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Directorate: Curriculum FET
TELEMATICS 2019
LIFE SCIENCES
Grade 12
LIFE SCIENCES PROGRAMME FOR GRADE 12:
Life Sciences Telematics resource Grade 12 2019
2
Date Time Topics
18 February 2019 16h00 – 17H00 Scientific investigations, Protein synthesis, mutations
04 March 2019 15h00 – 16h00 Meiosis 15 April 2019 16h00 – 17h00 Senses and homeostasis
22 July 2019 15H00 – 16h00 Natural selection, Punctuated equilibrium and speciation
1. TIPS FOR WRITING LIFE SCIENCES
The external examination for Life Sciences consists of two (2) question papers of 150 marks each. Each question paper covers a variety of content topics. Ask your teacher for an outline of the content topics and weighting of each topic in each question paper.
The duration of each question paper is 2½ hours and all questions are COMPULSORY.
Each Life Sciences question paper consists of THREE sections i.e. SECTION A (50 marks), SECTION B (two questions of 40 marks) and SECTION C (20 marks).
When answering a multiple choice question in Section A read the question and four options carefully, evaluate each option and eliminate each incorrect option.
In questions that require only a LETTER you only need to write down a LETTER e.g. ‘Give only the LETTER of the molecule that carries the amino acid’. Other questions might require you to write down both the LETTER and a NAME, for example of a part from a diagram.
Use the correct spelling when you use biological terminology in your answers. Use scientific names in terminology and avoid using common names e.g. .
You need to do all your drawings and graphs in pencil and labels should be in blue or black ink. You may not use graph paper when drawing graphs.
Make sure that you have all the necessary stationery for your examination e.g. blue or black pens, a pencil, an eraser, a ruler, a non-programmable calculator, protractor and a compass.
SCIENTIFIC INVESTIGATIONS:
Life Sciences Telematics resource Grade 12 2019
3
What is a hypothesis? A hypothesis is an attempt to explain some event or observation using whatever information is currently available. It is a testable statement that may be accepted or rejected. A hypothesis must: (a) have two variables (dependent and independent variables); (b) state the relationship between the two variables; (c) be testable; and (d) state the independent variable first (cause) and then the dependent variable (effect).
Variables:
Controlled / fixed variable – refers to the factors that should be kept constant so that the results of an investigation can be considered valid.
Independent variable – refers to the factor that is being investigated. This factor is usually manipulated by the investigator either at the start of or during the course of the investigation. The independent variable appears on the X-axis of a graph.
Dependent variable – refers to the effect of the independent variable. This effect is usually measured in some way and appears on the Y-axis of a graph What is reliability?
The idea behind reliability is that any significant results of an investigation must be more than a once-off finding and be repeatable.
For the questions which required learners to state how the reliability of the investigation could have been improved, the following answers apply: Repeat the investigation OR Increase the sample size.
What is validity?
Validity questions show how the experiment/investigation was carried out. It is important to be sure that all the factors/variables have been controlled/ fixed except the variable/factor being tested.
In questions which require learners to suggest some factors that might have decreased the validity of an investigation, the answers should centre on the criticism of the scientific process; for example, some factors/variables that were not fixed/controlled when carrying out the investigation.
Question:
NOTE: Independent and dependent variables should be identified from the AIM of the investigation.
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Protein synthesis is the process whereby proteins are made in living cells of an organism to form enzymes, hormones and new structures for cells. Amino acids are the basic building blocks of proteins. The nucleic acids DNA and RNA are involved in protein synthesis. The main steps of protein synthesis are transcription and translation.
Question:
Cell structure
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The nucleus of the cell consists of the nuclear membrane,
nucleoplasm, nucleolus and
chromatin network (which forms
chromosomes)
DNA is found in the nucleus of the cell and
forms part of chromosomes
Ribosomes are mainly found in the
cytoplasm of the cell and are sites of
protein synthesis
RNA is found in the niucleus and
cytoplasm of a cell and plays a role in protein synthesis
Life Sciences Telematics resource Grade 12 2019
6
Name and describe the process occurring in the nucleus which results in the formation of an mRNA molecule. Alternative question: Describe the process of transcription. Answer: The process is transcription The double helix DNA molecule unwinds When the hydrogen bonds breakthe DNA molecule unzips/2 DNA strands separate One strand is used as the template to form mRNA using free RNA nucleotidesfrom the nucleoplasm The mRNA is complementary to DNA/A-U, C-G This process is controlled by enzymes Question: Describe the process of translation. Answer: Each tRNA carries a specific amino acid tRNA carries the amino acid to the ribosome When the anticodon on the tRNA matches the codon on the mRNA Amino acids become attached in the sequence determined by the mRNA by peptide bonds to form the required protein Question:
Name/Give: Write down the answer without
further discussion
Describe: State in words the main points of a process or
structure or phenomena
Note: When answering questions with diagrams:
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Life Sciences Telematics resource Grade 12 2019
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(a) Parts A and B (1) (b) Part C (1) 3.2 Name the receptor found in part C. (1) 3.3 Explain TWO ways in which part A in the diagram is structurally suited to maintain balance. (4) Answers: 3.1 (a) Cerebellum (b) Cerebrum 3.2 Organ of Corti 3.3 The semi-circular canals/part A contain fluid/endolymph which moves when the person moves There are cristae present which convert the stimulus to an impulse/are sensitive to the movement of the fluid The canals lie on three different planes to detect movement in any directionQuestion: 4. While walking in the bush a boy hears a sound which he thinks is the roar of a lion. He immediately runs to safety. Describe how he hears the sound. Answer: 4. The pinna traps/directs the sound wavesinto the ear canal/meatus This causes the tympanic membrane to vibrate The vibration is transmitted to the auditory ossicles The ossicles amplify the vibrationand transmit it to the oval window The oval window vibratescreating wavesin the fluid/endolymph of the cochlea which stimulates the Organ of Cortito convert the wave into an impulse The impulse travels along the auditory nerveto the cerebrumwhere sound is interpreted
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Life Sciences Telematics resource Grade 12 2019
17
HOMEOSTASIS
Homeostasis is the process of maintaining a constant internal environment within the body. The internal environment refers to the blood and tissue fluid that surrounds the cells of the body. Homeostasis enables the body to function efficiently, despite changes that might occur in the external or internal environment. Changes in temperature, glucose levels, carbon dioxide levels, water levels and salt levels of the internal environment affects the homeostatic balance of the body. Negative feedback mechanisms operate in the human body to detect changes or imbalances in the internal environment and to restore the balance. Homeostatic control of blood sugar levels The pancreas, located just below the stomach, is composed of two types of cells:
Normal pancreatic cells that secrete digestive juice (pancreatic juice) which contains `enzymes for digestion.
The islets of Langerhans that secrete two hormones, namely insulin and glucagon. The pancreas is both an exocrine gland (secretes pancreatic juice into a pancreatic duct which opens in the duodenum) and endocrine gland (secretes the hormones namely, insulin and glucagon directly into the bloodstream).
Revise Homeostatic
control
(Grade 11)
Gaseous exchange:
Homeostatic control of breathing
Excretion:
Homeostatic control of water and
salts
Nutrition:
Hormonal control of
blood sugar levels
Hormones are organic chemical messengers secreted by endocrine glands into the bloodstream where it is transported to cells and organs on which it has a specific regulatory effect.
Exocrine glands release their secretions in ducts. Endocrine glands release their secretions directly into the bloodstream
Life Sciences Telematics resource Grade 12 2019
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Control of blood sugar levels (glucose concentration in blood)
When the glucose level in the blood increases above normal, the pancreas is stimulated The pancreas secretes insulin into the blood Insulin travels in the blood to the liver and stimulates the conversion of glucose to glycogen
which is then stored The glucose level in the blood decreases and returns to normal
When the glucose level in the blood decreases below normal levels, the pancreas is stimulated
The pancreas secretes glucagon into the blood Glucagon travels in the blood to the liver and stimulates the conversion of stored glycogen to
glucose The glucose level in the blood increases and returns to normal.
Homeostatic control of breathing
Receptor cells in the carotid artery and in the wall of the aorta are very sensitive to changes in the carbon dioxide concentration in the blood.
When the carbon dioxide level in the blood increases e.g. after or during exercise, the receptor cells in the carotid artery and wall of the aorta are stimulated
These receptors send nerve impulses to the medulla oblongata in the brain The medulla oblongata sends nerve impulses to the diaphragm and intercostal muscles
(breathing muscles) to contract more actively and increasing the rate and depth of breathing The medulla oblongata also sends nerve impulses to the heart muscle to increase the heart
rate More carbon dioxide is transported to the lungs and exhaled from the lungs The carbon dioxide level in the blood returns to normal.
Homeostatic control of water content of the blood (osmoregulation)
The hormone ADH (anti-diuretic hormone), secreted by the hypophysis (pituitary gland),
regulates the water content of the blood.
The hypophysis is an endocrine gland at the base of the brain that secretes a number of hormones in the blood.
Glucose – a carbohydrate and building block of some carbohydrates Glycogen – a carbohydrate and the storage form of glucose Glucagon –hormone that increases the blood glucose level
Life Sciences Telematics resource Grade 12 2019
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When the blood has less water than normal e.g. when a person is active and sweating a lot or taking in very little liquids
The hypothalamus is stimulated and sends impulses to the hypophysis to secrete more ADH ADH travels in the blood to the kidneys and makes the walls of the distal convoluted tubules
and collecting ducts more permeable to water More water is re-absorbed from the tubules and is passed to the surrounding blood vessels Urine becomes more concentrated and its volume decreases The water level in the blood increases and returns to normal
When the blood has more water than normal e.g. when a person is inactive and sweating less or taking in a lot of liquids
The hypothalamus is stimulated and sends impulses to the hypophysis to secrete less ADH Less ADH travels in the blood to the kidneys and the walls of the distal convoluted tubules and
collecting ducts become less permeable to water Less water is re-absorbed from the tubules and is passed to the surrounding blood vessels Urine becomes less concentrated (dilute) and its volume increases Large amount of water is excreted in the urine The water level in the blood decreases and returns to normal Homeostatic control of salt balance of the blood
The hormone aldosterone, which is secreted by the adrenal gland regulates the
concentration of salts e.g. sodium ions in the blood.
When the salt concentration in the blood becomes too low
The adrenal gland is stimulated to secrete more aldosterone Aldosterone increases the re-absorption of sodium ions from the distal convoluted tubules and
collecting duct into the surrounding blood vessels The concentration of sodium ions in the blood vessels increases and returns to normal.
When the salt concentration in the blood becomes too high
The adrenal gland is stimulated to secrete less aldosterone The re-absorption of sodium ions from the distal convoluted tubules and collecting duct into the
surrounding blood vessels decreases The concentration of sodium ions in the blood vessels decreases and returns to normal.
Adrenal glands are endocrine glands located at the top of each kidney
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