Life Sciences Survival Kit Gr 12 Paper 1 PDF 2022

Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 CAPE WINELANDS EDUCATION DISTRICT LIFE SCIENCES PAPER 1 Survival Kit 1 Life Sciences Gr 12...

Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 CAPE WINELANDS EDUCATION DISTRICT LIFE SCIENCES PAPER 1 Survival Kit 1 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Grade 12 Learner It is important for YOU to be successful in the NSC examination at the end of 2022, and to achieve this, it will take extra effort and work from YOU. We have taken time to prepare this kit to enable YOU to achieve this goal in Life Sciences. This document has been prepared as study material for the Final Examinations for Grade 12 Life Sciences. The materials have been arranged in such a way that studying can be undertaken topic-wise. Within each topic, core notes have been included according to the 2021 Examination Guideline Document. Questions were selected such that the core concepts and core skills are assessed and practiced. The action words have been underlined in the questions, so that you can follow the instructions of the question. 2 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 HUMAN REPRODUCTION – PAPER 1, 41 marks It is important that you can label and provide functions of the different parts of the male and female reproductive systems. MALE REPRODUCTIVE SYSTEM: The figure below shows the different parts of the male reproductive system and their functions. A possible question in the NSC exams: Describe the process of SPERMATOGENESIS – (the formation of male gametes, sperm cells) Under the influence of testosterone diploid cells in the seminiferous tubules of the testes undergo meiosis to form haploid sperm cells 3 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 It is very important that you can draw the structure of a sperm cell/ provide labels and functions of the parts Female reproductive system: Know the parts and functions of the following parts: Be able to describe oogenesis as follows: Oogenesis: the formation of female gametes - ovum Diploid cells in the ovary undergo mitosis To form numerous follicles At the onset of puberty Under the influence of FSH One cell inside a follicle enlarges and undergoes meiosis Of the four cells produced, only ONE survives to form a mature, haploid ovum This occurs in a monthly cycle 4 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Be able to draw the structure of an ovum and provide labels (jelly layer, haploid nucleus, cytoplasm) Structure of the ovum: Cross section of the ovary indicating the development of the follicles Process of You must know the names and functions of the following hormones that play a role in the menstrual cycle: Hormone Gland/structure that Function secretes hormone FSH (Follicle-Stimulating- hypophysis/ pituitary gland Stimulates the development Hormone) of the primary follicle into a mature Graafian follicle LH hypophysis/ pituitary gland Stimulates the release of the ovum (ovulation) Formation of the corpus luteum oestrogen Graafian follicle Starts the thickening of the endometrium (lining of the uterus) progesterone Corpus luteum Thickens the endometrium even further, preparation should fertilization occur 5 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 A. Events in the ovarian cycle: 1. Development of Graafian follicle 2. Ovulation 3. Formation of corpus luteum Development of Graafian follicle Formation of corpus luteum B. Events in the uterine cycle: Changes that take place in the thickness of the endometrium Menstruation Uterine cycle: 1. Oestrogen is responsible for the thickening of the endometrium 2. Progesterone thickens the endometrium even more Menstruation: - The blood vessel rich endometrium breaks down, and is bleeding occurs through the vagina. Progesterone levels will decrease if fertilization does NOT occur, menstruation will occur. If fertilization DOES occur, progesterone levels will remain high, endometrium will remain intact (will not break down) and no menstruation will occur. Negative feedback between progesterone and FSH: If progesterone levels remain high, the hormone FSH will not be secreted as no follicle will develop while the woman is pregnant. If progesterone levels decrease, FSH will be secreted, and new follicles will develop. 6 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Process of fertilization: The sperm cell(n) and the ovum(n) fuse to form a fertilized egg cell, a zygote(2n) Also know: Development of the zygote to embryo: Zygote undergoes mitosis to form a ball of cells called a morula Which continues to divide by mitosis to form a hollow balls of cells called a blastocyst QUESTIONS - HUMAN REPRODUCTION 1. The diagram below represents a part of the male reproductive system. 1.1 Give the LETTER and the NAME of the part that: (a) Is used in copulation (2) (b) Produces testosterone (2) 1.2 Give ONLY the LETTERS of the TWO parts in the diagram that: (a) Contribute to the formation of semen (2) (b) Provide a passage for the sperm cells (2) Answer: 1.1 (a) A ; penis (2) (b) E; testes (2) 2.2 (a) D (prostate) ; F (seminal vesicle) (2) (b) C (sperm duct/vas deferens); B; (urethra) (2) 7 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 2. The structure below represents a part of the female reproductive system. 2.1 Identify part D. (1) 2.2 State ONE function of part A. (1) 2.3 Describe the process of oogenesis as it occurs in part B. (4) 2.4 State ONE way in which structure C is suited for its function during pregnancy. (1) 2.5 A person undergoes a surgical operation to remove part B on both sides. Explain why this person will not menstruate. (3) Answer: 2.1 cervix (1) 2.2 site of fertilization passage for egg cells (1) 2.3 Diploid cells (2n) in the ovary undergo mitosis to form numerous follicles. At the onset of puberty and under the influence of FSH, one cell inside a follicle enlarges and undergoes meiosis. Of the four cells that are produced, only one survives to form a mature, haploid (n)ovum. This occurs in a monthly cycle. (3) 2.4 Muscular – can enlarge to house and protect the developing foetus/ contractions during childbirth (1) 2.5 The ovaries have been removed No Graafian follicles can develop No oestrogen will be secreted endometrium will not thicken, no thickening, no menstruation (3) 3.Draw a labelled diagram to show the structure of a sperm cell (4) and an ovum. (4) 8 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Answer: Remember to always give the diagram a heading, you will be awarded a mark for it SPERM CELL (4) OVUM (4) 4. The diagrams below show structures formed during human reproduction. 4.1 Identify part A. (1) 4.2 Name the organelle found in large numbers in part C. (1) 4.3 Give the NUMBER (1, 2, 3 or 4) only of the diagram that represents the following: (a) Morula (1) (b) Structure that will implant in the uterus (1) (c) Blastula/Blastocyst (1) 4.4 Give the LETTER and NAME of the part that will enter the ovum during fertilisation. (2) 4.5 Name the type of cell division that occurred to produce the structure in diagram 3. (1) Answer: 4.1 acrosome (1) 4.2 mitochondria (1) 4.3 (a) 3 (1) (b) 1 (1) (c) 1 (1) 4.4 B – haploid nucleus (2) 4.5 mitosis (1) 9 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 5. The diagram below shows a human sperm and ovum. The diagram is not drawn to scale. 5.1 Tabulate ONE difference between the structure of an ovum and a sperm cell. (3) 5.2 The head of the sperm contains a protein digesting enzyme. Explain the Importance of this enzyme during fertilisation. (2) 5.3 An active healthy sperm cell is able to swim about 4 mm per minute. If the distance from the cervix to the end of the Fallopian tube is 20 cm, how long will it take for the sperm cell to reach the ovum at the end of the Fallopian tube? Show your working. (3) 5.4 Semen has a pH of 7.5. Sperm cells have a high mortality rate in acidic conditions. How does the male body ensure that the sperm cells are not killed by acidic urine as they travel through the urethra? (2) 5.1 Answer: If you are asked to tabulate an answer, always draw the table, you will be awarded one mark for the table. Ovum Sperm cell No tail Contains a tail for transport No mitochondria Mid-piece contains many mitochondria (3) 5.2 - the digesting enzymes are responsible to break down the cell membrane of the ovum - to allow the haploid nucleus of the sperm cell to enter the ovum (2) 5.3 20 cm = 200 mm ✓ 200 mm 4 mm ✓ = 50 minutes ✓ (3) 5.4 the prostate gland secretes an alkaline substance that neutralises the acidic environment of the urethra (2) 10 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 6. Study the human male reproductive system below and answer the questions. 6.1 Identify part: (a) B (b) H (2) 6.2 What is the function of E? (2) 6.3 Discuss TWO structural adaptations of the sperm cells to reach the ovum in the Fallopian tube of the female. (4) 6.4 Test results show that a man has a low sperm count. The doctor advises the man that when he is working on his laptop (computer), which radiates heat, that he should not put the laptop on his lap. Why do you think this could have an influence on fertility? (3) Answer: 6.1 (a) B seminal vesicle (1) (b) H testes (1) 6.2 transport semen with sperm cells / transport urine (2) 6.3 Tail – to swim Mitochondria (in mid-piece) – for energy to swim (4) 6.4 Optimal sperm production occurs at 2-3 0 lower than body temperature The warm laptop will increase the temperature of the testes and sperm production will decrease/not be optimal decrease in fertility (3) 7. Study the diagram below of the sequence of events that takes place from the fertilisation of the ovum to the development of the embryo in a part of the human female reproductive system. The arrows indicate the direction of development of one ovum after fertilisation. 7.1 Identify: (a) Structure C (b) The stage of embryo development at E (c) The structure that develops from a combination of parts F and H (3) 7.2 Name the process that takes place: (a) At B (b) When G attaches to part F (2) 7.3 Give the chromosome number of: (a) The cells at D (b) Cell A (2) 11 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Answer: 7.1 (a) zygote (fertilized egg cell) (b) morula (ball of cells) (c) placenta (3) 7.2 (a) fertilization (b) implantation (2) 7.3 (a) 46 (b) 23 (2) RESPONDING TO THE ENVIRONMENT (HUMANS) PAPER 1, 54 marks Human Nervous System The importance/need for a nervous system in humans: To respond to internal and external change Co-ordinate the various activities of the body Know the difference between a stimulus and an impulse: STIMULUS – any change in the environment (eg. a loud noise, a flashing light) IMPULSE – a message carried/transmitted by nerves Central Nervous System Consists of Brain and Spinal Cord Know the following parts and functions of the brain: 1.Brain: 2 Functions of the spinal cord: Spinal cord ·Provides a pathway for nerve impulses to and from the brain ·The spinal cord serves as a centre for reflex actions PROTECTION OF THE Central Nervous System The brain is enclosed by the skull and the spinal cord by the vertebral column Both the brain and spinal cord are enclosed by the 3 membranes, called the meninges 12 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Our nerves are made up of millions of small neurons You must be able to draw and label a simple of a neuron, using the following labels: nucleus, cell body, cytoplasm, myelin sheath, axons and dendrites Heading - A motor neuron: cytoplasm Direction of impulse: from DENDRITES to AXONS Different types of neurons: Sensory neurons – transmit impulses interneuron from the RECEPTORS to the Central Nervous System Interneurons – link sensory neurons to motor neurons Motor neurons – transmit impulses from the Central Nervous System to the effectors Know the difference between a receptor and an effector: RECEPTOR: special cells that become aware of the STIMULUS (the change) and convert it into an IMPULSE (message carried by nerves) EFFECTOR: an organ or cell that acts in response to a stimulus (REACTS) Eg. muscles or glands interneuron 13 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Know the difference between: A Reflex Action and a Reflex Arc. Reflex action – a quick, automatic movement/action by an effector, in response to a stimulus received by a receptor (eg. quickly pulling your hand away from a hot stove) Reflex arc – pathway along which nerve impulses are carried from a receptor to an effector to bring about a reflex action. Structure and labels of a Reflex Arc: synapse Reflex arc: pathway is from- 1 receptor 2 sensory neuron 3 interneuron 4 motor neuron 5 effector The significance (importance) of a reflex action: Reflex actions protect the body from dangerous situations, protects us from serious injury The significance (importance) of a synapse: To ensure that impulses travel in one direction only (from dendrites to axons) Causes and symptoms of disorders: Alzheimers Degeneration of brain cells that destroys memory and thinking skills Multiple sclerosis Myelin sheath of neurons/nerve cells are damaged, making it difficult for impulses to be transmitted, impulses slower 14 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.1 The diagram below represents a human brain. Give the LETTER and NAME of the part of the brain responsible for: 1.1.1 Memorising a cell phone number (2) 1.1.2 Coordinating all voluntary movements (2) 1.1.3 Secretion of hormones (2) 1.1.4 Connection of two hemispheres of part B (2) 1.1.5 The reflex action that occurs when stepping barefooted on a sharp object. (2) Answer: 1.1.1 B – Cerebrum 1.1.2 D – Cerebellum 1.1.3 A - Pituitary gland/ Hypophysis 1.1.4 C - Corpus callosum 1.1.5 E – Spinal cord 1.1 The diagram below represents the structure of a neuron. 1.2.1 Name the type of neuron in the diagram above. (1) 1.2.2 Identify part: (a) B (b) F (c) A (3) 1.2.3 Give the LETTER and NAME of the part that: (a) Transmits impulses away from the cell body (2) (b) Insulates and speeds up the transmission of impulses (2) 1.2.4 Name the condition caused by the progressive degradation of part D. (1) Answer: 1.2.1 Motor neuron (1) 1.2.2 (a) B Nucleus /nuclear membrane (1) (b) F Cytoplasm (1) (c) A Dendrite (1) 1.2.3 (a) C- Axon (2) (b) D- Myelin sheath (2) 1.2.4 Multiple sclerosis (1) 15 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.3 Study the diagram of a reflex arc below. 1.3.1 What is a reflex action? (2) 1.3.2 Label the following: (a) the functional connection at D (1) (b) neuron B (1) 1.3.3 State the significance of the functional connection at D. (1) 1.3.4 Write down, in the correct order, the LETTERS ONLY of the neurons involved from the time a stimulus is received until a response takes place. (2) 1.3.5 Explain the consequences for a reflex action if neuron C is damaged. (2) 1.3.6 Draw a labelled diagram to represent the structure of neuron A (5) Answer: 1.3.1 A reflex action is a quick, automatic response to a stimulus (2) 1.3.2 (a) Synapse (1) (b) Interneuron (1) 1.3.3 It ensures that the impulse moves in one direction only It ensures that the impulse is transmitted from the sensory neuron to the motor neuron (1) 1.3.4 A → B → C (2) 1.3.5 The person will be able to receive a stimulus but will not be able to respond to it (2) 1.3.6 Heading: 1 mark Correct type of neuron drawn: 1 mark Any 3 correct labels: 3 marks (5) 16 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Human EYE: Know the structure and functions of the human eye, using a diagram Function of the iris: to control the amount of light that enters the eye Know the difference between EYE ACCOMODATION and PUPILLARY MECHANISM Eye Accomodation: is the adjustment/change of the SHAPE OF THE LENS to see clearly, whether objects are far away or close by. *Compare the SHAPE OF THE LENS in these two diagrams below: DISTANT VISION (objects further than 6m) NEAR VISION (objects closer than 6 m) Shape of the lens is flatter Shape of the lens is rounder 17 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Be able to describe eye accomodation for distant vision and near vision: Distant vision Near vision 1. Ciliary muscles relax 1. Ciliary muscles contract 2. Suspensory ligaments tighten(become stiff/taut) 2. Suspensory ligaments slacken 3.Tension on the lens increases 3. Tension on the lens decreases 4. Lens becomes flatter (less convex) 4. Lens becomes more rounded (more convex) 5. Light rays are bent less 5. Light rays are bent more 6. Light rays are focuses onto the retina 6. Light rays are focused onto the retina PUPILLARY MECHANISM: is dependant on the AMOUNT OF LIGHT that is available. Pupil becomes SMALLER (constricts) Pupil becomes BIGGER (widens) 18 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Visual defects: Questions: The eye 1.1 The diagram below represents a section through a human eye. 1.1.1 Identify (a) A (1) (b) B (1) (c) C (1) 1.1.2 Give the LETTER and NAME of the part that: (a) Regulates the amount of light entering the eye (2) (b) Contains a dark pigment that absorbs excess light in the eye (2) (c) Contains receptors sensitive to light (2) (d) Assists in the refraction of light rays (2) (e) Changes shape for near and distant (far) vision (2) Answer: 1.1.1 (a) A: Sclera (1) (b) B: Cornea (1) (c) C: Pupil (1) 1.1.2 (a) D – iris (b) G – choroid 19 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 (c) E – retina (d) B – cornea (e) F – lens (10) 1.2 The diagram shows two eyes (X and Y) focused on objects (represented by arrows) at different distances from the eye. Objects A and C were 2 metres away from the eye. Objects B and D were 7 metres away from the eye. 1.2.1 Write down the LETTER ONLY of the object that: (a) Eye X is focused on (1) (b) Eye Y is focused on (1) 1.2.2 Name and describe the process that allows eye Y to form a clear image on the retina. (6) 1.2.3 Describe the process that allows to form a clear image on the retina when a Cape cobra is 9 meters from a person. (5) Answer: 1.2.1 (a) B (b) C 1.2.2 Accommodation (* compulsory mark) Ciliary muscles contract Suspensory ligaments slacken Tension on lens decreases Lens becomes more convex (more rounded) Light rays are refracted (bent) more Light rays are focused onto the retina (6) 1.2.3 Ciliary muscles relax Suspensory ligaments tighten (become taut) Tension on lens increases Lens becomes less convex flatter Light rays are refracted (bent) less Light rays are focused onto the retina (5) 20 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.3 The table below indicates the changes in diameter of the pupil of the human eye Changes in pupil diameter over time: Time in (s) Diameter of pupil in (mm) 5 6 mm 10 6 mm 15 6 mm 20 6 mm 25 4 mm 30 2 mm 35 3 mm 40 3,5 mm 45 4 mm 50 4 mm 55 4 mm 60 4 mm 1.3.1 Which structure in the human eye is responsible for the changes indicated in the graph? (1) 1.3.2 During which period of time was the person moving from dim light to bright light? (1) 1.3.3 Describe the changes that took place in the eye that led to the diameter change indicated from 30 to 35 seconds. (3) 1.3.4 Draw a labelled diagram of the front view of the eye to illustrate pupillary mechanism when the light intensity is very high. (4) (9) Answer: 1.3.1 iris 1.3.2 (20 – 30) s 1.3.3 Radial muscles contract Circular muscles relax Pupil increases in diameter /dilates 1.3.4 Heading 1 mark *Pupil constricted 1 mark Any 2 correct labels 21 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.4 The diagram below illustrates how light refracted in the human eye leads to a visual defect. 1.4.1 Identify part: (a) B (b) C (2) 1.4.2 Name the visual defect that is illustrated in the diagram. (1) 1.4.3 Describe the consequences of the visual defect in your answer to QUESTION 1.4.2. (2) 1.4.4 Explain the consequences if the light rays were to fall on part A. (3) 1.4.5 Explain TWO ways in which the lens is structurally suited to perform its function. (4) Answer: 1.4.1 (a) B: Lens (1) (b) C: Choroid (1) 1.4.2 Long-sightedness (1) 1.4.3 Cannot see nearby objects clearly causing the image to be blurred (2) 1.4.4 No image will be formed /cannot see the object No receptors present Light will not be converted into an impulse (3) 1.4.5 Lens is elastic therefore can change shape /convexity/allow for accommodation Lens is transparent to allow light rays to pass through Lens is biconcave to refract/bend light rays (any 2 x 2) (4) 22 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 The HUMAN EAR The EAR houses receptors that are sensitive for hearing, but also plays an important role in the maintenance of balance in our bodies Know the parts and functions of the EAR How hearing takes place: Sound waves vibrations pressure waves Describe the pathway of sound waves until you hear: 23 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 HEARING: Sound waves are caught by the pinna And directed into the external auditory canal Sound waves hit against the tympanum(eardrum) and it starts to vibrate Vibrations are carried by the 3 bony ossicles to the oval window Oval window also vibrates The vibrations of the oval window cause the fluid in the inner to move, causing pressure waves Pressure waves (movement of the fluid) in the inner ear stimulates the receptors (hair cells in the Organ of Corti) in the cochlea Receptors become aware of the stimulus and convert it into an impulse The impulse is transmitted by the auditory nerve to the CEREBRUM, where hearing is interpreted. BALANCE: Describe the functioning of the human ear in BALANCE: 24 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Questions: HUMAN EAR 1.1 The diagram below represents the human ear. 1.1.1 Give the LETTER and NAME of the part that: (a) Transmits impulses to the brain (2) (b) Allows pressure to equalise between the outer ear and the middle ear (2) (c) A pressure wave in a liquid (2) (d) Releases pressure from the inner ear (2) 1.1.2 Give only the LETTER of TWO structures in the diagram of the ear that, when damaged, would result in the following: (a) when sound vibrations cannot be conducted through the outer and middle ear (2) (b) sound waves in the inner ear are not converted into nerve impulses (2) 1.1.3 Middle ear infection loorontsteking is a common cause for loss of hearing. Name ONE way which middle ear infection can be treated (1) Answer: 1.1.1 (a) F – auditory nerve (b) G – eustachian tube (c) E - cochlea (d) H – round window 1.1.2 (a) B ; C (b) E ; F 1.1.3 grommets or antibiotics 1.2 The diagram below represents the middle ear of humans. 1.2.1 Identify part: (a) A (1) (b) B (1) (c) C (1) 1.2.2 Explain the result if part E is blocked. (4) 1.2.3 Describe how the parts of the middle ear, including the membranes, assist with amplifying sounds. (3) 1.2.4 Explain why fusion of the ossicles may lead to hearing loss. (2) Answer: 1.2.1 (a) A Tympanic membrane (b) B Incus /Anvil (c) C Oval window (d) D Round window 1.2.2 Air will not be taken in /released 25 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 to equalise pressure on both sides of the tympanic membrane Tympanic membrane/ ossicles may not vibrate freely This may lead to the tympanic membrane bursting and therefore could lead to hearing loss /deafness/ pain (4) 1.2.3 The sound vibrations are transmitted from the large tympanic membrane to the smaller oval window through the ossicles which are arranged from largest to smallest This concentrates the vibrations, amplifying them (3) 1.2.4 The ossicles will not be able to vibrate and hence no vibrations will be passed to the inner ear /cochlea will not be stimulated/no amplification (2) 1.3 The diagram below represents a part of a human ear. 1.3.1 Identify part: (a) C (b) D (2) 1.3.2 Name the receptors that are found in part B. (1) 1.3.3 Describe how part B, the semi-circular canals, plays a role in maintaining maintaining balance when the body changes speed and direction. (6) 1.3.4 Describe how balance and equilibrium is maintained by the ear when a person changes his/her position of the head. (6) 1.3.5 A goalkeeper in a soccer match prevented a goal from being scored when he dived to his right after the ball was kicked towards him. Describe how he maintained his balance as he dived to save the ball. (6) Answer: 1.3.1 (a) C: Auditory nerve (b) D: Cochlea (1) 1.3.2 Cristae (1) 1.3.3 A change in speed/direction of movement stimulates the cristae The stimulus is converted to an impulse The impulse is transmitted to the cerebellum via the auditory nerve The cerebellum sends impulses to the muscles to restore balance (6) 1.3.4 A change in the position of the head stimulates the maculae The stimulus is converted to an impulse The impulse is transmitted to the cerebellum via the auditory nerve The cerebellum sends impulses to the muscles to restore balance (6) 26 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.3.5 A change in the direction and speed of the body causes the movement of fluid in the semicircular canals which stimulates the cristae A change in the position of the head stimulated the maculae The stimuli were converted into impulses which were transported along the auditory nerve and interpreted in the cerebellum which then sent impulses to the muscles to restore balance and equilibrium 1.4 Describe how the different parts of the ear and brain allow for hearing to occur. (7) The sound waves were directed by the pinna through the auditory canal to the tympanic membrane /eardrum causing it to vibrate The vibrations of the tympanic membrane were transferred to the ossicles in the middle ear which eventually caused the oval window to vibrate This set up pressure waves in the cochlea This stimulated the Organ of Corti in the cochlea to convert this stimulus into a nerve impulse which was then transmitted along the auditory nerve and interpreted in the cerebrum ENDOCRINE SYSTEM AND HOMEOSTASIS – PAPER 1, 34 marks Know the difference between an endocrine gland and an exocrine gland Endocrine glands: ductless glands that Exocrine glands – glands that release their release their secretions (hormones) secretions through ducts to a body cavity directly into the bloodstream. or to the outside eg. Ovaries, adrenal glands, pancreas , eg. salivary glands that secrete saliva hypophysis through ducts that open in the mouth cavity Hormones are chemical messengers. Hormones can stimulate (increase the secretion of hormones, allow a reaction to occur) or inhibit (slow down the secretion or stop the secretion) for a reaction Location of the following glands, the hormones they secrete: 27 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 Hypothalamus – ADH (controls water concentration in blood) Pituitary gland/hypophysis – Growth hormone, TSH, FSH, LH and prolactin Thyroid gland – thyroxin Pancreas – insulin and glucagon Adrenal gland – adrenalin, aldosterone Ovary – oestrogen, progesterone Testes - testosterone Homeostasis: the process of maintaining a constant, internal environment Negative feedback mechanism: operate in the human body to detect changes or imbalances in the internal environment and to restore the balance You should know and describe the negative feedback mechanism involving: Thyroxin levels Blood glucose levels (pancreas secreting insulin and glucagon) Blood carbon dioxide levels Water balance (osmoregulation) Salt levels Thyroxin and TSH – negative feedback Imbalance could be: Thyroxin levels are TOO HIGH: Thyroxin levels are TOO LOW: -Pituitary gland/hypophysis is stimulated -Pituitary gland/hypophysis is stimulated -To secrete LESS TSH -To secrete MORE TSH -Low TSH levels stimulates the thyroid -High TSH levels stimulates the thyroid gland gland -To secrete LESS thyroxin -To secrete MORE thyroxin -Thyroxin levels DECREASE -Thyroxin levels INCREASE -Back to normal -Back to normal Blood glucose levels Glucose levels in the blood are TOO Glucose levels in the blood are TOO LOW: HIGH: Pancreas is stimulated Pancreas is stimulated To secrete INSULIN into the blood To secrete GLUCAGON into the blood Insulin stimulates the conversion of Glucagon stimulates the conversion of excess glucose to glycogen which is stored glycogen back to glucose Glucose level in the blood decreases Glucose level in the blood INCREASES Back to normal Back to normal Have a careful look at these three terms: It is important that you do not confuse these terms with one another, and you have to spell them correctly or you will lose marks. Glucose Simplest sugar in the blood Glycogen Glucose is converted to glycogen and is stored in this form Glucagon The hormone that is secreted by the pancrea is blood sugar levels are too low 28 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 You only need to know how our body reacts when CO2 levels are too high: Regulation of water balance (osmoregulation): When blood has LESS water than normal: When blood has MORE water than normal: Hypothalamus is stimulated Hypothalamus is stimulated Send impulses to the pituitary gland Send impulses to the pituitary gland To secrete MORE ADH To secrete LESS ADH ADH increases the permeability of the ADH decreases the permeability of the renal tubules renal tubules MORE water is re-absorbed back into the LESS water is re-absorbed back into the blood blood Water level in blood returns to normal Water level in blood returns to normal The regulation of salt balance: Salt levels in the blood TOO HIGH: Salt levels in the blood TOO LOW: Adrenal gland is stimulated Adrenal gland is stimulated To stop secreting aldosterone/less To secrete MORE aldosterone aldosterone LESS salt is reabsorbed into the blood MORE salt is reabsorbed into the blood Salt level decreases Salt level increases Back to normal Back to normal Disorders caused by imbalance in the levels of: Imbalance of: Name of disorder Thyroxin Goitre (low levels of iodine) Blood glucose Diabetes mellitus Thermoregulation The role of: sweating vasodilation vasoconstriction 29 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 6 6 1 1 2 5 2 5 3 3 4 4 QUESTIONS: ENDOCRINE SYSTEM AND HOMEOSTASIS 1.1 The diagram below represents parts of the endocrine system in humans. 1.1.1 Identify gland: (a) A (b) B (c) C (3) 1.1.2 Give the LETTER and the NAME of the gland that secretes a hormoneresponsible for: (a) Starting puberty in males (b) Stimulating absorption of glucose by cells (c) Making the kidney tubules permeable to water (6) Answer: 1.1.1 (a) Hypophysis / Pituitary gland (b) Adrenal gland (c) Pancreas 1.1.2 (a) D - Testis (b) C - Pancreas (c) A – Hypophysis / Pituitary gland (9) 30 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.2 The diagram below represents the interaction between two important endocrine glands. The gland labelled A is found at the base of the brain, while the gland labelled C is present towards the front of the neck. 1.2.1 Give a label for gland A (1) 1.2.2 Name hormone B. (1) 1.2.3 State TWO functions of hormone D. (2) 1.2.4 Describe the negative feedback mechanism that operates when the level of hormone D is higher than normal in the blood. (5) 1.2.5 Describe the negative feedback mechanism that operates when the level of hormone D is lower than normal in the blood. (5) Answer: 1.2.1 A. Hypophysis / Pituitary gland (1) 1.2.2 B. TSH (1) 1.2.3 Controls metabolism Influences heart rate (2) 1.2.4 High levels of thyroxin are detected by the hypophysis which leads to a decrease in the secretion of TSH Activity of thyroid is slowed down /less thyroxin produced Thyroxin level drops to normal (5) 1.2.5 Low levels of thyroxin are detected by the hypophysis which leads to an increase in the secretion of TSH more thyroxin produced Thyroxin level rises to normal (5) 31 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.3 Study the flow diagram below. Identify: 1.3.1 Organ 1: (1) 1.3.2 Hormone 2: (1) 1.3.3 Hormone 3: (1) 1.3.4 The disorder caused when organ 1 fails to release sufficient amounts of hormone 2 (1) 1.3.5 Describe how the blood glucose level in the human body is returned to normal when the glucose level decreases to below normal. (4) 1.3.6 Describe how the blood glucose level in the human body is returned to normal when the glucose level increases to above normal. (4) Answer 1.3.1 Organ 1: Pancreas (1) 1.3.2 Hormone 2: Insulin (1) 1.3.3 Hormone 3: Glucagon (1) 1.3.4 Diabetes mellitus (1) 1.3.5 The pancreas /Islets of Langerhans is stimulated to secrete glucagon into the blood which stimulates the liver / muscles to convert glycogen into glucose The glucose level in the blood now increases and returns to normal (4) 1.3.6 The pancreas /Islets of Langerhans is stimulated to secrete insulin into the blood which stimulates the liver / muscles to convert glycose into glycogen The glucose level in the blood now decreases and returns to normal (4) 32 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.4 The diagram below represents one part of the negative feedback response that occurs when a person is dehydrated. The decrease in blood volume, as a result of the excessive loss of water, is detected by the brain. 1.4.1 Identify the (a) Hormone X (1) (a) Endocrine gland that secretes hormone X (1) (c) Target organ (1) 1.4.2 Describe the negative feedback response that occurs when a person is dehydrated, after it has been detected by the brain. (4) 1.4.3 Describe what happens when the blood has more water than normal (4) Answer: 1.4.1 (a) ADH (b) Hypothalamus / Pituitary gland / Hypophysis (c) Kidney 1.4.2 An increase in ADH causes the walls of the kidney tubule to become more permeable to water More water is reabsorbed and the blood volume increases Less urine is produced and the urine is more concentrated 1.4.3 A decrease in ADH causes the walls of the kidney tubule to become less permeable to water Less water is reabsorbed and the blood volume decreases More urine is produced and the urine is less concentrated (11) 33 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.5 Study the flow diagram below of a homeostatic mechanism used to regulate the concentration of salts in the human body. 1.5.1 Define homeostasis. (2) 1.5.2 Give the name of the following: (a) Organ A (1) (b) Gland B (1) (c) Hormone C (1) 1.5.3 Describe the response by the effector at D. (2) Answer: 1.5.1 The process by which the human body maintains a constant internal environment 1.5.2 (a) Kidney (b) Adrenal gland (c) Aldosterone 1.5.3 Walls of renal tubules become more permeable allowing for a greater re-absorption of sodium ions from the filtrate /into the blood capillaries (7) 1.6 Describe how the human body restores the carbon dioxide concentration the blood when it rises above normal levels. (6) Receptor cells in the carotid artery/aorta are stimulated to send impulses to the medulla oblongata in the brain which then stimulates the heart to beat faster and the breathing muscles /example to contract more actively This increases the rate/ depth of breathing More CO2 is taken to and exhaled from the lungs returning the CO2 level in the blood to normal. 34 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.7 The diagram below represents the skin of a person under different environmental conditions. 1.7.1 Identify part X. (1) 1.7.2 Give the LETTER of the diagram which represents the skin on a hot day. (1) 1.7.3 Name TWO visible reasons for your answer QUESTION 1.7.2. (2) 1.7.4 Name the part of the brain that regulates temperature. (1) 1.7.5 Name ONE hormone which will have the same effect as seen in diagram A. Answer: 1.7.1 sweat glands 1.7.2 B 1.7.3 vasodilation (widening) of blood vessels Sweat glands are active 1.7.4 hypothalamus 1.7.5 adrenaline Responding to the environment: Plants – Paper 1, 13 marks 35 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 The role of AUXINS in phototropism and geotropism: Question: 1.1 A Grade 12 learner performed an investigation to determine the effect of light on the growth of plant shoots. The learner divided the plants that were used into three groups as follows: Group A – The tip of the shoot was intact. Group B – The tip of the shoot was removed. Group C – The tip of the shoot was covered by a cap that does not allow light to pass through. The diagram below shows each shoot at the start of the investigation and next to each, the same shoot at the end of the investigation. The arrows indicate the direction of light in each investigation. 36 Life Sciences Gr 12 Cape Winelands Survival Kit – PAPER 1 2022 1.1.1 The influence of which plant hormone is being investigated? (1) 1.1.2 Explain the results observed in investigations A and C, as illustrated in the diagram above. (6) 1.1.3 Plants respond to gravity. Explain why the root grows in different directions when a pot plant is placed horizontally on the ground, receiving light equally from all directions. (6) Answer: 1.1.1 Auxins 1.1.2 In investigation A: Light from the right caused auxins to move to shaded side of the shoot leading to increased cell elongation and division There was therefore greater growth on the shaded side thus bending the shoot in the direction of the source of light In investigation C: Light has no influence on the distribution of auxins therefore the shoot grew upright 1.1.3 There is a high concentration of auxins on the lower side of the root which inhibits growth/cell elongation/cell division on the lower side There is a low concentration of auxins on the upper side of the root which stimulates growth/cell elongation/cell division on the upper side The upper side of the root grows faster /Uneven growth occurs causing the root to grow/bend downwards The root grows towards gravity /The root is positively geotropic 37