get older. This processis called __________________.F The production of young is called ____________________.G Waste substances are removed from organisms by theprocess of ____________________.H The seventh characteristic shown byall living organisms is ____________________, whichmeans that they are sensitive to things around them.B Classification of living organismsIf you have ever been to a library, you will know how much easier itGlossaryis to find a book on a particular subject if the books are arranged inCLASSIFICATION – grouping organismsaccording to structural similaritiessubject groups. When the librarian has a new book to add to thelibrary, he or she will group it with books on a similar topic, accord-ing to a classification system.The use of the hierarchical classification systemCLASSIFICATION helps us to impose order and a general plan on theHintIn print, Latin names are written in diversity of living things. Scientists have always tried to organizeitalics.and classify the objects, including living organisms, around them.Classification can be defined as grouping organisms according totheir structural similarities. This means that organisms that shareHintsimilar features are placed in one group. These groups are arrangedLiving things are called organisms.from the largest group of organisms to the smallest group of organ-isms. The groups, from largest to smallest, are arranged as follows:kingdom, phylum (plural phyla), class, order, family, genus (pluralgenera) and species. The species is the smallest group of organisms.As you go through the classification hierarchy, you will see thatscientists have used broader features to put organisms into king-doms, which are the largest groups of organisms. When you movedown towards the species, which are the smallest groups of organ-isms, features are becoming specific. In other words, two organismsthat belong to the same species share more features than those inthe same kingdom but in different species.A species can be defined as a group of organisms with similarfeatures, and these organisms are capable of breeding and producefertile offspring. You are probably aware of the fact that horses anddonkeys belong to the same kingdom, phylum, class, order, familyas well as genus but they are from different species. Therefore, if adonkey and the horse happen to breed, they produce an offspringcalled a mule. The mule is infertile, meaning that it cannot repro-duce offspring because it is a product of organisms of differentspecies.Classification hierarchy has many uses. First, it helps scientiststo sort organisms in order. Second, it helps them to identify neworganisms by finding out which group they fit. Third, it is easier tostudy organisms when they are sorted in groups.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore information6NSSC BiologyC The hierarchical classification systemThere are various sizes of groups into which living organisms areput. The largest group is the kingdom. There are five kingdoms:prokaryotes (which includes bacteria), protoctista, fungi, plantsand animals.HintEach kingdom is further divided into smaller groups calledone phylum, many phylaphyla, based on a few features that are shared by some taxon, many taxaFor example, the arthropod phylum contains all the animals with-one genus, many generaout a backbone that also have jointed legs and a hard coveringover their body, such as insects, crustaceans and spiders.HintA phylum is then subdivided into classes, orders, families,These names are given to help yougenera, and finally species. In this system of classification theunderstand classification. You do notvarious groups are called taxa (singular: taxon).need to learn this type of detail.This chart shows the hierarchical system of classification.kingdomphylumclassorderfamilygenusspeciesTable 1 shows how this system can be used to classify a humanbeing.KingdomAnimaliaall animals, same as zebraPhylumChordataall animals with a backboneClassMammaliananimals with a backbone, which have hairOrderPrimatemammals with hands and feetFamily Hominidaeapes, primitive humans and modern humansGenusHomoprimitive humans and modern humans onlySpeciessapiensmodern humans onlyScientific Homo sapiensnameTable 1 Classifying the human being© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore informationModule 1 Unit 17Two systems of classificationClassification can be based on two different systems, natural andartificial. We will look at natural classification first.Natural classificationThe hierarchical classification system described above is based ona natural classification system that uses common features sharedby organisms. Natural classification is based on two ideas:•homologous structures•evolutionary relationshipsHomologous structuresHomologous structures are features of organisms that are similarin structure but may look very different from each other and maybe used for different purposes. As shown in Figure 2, a horse’s frontleg, the human arm and a bat’s wing are all homologous struc-tures. They have the same number and arrangement of bones andthis means that they probably evolved from a single type of struc-ture that was present in a common ancester millions of years ago.A fly’s wing is not homologous with a bat’s wing. It may look simi-Hintlar and do the same job but it develops from a completely differentAnalogues look the same but areorigin. The fly’s wing has no bones and is not covered by feathers. Areally different, homologues look bat’s wing and a fly’s wing are termed analogous. A bat and a flydifferent but are really the same.would not be grouped together!ACTIVITY 4Spend about 10 minutes answering these questions.Look at Figure 4 that shows an example of three homologousstructures.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore information8NSSC BiologyFigure 4a Feel the bones in your own arm. Try to identify the bonesshown on the diagram of the human arm. Put one hand onyour lower arm and turn your lower arm over and back.You should be able to feel one bone twisting over the other.b Each of the vertebrates shown has carpals, metacarpalsand phalanges. Name three other bones shared by all threevertebrates.c Describe how the metacarpals of the horse differ fromthose of the human.d How do the phalanges of the bat differ from those of thehuman?e Complete these sentences:The human arm, the horse’s front leg and the bat’s wing aredescribed as ____________________ structures. The wing of thebat and the wing of a fly are described as _____________________structures.Evolutionary relationshipsIf you look at photographs of people who share a common ancestor,such as a grandparent or great grandparent, you often see star-tling similarities in appearance. The people in the photos areobviously related to each other and have inherited some featuresfrom their grandparents.In a natural classification system, biologists group togetherorganisms which are structurally similar and share commonancestors. Natural classification produces a branching set of rela-tionships as shown in Figure 5. This shows how the plants aredivided into major subgroups such as mosses, ferns, conifers andflowering plants. Each of these subgroups can be divided further.In this diagram only the two main groups of flowering plants havebeen shown. Where organisms are divisions of the same subgroup,such as the monocotyledons and dicotyledons, they are more close-ly related and may share more similar features than with themosses and ferns. Figure 5 shows the main subgroups of the plantkingdom.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore informationModule 1 Unit 19Figure 5In the animal kingdom, humans, Homo sapiens, are found, as isthe cockroach Periplaneta americanus. Humans and cockroachesshare a common ancestor, but that was more than 500 millionyears ago! You can see many structural differences betweenhumans and cockroaches and so there is no natural relationship.Because of this we classify Homo sapiens and Periplaneta ameri-canus into very different groups!Artificial classificationWith artificial classification you can use any grouping you like.You could put all the animals that fly in the same group. Thisgroup would then include birds, bats and many insects. You couldput all animals that live in water and have streamlined, fish-likebodies in the same group. This group would then include fish andwhales.Artificial classification systems are also used as the basis fordichotomous keys that biologists use to identify organisms.ACTIVITY 5Spend about 10 to 15 minutes answering these questions.In this activity you will see how an artificial classification workson the basis of using pairs of options; for example,yes/no has/has not in/out.© Cambridge University Presswww.cambridge.orgCambridge University Press978-0-521-68054-7 - NSSC Biology Module 1Ngepathimo KadhilaExcerptMore information10NSSC BiologyIf it is not one thing then it must be the other!Look at this list of organisms:fish whale seal duck house-fly bat eagleowl mosquitoIn your notebook divide these organisms into the following arti-ficial groups.1 Those organisms that can fly.2 Those organisms that fly only at night.3 Those organisms that swim.4 A category of your choice.D Binomial system of naming speciesCarl Linnaeus, a Swedish botanist who lived from 1707 to 1778,introduced the hierarchical classification system that we have dis-cussed so far. In addition to that, he gave each and every species ascientific name in Latin. The binomial system of naming speciesmeans giving organisms two names in Latin (scientific names). Theterm binomial literally means two names – ‘bi’ means two and‘nomial’ means name. Linnaeus derived scientific names from thegenus and the species to which organisms belong.When writing a scientific name, the genus name is written firstand starts with a capital letter, and the species name is writtensecond and starts with a small letter. The scientific name ought tobe printed in italics when typed and underlined separately whenhandwritten. The tiger belongs to the genus called Panthera andthe species called tigris, therefore its scientific name will be typedas Panthera tigris, or handwritten as Panthera tigris.Scientific names are universal because, for instance, every biolo-gist will understand that Felis catus means ‘house cat’ withoutresorting to the dictionary, no matter what language they speak.Can you think of the scientific names for some more organisms? ACTIVITY 6Spend about five minutes on this activity.1 In your notebook, write two reasons why living organisms areclassified into groups.2 Use your knowledge about classification system to classify alion into kingdom, phylum, class, order, family, genus andspecies.3 Look at the following three scientific names:(i) Merluccius Capensis(ii) homo sapiens(iii) Olea capensis© Cambridge University