Characteristics & Classification of Living Organisms - Biology Notes PDF

**CHARACTERISTICS & CLASSIFICATION OF LIVING ORGANISMS** **Characteristics of living organisms** **Movement**: action by an organism or part of an organism causing a change of position or place **Respiration**: the chemical reactions that break down nutrient molecules in living cells to release e...

**CHARACTERISTICS & CLASSIFICATION OF LIVING ORGANISMS** **Characteristics of living organisms** **Movement**: action by an organism or part of an organism causing a change of position or place **Respiration**: the chemical reactions that break down nutrient molecules in living cells to release energy **Sensitivity**: the ability to detect and respond to changes in the internal or external environment **Growth**: permanent increase in size and dry mass by an increase in cell number or cell size or both **Reproduction**: processes that make more of the same kind of organism **Excretion**: the removal of the waste products of metabolism and substances in excess of requirements **Nutrition**: the taking in of materials for energy, growth and development **Concept and uses of classification systems** Organisms can be classified into groups by the **features that they share** Classifcation systems aim to reflect evolutionary relationships (change of adaptive features of a population over time, as a result of natural selection) **Species:** a group of organisms that can reproduce to produce fertile offspring **Binomial system:** an internationally agreed system in which the scientific name of an organism is made up of **two** **parts showing the genus and species** (starting with a capital letter) and species (starting with a lower-case letter), written in italics when printed (therefore underlined when written) e.g. *Homo sapiens* - - - - - - **Features of organisms** **KING PHILIP CAME OVER FOR GOOD SPAGHETTI** **K**ingdom, **P**hylum, **C**lass, **O**rder, **F**amily, **G**enus, **S**pecies Kingdom \--\> Species = Similarity increases **Kingdoms** **Animal:** Multi-cellular ingestive heterotrophs (eats other plants or animals for energy and nutrients) **Plant:** Multi-cellular photosynthetic autotrophic (make their own food) organism with a cellulose cell wall. **Fungi:** Single celled or multi cellular heterotrophic organisms with cell wall not made of cellulose, spread by spreading of spores in moist/dark/warm environment, saprotrophs (feed off dead organisms) or parasites **Prokaryotes:** Single celled organism with no true nucleus **Protoctist:** Single celled organism with a nucleus **Vertebrates**(**MR FAB)** **Mammals** Fur/hair on skin Can live on land and in water 4 limbs Lungs to breathe Give birth to live young **Reptiles** Scales on skin Usually 4 legs Lungs to breathe soft eggs **Arthropods (Invertebrates with Legs) CAMI** **Classifying Plants** **Ferns:** Do not produce flowers They are plants with roots, stems and leaves Have leaves called fronds Reproduce by spores **Flowering plants:** They are plants with roots, stems and leaves Reproduce sexually by means of flowers and seeds Seeds are produced inside the ovary in the flower **Monocotyledons** **Dicotyledons** -------------------- -------------------------- One cotyledon Two cotyledon Parallel veins Veins netlike Fibrous root Taproot present Floral parts in 3s Floral parts in 4s or 5s **Viruses and Bacteria** **Virus:** Have a protein coat and genetic material  **Dichotomous key:** uses visible features to classify organisms. It is which gives you a choice of two features and you follow the one that applies: each choice leads to another choice until the organism is narrowed down to its genus and nally species. 2. **ORGANIZATION OF THE ORGANISM ** **Cell structure** - All living things are made of cells.  - **All typical cells** have:  - - - - - A typical animal cell (e.g. the liver cell) has all above Only **plant cells** have:  - - - - +-----------------+-----------------+-----------------+-----------------+ | **Cell ** | **Function ** | **Adaptations** | **Diagram** | +=================+=================+=================+=================+ | | movement of | |  | +-----------------+-----------------+-----------------+-----------------+ | Root | | | Root Hair Cell | | | | | Parts Diagram | | hair cell | | | (Trevor Mills) | +-----------------+-----------------+-----------------+-----------------+ | | | freely |  | +-----------------+-----------------+-----------------+-----------------+ | | | | | +-----------------+-----------------+-----------------+-----------------+ | | | waterproof | | +-----------------+-----------------+-----------------+-----------------+ | | Photo-synthesiz | | palisade cell 2 | | | es | | -- OL 001 \| | | | | | iBug | +-----------------+-----------------+-----------------+-----------------+ | | | Many | | | | | | | | | | chloroplasts | | +-----------------+-----------------+-----------------+-----------------+ **Size of specimens**  **Note:** 1cm = 10mm 1mm = 1000μm 3. **MOVEMENT IN AND OUT OF CELLS** **Diffusion** - - - - - - - - - **Osmosis** Osmosis is the 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 **In plants:** Conc. of solute outside cell = conc. inside cell → **no change in size**\ Conc. of solute outside cell \> conc. inside cell → **cell shrinks** (Plasmolysis)\ Conc. of solute outside cell \< conc. inside cell → **cell swells** (Turgid) **Increasing solute concentration** (low water potential) inside the cell causes [water to enter the cell by osmosis,] [vacuole swells up] and [increase in turgor pressure], **cell becomes turgid**. **Decreasing solute concentration** (high water potential) inside of cell causes [water to leave the cell by osmosis], vacuole gets smaller and **cell becomes flaccid**. Continuous loss of water causes the [cell membrane to get pulled away from cell wall] causing the cell to become **plasmolysed**. **3.3. Active Transport** Movement of particles through a cell membrane, from a **region of lower concentration to a region of higher concentration** against a concentration gradient, **using energy** released during respiration Active transport is needed when an organism wants to optimize the amount of nutrients it can take up - ion uptake by root hairs and uptake of glucose by epithelial cells of villi. **Protein carriers** move molecules or ions across a membrane during active transport. 4. **BIOLOGICAL MOLECULES** **Carbohydrates**: made from **Carbon, Hydrogen and Oxygen** (CHO)\ **Fats and oils:** made from **Carbon, Hydrogen and Oxygen** (CHO)\ **Proteins**: made from **Carbon, Hydrogen, Oxygen, Nitrogen** and sometimes Sulfur (CHON{S}) **\ Chemical Tests** +-----------------+-----------------+-----------------+-----------------+ | Food Test | Test Method | Reagent | -ve / +ve | | | | | Result | +=================+=================+=================+=================+ | Starch | Put a few drops | Iodine solution | -ve: Brown | | | of iodine | | | | | | | +ve: Blue-black | | | | | color | +-----------------+-----------------+-----------------+-----------------+ | Reducing sugar | Mix equal | Benedict\'s | -ve: blue | | | volume of | solution | | | | Benedict\'s | | +ve: (green, | | | solution and | | yellow, orange, | | | sample solution | | brick-red) | | | & heat in a | | | | | water bath | | | +-----------------+-----------------+-----------------+-----------------+ | Protein | Mix equal | Biuret reagent | -ve: Blue | | | volume of | | | | | Biuret solution | | +ve: Violet | | | & sample | | color | | | solution | | | +-----------------+-----------------+-----------------+-----------------+ | Lipids | Mix equal | Ethanol | -ve: colorless | | | volume of | | solution | | | Ethanol and | | | | | dried food | | \+ ve: | | | sample. | | milky-white | | | | | emulsion | | | Pour the | | | | | mixture into a | | | | | test tube of | | | | | water. | | | +-----------------+-----------------+-----------------+-----------------+ | Vitamin C | Add drops of | DCPIP solution | -ve: blue | | | DCPIP solution | | | | | into food | | +ve: colorless | | | sample solution | | | +-----------------+-----------------+-----------------+-----------------+ **Structure of a DNA** - - - -  5. **ENZYMES** **Catalyst:** a substance that speeds up a chemical reaction and is not changed by the reaction\ **Enzymes:** proteins that function as biological catalysts. **Enzymes** are important to all living organisms as they **maintain reaction speeds** of all metabolic reactions at a rate that can **sustain life.** The **shape of the active site of an enzyme is complementary** to its **substrate**. **Substrate:** the molecule(s) before they are made to react **Product:** the molecule(s) that are made in a reaction **Effect of Temperature on Enzymes** - Enzymes are [inactive at very low temperature], there is not enough kinetic energy for the reaction so it reacts too slowly. - Enzymes have an [optimum temperature]: the temperature at which they work best giving the fastest reaction ≈ 37°C in animals - When temperature increases, enzyme and substrate molecules [gain more kinetic energy], [molecules move faster resulting in more effective collisions]. [More enzyme-substrate complexes are formed] - If temperature is too high, enzyme molecules vibrate too vigorously and enzyme is **denatured**; it loses its shape and will no longer bind with a substrate. **Effect of pH on Enzymes** - - - - **Graphs for Changes in Enzyme Activity**  6. **PLANT NUTRITION** -  - - **Subsequent use and storage of the carbohydrates made in photosynthesis** - - - - - **Mineral Requirements**  Nitrogen fertilizers: provide nitrogen in the form of nitrate ions, nitrite ions or ammonium ions. But using fertilisers can lead to eutrophication, which is when the fertiliser is transported by rain and leaches into stagnant water e.g. pond or river **Chlorophyll Is Necessary for Photosynthesis** - - - - - - - **Light Is Necessary for Photosynthesis** - - - - - - **Carbon Dioxide is Necessary for Photosynthesis** - - - - - - **Limiting Factors** **Limiting factor:** something present in the environment in such short supply that it restricts life processes.   **Leaf Structure** **Cuticle:** waxy layer that prevents water loss from top of the leaf **Epidermis:** transparent cell that allows sunlight to pass through to the palisade cell **Palisade:** found at the top of the cell and contains many chloroplasts which absorbs sunlight. **Spongy mesophyll layer:** irregularly shaped cells which create air spaces to allow gaseous exchange to take place; do not contain many chloroplasts **Vascular Bundle:** made up of xylem and phloem Xylem: vessel which transports water and dissolved minerals and has lignified walls made of cellulose Phloem: vessel which transports nutrients **Stomata:** little holes that opens and closes to allow gaseous exchange to take place. The stomata close to prevent water loss and open to let gases come in and out. When guard cells lose water, the stoma close (at night), while the stoma open when guard cells gain water & swell (during the day). 7. **HUMAN NUTRITION** - **Balanced Diet**: getting all the right nutrients in correct proportions - Diet related to age/sex/activity: - - - - - **Main principle dietary sources and functions**  **Defciencies** **Vitamin C**: *[Scurvy]*; loss of teeth, pale skin & sunken eyes **Vitamin D**: *[Rickets]*; weak bones and teeth\ **Calcium**: *[Rickets]*; weak bones and teeth, also poor clotting of blood, spasms **Iron**: *[Anaemia]*: Fatigue (less iron → less haemoglobin → less oxygen transported → less respiration → less energy) **Digestive system** The human digestive system, IGCSE & GCSE Biology revision notes **Stages of Nutrition** 1. 2. 3. 4. 5. **Functions of the parts of digestion** **Mouth**: contains teeth used for mechanical digestion, area where food is mixed with **salivary amylase** & where ingestion takes place **Salivary glands**: produce saliva which contains amylase and helps food slide down oesophagus **Oesophagus**: tube-shaped organ which uses peristalsis to transport food from mouth to stomach. Starch digestion is continued. **Stomach**: has sphincters to control movement into and also has **pepsin** (a protease) to break down proteins into peptides, it also kills bacteria with hydrochloric acid. They also have elastic walls. **Small intestine**: tube shaped organ composed of two parts the: **Duodenum**: fats are emulsifed by bile, and digested by pancreatic lipase to form fatty acids and glycerol. Pancreatic amylase and trypsin (a protease) break down starch and peptides into maltose and amino acids. Maltase found in intestinal juice breaks down maltose to glucose. **Ileum**: This is where absorption takes place; adapted by having villi and microvilli. **Pancreas:** produces [pancreatic juice] which contains [amylase, trypsin and lipase] and [hydrogencarbonate]. **Liver:** produces bile, stores glucose as glycogen, interconverting them to keep glucose concentration constant. Also carries out interconversion of amino acids (transamination), deamination and removal of old red blood cells and storage of their iron. Also, site of breakdown of alcohol and other toxins. **Gall bladder**: stores bile from liver **Bile:** produced by liver and stored in gall bladder, its role is to [emulsify fats], [to increase surface area] for the action of enzymes. [Bile is an alkaline mixture that] [neutralises the acidic mixture] of food and gastric juices entering the duodenum from the stomach, to provide a [suitable pH for enzyme action] **Large intestine:** tube shaped organ composed of two parts: **Colon:** organ for absorption of minerals and vitamins, and reabsorbing water from waste to maintain body's water levels **Rectum:** where faeces are temporarily stored **Anus:** ring of muscle which controls when faeces is released. **Physical Digestion** Physical digestion is the breakdown of food into smaller pieces without chemical change to the food molecules Physical digestion increases the surface area of food for the action of enzymes in chemical digestion **Teeth** **Types of human teeth**  **Structure of a Tooth** **Enamel:** the strongest tissue in the body made from calcium salts\ **Cement:** helps to anchor tooth\ **Pulp cavity:** contains tooth-producing cells, blood vessels, and nerve endings which detect pain. **Dentine:** calcium salts deposited on a framework of collagen fibres **Neck:** in between crown and root, it is the gums **Chemical Digestion** - - - - - - - - - **Absorption** - - - - - - - - - - - - 8. **TRANSPORT IN PLANTS** Functions of xylem and phloem - -  **Adaptation of Xylem** - thick walls with lignin - no cell contents - cells joined end to end with no cross walls to form a long continuous tube **Water uptake** Root hair cells absorb water and minerals from the soil. **Root hair cell** They have an elongated shape for more surface area which increases the rate of absorption of water by osmosis and ions by active transport. **Pathway Taken by Water** Passage of water through root, stem and leaf - Biology Notes for IGCSE 2014 - - - **Transpiration** - -  - - - - - **Factors Affecting Rate of Transpiration** **Temperature:** higher temperatures increase water-holding capacity of air and increases transpiration rate **Humidity:** low humidity increases water potential gradient between leaf and atmosphere - increasing transpiration rate **Light intensity**: high light intensity causes stomata to open (to allow more photosynthesis) which causes increase in transpiration **Translocation** Movement of sucrose and amino acids in phloem; from regions of production (sources) to regions of storage or to regions of utilization in respiration or growth (sinks). Translocation in different seasons: **Spring:** sucrose transported from stores in roots to leaves **Summer & early autumn:** sucrose goes from photosynthesizing leaves to root stores, 9. **TRANSPORT IN ANIMALS** Describe the circulatory system as a system of blood vessels with a pump and valves to ensure one-way flow of blood **Transport Systems** - - - - - - - - **Advantages of a double circulatory system** - - - - - - - - Double circulation **The Heart**  - - - - - - - - - - **Heart Structure** - - - - - - - - - - - - **Exercise & Heart rate** - - - **Coronary Heart Disease** - - - - - **Arteries, Veins and Capillaries**  **Shunt Vessels** - - - - -  **Blood** **Components of blood:** **Red blood cells**: haemoglobin and oxygen transport **White blood cells**: - - **Platelets**: play a major role in blood clotting\ **Plasma**: transport of blood cells, ions, soluble nutrients, hormones, carbon dioxide, urea and plasma proteins Red blood cell phagocytes lymphocytes platelets  **Blood Clotting** - - 10. **DISEASES AND IMMUNITY** **Pathogens** - - - - - **Body Defences** - - - - - - - - - - - **The Immune System** - - - - - - **Active immunity** - - - - - - **Controlling the spread of disease**, it is important to consider: - - - **Passive immunity** - - - - - **Cholera** - - 1. 2. 3. 4. 5. 6. 7. 8. 11. **GAS EXCHANGE IN HUMANS** **Features of a gas exchange surface** +-----------------------------------+-----------------------------------+ | **Property of surface** | **Reason** | +===================================+===================================+ | Thin (one cell thick) | Short distance to diffuse | +-----------------------------------+-----------------------------------+ | Large surface area | Many molecules can diffuse at | | | once | +-----------------------------------+-----------------------------------+ | Moist | Allow gas to dissolve before | | | diffusion | | | | | | Cells die if not kept moist | +-----------------------------------+-----------------------------------+ | Well ventilated | Concentration gradients for | | | oxygen and carbon dioxide are | | | kept up by regular fresh supplies | | | of air | +-----------------------------------+-----------------------------------+ | Close to blood supply | Gases can be carried to/from the | | | cells that reproduce them | +-----------------------------------+-----------------------------------+ **Structure** - **Cartilage (in trachea):** prevents the trachea from collapsing during absence of air and also to protect it - **Ribs:** protect the vital organs found in the chest, including the heart, lungs, part of the liver, and spleen.They also maintain space in the chest, so the lungs can expand and contract during the breathing process. - **Intercostal (internal & external) muscles**: situated between the ribs that create and move the chest wall - **Diaphragm:** produces volume and pressure changes in the thorax leading to the ventilation of the lungs  **Difference between inspired and expired air** **Test for CO2**: Blow CO2 through limewater. +ve result = turn cloudy **Effect of Physical Activity on Breathing** - Physical activity increases the breathing rate -- more breaths per minute, and the tidal volume -- more air per breath - This is measured with a spirometer to produce a spirogram. - During exercise, tissues respire at a higher rate, the change in breathing volume and rate helps to keep CO2 concentration and pH at safe levels. **Breathing**  Explain the Mechanism of Breathing in Human Beings - CBSE Class Notes Online - Classnotes123 **Inhalation Exhalation** **Internal intercostal muscles:** are used in coughing and sneezing.\ **Mucus & cilia:** goblet cells produce sticky mucus to trap and eliminate particulate matter and microorganisms. **Ciliated cells have cilia:** little hairs which sweep back and forward in a coordinated way to brush mucus up the lungs into the mouth 12. **RESPIRATION** - Chemical reactions that break down nutrient molecules in living cells to release energy. - Uses of energy in the body of humans: muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses and the maintenance of a constant body temperature. - Respiration involves the action of enzymes in cells **Aerobic Respiration** - - - **Anaerobic Respiration** - - **In muscles:** *Glucose* → *Lactic Acid* *C*6*H*12*O*6 → 2*C*3*H*6*O*3 **In yeast (single-cell fungi):** *Glucose* → *Ethanol* + *Carbon Dioxide* *C*6*H*12*O*6 → 2*C*2*H*5*OH* + 2*CO*2 **Lactic acid:** - Transported in blood to the kidneys, which oxidize it - The liver needs extra oxygen to do this leading to an **"oxygen debt".** - This causes you to continue breathing heavily after exercise. This is known as **'repaying the oxygen debt'** 13. **EXCRETION IN HUMANS** - Excretion: the removal from organisms of **toxic materials**, the **waste products of metabolism** (chemical reactions in cells including respiration) and **substances in excess** of requirements. - Substances should include carbon dioxide, urea and salts. **Function of Kidney** - Removal of urea and excess water and the re-absorption of glucose and some salts - Urea is formed in the liver from excess amino acids - Alcohol, drugs & hormones are broken down in the liver **Structure of Urinary system**  Structure of the Bladder **Cortex:** contains Bowman's capsules and coiled tubules **Ureter:** carries urine from kidney to bladder\ **Medulla:** contains loops of Henlé and collecting ducts **Loop of Henlé:** selectively absorbs water/solutes Collecting ducts: reabsorbs water into blood and store wastes until they are passed into ureter **Urethra:** carried urine from bladder to the outside. Bladder: stores urine\ **Renal capsule:** Filters from blood: water, glucose, urea and salts.\ **Tubule:** reabsorbs 100% of glucose, most of the water and some salts back into the blood (red), leading to concentration of urea in the urine as well as loss of excess water and salts into the tubule.\ **Renal artery:** brings wastes and water from blood\ **Renal vein:** reabsorbs water and useful molecules and leaves wastes behind - Each kidney contains around a million tiny structures called **nephrons**, also known as **kidney tubules** - The nephrons start in the **cortex** of the kidney, loop down into the **medulla** and back up to the cortex  1. **Ultrafiltration:** blood from renal artery enters the glomerulus. Water, urea, salts and glucose are forced into the Bowman's capsule. Blood cells and large proteins cannot pass through. 2. **Selective reabsorption:** in the proximal tubule two thirds of the salt and water and all the glucose moves out of the nephron, by active transport. These substances are reabsorbed back into the blood capillary. 3. **Loop of Henlé:** this part of the loop of Henlé is permeable to water but not salt. Water is drawn out of the filtrate in the nephron by osmosis because of the low water potential of the medulla tissue fluid. 4. **Loop of Henlé:** this part is permeable to salt but not water. The loss of water from the filtrate in the previous stage increases the salt concentration. Some salt passively diffuses out of the loop here. 5. **Collecting duct:** the remaining substances move through the second coiled tubule (distal tubule), into the collecting duct. The permeability of this part of the nephron to water is controlled **Dialysis** - - - - - 14. **COORDINATION AND RESPONSE** **Nervous Control in Humans** - - - - - **Types of Neurons** - **Reflex arc** - - - - **How the reflex arc works:** - - - - -  **Reflex action:** means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands) **Synapses** - - - - - - - Cholinergic Synapses (15.1.7) \| CIE A Level Biology Revision Notes 2019 \| Save My Exams **Antagonistic Muscle** - - - - The sense organ responsible for sight  Eye Anatomy: Image Details - NCI Visuals Online **Cornea**: refracts light\ **Iris**: controls how much light enters pupil\ **Lens**: focuses light onto retina\ **Retina**: contains light receptors, some sensitive to light of different colours\ **Optic nerve**: carries impulses to the brain **Accomodation** Adjusting for near and distant objects.  eplain the accommodation of an eye with image or figure - Physics - TopperLearning.com \| k3x553uu +-----------------------------------+-----------------------------------+ | **When viewing a near object** | **When viewing a distant object** | +===================================+===================================+ | - The circular ciliary muscles | - The circular ciliary muscles | | contracts, reducing their | relax increasing their | | circumferences. Radial | circumferences. Radial | | muscles relax | muscles contract | +-----------------------------------+-----------------------------------+ | - They reduce pull (tension) on | - The suspensory ligaments are | | the elastic suspensory | pulled tight (tension is | | ligaments | increased) | +-----------------------------------+-----------------------------------+ | - With less force on the lens | - The lens is stretched to | | ,its elasticity allows it to | become longer and thinner, | | become wider (thicker and | less convex | | fatter), more convex | | +-----------------------------------+-----------------------------------+ | - Rays form the near object | - Rays from the distant object | | produce a focused image on | are brought to focus on the | | the retina | retina | +-----------------------------------+-----------------------------------+ **Pupil Reflex**  - **Rods and Cones**  - Three different kinds of cones, absorb light of different colours, for colour vision **Fovea** Part of the retina where the receptor cells are pushed most closley together\ Where light is focused when you look straight at an object **Hormones** - **Adrenaline** - - - -  **Nervous and Hormonal Systems**  - Hormones are used in food production, for example oestrogen is used to boost growth rate of chickens. - Advantage: chickens grow quickly meaning more promt. - Disadvantages: this may cause human males to develop feminine characteristics, and it is unnatural. **Trophic responses** **Auxin:** - Plant hormones or growth substances - Controls tropisms - It is produced by cells at the tip of roots and shoots of plants **Geotropism:** a response in which a plant grows towards (positive) or away (negative) from gravity. **Auxin's role in geotropism** - Tend to settle at the bottom end of the root. - However, this does not make the cells of the tip of the root grow longer; auxins prevent cells at bottom tip of root from growing, making cells at top of root grow faster. - When cells of top of the root grow faster, they push root deeper into soil and root gets longer. - The root grows in direction of the gravitational pull. **Homeostasis** - The maintenance of a constant internal environment. - Homeostasis is the control of internal conditions within set limits **Negative Feedback** - Feedback controls the production of hormones -- the hormones regulate their own production. - **A negative feedback control** is when the change in hormone level acts as a signal to cancel out that change, so when blood hormone level is low, hormone production is stimulated, when it is high, it is inhibited. **Glucoregulation** - **Blood** glucose levels are monitored and controlled by the pancreas - The pancreas produces and releases different hormones depending on the blood glucose level - **Insulin** is released when blood glucose levels are high -- the liver stores excess glucose as glycogen - **Glucagon** is released when blood glucose levels are low -- the liver converts stored glycogen into glucose and releases it into the blood Human Biology Online Lab / Sugar Homeostasis - When the control of blood glucose does not work, a person is said to have diabetes - **Type 1 diabetes** is caused by the death of the cells that secrete insulin - **Symptom**: hyperglycaemia (feel unwell, dry mouth, blurred vision and feel thirsty) or hypoglycaemia (tired, show confusion and irrational behaviour) - **Treatment**: eating little and often and avoiding large amount of carbohydrates, injecting insulin to reduce blood glucose concentration **Skin Structure**  **Constant body temperature is maintained by:** **Insulation:** provided by fatty tissue which retains heat. Hairs become erect to trap warm air by contracting erector muscles and vice versa. **Vasodilatation:** when it is hot, arterioles, which supply blood to the skin-surface capillaries, dilate (become wider) to allow more blood near to skin surface to increase heat loss (face redder) **Vasoconstriction:** when it is cold, arterioles, which supply blood to the skin-surface capillaries, constrict (become smaller) to allow less blood near to skin surface to decrease heat loss **Sweating:** the water evaporates giving a cooling eect Skin receptors: sense heat and sensory neurons send impulses to the hypothalamus **Shivering:** muscular activity generates heat Thermoregulatory centre: in the hypothalamus, it controls the use of corrective mechanisms (e.g. sweating and shivering). **HOT** Skin in Thermoregulation. Body Temperature Regulation Stock Vector - Illustration of follicle, layer: 169786434 **COLD**  **OSMOREGULATION** - It is the body's way of balancing water taken in by the diet and water lost by excretion. - This stops red blood cells from becoming crenated. - In the collecting duct, water is reabsorbed into the blood depending on how much is needed. This is controlled by the antidiuretic hormone, ADH released by the pituitary gland. - If we sweat then the volume of urine is reduced to compensate. - Isotonic sports drinks are used by athletes because they have glucose, salts and water to replace what is lost by sweating. **NEGATIVE FEEDBACK** The production of hormones is controlled by feedback -- the hormones regulate their own production. A negative feedback control is when the change in hormone level acts as a signal to cancel out that change, so when blood hormone level is low, hormone production is stimulated, when it is high, it is inhibited. **GLUCOREGULATION** - - - - **HOMEOSTATIC ORGANS** **Cells**: change composition of blood as they remove nutrients and O~2~ and add wastes and CO~2~ **Heart**: keeps blood pressure constant to deliver oxygen and nutrients around body **Skin**: to maintain heat exchange with external environment **Kidney**: regulate water and salt levels (osmoregulation) and the removal of wastes like urea (excretion) **Lungs**: regulate water and salt levels (osmoregulation) and the removal of wastes like urea (external environment) **Intestines**: supply soluble nutrients and water to blood **Liver**: regulates blood solutes and removes toxins +-----------------------------------------------------------------------+ | 16. **DRUGS** | | | | Any substance taken into the body that modifies or affects chemical | | reactions in the body. | +=======================================================================+ | **ANTIBIOTICS:** | | | | - - | | | | Antibiotic resistance **happens when bacteria develop the ability to | | defeat the drugs designed to kill them**. That means the germs are | | not killed and continue to grow. | | | | Commonly prescribed antibiotics are becoming **less effective** due | | to a number of reasons: | | | | - **overuse** and being prescribed when not really necessary. | | | | - patients **failing to complete the fully prescribed course** by a | | doctor. | | | | - large scale **use of antibiotics in farming** to prevent disease | | when livestock are kept in close quarters, even when animals are | | not actually sick. | +-----------------------------------------------------------------------+ | - only taking antibiotics when **absolutely essential.** | | | | - when prescribed a course of antibiotics, **ensure that the entire | | course is completed** even if you feel better after a few days. | | | | 15. **REPRODUCTION** | | | | **ASEXUAL REPORUDCTION** | | | | The process resulting in the production of genetically identical | | offspring from one parent. | | | | **Bacteria:** | | | | - Reproduce by binary fission, each bacterium divides into two. | | | | - The generation time is the time taken for a cell to divide | | into 2. | | | | **Fungi:** | | | | - Single-celled yeast reproduces by binary fission. | | | | - All other fungi produce via spores. | | | | - When the sporangium bursts it spreads the spores. | | | | - Spores land and grow mycelium (roots) for example mushrooms | | | | **Potato:** | | | | - The shoot from a potato goes back underground and the stem swells | | to form a new genetically identical potato. | | | | - The swollen stem acts as a storage organ. | | | | +--------------------------------+--------------------------------+ | | | **Advantages** | **Disadvantages** | | | +================================+================================+ | | | - Population can be | - competition for resources | | | | increased rapidly when | as all individuals are | | | | conditions are right | close together | | | | | | | | | - Can exploit suitable | - Limited genetic variation | | | | environments quickly | in population | | | | | | | | | - More time and energy | - Population is vulnerable | | | | efficient, no need to find | to changes in conditions | | | | mates, fertilise etc. | | | | | | - Disease is likely to | | | | - Good characteristics are | affect the whole | | | | passed on to offspring. | population as there is no | | | | | genetic variation | | | | | | | | | | - Increased risk of | | | | | inheriting harmful alleles | | | +--------------------------------+--------------------------------+ | | | | **SEXUAL REPRODUCTION** | | | | - Sexual **reproduction:** 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. | | | | - **Fertilisation**: the fusion of gamete nuclei | | | | - Nuclei of **gametes are haploid** and that the nucleus of a | | **zygote is diploid** | | | | +--------------------------------+--------------------------------+ | | | **Advantages** | **Disadvantages** | | | +================================+================================+ | | | - Increases genetic | - Takes time and energy to | | | | variation | find mates | | | | | | | | | - The species can adapt to | - Good characteristics can | | | | new environments due to | be lost | | | | variation | | | | | | | | | | - Disease is less likely to | | | | | affect population | | | | +--------------------------------+--------------------------------+ | +-----------------------------------------------------------------------+ **Sexual Reproduction in Plants** Insect pollinated, dicotyledonous flowering plant: foxglove  Wind pollinated flower structure: grass **Functions** **Sepal:** protect the flower bud. **Petal:** brightly coloured and scented and may have nectarines which are all used to attract insects, petals in wind pollinated flowers are tiny, and used for pushing the bracts apart to expose stamens and stigma **Anther:** has pollen sacs with pollen grains which contain the male nucleus (male gamete). **Stigma:** platform on which pollen grains land **Ovary:** hollow chamber, ovules grow from the walls. **Pollination** **Pollination:** transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma). **Agents of pollination:** insects, birds, mammals, water and wind +-----------------------------------+-----------------------------------+ | **Insect Pollinated** | **Wind Pollinated** | +===================================+===================================+ | - Large colorful petals | - Dull petals present / no | | | petals | | - Sweetly scented | | | | - No scent | | - Nectaries present | | | | - No nectaries | | - Moderate amount of pollen | | | | - Huge amount of pollen | | - Pollen is spiky/stigma | | | | - Pollen round and smooth | | - Anther & stigma inside flower | | | | - Anther & stigma hangs out | | - Stick stigma | | | | - Stigma hairy | | - Nectar-guides present | | +-----------------------------------+-----------------------------------+ **Pollen tube:** pollen grain lands on stigma and creates a tunnel down the style, through the micropyle, to the ovules. Structure of non-endospermic seed:  **Formation of a seed:** the zygote divides many times by mitosis to form the embryo. The **cotyledon** is the food store. The **testa** stops drying out of embryo. Wind and animal dispersal are used by plants to colonise new areas; done because new areas have less competition for light, space and nutrients, so seeds are more likely to develop. **Germination** A process controlled by enzymes **Water:** activates enzymes to turn insoluble food stores into soluble substances, and makes tissues swell so that the testa splits **Oxygen:** enters through the gaps in the testa (along with water),and is used in aerobic respiration. **Temperature:** must be suitable for enzymes to work (at optimum temperature). **Sexual Reproduction In Humans** Male reproductive system: Male Reproductive System: Structure & Function **Testes:** have many coiled tubes which produce sperm, and the cells between tubes produce testosterone. **Scrotum:** holds testicles **Sperm duct:** carries sperm from testicles to urethra. **Prostate gland:** makes seminal fluid **Urethra:** carries semen from sperm duct to tip of penis **Penis:** male sex organ, used to transfer semen to thefemale. Female reproductive system:  **Ovary:** contains follicles which develop into the ova and produces progesterone and oestrogen **Oviduct (fallopian tube**): carries the ovum to uterus **Uterus (womb):** where the fetus develops. **Cervix:** neck of uterus: a strong rigid muscle, moist by mucus with a small opening **Vagina:** receives penis during intercourse, and way out for baby at birth. Moist tube of muscle, flexible and secretes mucus **Menstrual Cycle** **Day 1 to 5:** In the ovary, FSH is secreted by the Pituitary Gland to stimulate the maturation of ONE follicle in the ovary. In the uterus: the endometrium breaks down: menstruation **Day 5 to 12:** In the ovary the follicle keeps maturing In the uterus, oestrogen is secreted by follicle and the ovarian tissues to prepare the endometrium **Day 13/14/15:** In the ovary, LH is also secreted by the Pituitary Gland to trigger the release of the egg from follicle into the fallopian tube **Day 15 to 28:** In the ovary, LH triggers formation of Corpus Luteum In the uterus: progesterone is secreted by Corpus Luteum to keep endometrium thick, waiting for possible embryo implant. **Day 28 -- Scenario 1:** Egg not fertilized No implantation takes place, the Corpus Luteum degenerates, causing a lack of progesterone. This means that endometrium is no longer thick, back to Day 1 **Day 28 -- Scenario 2:** Egg is fertilized Implantation occurs. This makes the hormones to keep the Corpus Luteum maintained which means that progesterone is high. This keeps the Endometrium thick for pregnancy **Hormones in Menstrual Cycle** - **Oestrogen** **is secreted by the ovaries.** It stops FSH being produced - so that only one egg matures in a cycle and it stimulates the pituitary gland to release hormone LH. - **Progesterone is a hormone secreted by ovaries**. It maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy. - **Follicle stimulating hormone (FSH) is secreted by the pituitary gland**. It causes an egg to mature in an ovary and it stimulates ovaries to release hormone oestrogen - **Luteinizing hormone (LH): is also secreted by pituitary gland** and causes mature egg to be released from ovary. **Fertilization** Fertilisation is the fusion of the **haploid** nuclei from a male gamete (sperm) and a female gamete (egg cell) to form a **diploid zygote**. **Adaptive Features of sperm cells**  **Adaptive Features of egg cells** +-----------------+-----------------+-----------------+-----------------+ | **Gamete** | **Size** | **Mobility** | **Number** | +=================+=================+=================+=================+ | Sperm | Smaller | Very mobile -- | Many more | | | | use its tail | | | | | | (300,000,000) | +-----------------+-----------------+-----------------+-----------------+ | Egg | Larger | Immobile -- | Fewer and | | | | moved by | limited | | | | peristalsis | | +-----------------+-----------------+-----------------+-----------------+ **Development of zygote** - - - - - - - - - -  **Growth and development in the uterus (not to scale)** **Sexually transmitted infections** - an infection that is transmitted through sexual contact. **HUMAN IMMUNODEFICIENCY VIRUS (HIV)** Human immunodeficiency virus (HIV) is a pathogen that causes an STI. HIV infection may lead to AIDS. **Transmission:** Intercourse, blood transfusion, organ transplant or sharing needle with infected person **Prevention:** - - - **How it affects the immune system:** - - - 17. **INHERITANCE** **Chromosome:** are made of DNA, which contains genetic information in the form of genes. **Gene:** is a length of DNA that codes for a protein. The sequence of bases in a gene determines the sequence of amino acids used to make a specific protein **Allele:** any of two or more alternative forms of a gene **Haploid nucleus:** a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg) **Diploid nucleus:** a nucleus containing two sets of chromosomes (e.g. in body cells) **Inheritance of gender in humans:** woman's gamete can only carry an "X" chromosome, and a male gamete can carry either an "X" or "Y" chromosome; females are "XX" while males are "XY". There is always a 50% chance of getting a boy and vice versa. **PROTEIN SYNTHESIS** DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters. - - - - - - - - Most body cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs. - **Haploid** nucleus is a nucleus containing a single set of chromosomes. - **Diploid** nucleus is a nucleus containing two sets of chromosomes. - In a diploid cell, there is a pair of each type chromosome and in a human diploid cell there are 23 pairs. **MITOSIS** - The nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes. - Stem cells as unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions **Mitosis is needed for:** **Growth:** in animals each tissue provides its own new cells when they are needed. **Repair** of damaged tissues: for example when you cut your skin, mitosis provides the new cells to cover up the cut. **Replacement** of worn out cells **Asexual reproduction:** in plants **MEIOSIS** - - - **MONOHYBRID INHERITANCE** **Inheritance** is the transmission of genetic information from generation to generation. **Genotype:** genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG). **Phenotype:** physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed) **Homozygous:** having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be **pure-breeding** **Heterozygous:** having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding **Dominant:** an allele that is expressed if it is present (e.g. T or G) **Recessive:** an allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g) **Monohybrid Crosses**  **TEST CROSS** - - - TEST CROSSES. - ppt video online download - - - - - - Parents' phenotype Carrier Normal Parents' genotype X^B^X^b^ X^B^Y 18. **VARIATION AND SELECTION** - - - - - - - **ADAPTIVE FEATURES** An **adaptive feature** as an inherited feature that helps an organism to survive and reproduce in its environment **Adaptive features of hydrophytes:**Plants adapted to live in **extremely wet conditions** - - - - - - - - - **SELECTION** There is a greater chance of passing on of genes by the best adapted organisms. **Steps of Natural selection** 1. 2. 3. 4. 5. **ANTIBIOTIC RESISTANCE** - - - - - - - - **SELECTIVE BREEDING** - - - - - **EXAMPLES** - Selective breeding by artificial selection is carried out over many generations to improve crop plants and domesticated animals. - Plant-breeders will select varieties for their high yield and resistance to fungal diseases. - The plants with the largest fruits might be selected and their seeds planted next year. - In the next generation, the plants with the largest fruits are again selected and their seeds planted. - Eventually it is possible to produce a true-breeding variety of tomato plant that forms large fruits.  19. **ORGANISMS AND THEIR ENVIRONMENT** **ENERGY FLOW** - - - **FOOD CHAINS AND FOOD WEBS** - **Food chain:** a chart showing the flow of energy (food) from one organism to the next beginning with a producer, for example: - **Food web:** a network of interconnected food chains showing the energy flow through part of an ecosystem. - **Producer:** an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis. - **Consumer:** an organism that gets its energy by feeding on other organisms. - **Herbivore:** an animal that gets its energy by eating plants. - **Carnivore:** an animal that gets its energy by eating other animals. - **Decomposer:** an organism that gets its energy from dead or waste organic matter (i.e. a saprotroph). - **Ecosystem:** a unit containing all of the organisms and their environment, interacting together, in a given area e.g. decomposing log or a lake. - **Trophic level:** the position of an organism in a food chain, food web or pyramid of biomass, numbers or energy. **Food chains usually have fewer than five trophic levels, because energy transfer is inefficient:** - - - - - **Humans eating plants is more efficient than humans eating animals because** - - **FOOD PYRAMIDS** **PYRAMID OF NUMBER PYRAMID OF BIOMASS** +-----------------------------------+-----------------------------------+ | - - | - - | +-----------------------------------+-----------------------------------+ **NUTRIENT CYCLES** **A. CARBON CYCLE**  Carbon is an element that occurs in all the compounds that make up living organisms. Plants get their carbon from carbon dioxide in the atmosphere and animals get their carbon from plants. the carbon cycle is mainly concerned with what happens to carbon dioxide **Photosynthesis** - Removal of carbon dioxide from the atmosphere **Fossilisation** - The carbon in the dead organisms becomes trapped and compressed and can remain there for millions of years. The carbon may form fossil fuels like coal, oil and natural gas. **Respiration** - Plants and animals obtain energy by respiration using carbohydrates and oxygen in their cells. This process produces carbon dioxide and water **Decomposition -** Decomposition releases essential materials from dead organisms. These organisms, which feed on dead material (saprophytes), secrete extracellular enzymes into the tissues and reabsorb the liquid products of digestion. **Combustion (burning) -** When carbon-containing fuels like wood, coal, petroleum and natural gas are burned, the carbon is oxidised to carbon dioxide (C + O2 → CO2). **B. NITROGEN CYCLE** Nitrogen Fixation: Definition, Process, Example & Equation - - - - - - **POPULATIONS** - - -  **FACTORS AFFECTING THE RATE OF POPULATION GROWTH** - - - **PARTS OF A SIGMOID POPULATION GROWTH CURVE** Growth of a bacterial population typically shows four phases. Note that\... \| Download Scientific Diagram **HUMAN POPULATION GROWTH** ***World population growth.** The greatest population* - One of the factors affecting population growth is **infant mortality** (the death rate for children less than 1 year old). - Populations in the newly industrialising world are growing, **not because of an increase in the number of babies born per family**, but **because more babies are surviving to reach reproductive age**. - Infant mortality is falling and more people are living longer. So, life expectancy is increasing. -- -- -- -- 20. **HUMAN INFLUENCES ON ECOSYSTEMS** The human population of the world continues to grow. This increases the demand for the resources that we need to survive. i. **FOOD SUPPLY** - a. - - - - - b. - - - c. - - - d. - e. - - - - **Advantages and disadvantages of large-scale monocultures of crop plants** - **[Advantages]** - - - **[Disadvantages]** - - - - - - - **The advantages and disadvantages of intensive livestock production** - - - - - **[Disadvantages]** - - - - - ii. **HABITAT DESTRUCTION** - - - - - - - - - - - - - iii. **POLLUTION** - - - - - - - - - - - - - - - - - - - - iv. **CONSERVATION** A **sustainable resource** is one which is produced as rapidly as it is removed from the environment so that it does not run out. Some resources can be conserved and managed sustainably. Some resources, like **forests** and **fish stocks**, can be maintained with careful management. - **Conservation of forests** 1. Local communities need to be educated about conservation so they understand why it is important. People are then more likely to care for the environment they live in and protect the species in it. Education helps to ensure logging companies are aware of sustainable practices and consumers are aware of the importance of buying products made from sustainable sources. 2. Areas where rare species of trees grow need to be protected to prevent them being felled for timber or to clear the land for other purposes. Conservation areas can be set up by governments where rare endangered species are protected by tree preservation orders (TPOs). A TPO prohibits any damage being done to the protected trees. 3. The Rainforest cooperation has introduced a scheme called ***Smartlogging***. This is a service, which gives a certificate to a logging company. This shows they are working legally and in a sustainable way to protect the environment. The timber can be tracked from where it is felled to its final export destination and its use in timber products. The customer can then be reassured that the timber in the product is from a reputable source and has not been removed illegally. 4. New plants are grown to recover large areas of rainforest that have been deforested for agricultural purposes. One tonne of waste paper is equivalent to about 17 trees. To conserve the forests, waste paper can be pulped and used again. Newspapers can also be de-inked and used again for newsprint. - **Conservation of fish stocks.** 1. In some parts of the world, local fishermen have over-exploited fish stocks. They have destroyed habitats by using dynamite and cyanide to kill and catch fish. These methods kill all the organisms in the area; whole coral reefs have been destroyed. Education helps the fishermen understand the effects of their methods. They know that if they protect the environment, the fish can survive, grow well, breed and provide them with a living for the future. 2. A closed season is a part of the year when it is illegal to fish for some species of fish in an area of water. This allows the fish to spawn and mature so that they can breed successfully. In this way, fish stocks are maintained. 3. Marine protected areas are clearly defined geographical spaces. They are managed (often legally enforced) to achieve the long-term conservation of nature in that space. They are a way of preventing the capture and removal of fish so that fish stocks can rebuild and the fisheries nearby become sustainable. 4. Some type of fishing nets such as Trawl nets can be very destructive. They are very large fishing nets which not only catch all the living organisms (not just fish) in their path, but they also destroy the sea bed. Fishing net types and mesh sizes are closely regulated in some parts of the world to ensure that fish are not caught randomly, and that undersized fish can escape capture. 5. The quotas help to manage fish stocks and protect species that are becoming endangered through overfishing. Quotas are set for each species of fish taken commercially and for the size of fish. This allows fish to reach breeding age and increase their populations. 6. Fisheries inspectors monitor commercial fish catches. They record catches and use estimates of fish populations, so helping to conserve fish stocks. Many countries use fisheries patrol vessels to make sure that fishing boats are licensed, not fishing in protected areas, using the correct equipment, and are keeping to their quotas. - **Why organisms become endangered.** Anything that reduces the population of a species endangers it (puts it at risk of extinction). Factors that endanger species include **climate change**, **habitat destruction**, **hunting**, **overharvesting**, **pollution** and **introduction of other species**. Endangered species can be conserved, limited by: - **monitoring and protecting species and habitats** - - - - - **Education** - - - **Captive breeding programmes** - - - **Seed banks** - - - **Reasons for conservation programmes:** - - - - - **Use of artificial insemination (AI) in captive breeding programmes** - - - - - - - **Use of in vitro fertilisation (IVF) in captive breeding programmes** - - - - - - - - - - **Risks to a species of decreasing population size** - - - - - 21. **BIOTECHNOLOGY AND GENETIC MODIFICATION** - - - - - - - - **Biofuels** - - - - - - - **Breadmaking** - - - - - - - - - - - - - **Fruit juice production** - - - - **Biological washing powders** - - - - - - - **lactose-free milk** - - - - - - - **Role of fermenters for the large-scale production of insulin, penicillin and mycoprotein** - - - - - - - - - - - - - - - - - - - - **MICOPROTEIN PRODUCTION** - - - - - - - **Genetic modification** - - - - **Genetic modification using bacterial production of a human protein** - - - - - - - - - **Examples of genetic modification:** - - - - **The advantages and disadvantages of genetically modifying crops** +-----------------------------------+-----------------------------------+ | **Advantages** | **Disadvantages** | +===================================+===================================+ | - Reduced use of chemicals such | - Increased cost of seeds | | as herbicides & pesticides | | | | - Increased dependency on | | - Increased yield from the | certain chemicals, such as | | crops | the herbicides that crops are | | | resistant to | | | | | | - Risk of inserted gene being | | | transferred to wild | | | | | | - Reduced biodiversity | +-----------------------------------+-----------------------------------+