0653 Combined Science Notes

Biology

B1. Characteristics of Living Organisms

• Living organisms share seven characteristics, which can be remembered using the acronym "MRS. GREN."

  • Movement: An action causing a change of position or place.

  • Reproduction: Processes that make more of the same kind of organism.

  • Sensitivity: The ability to detect and respond to changes in the environment.

  • Growth: Permanent increase in size and dry mass by an increase in cell number, cell size, or both.

  • Respiration: Chemical reactions in cells that break down nutrient molecules and release energy.

  • Excretion: Removal of toxic materials and substances in excess of requirements from organisms; waste products of metabolism.

  • Nutrition: Taking in materials for energy, growth, and development.

B2. Cells

• Living things are made of cells.

• Cells are very small and can only be seen under a microscope.

• Two types of cells: plant and animal cells.

• Similarities between plant and animal cells: both contain a cell membrane, cytoplasm, and nucleus.

• Differences: plant cells additionally contain a cell wall, chloroplasts, and a sap vacuole.

Cell Structures and Functions

• Cell wall: Non-living, thick, rigid layer surrounding the cell, made of cellulose. It gives the cell its shape (angular, rectangular, or rounded), prevents bursting, and allows the plant to support itself. Permeable to all substances.

• Cell membrane: Partially permeable membrane that controls the movement of substances into and out of the cell.

• Cytoplasm: Jelly-like substance made up of mostly water and structures where metabolic reactions occur.

• Chloroplasts: Green discs containing chlorophyll, which traps sunlight for photosynthesis.

• Nucleus: Controls all activities of the cell.

• Sap vacuole: Large room in the center of the cell containing cell sap, which stores dissolved sugars, mineral salts, and amino acids. It also controls the movement of water in and out of the cell.

Cell structure and Function

• Ciliated cells:

  • Found lining the trachea and bronchi.

  • Move mucus upwards to the back of the throat to trap bacteria and dust particles.

  • Mucus is swallowed to the stomach where acid kills the bacteria.

• Root hair cells:

  • Found near the ends of plant roots.

  • Absorb water and mineral salts from the soil.

  • Adapted with a large surface area, a large number of mitochondria, and a concentrated vacuole to support the absorption of water by osmosis.

• Xylem Vessels:

  • Found in stems, roots, and leaves of plants.

  • Transport water and mineral salts; help in support.

• Palisade mesophyll cells:

  • Found beneath the epidermis of a leaf.

  • Facilitate photosynthesis with closely-packed, long, cylindrical cells containing numerous chloroplasts for maximum light absorption.

• Nerve cells:

  • Found throughout the bodies of animals.

  • Transmit information in the form of electrical impulses.

• Red blood cells:

  • Found in the blood of mammals.

  • Transport oxygen.

• Sperm and egg cells:

  • Sperm in testes and egg cells in ovaries.

  • Sperm cells have a tail for swimming, a head with digestive enzymes, and a middle piece with numerous mitochondria to provide energy.

  • Egg cells (ova) possess a yolk which acts as a food store, and their spherical shape allows cilia lining the oviducts to easily move the ovum.

Calculating Magnification

• Magnification $= \frac{size \ of \ drawing}{size \ of \ real \ object}$ in mm

Movement In and Out of Cells

• Diffusion:

  • Net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

• Osmosis:

  • Net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane.

• Water moves into and out of cells by osmosis through the cell membrane and enters the roots by osmosis.

• Water potential:

  • Measure of the tendency of water molecules to move from one region to another.

• Dilute solutions have a higher water potential than concentrated solutions; pure water has the highest water potential.

• Immersing plant tissues in concentrated solutions makes them smaller (flaccid) due to water moving out.

• Immersing plant tissues in pure water can make them bigger (turgid) due to water moving in.

• Cell walls in plant cells prevent them from bursting, unlike animal cells.

B3. Biological Molecules

• Chemical elements that makeup:

  • Carbohydrates: carbon, hydrogen, and oxygen only.

  • Fats: carbon, hydrogen, and oxygen (less oxygen than in carbohydrates).

  • Proteins: carbon, hydrogen, oxygen, and nitrogen; sometimes contain sulfur and phosphorus.

• Large molecules are made from smaller molecules:

  • Starch and glycogen are made from glucose.

  • Proteins are made from amino acids.

  • Fats and oils are made from fatty acids and glycerol.

Food Tests

• Test for starch (Iodine test):

  • Add iodine solution (brown) to the sample.

  • If starch is present, the sample will turn blue-black.

• Test for reducing sugars (Benedict’s test):

  • Add Benedict’s solution to the sample and mix thoroughly.

  • Heat the mixture in a boiling water bath for 5 minutes.

  • The color of the solution changes from blue to green to yellow to orange to brick-red if reducing sugar is present.

• Test for proteins (Biuret test):

  • Add copper sulfate solution to a solution of the food sample, followed by either sodium or potassium hydroxide solution (Biuret reagent can also be used).

  • If proteins are present, a color change from blue to purple will be observed.

• Test for fats and oils (Ethanol emulsion test):

  • Dissolve fats in the sample by adding ethanol, then add water to the ethanolic mixture.

  • Fats will form a cloudy white emulsion.

• A table summarizing the food tests

• Water: About 70% of your weight is water. Water is an essential nutrient. The functions of water include:

  • As a solvent which dissolves reactants of metabolic reactions.

  • As a component of blood plasma in which red blood cells, nutrients, hormones and other materials are carried in.

  • It helps in lowering the body temperature in hot conditions in the form of sweat on the skin. The sweat evaporates using heat energy from the body, thus lowering the temperature.

B4. Enzymes

• Enzymes are proteins that function as biological catalysts, speeding up the rate of chemical reactions without being altered in the reaction.

• They are substrate-specific, and function using the lock and key hypothesis.

• Active site: Region on an enzyme molecule that the substrate binds to; usually a groove on the surface of the enzyme; only the correct substrate is able to fit into the active site.

• Enzyme action begins when the substrate molecule binds to the active site of the enzyme to form an enzyme-substrate complex, then the substrate is converted into product molecules. The product molecules depart from the active site, leaving the enzyme free to catalyse another reaction.

Factors Affecting Enzyme Activity

• Temperature:

  • At low temperatures, the rate of a reaction is very low because substrate particles are moving too slowly to react.

  • As the temperature increases, the rate of enzyme activity increases.

  • Enzyme activity increases up to an optimum temperature, beyond which it starts decreasing.

  • At extremely high temperatures, the enzyme is completely denatured and the rate of reaction drops to zero.

• pH:

  • Enzyme activity is highest at the optimum pH of the enzyme.

  • As the pH increases or decreases from the optimum, enzyme activity sharply decreases due to changes of shape of active site as the enzyme is denatured.

  • At extreme pH levels, the enzyme is completely denatured and the rate of reaction drops to zero.

  • The optimum pH differs for each enzyme.

B5. Plant Nutrition

• Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light.

• Word equation:

  • carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll

• Balanced chemical equation:

  • $6CO<em>2 + 6H</em>2O \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2$

• Chlorophyll converts light energy into chemical energy in molecules; chemical energy is then used for the synthesis of carbohydrates.

• Glucose, the product of photosynthesis, is the most important food of the plant.

• Plants make other nutrients from glucose, which is transported to other parts of the plant as sucrose, where it can be converted back to glucose for respiration, and part of it into starch for storage.

• Growing cells make cellulose for cell walls from sucrose.

• Fruits use the sucrose to make the attractive scent and tasty nectar to attract insects.

Importance of Photosynthesis

• Converts light energy from the Sun to chemical energy in the form of glucose, which can then be used by plants and animals.

Subsequent Use and Storage of Carbohydrates

• In the day, the leaf produces more glucose than can be removed. The excess glucose is then converted into starch and stored in the leaf, or converted to sucrose and transported to other parts of the plant via the phloem.

• At night, starch stored in the leaf is then converted to glucose for respiration. Excess glucose is converted to sucrose before being transported out of the leaf for use by other parts of the plant, or converted to starch for storage in the various storage organs.

• The stored starch can be used to make cellulose.

• Photosynthesis ensures that living things have a constant supply of oxygen.

Factors Affecting Photosynthesis

• The rate of photosynthesis increases as the amount of water, concentration of carbon dioxide, temperature and light intensity increase.

• Submerged aquatic plants can have reduced photosynthesis due to events like eutrophication which cause growth of algae on the surface of water bodies resulting in reduced light intensity reaching the submerged aquatic plants.

Leaf Structure

• Features to identify: chloroplasts, cuticle, guard cells and stomata, upper and lower epidermis, palisade mesophyll, spongy mesophyll, vascular bundles, xylem and phloem in leaves.

Palisade Mesophyll Cells

• Function is to facilitate photosynthesis, containing numerous chloroplasts to allow maximum absorption of light.

• Chloroplast arrangement ensures efficient sunlight absorption.

Stomata, Spongy Mesophyll Cells, and Guard Cells for Gas Exchange

• Spongy mesophyll cells have air spaces to allow for fast diffusion of carbon dioxide to all photosynthetic cells.

• Guard cells control the opening and closing of the stoma, allowing carbon dioxide to diffuse in, oxygen to diffuse out, and water vapor to escape.

• Plants open their stomata during the day for carbon dioxide intake and close them during the night to minimize water loss through transpiration.

• Guard cells control the opening and closing of stomata through regulation of water potential within themselves.

Xylem for Transport and Support

• The xylem transports water and mineral salts from the roots to the leaves.

• The xylem also adds mechanical support to the plant since its walls are made of strong cellulose and lignin

Phloem for Transport

• The function of the phloem is to transport sugars and amino acids from the leaves to other parts of the plant.

Importance of Nitrate and Magnesium Ions

• Magnesium ions ($Mg^{2+}$): Important for the production of chlorophyll. Lack of it results in lack of photosynthesis and yellowing between the veins of leaves.

• Nitrates: Source of nitrogen, required to make amino acids and proteins. Lack of it results in weak growth and yellowing of the leaves.

• Both mineral ions are absorbed from the soil.

B6. Animal Nutrition

• A balanced diet is a diet which contains all of the nutrients in reasonable proportions.

• Nutrient Sources and Dietary Importance

A table summarizing the function, source, and dietary importance of key nutrients:

Dietary Needs Based on Individual Factors

• Pregnant Women:

  • Need diets rich in protein, iron, calcium, and vitamin D for fetal development.

• Breast-Feeding Women (Lactation):

  • Require high protein, calcium, and vitamin diets to promote healthy infant growth.

• Growing Children (Passing Puberty):

  • Need extra proteins to develop cells and enzymes, calcium and vitamin D for bone development, and iron for haemoglobin synthesis.

• Other Considerations:

  • Men need more energy than women.

  • Teenagers need more energy, proteins, and calcium than adults.

  • Blue collar (industrial) workers need more energy than white collar (office) workers.

Effects of Malnutrition

• Is a consequence of an unbalanced diet, rich in some nutrients and low in others or even lacking.

  • Starvation: Body feeds on itself, first breaking down fats then proteins from muscles to release energy. Usually present in countries with famines.

  • Obesity: Eating too much of every nutrient, especially carbohydrates and fats, which can lead to high blood pressure, cardiac diseases, diabetes, stress on joints and bones, and psychological issues.

  • Constipation: Lack of fibre in the diet causes undigested matter to lack bulk, resulting in poor peristalsis and dry, hard stools.

  • Coronary heart disease: Over consumption of carbohydrates and fats leading to fatty deposits in organs and arteries.

  • Scurvy: Caused by a deficiency of vitamin C, with symptoms including bleeding gums.

  • Rickets: (soft and deformed bones) is the deficiency disease of both vitamin D and calcium. Bones are made of calcium, which vitamin D helps to deposit in the bones. If either calcium or vitamin D is lacking in the diet, rickets is developed.

  • Anemia: Is the deficiency disease of iron. The amount of haemoglobin decreases due to iron deficiency. This causes short breath and tiredness.

Alimentary Canal

• Ingestion: Taking substances (food and drink) into the body through the mouth.

• Digestion: Breakdown of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes.

• Mechanical digestion: Breakdown of food into smaller pieces without chemical change using teeth.

• Chemical digestion: Breakdown of large, insoluble molecules into small, soluble molecules by enzymes in the alimentary canal; saliva assists.

• Absorption: Movement of small food molecules and ions through the wall of the intestine into the blood, in small intestine

• Egestion: Passing out of undigested or unabsorbed food as feces through the anus.

• Main Regions of the Alimentary Canal: Mouth, salivary glands, oesophagus, stomach, small intestine, pancreas, liver, gall bladder, large intestine, anus.

Digestion Functions and Journey

• The significance of chemical digestion is that it produces small, soluble molecules that can be absorbed.

Journey of food from the mouth to the anus

1. Ingestion: Taking in pieces of food into the mouth

2. Digestion: The breakdown of large, insoluble food particles into smaller more soluble ones by chemical and mechanical means.

3. Absorption: Taking the digested food molecules from the alimentary canal and into the bloodstream

4. Assimilation: Movement of digested food molecules into cells where they are used e.g. to release energy or growth etc.

5. Egestion: The elimination of undigested food materials through the anus Don’t confuse egestion with excretion; excretion is to get rid of waste products of metabolism.

Enzymes in the Human Alimentary Canal

• Amylase: breaks down starch to simpler sugars (e.g., maltose).

• Protease: breaks down protein to amino acids.

• Lipase: breaks down fats to fatty acids and glycerol.

• Secreted:

• Amylase: in the mouth by salivary glands.

• Protease: in the small intestines.

• Lipase: in the small intestines.

Hydrochloric Acid

• In gastric (stomach) juices kills bacteria in food and gives an acid pH for enzymes to work well.

B7. Transport

Transport in Plants

• Xylem: Conducts water and dissolved mineral salts from the roots to the stems and leaves; provides mechanical support to the plant.

• Phloem: Transports manufactured food (sucrose and amino acids) from the leaves to other parts of the plant (e.g., the roots and flowers).

• Root hair cells take in water and minerals from the soil, then xylem vessels take this water to all parts of the plant.

• Water travels from the root to the stem and then to the leaf. The large surface area of root hairs increases the rate of the absorption of water.

• The pathway of water through parts of a plant can be investigated using stained water.

Transpiration

• Is the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.

• Factors affecting transpiration

  • Light intensity – transpiration is greater in light than in darkness

  • Temperature – as temperature increases, the rate of transpiration also increases

  • Humidity of the atmosphere – transpiration is low when the level of humidity is high

Explain the effects of variation of temperature, and humidity on transpiration rate

• Humidity: higher humidity means more water vapour in the air, which means water vapour has a higher concentration in the atmosphere than inside the leaf, so transpiration will be much slower because the diffusion of water vapour outside the leaf will be slow. The higher the humidity the slower the transpiration. [Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient, as a result of their random movement].

• Temperature: when the temperature is high, molecules move faster and evaporate faster, so transpiration rate increases. The higher the temperature the faster the transpiration.

Transport in Mammals (Circulatory System)

• The is a system of blood vessels with a pump and valves to ensure one- way flow of blood.

• Double Circulation: Humans have a double circulation system i.e circulation to the lungs and circulation to the body tissues. There is a low pressure circulation (between the heart and the lungs) and a high pressure circulation (between the heart and the rest of body).

• Advantages of double circulation

  • Oxygenated and deoxygenated blood are separated

  • Low pressure circulation prevents lung damage

  • High pressure circulation ensures oxygenated blood reaches all parts of the body

• Cardiac Cycle Steps:

1. Muscles of the atria relax allowing blood to enter the heart. Atrioventricular valves (bicuspid and tricuspid valves) open. Semilunar valves closed.

2. Muscles of the atria contract whilst muscles of the ventricles remain relaxed. Atrioventricular valves open. Semilunar valves closed. Blood is moved from atria to ventricles.

3. Muscles of the atria relax whilst muscles of the ventricles contract. Atrioventricular valves closed. Semilunar valves open. Blood moves out of the heart.

• Naming blood vessels to and from the heart: vena cava, aorta, pulmonary artery and pulmonary vein.

• Blood vessels to and from the lungs: pulmonary artery and pulmonary vein.

Blood Vessels and Blood

• Coronary Heart Disease: Caused by the blockage of coronary arteries; possible risk factors include diet high in fats or cholesterol, stress, smoking, genetic predisposition, age, and gender.

• Physical activity increases both the pulse and heart rate.

Function and Structure of Blood Vessels

• Arteries

  • Transport blood away from the heart to the lungs or other parts of the body. Blood in the arteries has high pressure. Arteries have a strong thick wall which is elastic and stretchable to withstand this high pressure and the lumen of arteries is very narrow.

• Veins

  • Transport blood from the body to the heart. The veins always have low blood pressure. To prevent backflow, veins have valves. Since veins have low blood pressure, they don’t need strong, thick walls like the arteries, instead they have thin and less elastic walls. Their lumen is much wider too.

• Capillaries.

  • Collect nutrient filled and oxygenated blood from the arteries and bring this blood closer to body cells. Collect nutrient filled and oxygenated blood from the arteries and bring this blood closer to body cells; also link arteries with veins. One cell think to reduce the diffusion distance of materials thus promoting faster diffusion and have pores in their walls between the cells, to allow the plasma to get out of the blood and become tissue fluid.

  *Components of blood include red blood cells, white blood cells, platelets and blood plasmaIdentifying red and white blood cells, as seen under the light microscope, on prepared slides and in diagrams and photomicrographs

Stating the functions of certain components of blood

1. Red blood cells transports oxygen from the lungs to the body cells; contain haemoglobin and are fully adapted to their function by the following characteristics:

   • Biconcave disc shape gives it large surface area to carry more oxygen

   • Haemoglobin to combine with oxygen

   • No nucleus that takes up space

2. White Blood Cells are part of the Immune System. Their role is to protect the body by killing bacteria which cause disease, also known as pathogens. White blood cells are much bigger than red blood cells, have a nucleus, and are present in fewer amounts. There are two types of white blood cells namely phagocytes and lymphocytes. Phagocytes important in phagocytosis (the process of killing bacteria by engulfing them, and digesting them using enzymes). Lymphocytes important in antibody production (Lymphocytes kill bacteria by secreting antibodies which kill the pathogens. Each pathogen is killed by a specific type of antibody).

3. Platelets prevent bleeding by causing clotting when the skin is injured.

4. Blood plasma makes up most of the blood and transports blood cells, ions, hormones, soluble nutrients, hormones and carbon dioxide from one place to another.

B8. Gas Exchange and Respiration

Gas Exchange

Naming and identifying parts in the respiratory system:

• Lung, diaphragm, ribs, intercostal muscles, larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries

• Air inhaled moves from nostril to larynx to trachea to either of two bronchi to bronchioles and then to alveoli (singular: alveolus). Bronchi form many smaller bronchioles. Bronchi, bronchioles and alveoli are in the lung.

Differences in Composition between Inspired and Expired Air

• Gas Inspired Air Expired Air

• Oxygen 21% 16%

• Carbon dioxide 0.04% 4%

• Water vapour Variable High

• Describing the factors related in the surface areas:

  • Large surface area for faster diffusion

  • Thin surface to make diffusion distance shorter and faster. Both the alveoli and capillaries are one cell thick.

  • Good blood supply and

  • Good ventilation with air

• Explaining the differences in composition between inspired and expired air

  • Oxygen decreases in exhaled air because some of it is used by body cells in respiration.

  • Carbon dioxide increases because respiring cells produce carbon dioxide which is then exhaled.

  • Exhaled air contains more water vapour because gas exchange surfaces are made of living cells which must be kept moist; some of this moisture evaporates into the air.

• Using limewater as a test for carbon dioxide to investigate the differences in composition between inspired and expired air: Exhaled air turns lime water more milky because of its high carbon dioxide content.

• Investigating and describing the effects of physical activity on rate and depth of breathing: Generally, the rate and depth of breathing increase with physical activity. An increased carbon dioxide concentration in the blood causes an increased rate and depth of breathing.

• Explaining the role of goblet cells, mucus and ciliated cells in protecting the gas exchange system from pathogens and particles:

  • Ciliated cells: Ciliated cells are present in the trachea and bronchi of our respiratory system. Their function is to use their cilia to move mucus up the trachea to the throat. The mucus traps bacteria and dust particles. When it reaches the throat, the mucus is swallowed to the stomach where the stomach acid kills the bacteria.

  • Goblet cells and mucus: The mucus used to trap bacteria and dust particles is secreted by goblet cells which are next to ciliated cells.

  • Tobacco smoking can cause chronic obstructive pulmonary disease (COPD), lung cancer and coronary heart disease Describing the effects on the gas exchange system of tobacco smoke and its major toxic components, limited to carbon monoxide, nicotine and tar Effects of Smoking tobacco

  • :Cilia can’t vibrate anymore, the air inhaled isn’t clean. Goblet cells release more mucus which makes the trachea narrower.Smoke particles get trapped inside the lungs. White blood cells try to remove them by secreting chemicals which unfortunately end up doing serious damage to the lungs resulting in chronic obstructive pulmonary disease (COPD).

  • Nicotine increases heart beat rate and blood pressure

  • Nicotine makes blood vessels get narrower. This can increase blood pressure, leading to hypertension.Carbon monoxide combines with haemoglobin in red blood cells. This reduces the amount of oxygen carried by blood to body cells because red blood cells end up carrying carbon monoxide (which binds with haemoglobin much easily and strongly than oxygen).

  • Tar contains carcinogens (cancer causing chemicals).

Respiration

• The uses of energy in the body of humans: Energy in the human body is used for muscle contraction, protein synthesis, growth and the maintenance of a constant body temperature.Defining aerobic respiration Aerobic respiration refers to chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.

• Stating the word and balanced chemical equation for aerobic respiration

• Word equation for aerobic respiration is Glucose + oxygen → carbon dioxide + water

• Balanced chemical equation for aerobic respiration is$C<em>6H</em>{12}O<em>6 + 6O</em>2 → 6CO<em>2 + 6H</em>2O$

B9. Coordination and Response

Hormones in Humans

• A hormone is a chemical substance, produced by a gland, and carried by the blood, which alters the activity of one or more specific target organs.

• Adrenaline is the hormone secreted in ‘fight or flight’ situations. Its effects are to increase breathing and pulse rate, as well as to widen the pupils.

• The role of the hormone adrenaline in the chemical control of metabolic activity, including increasing the blood glucose concentration and pulse rate;When adrenaline reaches the heart it causes the cardiac muscle to contract and relax rapidly so that oxygen and glucose reach the muscles of the body faster. Adrenaline also makes the liver convert glycogen into glucose and secrete it into the blood to be used in respiration. When adrenaline reaches the diaphragm and the intercostal muscles of the ribs, it makes them contract and relax faster too to increase rate of breathing. These changes cause an increase in the respiration rate so that lots of energy is being released.Giving examples of situations in which adrenaline secretion increases

• adrenaline is released in Fight and flight situations.

Tropic Responses

• Tropisms are directional growth responses to environmental stimuli

• Gravitropism is a response in which parts of a plant grow towards or away from gravity.

• Phototropism is a response in which parts of a plant grow towards or away from the direction from which light is coming.

• Since auxin is a chemical, phototropism and gravitropism of a shoot are examples of the chemical control of plant growthInvestigating gravitropism and phototropism in shoots and roots A seed is pinned in the dark as shown. The shoot will bend upwards whilst the root bends downwards due to gravitropism. The shoot displays negative gravitropism whilst the root displays positive gravitropism.; explaining the role of auxin in controlling shoot growth

• Auxin is made only in the tip of a shoot from where it spreads through to the plant. Auxin stimulates cell elongation/ growth. Auxin is only produced by the growing tip of the plant. If this is removed, growth ceases. The shoot is displaying negative gravitropism.: the root and shoot are displaying gravitropism. Tropism can be positive or negative. Positive tropism means growing towards. Negative tropism means growing away from. The root is displaying positive gravitropism.

B10. Reproduction

Asexual and Sexual Reproduction

• Asexual Reproduction: Asexual means not sexual. This means that this kind of reproduction does not involve sex. Asexual reproduction is the production of genetically identical offspring from one parent. It is simply a single organism growing a new organism from itself e.g. in bacteria, fungi and potato plants.Bacteria reproduce by a process called binary fission; the sporangium of Fungi produce productive structures called spores that can grow into other fungi; A potato plant starts as a lateral bud which grows from a potato tuber under the soil.

• Sexual reproduction: Sexual reproduction is a process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote and the production of offspring that are genetically different from each other.

Sexual Reproduction in Plants:

• Identifying and drawing the sepals, petals, stamens, filaments and anthers, carpels, style, stigma, ovary and ovules, of an insect-pollinated flower

• Functions of certain parts of a flowerSepals – Protect the flower when it is in bud stage; Petals –They are brightly coloured in insect-pollinated plants to attract insects, and form a platform for insects to land on; Anther – Contains pollen grains. Pollen grains in insect-pollinated plants are heavy and sticky; Stigma – Receptor of pollen grains. Secretes a fluid that stimulates germination of pollen grains; Ovary – Each ovary contains one or more ovules; Ovule – Contains female gametes.Identifying and describing the anthers and stigmas of a wind pollinated flower Distinguishing between the pollen grains of insect pollinated and wind-pollinated flowers

• Methods of Pollination: Pollination is the transfer of pollen grains from the male part of a flower (anther) to the female part of a flower (stigma). There are two methods of pollination, insect pollination and wind pollination. Some flowers pollinate by insects while others pollinate by wind. Part of flower Insect pollinated Wind pollinated

Stating and distinguishing flowers and methods of pollination

• Pollen grains: Fairly abundant, large and sticky. Sticky so that they easily attach to insects Very abundant, small and light so that wind easily carries them. Fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule Describing the structural adaptations of insect and wind pollinated flowers

• Insect pollinated: Brightly coloured and large petals to attract insects. Strong attractive scents to attract insects.Sticky or spiky pollen grains to attach pollen to bodies of insects. Contain nectarines (at the base of petals) to attract insects. Stigma inside flower such that insects brush past it to reach nectar. Produce fairly large quantities of pollen because some will be eaten or delivered to the wrong flower

• Wind pollinated. Small dull petals/ no petals at all. No scent . Smooth and light so that it travels easily in air. No nectaries. Large stigmas which hang outside the flower to capture pollen grains carried by the wind. Anthers hang outside the flower to easily distribute pollen grains in air. Produce very large quantities of pollen because some of it is blown away and lost