N5 Unit 2 Summary Notes 2024 - PUPIL COPY PDF

Douglas Academy Biology Department National 5 Summary notes Unit 2: Multicellular Organisms Biologist’s name: Topic Page 2.1 Producing New Cells 2-7 2.2 Plant Transport Systems 8-12 2.3 Reproduction...

Douglas Academy Biology Department National 5 Summary notes Unit 2: Multicellular Organisms Biologist’s name: Topic Page 2.1 Producing New Cells 2-7 2.2 Plant Transport Systems 8-12 2.3 Reproduction 13-17 2.4 Variation & Inheritance 18-24 2.5 Control & Communication 25-33 2.6 Animal Transport Systems 34-44 1  Topic 2.1: Producing New Cells N5 Success criteria I can… 1. Describe the sequence of events of mitosis using the keywords chromatids, spindle fibres and equator. 2. Explain why mitosis is needed by living things. 3. Explain what is meant by a diploid cell. 4. Describe what happens to the two matching sets of chromosomes found in diploid cells when thy undergo mitosis. 5. Define the term stem cell and state why stem cells are important. 6. State where stem cells can be found. 7. State what is meant by a multicellular organism. 7. Describe what is meant by specialisation of cells. 8. Define the terms cells, tissues, organs and organ systems and describe the hierarchy that exists between them. KEYWORDS Mitosis The process when a diploid cell divides after replicating it’s two matching sets of chromosomes. Chromatids The name given to the two identical copies that make up a chromosome after it has replicated. Equator An imaginary line down the middle of a cell. Spindle fibres Structures that pull the chromatids apart during mitosis and then pull each chromosome to opposite poles of the cell. Diploid Cells with two sets of matching chromosomes Chromosome A structure made of DNA that is tightly coiled and found 2  in the nucleus of animal, plant and fungal cells. Stem cell An unspecialised cell which can divide in order to self- renew and has the potential to become different types of cell. Embryonic stem cell A cell taken from a very early embryo (4-5 days old). Tissue stem cell A stem cell found in the body of adults. E.g. they can be found in our bone marrow Multicellular An organism made from more than one cell type and are made up of tissues and organs. Tissue A group of similar cells working together to perform a function. Specialisation A process which occurs in stem cells and leads to the formation of a variety of cells, tissues and organs. Organ A group of tissues working together to carry out a function. Organ system A group of organs that work closely together. 3 2.1 Summary note All cells in the body (except sperm and egg cells) are diploid. This means they have two matching sets of chromosomes. One set is inherited from the mother and the other set is from the father. Mitosis provides new cells for growth, repair of damaged tissues and replacement of dead or damaged cells. How do cells divide? Diploid cells divide by a process called mitosis. Mitosis maintains the diploid chromosome complement meaning that the two matching sets of chromosomes are replicated exactly during the process. 4 The steps involved in mitosis are shown below. Chromosomes shorten, thicken and replicate (make an identical copy of themselves) and become visible (under the microscope). Chromosomes that have replicated are made of two identical chromatids joined by a centromere creating an ‘X’ shape. The nuclear membrane disappears. Spindle fibres attach to the chromosomes. The chromosomes line up along the equator of the cell. The spindle fibres pull the chromatids apart. They are now known as chromosomes and the spindle fibres pull chromosomes to opposite poles of the cell. The nuclear membrane reforms. For a brief period the cell has two nuclei. The cytoplasm divides forming two new identical daughter cells. Each contains the same number of chromosomes as the original parent cell. 5 Stem cells Stem cells in animals (like humans) are unspecialised cells and this feature means they have the potential to become different types of cell. They can self-renew by undergoing cell division (to make more stem cells) that can be used for for growth and repair. There are 2 types of stem cells… Embryonic stem cells Tissue stem cells  Found only in embryos  Only found in the adult body but can be  Can only be obtained from an found throughout life embryo at a very early stage  Can specialise into a few different types  Can specialise into any type of of cell but not all types human cell. Specialisation of cells Specialisation of cells is a process that leads to the formation of a variety of cells, tissues and organs from stem cells. How is the human body organised? The human body is multicellular. This means that it is made up of more than one cell type, unlike bacteria which are unicellular. All similar specialised cells are organised into groups called tissues. Tissues join together to form organs which perform different functions. The cell in organs are specialised for their function and organs work together in systems. This method of organisation is called a hierarchy. 6 Example exam questions 1. Put diagrams 1-4 in order to show the steps of mitosis. (1 mark) 2. Name a type of stem cell. (1 mark) 3. State the number of chromosomes present in this cell. (1 mark) 4. Which row in the table below is correct if the original cell has 10 chromosomes? (1 mark) 3. Name structure L. (1 mark) 5. The diagram on the right shows the development of blood cells and nerve cells. a) Name a feature of stem cells that allows them to develop into many different types of cells. (1 mark) 7  2.2 Plant Transport Systems N5 Success Criteria I can… 1. State the names of 3 plant organs. 2. Label a cross section of a leaf using the keywords; upper epidermis, palisade mesophyll, spongy mesophyll, vein consisting of xylem & phloem), lower epidermis, guard cells and stomata. 3. Describe how the root hairs and xylem vessels are involved in water transport. 4. Describe the structure of xylem vessels. 5. Explain the purpose of lignin in xylem vessels. 6. Describe the process of transpiration 7. Describe the structures and processes involved as water moves through the plant from oil to air. 8. State the 4 factors that can affect the rate of transpiration. 9. State the effect that changing these factors has on the rate of transpiration 10. State the name for the piece of apparatus used to measure transpiration rate and describe it’s use. 11. State the function of the speciliased tissues: xylem and phloem 12. Describe the structure of phloem tissue. 8 KEYWORDS The specialised tissue that transports water upwards in from Xylem roots to leaves in plants. The substance that forms rings in xylem vessels. Xylem vessels Lignin are lignified to withstand the pressure changes as water moves through the plant. Phloem The tissue that transports sugar (glucose) in plants Companion cell Cells associated with the phloem. Sieve plate A structure found in the phloem. Upper epidermis The top layer of tissue in a leaf. Palisade mesophyll The layer of cells in a leaf where most photosynthesis takes place. These cells have chloroplasts which contain chlorophyll to trap light for photosynthesis. Spongy mesophyll A layer of cells with spaces for gases to diffuse in and out of the plant. These cells also have chloroplasts which contain chlorophyll to trap light for photosynthesis. Lower epidermis The bottom layer of a leaf. The structures that are found on the underside of a leaf that allow water to evaporate out of the plant. Stoma = 1, Stomata Stomata = many. The cells that control opening and closing of the stomata. Guard cells These cells have chloroplasts which contain chlorophyll to trap light for photosynthesis. Leaf vein The structure that contains the xylem and phloem. The process of water moving through a plant due to the loss Transpiration of water by evaporation through the stomata. Evaporation When liquid water becomes water vapour. Humidity The concentration of water in the air. 9 2.2 Summary Note Plants are made from cells, tissues and organs. The organs in a plant are the roots, the stem and leaves. How are substances transported between organs? There are two different tissues used for transporting substances in plants; The xylem is involved in water transport. The phloem is involved in the transport of sugar. Xylem vs Phloem Xylem Phloem Which substances Sugar Water and minerals are transported? Dead or alive? Dead tissue Living tissue Direction of Water and minerals move Sugar is transported up and transport? Upwards only down the plant in all directions Xylem cells are lignified Phloem cells have sieve plates (contain lignin rings) to Structure and associated companion withstand the pressure cells. changes from water. 10 Leaf structure Remember! Leaves have four layers of tissue. They also have veins Uppity running through them that contain the specialized tissues People called xylem and phloem. On the underside of the leaf Speak are structures called stomata, these open and close to Loudly control water loss from the plant. Stomata opening is controlled by guard cells. Transpiration – How does water move from the roots to the leaves? Transpiration is the process of water moving through a plant and its evaporation through the stomata. 1. Water and minerals enter the root hairs by osmosis. 2. Water moves up the stem in the dead xylem vessels. 3 4 3. Water travels to the leaf in the leaf vein. 2 4. Water evaporates and exits the leaf through the stomata. Which factors affect the rate of transpiration? 1 Factor Explanation Wind speed Higher wind speeds result in faster transpiration. Temperature Higher temperatures result in faster transpiration. Increased surface area (bigger leaves) result in more Surface area transpiration. Humidity Higher humidity will result in slower transpiration. Wind speed, temperature and humidity are all referred to as ‘environmental factors’ as they involve changing conditions around the plant. Surface area is not. 11 Example exam questions 1. The diagram shows a section through a leaf. a) Name tissue W. (1 mark) b) The cells in tissue W have more chloroplasts than other leaf cells. Suggest the advantage of these cells being nearer the upper surface of the leaf. (1 mark) c) Describe what structures are found in the leaf vein and explain their function. (2 marks) 2. The diagram shows the underside of a leaf. a) State the function of plant stomata. (1 mark) b) Name the cells that control the opening and closing of stomata. (1 mark) c) Another plant B has less stomata on the same area of leaf. Suggest an advantage this might give plant B. (1 mark) 3. The diagram shows scientific apparatus used to measure the rate of transpiration. a) Explain how this apparatus works. (2 marks) b) Name an environmental change that can affect the rate of transpiration in a plant and describe the effect caused. (2 marks) 12  2.3 Reproduction (animals & plants) N5 Success Criteria I can… 1. State that gametes are haploid and explain what haploid means. 2. State where male and female gametes are produced in plants and animals. 3. Identify the location of the organs that produce the gametes. 4. Describe the basic structure of a sperm and egg cell. 5. Define fertilisation. 6. Explain why a zygote is diploid and state that it divides to form an embryo. 13 KEYWORDS diploid A cell with two sets of chromosomes. haploid A cell with only one set of chromosomes. gamete A sex cell. sperm The male animal gamete made in the testes. egg The female animal gamete made in the ovaries. pollen The male gamete in plants which is made in the anther. The part of a flower that makes pollen which is made in the anther ovary. fertilisation The fusion of the nuclei of two haploid gametes to produce a diploid zygote. zygote A diploid cell produced after fertilisation. What the zygote becomes once it begins dividing following embryo fertilization. 14 2.3 Reproduction Summary Notes In order to reproduce sexually, plants and animals need to produce special cells called gametes. These cells are haploid because they only contain one set of chromosomes. Producing gametes in animals In animals, the male sex cells are called sperm cells. These are produced in the testes. The female sex cells are called egg cells. These are produced in the ovaries. The male and female reproductive systems are shown below. Producing gametes in plants In plants, the male sex cells are called pollen. These are produced in the anthers. The female sex cells are called ovules and are produced in the ovary. The sex cells are produced by the flower which has both male and female organs. anther ovary 15 How are sperm and egg cells adapted for their function? Sperm Egg Large starch food store Head containing the nucleus Tail Streamlined shape Both sex cells are haploid which means they contain only 1 set of chromosomes. What is fertilisation? Fertilisation is the fusion of the nuclei of the two haploid gametes to produce a diploid zygote, which divides to form an embryo. Fertilisation in humans Summary table Name of gamete Where is it produced? Animal Sperm (male) Testis Egg (female) Ovary Plant Pollen (male) Anther Ovule (female) Ovary 16 Exam questions 1. Look at the diagram. Circle to one word for each picture to show whether each cell is haploid or diploid. (3 marks) 2. Identify cell F (1mark) 3. Explain the terms haploid and diploid in terms of chromosome complement (2marks). 4. Look at the diagram on the left. a) Identify organ R. (1mark) b) Describe what happens during fertilisaton. (2marks) 1. Which row in the table correctly shows the gamete produced by the anther of the plant? (1 mark) 17  2.4 Variation and inheritance N5 Success Criteria I can… 1. Define what is meant by continuous variation (polygenic inheritance) and discrete variation (single gene inheritance). 2. Categorise example of variation (into either discrete or continuous) 3. Describe how sexual reproduction contributes to variation within a species 4. State what is meant by polygenic inheritance 5. Understand the genetic terms; gene, allele, phenotype, genotype, dominant, recessive, homozygous, heterozygous, P, F1 and F2. 6. Use a family tree to identify phenotypes and genotypes. 7. Carry out monohybrid crosses (Punnett squares) from parental generations through to the F2 generation to explain inheritance. 8. Explain why predicted phenotype ratios among offspring are not always achieved. 18 KEYWORDS Variation The differences between members of a species. The phenotype being measured can be placed into distinct Discrete variation groups. Continuous There is a range of values for the phenotype between a variation maximum and a minimum. Single gene Inheritance where one characteristic is controlled by a single inheritance gene and results in discrete variation. Polygenic Inheritance where one characteristic is controlled by many inheritance genes and results in continuous variation. Gene A section of DNA that codes for a protein. Allele Different forms of the same gene. Phenotype The physical description of appearance. Eg. "blue eyes". Genotype A description of the alleles an organism possesses. Eg. "BB". An allele that will determine the phenotype even if only one Dominant copy is present. An allele that can be masked by another therefore two copies Recessive are required for it to determine the phenotype. Homozygous Both alleles are the same. Eg. BB or bb. Heterozygous Both alleles are different. Eg. Bb. P1 The parent generation. F1 The first generation of offspring. F2 The second generation of offspring. A cross involving two different alleles of a single gene. The parents are said to be true breeding if each parent is Monohybrid cross homozygous and each possesses a different phenotype. The diagram used to show a monohybrid cross and predict the chance of offspring inheriting a particular phenotype or Punnett square genotype. 19 What is variation and what causes it? The differences within a population are known as variation. Combining genes from two parents contributes to variation within a species. Look at the rabbits above. There is a Particular characteristic descriptions are range of phenotypes (different known as the phenotpye of an individual. colours shapes and sizes). This is Phenotypes are determined by the genes because they have each inherited present in an organism's DNA. different genes from their parents. Continuous vs discrete variation Discrete Variation Continuous variation A result of single gene inheritance A result of polygenic inheritance (characteristics only dependent on (characteristics caused by a number of gene). genes). The measurements fall into distinct There is a range of values between a maximum and minimum. Examples Examples Eye colour in humans, Long and short hair Height in humans, leaf length in plants, in cats, flower petal colour, presence of milk yield of cow. ear lobes. Discrete variation can be shown in a bar Continuous variation can be shown chart. diagrammatically in a histogram or line graph. 20 Dominant alleles and recessive alleles Diploid cells have 2 sets of chromosomes. This means they have 2 versions of every gene needed for an organism. These different versions are called alleles. Question Answer If one allele is a green eye If the alleles are different then the phenotype and the other phenotype depends on which allele is allele is a brown eye dominant. The other allele is called phenotype, then why might recessive. In this case brown is dominant someone have brown eyes? and therefore the phenotype will be ‘brown eyes’. Dominant alleles are always shown with a capital letter. Recessive alleles are always shown with a lower case letter. In this case we could show the brown allele with ‘B’ and the green allele with ‘b’. Homozygous and heterozygous The combinations of alleles is known as the genotype. Homozygous means both alleles are the same, heterozygous means both alleles are different. The table below shows the genotypes and phenotypes using the brown eye/green eye example. Genotype Description Explanation Phenotype BB Homozygous Both alleles are the same (homozygous) Brown eyes dominant and both are capital letters (dominant). bb Homozygous Both alleles are the same (Homozygous) Green eyes recessive and both are lower case (recessive). Bb Heterozygous The alleles are different Brown eyes (heterozygous). 21 How to draw a Punnett square Biologists can predict the chances of offspring with different phenotypes by carrying out a monohybrid cross. The diagram below shows how to draw a Punnett square P = purple petals p = white petals 1. Draw the gametes 3. Assign a phenotype to each 2. Combine each pair of the parent can produce. gametes to represent genotype in each box. Predicted versus observed phenotype ratios In this example we can predict a 3:1 ratio of purple flowers to white flowers. Predicted phenotype ratios amongst offspring are not always achieved in practice as fertilisation is a random process with an element of chance! 22  Using family trees to find out phenotypes and genotypes The family tree shows three generations (P, F1 and F2) and the inheritance of eye colour. The key allows us to identify the sex and phenotypes of the individuals. We can also tell that green is recessive and therefore 2, 6 and 8 must all have genotype bb How many other genotypes can you work out? (homozygous recessive). 23 Example exam questions 1. The following diagram represents part of a family tree showing the inheritance of a hitchhiker’s thumb, where the thumb can bend back as shown below. Complete the table for individuals A and C (2 marks). 2. One type of deafness in humans is caused by a single gene. The diagram below shows the pattern of inheritance in one family. H represents the hearing form of the gene. h represents the non-hearing form of the gene. a) Using Jon as an example, explain how it is known that the hearing form of the gene is dominant. (1 mark). b) Complete the table. (2 marks) c) Fiona has a child with a man who has the same genotype as her. State the chance of their child being able to hear. (1 mark) 24  2.5 Control and communication N5 Success Criteria State what the nervous system is made up from I can state what the Central nervous system is made up from I can identify the 3 main part of the brain I can describe the function of the cerebrum, cerebellum and medulla I can name the 3 types of neuron I can describe the function of each of the 3 types of neuron I can describe the function of a receptor I can describe how messages are transferred along neurons I can state that messages are passed along neurons rapidly (and produce a response more quickly than a hormone message can) I can describe how messages are transferred across the synapse I can describe the structure of a reflex arc I can describe what a reflex action is I can describe the function of a reflex action I can describe the function of an effector and give two examples of effectors I can state the type of gland that produces hormones and releases them into the bloodstream and give 3 examples I can state that hormones are chemical messengers 25  I can… I can state that a target tissue has cells with complementary receptor proteins on their surface for specific hormones I can explain why only target tissues are affected by specific hormones. I can describe the role of insulin in blood glucose regulation I can describe the role of glucagon in blood glucose regulation I can describe the role of glycogen in blood glucose regulation I can describe the role of the liver in blood glucose regulation I can describe the role of the pancreas in blood glucose regulation I can state that a response to a stimulus can be a rapid action from a muscle or a slower response from a gland. 26  KEYWORDS – 2.2 – Nervous control Central nervous The part of the nervous system made up of the brain and spinal cord. system Cerebrum The part of the brain that controls personality and memory. Medulla The part of the brain that controls breathing and heart rate. Cerebellum The part of the brain that controls balance and coordination. Sensory neuron A neuron that carries an electrical signal from a receptor to the central nervous system. Inter neuron Carries the signal from a sensory to a motor neuron in the CNS. Motor neuron Carries the signal from the CNS to an effector. Stimulus Something (sound, light, touch, taste) that activates a receptor to produce an electrical signal in the nervous system. Receptors A tissue that can change a stimulus into an electrical signal. Effector A muscle or gland that causes a response (eg. movement, hormone release). Electrical The method by which signals travel along neurons. impulse Synapse A gap between two neurons that requires a chemical signal to cross. Reflex A response that is automatic to protect the body from harm. 27 The Nervous System The nervous system allows the body to detect stimuli (eg. Sound, touch) from the environment and cause a response (eg. movement). The nervous system consists of the central nervous system (CNS) and other nerves. Central nervous system The central nervous system consists of the brain and spinal cord. Part of brain Function Parts of the brain Cerebrum Memory and muscle cerebrum movement Cerebellum Balance and coordination Medulla Breathing and heart rate medulla cerebellum Nerves Synapses Nerves are made of nerve cells called neurons. Gaps between neurons Neurons carry signals by electrical impulses. are called synapses. There are three types of neurons. Sensory, inter The electrical impulse and motor neurons. is unable to cross these Sensory neurons pass the information to the gaps. The signal is CNS. Inter neurons operate within the CNS, transferred across the which processes information from the senses synapse by chemicals. that require a response. Motor neurons enable a response to occur at an effector (muscle or gland). 28 Receptors and effectors Receptors Eg. Ears, eyes, Receptors are cells that can detect a stimulus and change skin cells this signal into an electrical impulse to send to the brain. Effectors Eg. Muscles, Effectors enable a response to occur. The response is either glands movement (muscle) or a chemical/hormone is released (gland). Pathway of an impulse The diagram shows the pathway of an electrical impulse through the nervous system from stimulus to response. 29  KEYWORDS – 2.2 – hormonal control Endocrine glands A group of organs that make hormones. Hormones A chemical messenger, made from protein, that travels in the bloodstream. Target tissue An organ with receptor proteins that is the target for a specific hormone. Glucose A type of sugar that is easily transported in the blood. Insulin A hormone that decreases blood sugar. Liver An organ where glycogen is stored. Glucagon A hormone that increases blood sugar. Pancreas The organ that makes insulin. Glycogen A carbohydrate made of lots of glucose bonded together. 30 The Endocrine System The endocrine system produces hormones. Hormones are chemical messengers that travel in the blood stream to a target tissue. The target tissues have cells with complementary receptor proteins. The receptors are specific for hormones, so only that tissue will be affected. How do hormones work? How are blood glucose levels kept constant? The hormones insulin and glucagon control the levels of glucose in the blood. Hormone Gland where Effect on blood Target tissue and it is made? glucose action Insulin Pancreas Lowers blood sugar Liver – glucose converted to glycogen Glucagon Pancreas Increases blood Liver – glycogen sugar converted to glucose 31 Comparing nervous and hormonal communication a response to a stimulus can be a rapid action from a muscle or a slower response from a gland. Exam questions – nervous system 1. Look at the picture of the brain and name structures 1-3 (3 marks) 2. State the function of each part. (3marks) 3. The diagram shows a reflex arc. a) Identify neurons P, Q and R (3 marks) b) Identify the synapses on the diagram. (1 mark) c) Mark on the diagram the direc3on that the signal is travelling. ( 1mark) 4. Describe how messages move across synapses (1 mark). 5. Explain why reflexes are needed by the human body. (2 marks) 32 Exam questions – Endocrine system 1. Name a type of gland that releases hormones into the bloodstream. (1mark) 2. Name the organ which produces insulin. (1mark) 3. The diagram shows a hormone binding with its specific target tissue. a) Explain why target cells are affected by this hormone. (1 mark) b) What is the target tissue for the hormone glucagon? (1 mark) 4. People with Type 1 diabetes need to inject insulin. The table below contains informa3on about different types of insulin available. a) A fast acting insulin can be injected just before meals. Identify the type of insulin from the table that is best suited for this. (1 mark) b) Another type of insulin can be used once per day to provide a steady supply of insulin. Identify the type of insulin that would be most effective at doing this. (1 mark) 33  2.6 Transport systems - animals N5 Success Criteria – Part 1 1.Compare arteries, capillaries and veins in terms of their central channel, wall thickness, blood pressure, direc3on of travel, presence of valves. 2.Explain why capillaries are effec3ve at exchanging materials. 3.Describe the pathway of oxygenated blood and deoxygenated blood through the heart, lungs and body. 4.Label a diagram of the heart including the 4 chambers and the 4 associated blood vessels. 5.State the components that make up the blood. 6.Describe the func3on of red blood cells and explain how they are adapted for this. 7.Describe the function of white blood cells & state the two different types. 8.Explain how lymphocytes work. 9. Explain how phagocytes work. 34  KEYWORDS – 2.6 (part 1) Plasma The liquid that carries the blood cells. Red blood cells The blood cells that carry oxygen. Biconcave The shape of a red blood cell. Haemoglobin The protein inside red blood cells. Oxyhaemoglobin When oxygen combines with haemoglobin. White blood cells The blood cells that destroy pathogens. Pathogen A microorganism that causes disease. Phagocyte A type of white blood cell that engulfs pathogens. lymphocyte A type of white blood cell that makes antibodies. Phagocytosis The process used by phagocytes. Antibody Proteins produced by lymphocytes that kill pathogens. Atrium (atria) The upper two chambers of the heart. Ventricle The lower two chambers of the heart. Valve A structure that prevents backflow of blood. Aorta The largest artery in the body. Vena cava The largest vein in the body Pulmonary artery The blood vessel that takes blood to the lungs. Pulmonary vein The blood vessel that takes blood from the lungs to the heart. Coronary arteries The blood vessels that supply blood to the heart. Artery A blood vessel that carries blood away from the heart. Vein A blood vessel that takes blood towards the heart. capillary Tiny blood vessels that allow exchange of materials. 35 N5 Success Criteria – Part 2 1. State which materials need to be absorbed into the bloodstream and whether they are being delivered to cells or removed from cells 2. Explain the importance of capillary networks. 3. Name 3 features of surfaces that increases the efficiency of absorp3on. 4. Explain what alveoli are. 5. Explain how gas exchange happens in the lungs. 6. Explain what a villus is and be able to label a diagram including capillaries and lacteals. 7. Describe how glucose and amino acids are absorbed. 8. Describe how fatty acids and glycerol are absorbed. KEYWORDS – 2.6 (part 2) Absorption A process where a substance is ‘taken up’ into a tissue, usually crossing a membrane. Capillary network A group of capillaries that deliver blood to a particular tissue. Gas exchange The process of oxygen entering the blood and carbon dioxide leaving the blood. Alveoli The tiny air sacs found inside the lungs. Alveolar wall The boundary between the air sac and the capillaries. Small intestine The organ responsible for the absorption of nutrients. Villi The tiny ‘finger like’ folds in the wall of the small intestine that increase surface area. Lacteal The structure in a villus, like a pipe, that absorbs fatty acids and glycerol. Fatty acids Chemicals that make up part of fats. Glycerol A chemical that combines with fatty acids to form fats. 36 The Circulatory System Arteries Veins Capillaries Carry blood away from Carry blood into heart. Form networks that heart Thinner walls. connect arteries to veins. Thick, muscular walls. Wider channel. Very thin walls. Narrower central channel Carry blood under lower Large surface area. Carry blood under high pressure. Allow efficient exchange pressure. Veins have valves to of materials. prevent blood backflow. 37 The Heart The right side of the heart pumps deoxygenated blood to the lungs. Once it returns, the left side of the heart pumps oxygenated blood to the body. The heart has four chambers, two atria and two ventricles. It also has four valves to keep blood flowing in one direction/prevents it flowing backwards.. The pathway of blood Parts of the heart through the heart Oxygenated Vena cava blood pathway Deoxygenated blood pathway Right atrium A Vena cava B Pulmonary artery Right C Aorta ventricle D Pulmonary vein Pulmonary E Right atrium artery F Left atrium G Right ventricle The lungs Right side Left side H Left ventricle Pulmonary vein Where are the valves? Left atrium Coronary arteries Left ventricle The heart muscle needs its own, separate, supply of blood. The coronary arteries run over the surface of the heart and supply oxygen and Aorta glucose to the muscle cells. Coronary arteries The body 38 39 How do cells get what they need for respiration? Oxygen and nutrients from food must be absorbed into the bloodstream and delivered to cells for respiration. Waste products, such as carbon dioxide must be removed from cells into the bloodstream. Tissues contain capillary networks to allow the exchange of materials at cellular level. What makes a surface good at absorption? Surfaces involved in absorption have certain features in common; 1. A good blood supply – to take away the materials absorbed 2. A large surface area – to absorb more materials 3. Thin walls – to speed up absorption Capillary networks provide all three features to improve the efficiency of absorption Remember – BLT Blood supply Large surface area Thin wall Capillary Artery network Vein 40 How are the lungs adapted for gas exchange? Lungs are gas exchange organs. They consist of a large number of alveoli providing a large surface area. The alveoli also have a good blood supply an thin What happens during gas exchange in the walls. alveoli? Alveolus Blood capillary Oxygen Breathed in and crosses the thin alveolar walls, into the bloodstream Carbon A waste product from dioxide respiration. Leaves the Alveoli are tiny air sacs shaped like capillaries and crosses into the alveoli. It is then breathed out. bunches of grapes. They are surrounded by lots of capillaries. How does the small intestine absorb nutrients from food? The walls of the small intestine are Structure Function folded into thousands of tiny villi. Capillaries To absorb glucose and This increases the surface area to amino acids. allow more nutrients to be absorbed. Each villus has a capillary Lacteal To absorb fatty acids and glycerol. network that provides a good supply and a lacteal. Their lining is also thin which makes them efficient at absorption. lacteal Capillary A villus 41 Exam questions – Part 1 1. The diagram shows part of the circulatory system in humans. a) Describe the difference in oxygen concentra3on in the blood travelling through blood vessels P and Q. (1 mark) b) Name the heart chamber labelled R. (1 mark) 2. Look at the diagram of the heart. a) Name the heart chambers labelled W and Y. (2 marks) b) Which chamber receives blood from the lungs? (1 mark) c) Name the blood vessel that supplies the heart muscle with blood. (1 mark) 3. The table shows informa3on about three different types of blood vessel. a) Complete the table. (2 marks) b) State another difference between arteries and veins. (1 mark) c) Explain why arteries do not require valves. (1 mark) 42 Exam questions - Part 2 1. Name structure W. (1 mark) 2. Describe two features of these structures which improve the efficiency of gas exchange. (1 mark) 3. The diagram shows an undamaged alveoli and alveoli that have been damaged by smoking. Iden3fy a feature of the alveoli that will be affected by this damage. ( 1 mark) 4. The diagram shows a villus in the small intes3ne. 5. a) Name structures A and B (2 marks) b) Name a type of molecule absorbed by A. (1 mark) c) Name a type of molecule absorbed by B. (1 mark 43 44