Form 3 & 4 Biology: Cells and Organisation

• The document contains biology notes for forms 3 and 4.

Cells and Levels of Organisation

• Different types of cells perform specific functions, with each cell dependent on others for collaborative support.
• Specialised cells carry out specific jobs and develop distinct shapes to aid their function.
• Lack of a nucleus increases surface area for oxygen absorption in red blood cells, also, their biconcave shape allows them to pass through capillaries.
• Haemoglobin is a red pigment that carries oxygen for cell respiration.
• Muscle cells contract in response to nerve stimulation, enabling movement.
• Muscle cells are long, thin, and capable of changing shape during contraction, containing numerous mitochondria to power muscle function.
• Palisade cells, located in leaves, are packed with chloroplasts for photosynthesis
• Chloroplasts contain chlorophyll, essential for light absorption in photosynthesis.
• They are columnar and closely packed to maximize surface area for sunlight and carbon dioxide absorption.
• Root hair cells absorb water and salts from the soil, facilitated by thin cell walls and numerous close-contact surface areas
• A hair-like projection increases the absorbing surface area and a large vacuole stores water.

Ecosystems

• An ecosystem is a self-contained system where organisms interact with each other and their physical environment.
• Ecosystem has two parts: abiotic (non-living factors like temperature, humidity, and light) and biotic (all living organisms like plants, fungi, animals, and bacteria).
• The natural environment influences species survival, showing a balance where adapted organisms mature and reproduce.
• Decomposers naturally recycle nutrients, and pests/diseases are inherent without control measures.
• A food chain is a nutritional sequence, where energy is transferred through the organisms, starting from the green plants.
• A food web is created by interconnected feeding relationships among plants and animals.
• Organisms in a food web have multiple food sources/consumers.
• Biomass is living material, with producers having more biomass than herbivores, which have more than carnivores in balanced ecosystems.
• Available energy decreases at each trophic level.
• The sun is the fundamental energy source; producers at the first level capture energy at 100%.
• Consumers lose energy as heat and through life processes.
• 90% of energy is lost at each food chain link, with 10% transferring to the next level.
• Decomposers consume unused materials.
• The population decreases with increasing food chain levels due to energy loss.
• Carbon is recycled as carbon dioxide and is a compoent of all organic compounds
• Plants take carbon dioxide from the air to make carbon compounds during photosynthesis.
• Animals ingest carbon by consuming plants.
• Carbon dioxide is released by animals, plants, and microorganisms as they respire and decompose.
• Human activities like burning fossil fuels also release carbon dioxide.
• Nitrogen is present in proteins of plants and animals
• Decomposing organisms convert dead plants/animals into ammonium.
• Nitrifying bacteria like Nitrosomonas convert the ammonium compounds into nitrites; Nitrobacter convert the nitrites to nitrates, the form absorbed by plants.
• Lightning converts a small part of atmospheric nitrogen into ammonia for plant absorption.
• Nitrogen-fixing bacteria directly convert another small part of atmospheric nitrogen into nitrates.
• In poor aeration, denitrifying bacteria release nitrogenous gas into the air.
• Artificial ecosystems rely on human intervention such as monoculture, crop production, and animal husbandry.
• The balance is destroyed in artificial ecosystems because of single species farming which can be supplemented with strict control measures against pests.
• Artificial nutrients are added into the soil.
• Controlled grazing is practiced in order to avoid overgrazing.
• Biodiversity refers to the variety within species, among species, and among ecosystems.
• Limited biodiversity causes pest problems and disease outbreaks,
• It also makes ecosystems unstable, while limiting nutrient recycling, increasing soil infertility, and causing overgrazing.
• Advantages of biodiversity include a wide food variety, self-sustaining ecosystems, less disease spread, and provisions of shelter and medicines.

Plant Nutrition

• Leaves are covered with a waxy cuticle, which is waterproof and protective, with veins transporting substances
• Leaves are attached to the stem by a petiole to maximise sunlight.
• Most leaves are thin, flat, with a large surface area-lamina, its edge known as margin.
• The cuticle waterproofs the leaf.
• The epidermis is thin, transparent, and protective, with stomata for gaseous exchange
• Palisade cells conduct photosynthesis and are packed with chloroplasts.
• Spongy cells contain chloroplasts and permit gaseous exchange through air spaces.
• Vascular bundles in leaf veins contain xylem and pholem-xylem transports water, pholem transports sugars.
• Stomata are controlled by guard cells, facilitating gas exchange for photosynthesis, transpiration, and respiration.
• Broad, flat leaves maximize the surface area for sun and carbon dioxide.
• Thin leaves allow carbon dioxide and light to diffuse fast for inner cells.
• Palisade cells packed with chloroplasts optimize sunlight absorption.
• Leaf spaces allow easy diffusion of carbon dioxide.
• Abundant stomata allow exchange of carbon dioxide and oxygen.
• Closely packed palisade cells maximize sunlight absorption.
• Vein networks supply water and minerals.
• Photosynthesis rate increases with light intensity.
• Photosynthesis rate also increases with increasing carbon dioxide.
• Water is essential for photosynthesis; its deficiency causes stomata to close.
• Chlorophyll is vital for trapping light energy for photosynthesis which enables light energy to be converted to chemical energu.
• photosynthesis rate increases with temperature up to a point.
• End-products include glucose to starch, amino acids, cellulose or lipids, and oxygen.
• To conduct a starch test on a leaf: Boil the leaf in hot water, followed by alcohol, then add iodine. A blue-black color indicated a starch presence.
• To test for oxygen: Put pond weed in water with an inverted stem funnel and test tube. Oxygen presence is confirmed by a glowing-splint test.
• Photosynthesis products: glucose is converted into starch, or sucrose, used for cell wall production as cellulose, or made into lipids for cell membranes, while oxygen is released.

Human Nutrition

• Balanced diet includes all essential nutrients in correct amounts.
• Carbohydrates, abundant in starch and sugars, are energy-rich and provide dietary fibre.
• Glucose and fructose are sugars in fruits.
• Lipids, including fats and oils supply heat/energy.
• Lipids help absorb vitamins, form cell membranes, aid in blood clotting and support organs.
• Proteins are for growth, repair, immunity, and enzymes, found in meat, eggs, soybeans, seeds, and nuts.
• Vitamins aid growth, metabolism, and immunity. Vitamin A (retinol) aids vision and strengthens tissues; Vitamin C (ascorbic acid) boosts healing and iron use.
• Vitamin D (calciferol) is for bones and teeth and can be obtained from sunlight.
• Minerals are key for chemical reactions and tissue builds.
• Iodine influences thyroid gland. Calcium strengthens bones and regulates nerves. Iron supports red blood cells.
• Dietary fiber, from cellulose (plant fibre), aids digestion and lowers cholesterol.
• Water comprises around 70% of tissue and acts as a solvent, reactant, and temperature regulator.
• Toddlers need extra protein, not too many starchy foods, and a variety of fruits and green/yellow vegetables.
• Adolescents need protein, calcium, vitamin D, phosphates and starches for development, and should drink safe water.
• Manual workers needs balance, with energy and added amounts of water and salts.
• Sedentary workers need less energy and should avoid high fat food.
• The alimentary canal;mouth, tongue, stomach, liver, gall bladder, duodenum, pancreas, ileum, caecum, appendix, colon rectum and anus.
• Ingestion involves taking food through mouth, starting the digestion.
• Teeth grind the food, increasing the surface volume and easier digestion. Saliva moistens and contains salivary amylase, which digests starch.
• Swallowing is automatic after food is at the back of the mouth to the oesophagus.
• Peristalsis moves food through the oesophagus.
• In the stomach, food mixes with gastric juice turning into chyme.
• Hydrochloric acid kills some bacteria, and provides buffer so pepsin which breaks down proteins into polypeptides.
• Mucus protect the stomach tissues from hydrochloric acid.
• In the duodenum, pancreatic juice and bile are added to the chyme.
• Pancreatic amylase act on starch, trypsin breaks down proteins, lipase hydrolyses fats.
• In the ileum, intestinal juices complete digestion with enzymes like maltase, sucrase, lipase, and trypsin and helps turn food into glucose.
• Digestion reduces food to sizes that improves solubility so it can be transported through the body.
• Absorption is the process of taking in soluble food through the epithelium of ileum to the bloodstreem.
• Villi increases the surface area volume for absorption-epithelium allows rapid fluid passage and blood capillaries transport material
• Products of digestion into the bloodstream. Fats enter lacteal tube.
• Ileum traits like long length, villi, thin epithelium, and capillaries promote efficient absorption of the nutrients and fatty acids.
• Large intestines absorb water/vitamin B, mainly made of cellulose and fibers.
• Assimilation occurs when body cells utilize the nutrients to produce energy and repair cells which are carried from the blood and used by living cells.
• Glucose is oxidized to produce energy, used to build structural components.
• Fats build the cells and also form an important source of metabolic energy.
• Amino acids are transformed into proteins which repairs cells and provide structure-excess is converted to glycogen.
• Egestion eliminates undigested substances as faeces through the anus.
• Malnutrition is where an individual is under or over nourished stemming for an imbalanced lack of diet.
• Obesity is caused by high fat intake results in weight gain. This leads to multiple diseases, such as heart diseases.
• Anorexia means self starvation resulting in heart failure and fatigue.
• Diabetes is generally caused by obesity.
• Deficiency diseases are caused by dietary nutrient deficiencies.
• Lack of protein causes Kwashiorkor, with enlarged abdomen.
• Lack of iodine causes Goitre, with stunted growth/ enlarged thyroid.
• Lack of Vitamins C cause Scurvy, with joint pains.
• Iron deficiency causes Anaemia ,with fatigue.
• Vitamin A and B deficiency causes night blindness and Berberier

Food Tests

• Starch is tested with iodine which results in a blue-black colour.
• Benedict's solution is used to test for sugar , where heat causes it to form brick colored precipitate.
• Sodium hydroxide and copper sulfate identify proteins by producing a purple colour.
• The presence of fats is confirmed with ethanol and water to cause a cloudy emulsion.

Respiratory System

• Alveoli are respiratory surface.
• Oxygen and carbon dioxide pass to and from the surface. There is more oxygen than carbon dioxide, vice versa for blood capillaries.
• Alveoli are globular to maximise exchange, surfaces are thin and moist.

Adaptation of alveoli

• Includes large surface area, moist surfaces, thin walls, network of capillaries and the number of alveoli..
• Rate of oxygen exhaled is less than CO2-water vapour exhaled is less than CO2 as well,.
• Bicarbonate indicator is connected to tubes to show proportions.

Respiration

• Involves breakdown which breaks down glucose, releases C02, water and energy.
• The process requires the special energy molecule (ATP)which is released back into the cell
• Glucose then lactic acid.
• Germinating seeds are soaked and disinfected. Thermos flasks are set up and checked, one with a thermometer. Increase indicates germination.

Transport System

• Transpiration, where water goes through a vapour to the atmosphere. Turgor occurs as water is released through osmosis.
• The latent heat causes water to evaporate from the mesophyll cells, resulting in the temperature to rise and rate to increase.
• Transpiration can be measured with a potometer which measures loss of water over set time.
• Leaves may have sunken in stomata or waxy cuticles to minimize water loss.
• Plants in salty solutions are immersed gaining a turgid shape through osmosis, which causes water diffusion out.

Transport in Humans.

• Double circulatory system pushes oxygen into all parts of the body, before proceeding to the lungs to be oxygenated again.
• Blood transports all water, glucose, and hormones. it also help with body defence against any infection.
• Arteries oxygenate blood from the heart, with a thick wall tissue to propel the pressure needed for circulation.
• Valves prevent backflow.
• Veins are thin tissue to carry blood, with large lumens which allows flow.
• Capillaries have permeable walls that helps the blood through.

Reproductive Systems

• See structure above. Germination is when water enters a tiny pore which helps cause the seed to break open.

Health and Hygiene

• Early treatment leads to antibiotic.
• Syphilis, infection.
• Genital hurts
• Avoid unprotected sex and make regular tests.
• Malaria, protozone infection.
• Cholera is intestinal, through bacteria, diarrhea. Give antibiotics and personal hygiene
• Ebola, bloody fees from gorillas which leads to death.
• Typhoid, Salmonella, waterborne disease. High.
• Substance abuse. damages health, alcohol causes sclerosis.
• Low memory loss due to brain damage.
• immunity, active form of Acquired (virus/disease), Antibodies is immunity. Vaccine may be administered
• Passive immunity is where the body is ready to fight of viruses that are already within the system, for a limited time.
• breast feeding by placenta.
• Immunisation schedule is what one requires for vaccines, tetanus There is also BCG jab birth, Months: DPT at birth, Polio and Measles.