Contents Acknowledgments Introduction Preliminary Unit The importance of Biology Unit 11.1 Living Things Topic 1: Cells, tissues and organs Topic 2: Cell structure and function Topic 3: Cell processes — movernent of materials Topic 4: Cell processes ~ enzyme activity Topic 5: Classification systems. Topic 6: Diversity of animals Topic 7: Diversity of plants. Topic 8: Uniceliular organisms — the protista Unit 11.2 Nutrition Topic 1: How plants feed — autotrophic nutrition... Topic 2: Plant nutrition Topic 3: Cell processes — photosynthesis Topic 4: How humans feed — heterotrophic nutrition, Topic 5: How animals feed — heterotrophic nutrition. Unit 11.3 Transport Systems Topic 1: Transport systems in plants. Topic 2: Transpiration Topic 3: Transport systems in animals Topic 4: The human circulatory system Topic 5: Excretory systems in animals and humans Unit 11.4 Respiration and Gas Exchange Topic 1: Respiration and gas exchange in plants Topic 2: Respiration, breathing and gas exchange... Topic 3: Gas exchange in animals Unit 11.5 Response to Stimuli Topic 1: Growth and response in plants Topic 2: Sensitivity and coordination in animals. Topic 3: Maintaining stable internal conditions — homeostasis. Unit 11.6 Reproduction Supplementary Unit: Micro-organisms Topic 1: The structure and function of micro-organisms Topic 2: Human responses to micro-organisms : Topic 3; Respiration and gas exchange in micro-organisms. Answers. Glossary/index iv ul 25 37 woe 43 51 57 61 69 83 93 oF lll 121 137 143 149 179 193 197 203 223 233 243 259 269 301 329 341 353 355 423Acknowledgments There are many people to be thanked for their help and assistance in enabling the publication of this series to happen. First, the cooperation and generosity of Mark Sayes at ESA Publications in New Zealand who responded with interest and support when the proposal to adapt his Study Guide series was put to him The authors of the original edition were Martin Hanson and Maria Sinclair. This adaptation has been produced to provide Grade 11 Biology students in PNG with a book that they can use as a compact summary of content and skills related to the PNG Grade 11 syllabus. lt was produced with the assistance of: Takis Solulu, MSc Oxford, BScAg PNGUoT; Grade 12 Biology Examiner since 2007, Lecturer in Biology, UPNG. Beatrix Marjen-Waiin, MSc Imperial UK, PGDSc UPNG, BSc-UPNG; Grade 12 Biology Examiner since 2008; Lecturer in Biology, UPNG. Diaiti Zure, MSc PNGUoT, BScF PNGUoT, Forest Soils and Plant Biologist, Department of Forestry, PNG University of Technology. We would also like to acknowledge many other individuals who have been happy to advise and assist in different ways: Joy Sahumlal, Michael Uglo, Greg Kapanombo and ‘Anne Dandava SangiIntroduction This book has been published to provide the information required by students in order to successfully complete the Upper Secondary course in Biology at Grade 11 in Papua New Guinea. The book is written in a manner that best develops an overall understanding of the biological concepts and processes set out in the PNG Grade 11 Syllabus. The order of Units in this book follows the order of Units presented in the Biology syllabus for Grade 11; Unit 11.1 Living Things Unit 11.2 Nutrition Unit 11.3 Transport systems Unit 11.4 Respiration and Gas Exchange Unit 11.5 Response to Stimuli Unit 11.6 Reproduction Supplementary Unit: Micro-organisms ‘Within each Unit there are a number of Topics which follow the main sub-headings and bullet points set out within each Unit in the syllabus. The aim is to provide structure and content in a concise and compact format for students to use as an effective resource to support the classroom experience. It is acknowledged that Biology is more interesting and meaningful when students are exposed to a variety of resources and materials and we encourage students and teachers not to rely on this book as a sole source of information. For each of the above Units we look at plants, animals and humans but for micro- organisms, instead of treating them within those Units, we have instead created a Supplementary (7th) Unit. Within this Supplementary Unit, we look at micro-organisms in relation to nutrition, transport systems, respiration and gas exchange, responses to stimuli, and reproduction. In this respect, the study of micro-organisms can show how interrelated these aspects of an organism’ existence are. Much of the content in the Supplementary Unit is not in the Grade 11 Syllabus, but it is important — and an understanding of micro-organisms is extremely important in relating the study of Biology to real life, real issues and the local environment (as stated in the Secretary's Message on p. iv of the Biology Teacher Guide Upper Secondary (2009). If you have any suggestions about how this book might be improved in future editions, please make contact with Oxford University Press: Fax: 00 61 3 9934 9100 Customer Service Email: exportsales.au@oup.com ‘We wish you every success in your studies. The authorsPreliminary Unit The importance of biology Authors: David Blaker with Takis Solulu The content of this Preliminary Unit is intended as an introduction to the importance of biology knowledge by looking at: * How biology knowledge can be used. + Carrying out an assignment ~ choosing a topic; collecting, sorting and interpreting the information; making a report or essay. Biology knowledge Biology knowledge is becoming increasingly important as the world faces some major issues and people demand practical solutions. Biology knowledge is about ideas. Its main aim is to find out how living things ‘work’ and to develop ideas about what has been discovered “The biology learning outcomes set out in the PNG syllabus require you to process information you discover about biology knowledge and discuss how it is or can be used. Your teacher should provide you with direction with regards to the type of biology knowledge you are to find out about, how itis used and how to process it. Biology knowledge can be used in several different ways. You may choose to focus on one of the following areas. + A technological application. While biology knowledge is driven by human curiosity and a desire to learn, technology is driven by human needs and demands for such things as better safety, food quality or production, health or convenience. Technology is about finding practical uses for the biology knowledge that has been accumulated. Biology knowledge can have many different technological applications. For example, many types of food production (cheese, chocolate, wine, beer); improving health or fighting disease (kidney dialysis, managing diabetes, repairing damaged tissue organs, fertility treatments); biotechnology (including genetic engineering, cloning, tissue culture). + Amanagement practice Biology knowledge may be used to bet:er manage a useful or commercial plant crop or animal. For example, improving the fishing quota system so fishing is sustainable, or applying good horticultural practices to maximise the yield of a food crop or a forest. © Resolving an issue, An issue is often something that is a problem in society and affects a large aumber of people. Issues can range from the best way to control an introduced pest, to addressing the growing problems of obesity, heart disease or diabetes, to better ways of dealing with waste + Development of a theory A theory is the use of biology knowledge to explain an event or a phenomenon, eg the evolution of PNGS flightless birds such as the cassowary, climate change + Development of a model. Biology knowledge can be used to model o: describe what is happening now. This model can then be used to make predictions about what could happen in the future, For example, the possible effects of climate change on agriculture or the spread of disease in developing countries.2 Preliminary Unit Carrying out a research assignment Finding out how biology knowledge is used is not original research. It will use secondary data — information already produced by others. However, the way information is selected and organised, and how the links are explained, should be original. This chapter gives step-by-step directions on how to carry out a research assignment. Most of the planning is set out below, but students will need to do some planning of their own Before starting @ topic, it is essential to find out + The due date(s) + That the topic is approved by the teacher. + Whether it will be reasonably easy to get the information needed. + What kind of report format is acceptable + How the final report will be evaluated Choosing a topic It can be helpful to state the research title in the form of a question, as that can give more focus to the research. Example questions for research titles 1. In what ways does a kidney dialysis machine imitate the normal working of a kidney? 2. Are current logging practices sufficient to ensure sustainable forestry? 3. What is the link between smoking and respiratory illnesses? 4 . How has biology knowledge about nitrogen-fixing bacteria helped farming become more productive? wu In what ways does the quality of paper depend on knowing about the cell structure of wood? How are antibiotics developed and made, and why don't they work on viruses? What is plant tissue culture, and what biological principles does it depend on? The whole island of New Guinea is about one-half of one percent (0.5%) of the Farths surface but it contains between 5% and 10% of the total species on the planet — why might this be so? Pann production of food in the Highlands change if climate ity? 10. What goes wrong when a person develops diabetes, and exactly how do insulin injections help them? © Oxford University Press www.oup.cor.80The importance of biology 3 Collecting information Library books and the internet will provide more information than a person can manage, so it helps to do some selection before even starting, It may be best to avoid heavy technical sources {too hard) and popular magazines (probably too simple). Having found the right ‘level’, a researcher should aim to use at least three or more cifferent sources, in order to get a range of information Ifa research starts with known websites, this can save a lot of time. Search engines such as Google.com find much more information, but can waste time if not used wisely, When using a search engine, it helps to know how to narrow down the number of websites ed. The trick to saving time lies in choosing the best combination of search words. Entering Gives this many websites ) “deaf” 1 800 000 “deafness” 269 000 “deafness” + “technology” 87 400 deafness + technolog 87 400 [aeatness + technology + cochlear 7 560 deafness + technology + cochlear + implant 1.060 hearing + technology + cochlear + implant 2140 Not all search engines need the “quote” marks, and in the case of Google.com they can be left out. The example given is for the issue of hearing loss and cochlear implants, searched by Google. Even when using the + sign correctly, there may be dozens of suitable websites. Instead of printing out whole sections, it helps to copy one single page from each site, then paste it to a ready-made document Guidelines for a report or essay Performance criteria Satisfactory | High Very high achievement _| achievement | achievement Information used is appropriate to the topic | Yes Yes Yes A range of information source types Yes Yes Yes Sources clearly recorded Yes Yes Yes Information sorted and arranged Clearly Clearly Clearly processed processed processed Kind and format and length of the report | Yes Yes Yes are all suitable How are the links between biology Describes Explains how/ | Discusses knowledge and its use dealt with in the biology and | why biology | how/why report? use separately | knowledge —_| biology applies to the | knowledge use applies to the use 2 © Oxford University Beess www oup.comaa4 Preliminary Unit Sorting the information A large collection of information on a topic may look impressive, but is not muck use in its original form, A first step is to make summary notes, and to highlight key bits from internet printouts. ‘The next step can be to sort the information into categories, such as: + Too hard or too simple or not zelevant — so not wanted. + Biology facts and ideas and principles. + Details of the use + Anything that shows how biology knowledge and use are related. Processing the information Assignments often ask for a situation to be ‘discussed’. This needs a different kind of input to ‘describing’ something. ‘Describe’ usually means giving the reader a picture of how something works and what it looks like. The facts are left to speak for themselves. A ‘discussion’ of the links between biology and a use could include the following * Saying which seemed to come first, the biology or the use. + Clearly saying how the biclogy and the use interacted. + Suggesting why the discoveries and links happened at that particular time. While descriptions of biology knowledge or its use can be lists or bullet points, a discussion must be more than this. A discussion would be expected to involve paragraphs in which several ideas (descriptions and explanations) are linked. Furthermore, the discussion must clearly link the biology knowledge and its use, eg a discussion of how current knowledge of the orange roughy reproductive rate and methods have resulted in a change in the fishing quota. The assessment The assessment often takes the form of a report or essay, as these formats are better for writing a discussion than a PowerPoint™ presentation or a poster. Before beginning the assignment, students need to find out how long the report needs to be, and which format — or combination of formats — is acceptable. One format that is never acceptable is a cut-and-paste of internet material. Whichever format is used, the balance between visual material and text needs to be thought about. In the case of the topics in this chapter, the visual should not dominate. Words matter. Asa general guide to writing text, ‘keep it simple’. It should be aimed at an average-to-better member of the class. Some guidelines for good quality writing are * Use short sentences. * Use short paragraphs, with line breaks. + Avoid listing or bullet points as these are difficult to integrate into a discussion, + Cutout ‘padding’ © Oxford University Press wawoup.cor. aitUnit 11.1 Living Things Topic 1: Cells, tissues and organs Authors: Martin Hanson with Diaiti Zure Millions of plant and animal species live in the world and PNG has over 5% of the total species on the planet, All these living things are made up of cells. Topic 1 in Unit 11.1 relates to living cells (ref. p. 9 in the Syllabus) which is important for understanding biological concepts throughout this book and includes: + The discovery of cells. * Cells, tissues and organs. + How substances enter and leave cells. Note that micro-organisms are covered in the Supplementary Unit (p. 329). The discovery of cells Robert Hooke in 1665, following the invention of the microscope, examined a thin slice of cork, noting thousands of ‘little boxes’ h ied cells. Cork is dead — Hooke did not realise that the ‘ttle boxes’ had been produced by a transparent, jelly-like material that had died by the time the cork had fully developed. The importance of this jelly-like material was only appreciated many years later when biologists could see cells more clearly by staining them. cell membrane Z cell membrane vacuole (large) nucleus cytoplasm. chloroplast nucleus —_— el Animal cell Plant cell (from the lining of a human cheek) (from the epidermis of an onion) Cells. The cell theory During the 18th and 19th centuries, scientists gradually realised cells are the units of life, an ‘dea that became known as the cell theory + Allliving things consist of cells. Some organisms are said to be unicellular because they consist of only one cell. Even gametes (eggs and sperms) are cells. + Activities of living things are the outward signs of processes occurring in their cells (eg saliva poured into the mouth is made in cells of the salivary glands; the pumping of the heart is due to the contraction and relaxation of its muscle cells) + New cells Cells Most organisms seen with the naked eye are multicellular (consist of many cells). Many microscopic organisms are said to be unicellular (consist of a single cell). Animal and plant cells differ in several important ways. ise when a parent cell divides into two.6 Unit 11.1 Living Things Animal cells plasma ae membrane = Golgi body / ? 3 ~ BY 4 mitochondrion cytoplasm nucleus endoplasmic reticulum and ribosomes In reality, no cell looks just like this, because cells are specialised for carrying out particular functions. General features of an animal cell. A cell consists of a number of distinct parts or organelles, each specialised for carrying out a particular function. + The muclens — the contro! centre; contains ‘instructions’ the cytoplasm needs to perform its tasks. These instructions are genetic information inherited from the parent, stored in & chemical called DNA, organised into threads called chromosomes. Each chromosome consists of thousands of genes, arranged like beads on a necklace. The nucleus is separated from the surrounding cytoplasm by a nuclear envelope. + The plasma membrane ~ the outer boundary of the cytoplasm, Controls the movement of substances into and out of the cell + Mitochondria (singular, mitochondrion) ~ the site of respiration, in which food is oxidised to generate useful energy for the cell. Particularly common in active cells such as those found in the liver, kidney and muscle + Ribosomes — these tiny particle-like organelles make proteins using information copied from the genes in the nucleus. Particularly abundant in cells making proteins, such as those cells that secrete digestive enzymes into the gut. Ribosomes are closely associated with a network of membrane-bound sacs called the endoplasmic reticulum. + Golgi body ~ after being produced by the ribosomes, some proteins ave further modified in the Golgi body. For example, the iron-containing part of haemoglobin is added in the Golgi body. Proteins destined for secretion (eg digestive enzymes), are assembled into ‘packets’ in the Golgi body. Plant cells Plant cells have a number of features that animal cells lack. + The cell wall surrounds the plasma membrane and is made mainly of a carbohydrate called cellulose, which is strong enough to give the cell firm shape. In some plant cells © Oxford University Press wwwoup.comau,Topic 1: Cells, tissues and organs 7 the living part (nucleus and cytoplasm) dies as the cell matures, leaving only the cell wall - eg, cork cells and the water-conducting cells of the xylem, + Inleaves and other green parts of plants, cells contain small organelles called chloroplasts. ‘These contain the green pigment chlorophyll and carry out photosynthesis + Most plan cells have a large cavity called a vacuole, containing cell sap, a solution of mineral salts and other substances. Because of the vacuole, the chloroplasts are close to the cell wall, so they are near the source of CO, chloroplast chloroplast cell wall | nucleus cell wall | nucleus {o, \) | So co An entire plant cell seen A section of a plant cell seen under a light microscope under a light microscope Golgi nucleus body endoplasmic reticulum and ribosomes mitochondrion cell wall vacuole chloroplast A section of a plant cell seen under the electron microscope An entire plant cell. Differences between animal and plant cells under the light microscope (Structure Plant cells Animal cells Nucleus Present Present Cell wall Present Absent Large vacuole | Usually present Absent, Chloroplasts | Present in photosynthetic cells | Absent Comparison between animal and plant cells. © Oxford University Press www oup.com.au8 = Unit 11.1 Living Things Prokaryotes and eukaryotes Plants, animals and fungi are eukaryotes — ie the cells have chromosomes surrounded by a nuclear envelope to form a distinct compartment, the nucleus. In prokaryotes, which are bacteria, the DNA is not clearly separated and forms a closed loop (in eukaryotes, chromosomes are open-ended). Prokaryotes do not have any nuclear membrane or envelope surrounding their chromosomes. Tissues In multicellular organisms such as humans, all cells carry out certain basic processes, such as respiration and making proteins. Besides these fundamental processes, most cells are specially adapted for concentrating on a particular task, ie cells are specialised for certain functions. In most cases cells act in groups called tissues (groups of cells specialised for carrying out a particular function). Usually, the cells are organised so the group works more effectively than the individual cells can do (eg, nerve cells are not randomly arranged but are organised into complex networks; adjacent muscle cells in the heart are aligned in the same direction and so pull together). Examples of animal tissues include: + Epithelia (singular, epithelium) — form coverings or linings and perform fimnetions such as protection (eg the skin, arid lining of the breathing passages). Glandular tissue consists of ‘in-tuckings’ of epithelium specialised for secretion of substances the cells produce (eg, glands in the stomach secrete gastric juice that helps digest food). * Muscular tissue — consists of cells modified for changing chemical energy into mechanical energy for force and movernent. + Nervous tissue — consists of cells specialised for carrying electrical signals. Examples of plant tissues include: * The epidermis of a leaf ~ consists of cells that fit together like jigsaw pieces, They are covered by a continuous waxy cuticle that helps reduce water loss + The water-conducting cells of plants — consist of dead cells with no end walls and which fit together like drainpipe sections. Only by fitting together in this way can they carry water eifectively. Organs An organ is a group of tissues that cooperate to perform a more complex function than the component tissues. The heart consists of muscular tissue, epithelial tissue and nervous tissue, held together by connective tissue. The tissues of the heart work togetixer to pump blood. The small intestine also contains the same types of tissue, but they are organised in a quite different way to carry out the completely different function of digesting and absorbing food Other examples of organs are the stomach and kidney, and in plants, leaves, stems, and roots. © Oxford University Press wnrwoup.com.atTopic 1: Cells, tissues and organs 9 How substances enter and leave cells Cells are like miniature factories, constantly taking in raw materials and generating waste products, glucose brain cell leaf cell (in light) Movement of substances into and out of an animal cell and a plant cell. Substances enter and leave cells by various kinds of process ~ the most important are diffusion, osmosis, and active transport. Diffusion Diffusion is the movement of a substance from where it is more concentrated to where itis less concentrated potassium permanganate (purple) concentration concentration potassium permanganate crystal The effect of dropping a potassium permanganate crystal into a beaker of still water illustrates diffusion. As the crystal dissolves, the purple colour spreads very slowly outwards to where it is less concentrated. Diffusion of potassium permanganate in water. Diffusion depends on the random movement of particles (either molecules or ions). Anima! cells use oxygen, so oxygen is less concentrated inside than outside, causing it to diffuse in CO, is produced in an animal cell, so it is more concentrated inside than outside and diffuses out. © Oxford University Press wwrw.oup.com.au10 Unit 11.1 Living Things Osmosis Osmosis is really a special kind of diffusion — it involves the movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane (a partially permeable membrane is an extremely fine sieve, allowing water molecules to pass through, but not larger molecules such as sugat). solution |__— water sugar sugar solution molecules | — water —=—& dialysis tubing molecules Demonstration of osmosis. Active transport The plasma membrane that forms the surface of the cytoplasm is permeable only to small substances like water, oxygen, and CO,, which enter and leave cells by diffusion, Cells must absorb larger molecules such as glucose by a process called active transport. Active transport moves substances from a low concentration to a higher concentration (je in the opposite direction to the ‘natural’ direction that occurs from diffusion), so active transport uses energy. Energy is supplied by respiration (this is why it takes a lot of enezgy to absorb digested food after a meal). (© Oxford University Press wwwoup.comas,Unit 11.1 Living Things Topic 2: Cell structure and function The content in Topic 2 includes explanation and description of the structure and function of cell organelles (ref. p. 9. in the Syllabus and p. 25 in the Teacher Guide). The Topic deals with: * The structure and function of cellular components and organelles - cell wall, cell (plasma) membrane and nuclear membrane, nucleus, chromosomes, centrioles, cytoplasm, endoplasmic reticulum, ribosomes, mitochondria, chloroplasts, Golgi body, lysosomes, vacuoles, contractile vacuoles, cilia, flagella, eye spots. Factors that affect cell structures. Reasons for similarities and differences between cells. Cells were first observed in 1665 by Hooke through one of the first microscopes. Nearly 200 years later (1839), the cell theory was proposed. This states that ‘cells occur universally and are the basic units of living organisms’; the theory is still current. Prokaryotes and eukaryotes All cells belong to one of two categories ~ they are either prokaryote cells or eukaryote cells. + Prokaryote cells are found only in bacteria and cyanobacteria (the Monera), and are distinguished by not having a true nucleus, only a central nuclear area containing a loop chromosome, and small circular DNA plasmids. The cytoplasm does not have membrane-bound organelles such as mitochondria, * All other organisms are made of eukaryote cells. These have a true nucleus (one enclosed in a membrane) containing chromosomes and a variety of membrane-bound organelles in the cytoplasm The rest of this chapter refers to eukaryote cells only ‘The structure of a cell is linked to its function. The size and shape of a cell and the organelles within it are linked to the way it carries out its function within the organism Examples Animal and plant cells show differences in size, shape, structure: smooth muscle cell Animal cells <> plant vessel 2 element (tip) Crm hair cell | leaf palisade Plant cells cell12 Unit 11.1 Living Things Basic cell structures of animal and plant cells Basic cell structures of animal and plant cells can be seen using a light microscope. cell membrane SD cytoplasm chloroplast nucleus. 7 < cer Animal cell cell membrane vacuole (large) nucleus Plant cell An animal cell viewed through a light microscope shows a nucleus, cell membrane and cytoplasm. The light microscope shows that plant cells also contain chloroplasts, vacuoles and have a cell wall outside the cell membrane. Cell structures visible under a modern compound light microscope It is the presence of the cell wall that distinguishes plant from animal cells. Plant cells taken from a leaf (or the outside of greens stems) will have chloroplasts and large vacuoles (which store the products of photosynthesis). Vacuoles are common in animal cells but ave never large. So ateeil pee a Cells lining the cheek of a human ~ visible in each is cell membrane, cytoplasm, nucleus Cells from the epidermis of an onion cell ~ visible in each is cell wall, cytoplasm, nucleus. The cell membrane under the cell wall is not distinguishable from the cell wall. There are no (large) vacuoles or chloroplasts, as the cells are not photosynthetic Photomicrographs (photos taken from a light microscope) taken at 400 x magnification using @ compound light microscope. ‘© Oxford Univesity Press wonkoup.com. atTopic 2: Cell structure and function 13 Cell detail Cell detail is revealed under the (transmission) electron microscope or TEM, as this can magnify up to 400 000 times A ‘typical’ animal cell A typical’ plant cell + 70-30 pm > « 10-100 1m. chloroplast cell membrane vacuole Golgi apparatus cytoplasm lysosome endoplasmic reticulum nucleus nucleolus ribosome - (granules) vacuole mitochondrion es) communication channel to adjacent cell centriole Cell detail of a ‘typical’ animal and a ‘typical’ plant cell as revealed by a TEM. Organelles found in animal and plant cells Cell (or plasma) membrane All cells are bound by a cell membrane. In plant cells, this is enclosed by a rigid cell wall mace of cellulose. Membranes are very thin (about 8 nm or 0.000008 mm) and act es a boundary between the cell and its environment (so maintaining the concentrations of substances inside and outside the cell). The membrane is made of a phospholipid bilayer embedded in which are many different proteins. The bilayer is fluid, allowing the proteins in it to move. The bilayer has ‘heads’ of glycerol-phosphate, which are hydrophilic Cwater loving) and ‘tails’ of fatty acids, which are hydrophobic (water hating’). This hydrophilic/hydrophobic arrangement (known as amphipathic) allows the membrane to assemble/reassemble itself and also to seal itself if damaged. The structure of the membranes of cell organelles is similar. © Oxford University Press wwwoup comm ax14 Unit 11.1 Living Things glycerol-phosphate — ‘heads! phospholipid bilayer membrane proteins Membrane structure (of an animal cell). Proteins on the outside of the membrane may be receptors for chemicals such as hormones and neurotransmitters. Other proteins on the surface llow the cell to recognise ‘self’ from ‘foreign’ cells The proteins that penetrate through the membrane are likely sites of transport of substances into/out of the cell (via facilitated diffusion and/or active transport) Membranes are semi-permeable, meaning that they allow passage of only certain substances, Small molecules (eg ©, CO,, glucose) typically freely diffuse through the membrane, while large molecules, (eg starch) are excluded or have to be actively transported across the cell membrane ‘The membrane may be thrown up in many folds, known as microvilli, which greatly increase its surface area, Microvilli are found in cells that are very active in secretion (eg pancreatic cells) and/or absorption (eg cells lining the kidney tubules and the small intestine) TEM micrograph of membrane of a cell lining the small intestine. The membrane is folded into microvilli to increase surface area for absorbing nutrients. Cell nucleus The nucleus is often called the control centre of the cell because it contains DNA, the genetic material that organises all cell processes. DNA is scattered throughout the nucleus as chromatin, which only forms into visible structures called chromosomes just before a cell is going to divide (ie mitosis, meiosis) The nucleolus inside the nucleus produces the RNA component of ribosomes, which are involved in the production of protein (© Oxford University Press worwoup comaTopic 2: Cell structure and function = 15 The nucleus is contained in the nuclear envelope, a double membrane that has intervals ~ these allow materials to move between the nucleus and cytoplasm. res at double membrane of nuclear envelope RD fo \~ endoplasmic reticulum (ER) op mitochondrion nuclear pore nucleolus chromatin material Chromosomes chromatids During the early stages of cell division, the chromatin material condenses to form chromosomes. The chromatin coils up tightly into looped structures made of two chromatids joined by a centromere centromere A chromosome. Cytoplasm Cell organelles are embedded in the cytoplasm. The cytoplasm is made of fluid called cytosol, which is mainly water but with many substances dissoived in it (eg sugars, amino acids, mineral ions), and it is where many of the chemical reactions of the cell occur (eg glycolysis) Endoplasmic reticulum (ER) The endoplasmic reticulum (ER) is a network of membranes running through the cytoplasm and takes up most of its space. The membranes enclose tubes, which, in certain places, may be enlarged to form flattened areas called cisternae (which may temporarily store substances) ER may have ribosomes attached (rough ER), concerned with protein production. Rough ER 's therefore common in celis that make and secrete proteins (eg digestive cells that produce enzymes, white blood cells that produce antibodies) (© Oxford University Press woewoup comsu16 Unit 11.1 Living Things ribosomes membranes re rat TEM micrograph of rough ER. ER that does not have ribosomes attached, smooth ER, is associated with production of lipids common in cells that produce steroid hormones ER also functions as a transport system, carrying materials from one part of the cell ta another, as well as the nucleus and to the outside of the cell Ribosomes Ribosomes are the site of protein synthesis, They are made in the nucleus (in the nucleolus) and pass out via the nuclear pores to the cytoplasm. They may attach to the ER (where they typically make protein for use inside the cell), or be free in the cytoplasm (where they typically make proteins for use outside the cell, ie are secreted), or are used in the cell’s membranes. Ribosomes are made of two subunits (one small and one large), which combine to form the protein-synthesising unit small subunit, ooo Vom aed ‘eae Pe om Particles are Later, more of the particles Eventually, the concentration moving randomly. are on the right. of particles is the same The concentration is throughout. The particles higher on the left than are still moving randomly, on the right. but overall there is no. net movement. The difference in concentration between two areas is called the concentration gradient ‘The higher the concentration gradient, the faster the rate of diffusion. Other factors that affect diffusion are + Size ~ smaller pa cles diffuse fas Temperature — particles diffuse faster in warmer than in colder temperatures, + State — gas particles diffuse faster than particles ina liquid. + than larger ones26 = Unit 11.1 Living Things high concentration Small molecules (eg O;, CO,, glucose) diffuse small molecule freely across membranes, with the direction 8 @ — cexterior) of movement being dependent on their ee concentration. Large molecules (eg starch) : ® are prevented from diffusing through the membrane phospholipid bilayer low concentration & 8 (interior) Facilitated diffusion Molecules that cross the membrane faster than is possible from their concentration gradient do so by facilitated diffusion. Special transport or carrier proteins in the membrane provide channels for the process. Carrier proteins are specific (ie carry only one type of molecule). Example Both glucose and oxygen can be facilitated in their diffusion into cells * The protein cytochrome P450 can transport O, up to 1.8 times faster across the membrane than by simple diffusion, * The diffusion of glucose into cells may be facilitated by the hormone insulin (a protein) which may activate transport channels. transport Facilitated diffusion proteins is a passive process, exterior e ®e 6 ® @,% Osmosis as the molecules can Osmosis is a passive process. Osmosis is a special case of diffusion. It is the movement of water only diffuse from high concentration to low across a semipermeable membrane (SPM) from where itis in high concentration to where it ts in low concentration. concentration across the membrane phospholipid bilayer interior Water is in high concentration when it has few particles (solute) dissolved in it + Freshwater/tap-water will have few particles dissolved in it, so the concentration of water will be high + Sea water/marine water will have many particles (salts, ions) dissolved in it, so will have a comparatively low concentration of water. © Oxtord University Press wwwup.com atTopic 3: Cell processes movement of materials 27 Example A saline solution is a salt solution (eg sea water). A 5% saline solution would have a higher concentration of water than a 10% saline solution, therefore water would move across a membrane from a 5% saline solution into a 10% saline solution. Aweak or dilute solution (little dissolved solute) is a hypotonic solution. A strong or concentrated solution (much dissolved solute) is a hypertonic solution Two solutions with the same concentrations (ie same concentrations of water and solute) are isotonic solutions. Solute particles large (eg sucrose) net H,O movement O sucrose molecules «water molecules Sucrose molecules too large to pass through the SPM. Net water movement is from LHS to RHS until concentrations are equal (ie isotonic) dilute sucrose SPM concentrated sucrose solution (hypotonic) solution (hypertonic) As diffusion and osmosis result from random movement of particles, the particles will move in both directions across the membrane. However, the net movement will be towards the area of lower concentration Solute particles small (eg salt/ions) 9 salt fons (Na', Cr) » water molecules Salt ions small enough to pass through the SPM. Net salt movement is from RHS to LHS. Net water movement is from LHS to RHS. Net movement ceases when solutions are isotonic. dilute saline/sait_ SPM concentrated saline solution (hypotonic) solution (hypertonic) © Oxford University Press wwwoup.com.au28 Unit 11.1 Living Things When both solute (eg salt/ions) and water are moving across a membrane, water moves much more rapidly, so its effect is more apparent than that of the solute diffusion (eg plant cells plasmolyse rapidly when placed in a concentrated salt solution because water tends to flood out of the plant cells) Dialysis demonstration Acommon way to demonstrate osmosis is to put a concentrated syrup/sugar solution in a dialysis bag (the dialysis bag represents a semipermeable membrane) tied to a long glass tube and suspend the bag in a beaker of tap water. The water moves into the dialysis bag (as it is more concentrated in the beaker than in the bag) and up the glass tubing, typically spilling over the top, glass tubing dialysis tubing syrup solution water movement in Osmoregulation Osmoregulation is the control of water inside a cell/organismn. Both plant and animal cells: + Will have no net loss or gain of water in isotonic solutions. + Will have a net loss of water through osmosis in hypertonic solutions. + Will have a net gain of water through osmo: olutions. n hypoton: Animal cells Animal cells have no cell wall around their membrane. Therefore they will: + Show no change in isotonic solutions. + Shrivel up in hypertonic solutions. + Expand and burst (lyse) in hypotonic solutions. (© Oxford University Press wwww.oup.com au29 Normal animal cell in isotonic Dehydrated animal cell Burst animal cell in solution; no net loss or gain shrivels in hypertonic hypotonic solution; follows of water. solution; net loss of water. excessive net gain of water. Plant cells The presence of a cell wall around plant cells influences osmoregulation, Plant cells have a rigid cell wall surrounding the membrane, Therefore they will: + Show no change in isotonic solutions + Become plasmolysed in hypertonic solutions ~ as water drains from the vacuole and the membrane pulls away from the cell wall. The cells become flaceid (or floppy) and the plant wilts if itis non-woody. * Become firm in hypotonic solutions ~ as water fills the vacuole and the cell membrane presses against the wall; they are said to be turgid. The cell wall stops plant ceils from bursting; no more water can enter. The resulting pressure from all cells being turgid (turgor pressure) acts to keep 2 plant upright if it doesn’t have a woody stem vacuole Sone ine fenach (enclosed in col (FSS [orn membrane) oS memvre | TE S) oe orensn A presen) cell wall ee Normal plant cell in isotonic Plasmolysed plant cell in Turgid plant cell in solution; no net loss or gain _ hypertonic solution; net loss of hypotonic solution; net of water, water. gain of water. Unicellular organisms Unicelhular organisms living in fresh water use their contractile vacuoles to osmozegulate Contractile vacuoles collect the water that enters from osmosis and expel it to the outside This requires energy, so is a form of active transport. Active transport Active transport moves substances (individual molecules/ions) across membranes against a concentration gradient, ie from low to high concentration, eg + Reabsorption of all glucose by cells of kidney tubules. + Uptake of nitrates, NO,", by root hairs * Removal of Na’ ions from cells of gills in marine fish. Research suggests that active transport of substances across membranes is via the large proteins embedded in the phospholipid bilayer. The substance temporarily combines with the carrier protein, which changes shape as it discharges the substance to the other side of the membrane. Such carrier proteins are likely to be specific (ie carry only one particular substance). © Oxford University Press worm oup.com.an30 = Unit 11.1 Living Things ~ phospholipid Substance combines bilayer with carrier protei a L carrier protein V4 () carrier protein changes shape... sea .. substance released to other side of membrane. oO This process requires energy (in the form of ATP) - about a third of a cell energy requirement may be needed for active transport. Cells undergoing a lot of active transport will have large numbers of mitochondria and use up large amounts of glucose and oxygen while producing large amounts of carbon dioxide and heat (in respiration) + Cytosis is the movement of large amounts of substances into/out of cells by the folding of membranes. + Endocytosis is the taking of substances into the cell by the infolding of the cell membrane Fluids are taken in by pinocytosis (‘cell drinking’), in which the membrane makes small infoldings which pinch off the liquid forming a vesicle ~ common in all cells. Large particles (food’) are taken in by phagocytosis (‘cell eating’), in which the membrane appears to flow around the particles and close off to form a (food) vacuole (eg white blood cells/phagocytes consuming bacteria, Amoeba consuming food). Typically, lysosomes join with the food vacuole and the food is digested + Exocytosis is the removal of substances from the cell, and essentially is the reverse of endocytosis. It occurs when a cell needs to secret a substance (eg a hormone). Endocytosis removes part of the cell membrane, while exocytosis adds to the cell membrane. Energy is involved in the movement/removal/addition of membranes, so cytosis is active transport © Oxford University Press wwwoup.com.au,Topic 3: Cell processes ~ movement of materials 31 Pinocytosis \ membrane PaaS Cell membrane invaginates and fluid droplets enter. . membrane pinches off the droplets... membrane which become a vesicle Y inside the cell. vesicle Process also works in reverse, removing droplets from a cell Phagocytosis Zz ay Cell membrane flows e out and around the food membrane particle... e -- membrane outflowings (‘pseudopodia’) meet and fuse, Uy engulfing the food particle, «which becomes a food vacuole in the cytoplasm. © Oxford University Press wowoup.com.au,32 © Unit 11.1 Living Things Cell size, shape and diffusion Cells are typically microscopic (the exceptions are some eggs - technically, the yolk of birds’ eggs is a cell; frogs’ eggs are visible to the naked eye; the human egg is the size of a full stop) The need for cells to be so small relates to their dependency on diffusion for getting substances into and out of the cell When cells grow, their volume (the cytoplasm and contents) increases at a much faster rate than their surface area (the cell membrane). This is because volume (V) increases by a cube factor, while surface area (SA) increases as a square factor. As a cell grows, the ratio between surface area and volume (SA:V) decreases. Thus as a cell grows, there is comparatively less membrane for substances to diffuse through and comparatively more cytoplasm/orgenelles that need these substances. Diffusion gets less efficient, and, beyond a certain size, the centre of the cell does not receive the needed substances. At this stage, the ceil stops growing, It may then divide to form 1wo new, smaller cells, which will have a larger SA:V ratio so substances can diffuse efficiently throughout the cell. Cells may also increase their SA:V ratio by having: + An elongated shape — eg nerve cells/neurons, zoot hair cells. + Having a biconcave shape ~ eg red blood cells for efficient diffusion of O, + Folding of the cell membrane ~ microvilli occur in both secretory cells (eg pancreatic cells, producing enzymes) and cells that absorb large quantities of substances (eg cells lining the small intestine absorbing nutrients, and cells lining the kidney tubules re-absorbing essential substances such as glucose) ~ allows for rapid diffusion. Plant cells are usually larger than animal cells, because their centre is typically occupied by the large storage vacuole. The vacuole is centrally placed as it is not dependent on receiving substances diffusing in across the membrane. The organelles that are dependent on diffusion of substances — eg chloroplasts (CO, in, O, out) and mitochondria (O, in, CO, out) ~ must be close to the membrane. (Chloroplasts also have better exposure to light when closer to the membrane.) Effect of cell size on transport of materials Consider a cube (Block 1) of dimensions 2 cm x 2 em x 2 em. Suppose further that it takes too long for materials to be of any elfective use if they diffuse or are transported over a distance > 1 cm. This means that materials just reach the centre of this block in time, since the centre of, the cube is 1 cm in from each face. Block 2 is 3 em x 3 cm x3 em. Itis bigger than Block 1 and its centre is now over 1 cm from the faces of the cube, so materials would not reach the centre area (shown as a grey dashed cube) in time to be effective. This central area would thus need to be full of substances such as water or storage materials 2 Lr, | 4 atl itr cent ‘Block 1 Block 2 2% 2x2 em cube 3x3x3.cm cube. © Oxlord University Press wwwroup.com.au,Topic 3: Cell processes - movement of materials 33 (i) 4 Block 2 The centre of each new block is within 1 cm of the faces and would be easily supplied with materials. By dividing into two smaller ‘cells’ the distance materials must travel has been reduced. Block 5 has the same volume as Block 2, but it is elongated. 12 15 1S Block 5 Despite having over three times the volume of Block 1, the centre of Block 5 is within 1 cm of the faces, and so would be readily supplied with materials. Example Effect of surface area to volume ratios The surface area, volume, and SA:V ratios for Blocks 1-5 are as follows: Blocks SA (cm) V (cm?) SAV 1 6x (2% 2)=24 2x2x2=8 a3 | 54 2 x(3x3)= «33227 34 <2; 6x (3x3) =54 3x3x3 34 = 20 2x (x3) +4xBx1.5) 3and4 | =18+18 15%3x3=135 | 38 2274 3S =36 2x (15x15) +4x(12x1.5) 5 =4.5472 1.5«1.5*12227 763 = 28:1 = 76.5 A SAN ratio that ‘had! to be greater than 2.5 would explain why Block 2 ‘had to ‘divide’, (Small) Block 1 is more efficient at diffusing materials than Block 2. Block 3 and 4 are more efficient at diffusing materials than (larger) Block 2. ‘Elongation’ of Block 2 into Block 5 increases diffusion efficiency. (© Oxford University ress wowwoup.com.au34 = Unit 11.1 Living Things The principle of greater rate of activity with an incx biological organisation: intestine for increased absorption of food. Organism level — native Africans are generally t overheating in the hot environment; elephants rease in SA:V ratio occurs at all levels of Organ level — villi, small projections from the wall of the small intestine, project into the all and thin, allowing rapid heat loss to stop have large, thin ears to allow rapid heat loss. Unit 11.1 Activity 3A: Movement of materials 1. Distinguish between the following pairs of terms: a. Passive and active transport. b._ Diffusion and osmosis. ¢. Hypertonic and hypotonic. 2. Describe the process of facilitated diffusion. 4. Dihute and concenirated solutions, Exocytosis and endocytosis. £. Phagocytosis and pinocytosis. e 3. The diagram alongside represents a human red blood cell and the movement of sodium ions into the cell and potassium ions out of the cel. The relative concentrations of sodium ions and potassium ions in red blood cells and in the surrounding plasma are lon Plasma Red blood cell K 9 Nat 146 shown, a. red blood cell and the plasma. Give reason: ‘b. When red blood cells are separated from b! Describe the method(s) of transport for the movement of Na* and K* ions between the s for your choice of method(s) ood plasma and placed in distilled water, they burst open. Explain why this happens. Explain the relationship between the SA:V rati io and diffusion in cells. The diagram below represents two solutions separated by a semipermeable membrane (SPM). water solute ° fgeeeseeeeay = Ni . ze oa. . : . oo oO. Oo. . . - O - 0 7 : . oO Li 1@) -OoO-e. _ oe SPM Explain the movement of the particles across the semipermeable membrane for both water and solute. 6. The three identical dialysis tubing bags (X, Y, and Z) suspended as shown contain equal quantities of a solution of 5% sucrose in water: © Oxford University Press www.oup.com auTopic 3: Cell processes — movement of materials | 5% sucrose 5% sucrose 5% sucrose solution solution \ solution \ 10% sucrose solution 5% sucrose solution distilled water in beaker in beaker in beaker Dialysis tubing is permeable to water but not to sucrose. Explain any changes that you would expect to see to each of the three bags (X, Y, Z) after 24 hours. 7. The diagram following shows an experimental set-up in which two solutions were placed in the arms of a U-tube separated by a semipermeable membrane (SPM). The semipermeable membrane is permeable to potassium chloride (K" and Cl ions), but not to sucrose. | Concentrated | solution of Dilute solution of sucrose and | sucrose and potassium potassium chioride chloride Discuss what would happen to the solutions. 8. The following graph shows the data obtained when 6 potato cubes of equal weight were placed in 6 different concentrations of salt water +4 Weight of potato cubes (g) z & Z ° 0 0.5 1.0 15 2.0 % concentration of salt in solution © Oxford University Press worwoup.comau36 Unit 11.1 Living Things a. Draw a clear, labelled diagram of what a cell from one of the potato cubes from the 2.0% salt solution would look like under 400 x magnification of a school microscope. b. Discuss the reasons for the gain and loss of weight by the potato cubes. 9. A unicellular organism that lives in a marine habitat was found to have much higher concentrations of iodine (a small molecule) in its cytoplasm than there was in the surrounding seawater, a. Explain how the organism may maintain this high level of iodine. b. Cyanide is a poison that inhibits respiration. Explain how the presence of cyanide in seawater would affect the iodine concentration in the organism. 10. The diagram following represents a cell from the lining of a human kidney tubule. A major role of the lining of the tubule is to absoth all the ghucose from the fluid flowing along the tubule and pass it into the blood, as shown by the arrows on the diagram. ANIA inside of tubule pore movement). ere re gion of glucose AWWW OVW celllining kidney ~~ tubule blood flow The tubule cell contains a large number of mitochondria. Explain the importance of mitochondria in the movement of all the glucose from the tubule to the blood. © Oxford University Press vwwwoup.com auUnit 11.1 Living Things Topic 4: Cell processes — enzyme activity The content presented in this Topic continues the description of the structure of cells and how they function. This Topic deals with: © Structure of enzymes. * ‘Lock and key’ and ‘induced fit’ models of enzyme function. * Role of enzymes as biological catalysts. Enzyme specificity. + _ Factors affecting enzyme activity. Enzyme activity Enzymes are part of the group of chemicals called proteins. Proteins, along with carbohydrates and fats, are the chemicals that make up most of the diet of animals. Proteins are made of amino acids, of which 20 different kinds exist in our cells. Essentially, there are two groups of protein: + Fibrous ~ these are long and stringy and form much of the structural elements of the body (eg collagen in muscles and tendons; elastin in the connective tissue of the skin; keratin in hair, horns, nails). «Globular - these are much-folded into a ball shape, and perform much of the regulatory processes of the body (eg hormones such as insulin, transporters such as haemoglobin, enzymes such as sucrase, antibodies, antitoxins). It is these essential functions that make proteins so important. Proteins are coded for by DNA, with one gene of DNA coding for one specific protein Enzymes act as biological catalysts, controlling the speed of chemical reactions in all organisms. Enzymes increase the rate of chemicel reactions ~ without them, metabolism would take place too slowly for life to exist Metabolism (metabolic reactions) refers to all the chemical reactions oceurting in a cell. All the metabolic reactions of cells are controlled by enzymes. reactions that synthesise large molecules from smaller ones (eg proteins from amino acids in protein synthesis) are anabolism (anabolic reactions) + The reactions that break down large molecules into smaller ones (eg carbohydrates into glucose in digestion) are catabolism (catabolic reactions). Enzymes are specific, ie one enzyme catalyses only one type of reaction. An enzyme is usually named after the substance it catalyses, by having the suffix ‘ase’ added, eg, + Lipase catalyses the catabolism of lipids into fatty acids and glycerol + Maltase catalyses the catabolism of the suger maltose into two glucose molecules. + Peroxidase catalyses the breakdown of hydrogen peroxide, H,O,, into H,O and O, The reason that enzymes are specific relates to their shape. Fach enzyme hes a specific shape, determined by the sequence of amino acids thet it is made of. The amino acids in a protein may be cross-linked by hydrogen bonds (in some cases sulfur bonds), and this is what gives the protein its distinctive shape, The shape of the enzyme in an area known as its active site corresponds to that of the substance(s) it catalyses — the lock-and-key model of enzyme action In the way that a key fits into a particular lock, so the substrate fits into the active site of the enzyme. As the enzyme and substrate fit together (forming the enzyme-substrate complex), chemical bonds form or are broken. The enzyme’ active site changes its shape slightly (through the weak hydrogen bonds that hold the shape) when combined with the substrate (called an induced fit). This distorts the substrate molecule(s), making reaction more likely.38 Unit 11.1 Living Things subunit substrate intermediate state active site <——<—> enzyme enzyme substrate temporary complex chemical bond ‘This is a catabolic reaction, ie the breaking down of a substance. A different enzyme would be used to reverse the reaction (je bond the two smaller compounds together to synthesise the large one in an anabolic reaction). Lock-and-key model of enzyme action. Enzymes are not consumed or broken down in reactions, so one enzyme molecule can catalyse the same reaction many times and do so at a very fast rate (eg peroxidase in liver cells can catalyse the breakdown of several million hydrogen peroxide molecules into water and oxygen every minute). Because their shape is maintained by weak hydrogen bonds, enzymes are susceptible to denaturing at high temperatures, as the hydrogen bonds are broken and the enzyme loses its shape — it can no longer catalyse the reaction. Factors that affect enzyme activity Temperature ‘The warmer the temperature (usually up to about 40-45°C), the faster enzymes will catalyse a reaction. This is because increasing the temperature increases the speed at which the reacting particles move, so they collide more often, It is necessary for particles to collide for them to react. However, above 40-45°C, enzymes are usually denatured and can no longer catalyse the reaction Rate of reaction optimum temperature is 45°C 0 10 20 30 40 50 60 temperature (°C) Enzyme reaction rate and temperature. (© Oxford University Press wwwwoup.cor.atTopic 4: Cell processes — enzyme activity 39 The temperature at which the reaction rate is fastest is the optinvarn temperature. In homeotherms ‘warm-blooded’ animals ~ birds and mammals), the optimum temperature will be their core body temperature (37°C in humans) In poildlotherms (cold-blooded’ animals/organisms), the optimum temperature will depend on their habitat; it may be low if the organism lives in cool habitats (eg some fish in the Antarctic seas have an optimum temperature approaching 0°O), and high in hot habitats (eg bacteria that inhabit geothermal hot pools have an optimum temperature approaching 100°C). pH Most enzymes work within cells, so their optimum pH will be approximately 7 (je close to neutral); exceptions are the digestive enzymes (eg pepsin) When the pH is outside the range for an enzyme, the enzyme denatures, and can no longer act as a catalyst amylase rate of reaction poor optimum pH [pH=7is acid pH =7 is neutral pH>7 is basic | pancreatic lipase pH scale Pepsin breaks down protein in the stomach and works well in acidic conditions. The stomach contents have a low pH because of the presence of dilute hydrocholoric acid The optimum pH for amylase (an enzyme in saliva which breaks down starch) is about 7. Saliva has a neutral pH. Pancreatic lipase breaks down lipids in the small intestine, where conditions are slightly basic (pH is greater than 7), because of the presence of bicarbonate ions. Enzyme reaction rate and pH. Substrate concentration The rate of enzyme activity will increase as the concentration of the substrate increases up until a saturation point occurs (fe no free enzymes/active sites) Co-factors Many enzymes need another molecule to assist in catalysis. These co-factors may be (small) inorganic ions such as cobalt, Co, selenium, Se, or (large) organic molecules such as some vitamins. These organic co-factors are called co-enzymes. © Oxford University Press wweoup.com.au40 Unit 11.1 Living Things + The carrier molecule NAD (required in respiration) is « co-enzyme derived from nicotine acid, a member of the vitarnin B complex. + Hydrolases, which control a transcription factor that turns on specific genes, need vitamin C to be activated Co-enzymes are necessary when only weak bonds form ee eee between the enzyme and substrate; the co-enzyme acting as a bridge, locking the enzyme and substrate more tightly together. enzyme Inhibitors Inhibitors are substances that prevent enzymes catalysing reactions, and so are poisons. + Heavy metal ions (eg lead, Pb, and mercury, Hg) prevent enzymes in cells of the nervous system functioning. * Cyanide prevents the action of an enzyme in the electron transfer chain of respiration (causing death, as respiration ceases). An inhibitor can act by: + Taking over the active site of the enzyme, so stopping the substrate from binding to the active site — eg the antibiotic penicillin inhibits an enzyme that bacteria use to make their cell walls + Bonding to another part of the enzyme and altering the shape of the active site so that it can no longer bind to the substrate — this is usvally temporary, and can be a way in which the cell can control a metabolic pathway. Unit 11.1 Activity 4A: Enzyme activity 1. Explain why enzymes are known as ‘biological catalysts’. 2. Use the diagram following to help explain the ‘ock-and-key’ model of enzyme action pee 3. Explain why enzymes are essential to the survival of organisms. 4. Explain the role of co-factors in enzyme activity, (© Oxterd University Press wwwoup.com.auTopic 4: Cell processes — enzyme activity 41 5. Explain the relationship between enzymes and pH. 6. Discuss the relationship between enzymes and temperature 7. Bread can be made by mixing flour, water, salt, sugar and a small amount of yeast. Carbon dioxide is produced from the fermentation of simple sugars. Fermentation is controlled by enzymes from the yeast. Explain why the shape of an enzyme is important for the way it functions, (You may use a diagram to help with your explanation.) b. In relation to enzyme structure, explain why the enzymes involved in bread production will not function at or above 45°C. c. Researchers have investigated the effect of temperature on yeast activity. The following tables are a summary of their results Temperature | Fermentation Temperature Cell division -20°C | _No fermentation Less than 20°C, Cell division | greater than 40°C | significantly reduced | Optimum Eee eee eae Peace 27°C to 38°C | fermentation 20°C 10. 27°¢ | Most favourable range range for yeast to multiply Optimum Optimum temperature 35°C fermentation 26°C temperature Greater than 60°C Nil Between two and three hours are needed for yeast to ferment dough before itis baked in an oven Discuss, with respect to the number of yeast cells and the fermentation rate, why it is important to have the temperature at: + 26°C for the first hour and; + 35°C for the next two hours, before the dough is baked d. Heavy metals, such as mercury and lead, are enzyme inhibitors. Explain how an enzyme inhibitor affects enzyme activity. (You may use a diagram to help with your explanation.) © Oxford University Press wworoup.com auUnit 11.1 Living Things Topic 5: Classification systems The Content presented in this Topic relates to biological classification systems including the binomial nomenclature and the Linnaean system of classification. The Topic deals with: * Characteristics of the three evolutionary lineages or domains and the groups within them. The main taxonomic groups and simple classification of organisms. Specific names. Biological keys. Characteristics of life (MRS GREN). + Characteristics of viruses. Classification There are millions of plant and animal species on Earth. In PNG we have over 20,000 species of plants, more than 200 species of mammals and almost 1000 species of birds. Scientists need to classify species in an orderly manner. How do they do this? In the Linnaean classification system, every living thing has a double name in Latin. This is called the ‘binomial nomenciature’. The Linnaean classification system is a scientific method of classifying living things into increasingly smaller and specific groups with a hierarchy. It uses seven main categories: Kingdom, Phylum, Class, Order, Family, Genus, Species. Kingdom is the largest and Species is the smallest. You are expected to know the main classification (taxonomic) groups and be able to place common organisms in them. Specific names should be identified and correctly written. You should be able to use keys to idensify organisms or their groups. Example If an exam question included information about the ‘endangered indigenous reptile the giant monitor lizard (Veranus salvattoriiy, a student, besides knowing the meaning of the terms ‘endangered’ and ‘indigenous’, would be expected to: + Know why the giant monitor lizard was placed in the group known as the ‘reptiles’. * Know that ‘giant monitor lizard’ was the common name, ’Veranus salvatiori’ was the scientific name, and ‘Veranus’ referred to the genus while ‘salvattori’ referred to the species. Classification systems ‘The first living creatures (organisms) appeared on Earth about 3.5 billion years ago. Since then, evolutionary processes have produced a large diversity of different organisms occupying a range of ecological niches. All organisms living today are related and share common ancestry; this is seen in the universality of DINA, the genetic code, found in the chromosomes of all life forms. The structure of all organisms is based on the cell, which carries out all the essential life processes (eg respiration, photosynthesis, protein synthesis) The degree of relationship between organisms can be seen in their taxonomic (classification) groups. Classification is a changing area of biology, with DNA sequencing providing new evidence of the relationships between groups of organisms; therefore, differences in classification occur, depending on the source and date of the information. Classification systems found in most textbooks place all organisms into one of two large domains, based on their cell type - prokaryotes (cells without a true nucleus) and eukaryotes (cells with a true nucleus), then into one of five large kingdoms ~ monera, protista, fungi,44 Unit 11.1 Living Things plants and animals. The monera (bacteria and cyanobacteria) is the only kingdom wid prokaryote domain; the other four kingdoms are all within the eukaryote domain. in the Within the last decade, DNA analysis has indicated that life represents not two but three evolutionary lineages (domains) — the Archaea, Eubacteria and Eukarya (these names may vary, depending on the reference used) Organisms of the monera kingdom are now placed into either the archaea or the eubacteria. These organisms are all one-celled, with the cell lacking a true nucleus, as their genetic material/ DNA/chzomosome is not contained in a nuclear envelope (such cells are prokaryotic cells). + Archaea includes the archebacteria — the oldest type of bacteria; inhabit environmental extremes (eg geothermal pools, methane vents in the deep oceans, salt marshes), so commonly called extremophiles + Eubacteria includes the bacteria and cyanobacteria ~ moze recently-evolved forms; inhabit moderate environments, and include all common forms, such as those pathogenic to humans. Bacteria may be autotrophic (make their own food in chemosynthesis), ot heterotrophic (either parasites or saprophytes). The cyanobacteria are autotrophic, making their food in photosynthesis. These bacteria are believed to have been the first life forms that appeared on Earth, Bacterial shape may be rod (bacilli), sphere (cocci), spiral (spirilli) Spiral Protista, Fungi, Plants and Animals b of eukaryotic cells — ceils with Gomain Eukarya because all are made true nucleus (ie one that has chromosomes c anuclear envelope, and, in the cytoplasm, are membrane-bound organelles). Protista (also known as Protoctista) Most of these organisms are one-celled (eg Euglena, Amoeba, Paramecium). Some are simple threads of repeating cells eg Spirogyra). Other are multi-celled but simplistic in structure, lacking systems (eg seaweeds such as Hormosiva, Corallina) Protists may be autotrophs (make their own food in photosynthesis) or heterotrophs (obtain their food from other organisms — herbivores carnivores, omnivores, parasites) © Oxford University Press worseoup.com.atTopic 5: Classification systems 45 Fungi may be single-celled (eg yeasts), or made up of threads called hyphae (eg breed mould) These threads may be combined into a dedinite body (:he mycelium), with reproductive and feeding parts (eg mushrooms — the ‘mushroom’ is the spore-producing reproductive structure; the feeding hyphae are in the ground), Feeding is extra-cellular, and fungi are all heterotrophs (parasites and saprophytes). Cells are enclosed in a cell wall, but it is made of chit cellulose, as in plants). Mushroom Bracket fungus Toadstool Penicillium Yeast Rhizopus Plants Plants are autotrophic, making their food in photosynthesis (exceptions are some parasitic species). All are multicellular, with the cells contained in cellulose cell walls; cytoplasm contains chloroplasts (with chlorophyll) for photosynthesis. Plants are classified on the basis of their reproduction (eg conifers have cones, angiosperms have flowers). Tree fern & ality Ground fern Moss Kunai grass Pinus, and needles and cone © Oxford Universey Press www.oup com.au46 Unit 11.1 Living Things Animals Animals are all heterotrophic (herbivores, carnivores, omnivores, parasites, scavengers, filter feeders) and multicellular. Cells are varied in shape and function; the cell membrane is not enclosed in a cell wall. Many have complex internal systems and may be highly mobile. A wide diversity of forms exist Tree kangaroo The evolutionary relationships of the living representatives of these groups is under constant review; classification wall always be a work in progress, as we continue to learn more about organisms and their relationships. At the time of writing, the following diagram is the most accepted ‘tree of life’ Archaea Eukarya Eubacteria Rae Archebacteria Bacteria Animals. Fungi Cyanobacteria Plants Protista Common ancestor “Tree of Life’ showing the likely evolutionary relationships between the three domains and their large taxonomic groups. The common ancestor refers to a simple cellular form of life that existed millennia ago, which, from mutations in the DNA and the process of natural selection, has evolved into the present-day life forms. The unnamed branches in the tree represent groups that have arisen, lived, then become extinct. © Oxford University Press worwonsp.comatTopic 5: Classification systems 47 Taxonomic groups Organisms are placed into the various taxonomic groups depending upon their relation to other organisms. + ‘Domain’ is the largest grouping, so has the largest number of different organisms. + ‘Species’ is the smallest grouping, and has only one kind of organism. For animals, the most common taxonomic groups ~ from largest to smallest — are! + Phylum + Class + Order. + Family: * Genus. + Species Many of these groups may be subdivided again (eg ‘super class’, ‘suborder’. The more groups that different organisms have in common, the more closely related they are. ‘The smallest taxonomic group, the species, is usually defined asa group of organisms that interbreed to produce fertile offspring’. They share a common gene pool and are reproductively isolated ‘rom other species. Sometimes, a species may have subspecies; these are capable of interbreeding, All species have a scientific name which is from Latin or Greek (many species also have a common name in the local language). The scientific name includes the genus followed by the species, a system devised by Linneaus nearly 250 years ago and known as the binomial system of naming organisms. Both the genus and species names are written in italics or underlined. The genus name starts, with an upper case letter, the species with a lower case letter, eg ‘Common name —_ Scientific name Human Homo sapiens or Homo sapiens Ship rat Rattus rattus or Rattus rattus Dog Canis familiaris or Canis familiaris Betel nut Areca catechu or Areca catecht Once the scientific name has been used, subsequent use may be abbreviated (eg H. sapiens, R. rattus). If the species being referred to is unknown or the reference is to all the species in the genus, then the abbreviations Rattus sp (singular) or Rattus spp (plural) may be used Although a species is typically reproductively isolated from other species, closely related species (eg members of cat families, dog families, horse families) may interbreed, forming hybrids. Hybrids typically happen in unnatural conditions (eg zoos, aquaria), where mating opportunities with the same species may be limited. When hybrids do breed, the offspring are infertile (ie are unable to breed), eg’ + Horse x Donkey —® Mule; Horse x Zebra Zebroid + Lion x Tiger Liger or Tigroid (depends on sex of parents); Lion x Leopard -& Leopon. {© Oxford University Press wwwraup.comau48 Unit 11.1 Living Things Keys A key is a way of identifying organisms into their taxonomic groups (eg class, family, species) Keys are typically dichotomous ~ each step in the key involves a choice of two (either/ox) The choice leads to the next step and choice, until the organism is identified Classifying arthropods Below are five arthropods found in a beech forest: AE a8 SP The key below is used to identify the five arthropods Key: 1. Wings present goto2 ‘Wings absent gotoS 2. Abdomen thin when joins thorax Apantales (D) Abdomen same thickness as thorax Tenthredo (A) 3. More than 10 legs Lithobius (E) Fewer than 10 legs goto4 4. Short fat body Pergamasus (B) Long thin body Agriotes (C) Unit 11.1 Activity SA: Classification or Dichotomous keys 1. Shown below are diagrams of the five native beeches (Nothofagus) which are found in New Zealand. Red beech 2) Mountain beech Silver beech Q@ rk os Hard beech SS &5) Black beech Use the key below to give the scientific names of the five beech species Key: 1. Leaves toothed (on edges) goto 2 Leaves not toothed go to 4 © Oxford University Press wwrw.oup.com.au2. Teeth on leaves sharply pointed Teeth on leaves not sharply pointed 3. Leaves 8-12 mm long and doubly toothed Leaves 25-40 mm long and singly toothed 4. Leaves oval shaped Leaves triangular Classification systems 49 N. fusca goto 3 N. menzicsii N. truncata N. solandri var solandri N. solandri var cliffortioides 2. Use the following diagrams and key to find the scientific names of the six common grasses. Note: Diagrams not to scale Yorkshire fog Browntop Couch iii! nT “yy wy Y Perennial ryegras Paspalum Key to some common grasses: 1. a. Auricles present b. Auricles absent 2. a, Ligule very short (0.5 mm) Sheath and leaf blade hairy b. Ligule up to 2 mm long Sheath and leaf blade hairless leaf blade sheath auricle goto p0 103 Agropyron repens Lolium perenne 3. a. Ligule hairless goto4 b. Ligule hairy goto Ss 4. a. Sheath and leaf blade hairless Agrostis tenuis b. Sheath hairless; leaf blade also hairless except for tufts of long hairs on the collar Paspalum dilatatum 5. a, Ligule 1+ mm long and hairy Holeus lanatus b. Ligule 2-3 mm long with distinct fringe of airs Pennisetum clandestinum Viruses All organisms (ie all members of the three domains) are able to carry out the seven life processes, given in the acronym MRS GREN: + M—movernent. + G— growth. + R=respiration. + R— reproduction, + S—sensitivity. + E-excretion + N-nutition. © Oxford University Press wirwoup.com au50 Unit 11.1 Living Things Viruses are only able to carry out the process of reproduction, and can only do that using living cells, using the energy supplies and raw materials from the host cell (eg viruses called bacteriophages use bacteria as host cells). Viruses do not fit into the three domains system (since they only show Reproduction in terms of MRS GREN); itis thus debatable whether they are living things. Their structure comprises 4 protein coat enclosing the genetic material of the virus, The genetic material of the virus is a nucleic acid, either DNA (eg Herpes virus) or RNA (eg retroviruses such as HIV). Bacteriophage Flu virus Tobacco mosaic virus Protein coat Protein ‘ spike Protein coat Nuclei acid (DNA) Nucleic acid Nucleic acid (RNA) (RNA) Flu virus — nucleic acid is RNA. Tobacco mosaic virus — nucleic acid Bacteriophage —nucteic acid _ The protein spikes attach to receptor is RNA MONK molecules on the membrane of the host cell. Common shapes of viruses. All viruses can be considered as a type of obligate intracellular parasite; all are instrumental in causing disease in plants and animals, including humans, Unit 11.1 Activity 5B: Classification 1. Describe the binomial system of naming organisms (also known as ‘binomial nomenclature’) 2. Describe how the scientific name of an organism is written. 3. Explain what is meant by a taxonomic group. 4. Explain the difference between prokaryotes and eukaryotes 5. Name the main groups of a. Prokayotes. b. Eukaryotes 6. Older classification systems classified fimgi as plants. Give the main reasons why fungi are no longer considered plants 7. Distinguish between autotrophs and heterotrophs 8. Define the following terms: a. Species. b. Hybrid. c. Infertile. 9. Explain what is represented by the acronym MRS GREN. 10. Explain why viruses are not classified as living organisms. ‘© Oxford University Press ww wonp com. atUnit 11.1 Living Things Topic 6: Diversity of animals The content presented in this Topic describes the diversity in the structure and function of animals and is a continuation of Topic 5 on the classification of living things. Students of Biology at Upper Secondary level are expected to describe and give reasons for the diversity of aspects of the structure and function of multicellular animals in relation to a biological rOcess: + Internal transport. + Support and movement. + Gas exchange, + Sensitivity and co-ordination. + Nutrition, * Reproduction, + Excretion. To fully appreciate the diversity of animals, there are many Topics that could be studied in conjunction with this Topic Unit 11.2 Nutrition, Topic 4: How humans feed — heterotrophic nutrition (p. 97) Unit 11.2 Nutrition, Topic 5: How animals feed — heterotrophic nutrition (p. 111) Unit 11.3 Transport Systems, Topic 3: Transport systems in animals (p. 143) Unit 11.3 Transport Systems, Topic 5: Excretory systems in animals and hurnans (p. 179) Unit 11.4 Respiration and Gas Exchange, Topic 2: Respiration, breathing and gas exchange (p. 197) Unit 11.4 Respiration and Gas Exchange, Topic 3: Gas exchange in animals (p. 203) Unit 11.5 Responses to Stimuli, Topic 2: Sensitivity and coordination in animals (p. 233) Unit 11.6 Reproduction, Topic 1: How animals reproduce (p. 259) Diversity Diversity is about differences. All animals carry out the same seven essential life processes (MRS GREN), but they may do them in different ways and using different structures. These differences reflect the way that the animal/group has evolved to be successful in its ecological niche Classification of animals Taxonomic groups refers to the groups into which an animal is classified (eg mammal, insect, annelid) Example Classification of humans Classification group _| Human Towest| [Kingdom ‘Animalia (animals) level of | [Phylum Chordates (have backbones) similarity Class Mammals (warm-blooded, hairy, suckle young) t ‘Order Primates (monkeys, apes) ne Family Hominins (large brain, ‘intelligent’, walk upright) level of similarity| [Genus ‘Homo (human) Species sapiens (‘intelligent’) The scientific name for humans is Homo sapiens, and this identifies us from all other species. It must be written in italics or underlined (eg Homo sapiens)52 Unit 11.1 Living Things Example eee Humans belong to the chordates phylum — along with fish, amphibians, reptiles, birds — as we all have a spinal cord (housed in a spine/vertebral column). Within this phylum we belong to the class called mammals — along with many other groups ~ because we are ‘warm blooded” (homeotherms), our bodies are hairy, our young are born alive and are suckled on milk from the mother. gest grouping in the kingdom). The ‘The animal kingdom has 21 phyla (singular = phylum, the I following phyla are the most significant Phylum Cnidaria Includes the jellyfish, sea anemones, corals, hydra (only freshwater member). All have a simple, sac-like body with one opening (‘mouth’) surrounded by tentacles. The body is of two cell layers, with a middle, jelly-like layer. The old terra for cnidaria is coelenterates. Jellyfish Coral Phylum Platyhelminthes (flatworms) Includes the free-living planarian worms and the parasitic flukes and tapeworms. Alll are flattened dorsal-ventrally, not segmented, and have one body opening (‘mouth’) Fluke Tapeworm Phylum Annelida (segmented worms) Includes the earthworms, marine worms, leeches, Body is elongated and divided into many repeating segments. There are two openings (mouth and anus), and the body cavity is a fluid- filled coelorn which acts as a hydrostatic skeleton. (© Oxford University Press wwwoup.comanTopic 6: Diversity of animals 53 Phylum Mollusca Includes all the snails, shellfish, octopuses. Body is soft and not segmented, often enclosed in a shell. Movement is by 2 muscular foot (except for octopus), feeding by a rasping radula (except for bivalves such as mussels, which are filter feeders). Mucus is an important lubricant. There are three major classes: + Gastropoda ~ includes the slugs and snails Soft body is enclosed in a (typically coiled) shell (slugs have lost their shell in their evolution). Includes the only terrestrial members of the molluscs, + Bivalvia — includes the mussels, scallops, oysters, pipi. Soft body enclosed in two shells (valves); typically filter feeders. = Cephalopoda — includes the octopus and squid. Soft body, shell no longer present (or greatly reduced). Tentacles present for moving and feeding; movement by ‘jet propulsion’; eyesight well developed, as is a brain Octopus Phylum Arthropoda Inchades the insects, spiders, centipedes and millipedes, crabs and shrimps. The most numerous group of animals, comprising over 75% of all species. Body has an exoskeleton ~a cuticle of (mainly) chitin, with jointed limbs for movement. Exoskeleton is shed for growth. Body is segmented (not usually obvious), and divided into a head and one or two other regions (thorax, abdomen). Blood system is open. Four classes: + Insects ~ includes grasshoppers, flies, moths, butterflies, bees, beetles. The most numerous of the arthropods, comprising over 75% of all arthropod species; the beetles are the most common insects. Body has three parts (head, thorax, abdomen) and three paits of legs attach to the thorax, Many have wings (one or two pairs). Head has a pair of compound eyes and a pair of antennae. Tracheal system for gas exchange Housefly Beetle Butterfly + Arachnida ~ includes the spiders, ticks, mites, scorpions. Body of two parts Goined head and thorax, separate abdomen), with four pairs of legs; no antennae. Many sting Mite (© Oxford University Press wrwoup.com.at54 Unit 11.1 Living Things + Myriapoda — includes the centipedes and millipedes. Body of many segments, with a head (has antennae). Centipedes have one pair of legs per segment, and are carnivorous millipedes have two pairs of legs per segment, and are herbivorous. Tracheal system of gas exchange. Centipedes have far fewer than 100 legs, millipedes have beween 80 and 750 legs. Millipede Centipede + Crustacea — includes the crabs, crayfish, shrimps, slaters (‘woodlice’), barnacles. Aquatic habitats (or need damp conditions, eg slaters). Often have a very hard exoskeleton (a carapace, eg crabs), Have many legs, which are often modified (eg for swimming, egg carrying, feeding) Distinct head with antennae. Gas exchange using gills, Barnacle Shrimp All the above phyla are invertebrates, ie the animals do not have a spinal column and spinal nerve cord. The nerve cord of invertebrates is either ventral (eg annelids, arthropods) or a network (eg cnidaria). The animals are also ‘cold blooded’ (poikilotherms), and cannot regulate their body temperature (which thus follows that of the environment) Vertebrates ate animals that have a spinal column (of bones called vertebrae). Technically, the vertebrates are a sub-phylum of the chordata. Apart from a very few primitive forms (eg sea squirts, lancelets), all chordates have a vertebral column enclosing their spinal cord at some stage during their life. Species of vertebrate animals are far less numerous than species of invertebrates, but typically much larger. Phylum Chordata The tnajor classes of chordata are Pisces (fish), Amphibia, Reptilia, Aves (birds), Mammalia Fish/Pisces The class ‘fish’ is more accurately given as several distinct classes, of which the two main ones: + Osteichthyes (bony fish) — have a skeleton made of bone ~ the majority of fish, eg snapper, tuna, salmon, trout. + Chondrichthyes (cartilaginous fish) ~ have a skeleton made of cartilage, eg sharks and rays. All fish are aquatic. Outer covering of scales, gills are used for gas exchange, bload system is closed with single-loop circulation. Anne Shark Trout Stingray © Oxford University Press wwwroup com.atTopic 6: Diversity of animals 55 Includes frogs, toads, and the lizard-like newts and salamanders, PNG is home to an abundance of frog species. Many are unusual (such as one which is just | cm in length and another that has vampire-like fangs) and are found nowhere else in the world. Amphibians are restricted to an aquatic or damp/numid environment by: + Their skin — lacks scales and needs to be moist for ges exch also present, + Reproduction ~ fertilisation is typically external, and the eggs do not have a hard shell rage, though lungs Young may have a different form from adult and metamorphose into the adult (eg tadpole 10 frog) =) ‘Salamander Reptilia A diverse class, including lizards (eg geckos and skinks), snakes, crocodiles and turtles. Skin is dry and scaly; reproduction is by shelled eggs, and fertilisation is internal, therefore reptiles are adapted fully to terrestrial living, unlike amphibians. sy Monitor lizard Birds/Aves Birds are feathered homeotherms with beaks, scaly legs, wings for flight. However, some forms have lost power of flight - eg kiwi, ostrich, takahe (wings are vestigial), penguins have wings modified as flippers for swimming, Fertilisation is internal and hard-shelled eggs are laid. Energy needs are high, and blood system is closed, with a 4-chambered heart and complete, double circulation Bird of paradise Cassowary Mammalia Mammals are hairy (hair lost in whales) homeotherms. Fertilisation is internal and young are born alive and suckled on mother’s milk from mammary glands. Brain is large. A diverse group, divided into three large sub-classes, dependent on method of reproduction: + Monotremes ~ the egg-laying platypus and echidna of Australia. Young hatch and suckle on. mother’s milk. a Echidna ia ae “Playtpus + Marsupials — young are born in embryonic state and complete development attached to teat in mother’s pouch, eg kangaroo, possum © Oxlord University Press wwowoup.56 Unit 11.1 Living Things + Placentals — the majority of mammals, Young retained in uterus and nourished by a placenta until birth, when they suckle from mother, eg human, cat, monkey, whale, bat Cuscus Human Dog ‘© Oxford University Press wwwoup.com.at,Unit 11.1 Living Things Topic 7: Diversity of plants The content presented in this Topic describes the diversity in the structure and function of plants Students are expected to describe and give reasons for the diversity of aspects of the structure and function of multicellular plants in three different taxonomic or functional groups in relation to a biological process. The biological process is selected from: * Nutrition (see Unit 11.2). * Transpiration (see Unit 11.3). \+ Transport of materials (see Unit 11.3). _+_ Reproduction (see Unit 11.6) Classification of plants Taxonomic groups refers to the groups into which a plant is classified (eg fern, moss, coniler). Classification group | Example - tomato Lowest Kingdom Plantae (plants) | level of Division Tracheophytes (have conducting vessels) [similarity | | class Angiosperms (flowering plants) J Order Scrophulariales (flower structures similar) Timgnea) | Farnily Solanaceae (flower structures very similar) ease Genus Lycopersicon similarity | | Species esculentum (tomato) Example Taxonomic scientific names must be written in italics or underlined. The scientific name identifies a species from all other species Tomato plant The scientific name Lycopersicon esculentum (or Lycopersicon esculentum) identifies the tomato from all other species. The taxonomic groups show the degree of Tomatoes belong to the angiosperms, relatedness to other plants. along with all other plants that reproduce using flowers. Photosynthesising organisms are found in two groups + The Protista (also called Protoctista) — all the seaweeds ~ eg Hormosira (Neptunes necklace), Coraltina, kelp, as well as the unicellular forms (eg Euglena) + The plant kingdom — ‘the plants’ ‘There are two major divisions (also known as phyla) of plants: + Bryophyta - the non-vascular plants. + Tracheophyta — the vascular plants. Vascular tissue is transport tissue — xylem and phloem$8 Unit 11.1 Living Things Bryophyta Bryophytes, the non-vascular plants, live in damp areas and are suffice have no vascular tissue. Two groups exist - mosses and liverworts small plants that they Mosses All mosses are smail, with no true roots (have hair-like rootlets called rhizoids). Mosses have thin, leaf-like structures surrounding a central, stem-like structure. Mosses have two distinct generations: + Conspicuous leafy plant is the gametophyte (n) which is dependent on water for fertilisation + Rising out of the gametophyte is the spore containing capsule of the sporophyte (2n) generation. sporophyte gametophyte: Liverworts Much simpler plants than the mosses, liverworts look like leaves lying flat on the ground Liverworts are found only in wet areas Tracheophyta These are the vasctlar plants, ie they have transport tissue in the form of xylem and phloem Vascular plants are typically much taller than non-vascular plants. Three major groups exist — ferns, conifers and angiosperms © Oxford University Press warwcoup.com.at59 Ferns Ferns have two distinct generations. + The sporophyte (2) — forms spores (not seeds) in capsules under the fronds. This is the fern plant we interpret as a ‘fern’ Ground fern Tree fern + The gametophyte (n) generation — a small, leafy structure, still dependent on water for fertilisation (which is why ferns are restricted to living in damp habitats). This is usually so inconspicuous it is not seen. Conifers Conifers (the cone bearers) are members of the larger group called the gymnosperms (= naked seeds’, as their seeds do not develop within closed chambers) ayte (2m); the Seeds The obvious tree is the spor gametophyte is micn are produced in cones. Ct lange trees ~ eg kauri, totata, rimu, and the introduced radiata pine. Conifers have true roots, stems (trunks) and leaves (may be needle-like) Large pine tree with needle-like leaves Typical cones (‘pine cones’) (© Oxford University Press woww.oup.comau