Chapter 3.2 The organisation of multicellular organisms

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1 biology sample book.indd 25 28/06/2016 7:49:20 PM TOPIC 3 MULTICELLULAR ORGANISMS Chapter 3.2 The organisation of multicellular organisms Understanding Multicellular organisms have a hierarchical structural organisation of cells, s, organs and systems. Use examples from plants and animals to explain organisation of cells into s, s into organs, organs into systems. Illustrate the relationship between the structure and function of cells, s, organs and/or systems. Organ systems in a multicellular organism are interdependent and function together to ensure the survival of the organism. Lifestyle choices affect the functioning of organs and systems. Hierarchical structure of organisation SACE 2016 A system that is based on different levels of organisation in which each level of organisation forms part of the next higher level is called a hierarchy; for example, in an army, soldiers report to Sergeants who report to Majors who themselves report to Colonels who are supervised by Generals. All multicellular organisms have a hierarchical structure of organisation. Their cells are organised into s, different s are organised into organs, and organs are organised into organ systems. The hierarchy of organisation of multicellular organisms is shown in Figure 321. A multicellular organism make up Organ Systems make up Organs make up Tissues make up Cells Animal cells and s Figure 321 The hierarchy of organisation in living things A good example of the way an animal is organised is a human being. The human body is made up of 230 different specialised cell types. A collection of these specialised cell types grouped together to perform a specific function is called a. Four types of human are: Nervous ; for example, nerve in the brain made of nerve cells called neurons. Muscle ; for example, muscle in the arm made up of muscle cells called fibres. Connective ; for example, blood that is a made up of red and white blood cells. Reproductive ; for example, in a male, in the testes that produces sperm. 22 Essentials Education Ch 3.2 layout.indd 22 22/06/2016 8:35:45 PM Ch 3

2 M Ch 3.2 layout.indd 23 22/06/2016 8:35:45 PM biology sample book.indd 24 28/06/2016 7:49:19 PM THE ORGANISATION OF MULTICELLULAR ORGANISMS CHAPTER 3.2 Some types of human cells and s are shown in Figure 322. cell body of neuron a motor neuron in a nerve dendrites axon Nervous Consists of bundles of cells called neurons that transmit nerve impules a muscle fibre in a muscle Muscle Consists of muscle fibres which contract under nervous stimulation. Blood Tissue A consisting of cells which are located in a liquid called plasma. red blood cells white blood cells Sperm Reproductive Tissue Produces reproductive cells called sperm in males and ova in females Nucleus Flagellum Ovum Figure 322 Some human cells and s The structure and function of animal s Different s in the body consist of different specialised cells to permit them to perform a specific function. Nerve is able to transmit nerve impulses because it consists of a bundle of neurons. Many nerves contain two types of neurons; sensory neurons and motor neurons. The bundle of fibres structure of muscle allows it to contract and cause movement. This relationship between the structure and function of animal is shown in Figure 323. motor neurons a nerve muscle fibre sensory neurons muscle Figure 323 (a) Nerve (left) and (b) muscle (right) Essentials Education

3 biology sample book.indd 23 28/06/2016 7:49:18 PM TOPIC 3 MULTICELLULAR ORGANISMS Plant cells and s A good example of the way a plant is organised is a flowering plant; for example, a rose or a eucalypt. Like animals, specialised cell types group together to form s in flowering plants. Four types of flowering plant are: Epidermis ; for example, epidermis in which cells with a root hair are found near root tips. Xylem ; for example, xylem inside the stem made up of tube-like cells called xylem vessels. Mesophyll ; for example, mesophyll in leaves made up of palisade and spongy mesophyll cells. Reproductive ; for example, in a flower cells in the ovary that produce ova. Some types of flowering plant cells and are shown in Figure 324. flower Leaf consists of several cell type e.g. palisade cells stem Stem consists of several cell type e.g. xylem vessels Root consists of several cell type e.g. tap root root epidermis cells lateral root Figure 324 Some plant cells and s The structure and function of plant s Flowering plants have different s made up of groups of different specialised cells to enable them to carry out a specific function. Near root tips, epidermis is a one-cell thick layer of that includes root hair cells with an extension to maximise uptake of water/minerals from soil. The chains of xylem vessels structure of xylem in the stem allows it to transport water and dissolved minerals from roots to other parts of the plant. This relationship between the structure and function of plant is shown in Figure 325. root hair root epidermis cell Figure 325 (a) Epidermis near a root tip and (b) Xylem in the stem 24 Essentials Education 2016.

4 THE ORGANISATION OF MULTICELLULAR ORGANISMS CHAPTER 3.2 Animal s and organs A collection of different s grouped together to perform a specific function is called an organ. Examples of human organs are: The heart that includes a muscle called cardiac muscle, nerve and blood. Bones that include mineralised or strengthened connective, nerve and blood. The structure and function of animal organs The structure of an animal organ is related to its function. The function of the stomach is to help mechanically digest food, kill bacteria and start chemical digestion of protein. Mechanical (or physical) digestion involves forces breaking down food into smaller pieces. The stomach can contribute to this type of digestion because its walls contain smooth muscle that can contract, slowly turning its contents. This function of the stomach is supported by the presence of loose connective in the walls. The stomach can kill bacteria in food because cells in its epithelial can produce and release a lethal-to-bacteria acid into the stomach called hydrochloric acid. The stomach is able to begin chemical digestion of proteins in food because there are also cells in its epithelial that produce and release protein-digesting enzymes called proteases. These types of and how they are organised in the stomach is shown in Figure 326. L umen Epithelial S TOMACH C onnective Nerve Smooth muscle C onnective Animal organ systems Figure 326 Some tisues of the stomach Different organs grouped together to carry out a function is called an organ system. Some human organ systems, organs they consist of and its main function are shown in the following table. ORGAN SYSTEM Major organs Main function in the body Respiratory system Digestive system Trachea, lungs, bronchi, broncioles, diaphragm Mouth, stomach, small intestine, large intestine, pancreas, liver, anus Uptake of oxygen, removal of carbon dioxide, maintaining blood ph Breakdown of food to form products that may be absorbed Excretory system Kidneys, ureters, bladder, urethra Removal of nitrogen waste, maintaining blood concentration Circulatory system Heart, arteries, veins Transport of materials, maintaining body temperature Nervous system Brain, spinal cord, sense organs Coordination of body activities, detection of/response to stimuli Essentials Education

5 TOPIC 3 MULTICELLULAR ORGANISMS Plant s and organs Like animals, plants have organs that consist of different s grouped together to perform a specific function. Examples of flowering plant organs are: Roots that include epidermis, s called parenchyma and endodermis, a central collection of xylem, another tube-like called phloem, and an inner-most called pith. The stem that includes epidermis, called cortex, bundles of xylem and phloem and pith. The root and stem in flowering plants that are dicotyledons is shown in cross-section in Figure 327. phloem xylem pith endodermis parenchyma epidermis epidermis cortex phloem xylem pith Figure 327 (a) Tissues in a dicotyledon root and (b) stem The structure and function of plant organs The structure of a plant organ is related to its function. The function of the leaf is to carry out photosynthesis to produce organic molecules; for example, glucose. Photosynthesis can take place in leaves because its mesophyll contains cells packed with organelles called chloroplasts. The structure of the leaf enables it to provide the mesophyll with the simple inorganic molecules it needs for photosynthesis carbon dioxide and water. Carbon dioxide can enter the mesophyll because there are pores in the lower epidermis called stoma. Water can reach the mesophyll because veins in the leaf contain xylem that transport water to it. Enough light can enter the mesophyll because the upper epidermis of the leaf is only one-cell layer thick. These types of and how they are organised in the leaf is shown in Figure 328. cuticle upper epidermis mesophyll leaf vein xylem vessel (transports water) phloem tube (transports food) nucleus choroplasts lower epidermis pore (stoma) Figure 328 Tissues of a plant leaf 26 Essentials Education 2016.

6 THE ORGANISATION OF MULTICELLULAR ORGANISMS CHAPTER 3.2 Plant organ systems Plants have two organ systems; the root system and the shoot system. These are shown in Figure 324. Flowering plants that are dicots have a root system that consists of a central root called the taproot from which extend branching roots called lateral roots; for example, roses and eucalypts. Flowering plants that are monocotyledons lack a taproot the monocot root system consists of many shallow roots that extend from the base of the stem; for example, grasses. The base of the stem in some monocots is specialised to form a bulb that stores food for the plant; for example, daffodils. The shoot system of flowering plants usually consists of a stem and leaves and, at certain times of the year, specialised parts of the shoot system called flowers. The organ systems of a flowering plant, the organs they are composed of and their main function is shown in the following table. ORGAN SYSTEM Major organs Main function in a flowering plant Root system Shoot system Taproot, lateral roots in dicots Shallow roots in monocots Stem Leaves Anchor the plant and take up water and minerals from the soil Transport of materials Produce organic molecules and exchange gases The interdependence of organ systems Organ systems do not operate in isolation. They are interdependent. The function of each one is dependent on the proper function of the other organ systems in the multicellular organism. The interdependence of a multicellular organism s organ systems ensures all of them can function effectively together to ensure its health and survival. Some examples in the human body include: The respiratory system; that permits the uptake or entry of oxygen into blood for transport to the cells of all organ systems; e.g. to make energy available. The digestive system; that breaks food down to products that are absorbed or pass into blood for transport to the cells of all organs; e.g. amino acids used to produce protein molecules. The circulatory system; that transports oxygen and the products of digestion to the cells of all organ systems; e.g. glucose to make energy available. The nervous system; that regulates the activity of organs in all organ systems; e.g. the rate at which the diaphragm contracts and how quickly the heart pumps. Lifestyle choices and the function of organ systems A person whose organ systems are functioning efficiently is said to be in good health, or healthy. The lifestyle of an individual plays a major role in determining how efficiently their organ systems function dayto-day. This not only affects how healthy they are now but also the state of their health when they are older. People can control many aspects of their lifestyle. These are called lifestyle choices. Over time an individual s lifestyle choices may enhance their health and well-being, or harm it. The possible implications of some lifestyle choices are shown in the following table. Lifestyle choice Well-being is enhanced Well-being is harmed Following a balanced diet Doing moderate exercise Taking prescription medications Drinking moderate amounts of alcohol Reduced risk of cancers like bowel cancer, high blood pressure and heart disease Moderate exercise reduces the risk of heart disease and increases muscle strength Using antibiotics treats bacterial infection and anti-cancer drugs help treat cancer Drinking alcohol in moderation makes it easier to relax, to socialise more, or to cope better with stress Regular buying of food for a balanced diet is expensive and may cause stress over money Excessive exercise leads to muscle soreness, increased risk of injury and fatigue Increased risk of an allergic response, other side-effects, or in some cases, dependency Excessive drinking of alcohol leads to dependency, domestic violence and heart and/or liver disease Essentials Education

7 TOPIC 3 MULTICELLULAR ORGANISMS Key Concepts 1. Multicellular organisms like animals and plants have a hierarchical structure of organisation 2. Cells form into s, s make up organs, and groups of organs form organ systems 3. The structure of s and organs is related to their function 4. The organ systems of multicellular organisms are interdependent 5. A person s lifestyle choices affect the function of their organ systems, and therefore their health What have you learned? Key Terms hierarchy organ organ system respiratory system digestive system excretory system circulatory system nervous system neuron cardiac muscle proteases interdependence epidermis xylem mesophyll reproductive parenchyma endodermis phloem cortex pith chloroplasts dicotyledons root system shoot system monocotyledons lifestyle choices well-being 28 Essentials Education 2016.

8 THE ORGANISATION OF MULTICELLULAR ORGANISMS CHAPTER 3.2 Knowledge and Understanding 1. Write the meaning of the following: xylem in the stem consists of chains of xylem vessels. 2. Draw a diagram of a layer of epidermis with a root hair cell. Label one structure specific to the root hair cell and briefly outline how this structure permits the cell to function. 3. The human stomach is a vital organ in our body: a) List two different s present in the stomach b) Describe two functions of the human stomach. 4. Explain, giving examples, the difference between a lifestyle choice that harms well-being and one that enhances well-being. Application, Analysis and Evaluation 5. Epithelial cells in the stomach lining of a person stop releasing hydrochloric acid. How might that affect the risk of food poisoning? 6. Roots do not have any mesophyll. Why not? 7. Compare the function of the human respiratory system with the excretory system s function. 8. Identify the organ system that the cells of all other organ systems in the body depend on for the oxygen they need to produce energy. digestive system excretory system respiratory system endocrine system immune system Essentials Education

9 TOPIC 3 MULTICELLULAR ORGANISMS 9. The following diagram shows a very thin piece of a flowering plant organ as it would look when viewed using a light microscope. endodermis parenchyma epidermis xylem Is the organ part of the stem? Justify your decision. Extension 10. Animals are used in experiments to develop new drugs to use in medicine and to test the safety of medical procedures. Certain types of experiments cause animals to experience pain, or reduce their quality of life in other ways. Using animals like this leads to questions about whether or not it is the right thing to do. The process of asking questions about human conduct is called ethics and in Biology it is often called bioethics. Carry out research into animal experimentation. How strong is the case for experimenting on animals? What is the case against using animals in experiments? After you have looked at each case, make a decision: Do you think using animals in experiments is the right thing to do, and explain why or why not. Helpful Online RESOURCES for bioethics To help you learn more about bioethics use this QR code to go to: < 30 Essentials Education 2016.

10 THE ORGANISATION OF MULTICELLULAR ORGANISMS CHAPTER 3.2? Inquiry Skills PRACTICAL Dissecting a daffodil flower Introduction A daffodil is a flowering plant that is a monocotyledon. Like some other types of monocots, it germinates from a bulb in winter and a shoot system grows in spring. The shoot system consists of a long green stem, narrow and long leaves and a large, distinctive flower. A flower is a specialised part of the shoot system. It has organs called petals, stamens and the pistil, or carpel. Many have leaf or petal like sepals. Stamens produce pollen that contain sperm and part of the carpel produces ova. Equipment and materials Daffodil including roots, bulb, stem, leaves and a flower Dissection board Scalpel and/or scissors Dissection probe Forceps Hand lens Part A: Viewing the structure of a daffodil 1. Place the daffodil flower on the dissection board. 2. Locate the roots, bulb, stem, leaves and the flower. 3. Use the adjacent Figure to help you. 4. Look closely at the flower note that it has two layers of petals. a) Both layers consist of three petals. b) The external layer of petals are separate from each other. c) The inner layer of petals is fused to form the cup or corona. d) Also note that a daffodil flower does not have sepals. 5. Prepare a table to classify the roots, bulb, stem, leaves and flower as part of the root system or part of the shoot system. leaf bulb ovary style stigma pistil stem soil level roots petal filment anther cup stamen Essentials Education