Biology Past Paper PDF

BIOLOGY → study of living things 6 Characteristics of Living Things 1. Need for energy (eats/makes waste) 2. Exchanges gas (respiration) 3. Grows 4. Moves 5. Responds to stimuli 6. Reproduces Where do living things come from? Abiogenesis → theory that states life can be made from...

BIOLOGY → study of living things 6 Characteristics of Living Things 1. Need for energy (eats/makes waste) 2. Exchanges gas (respiration) 3. Grows 4. Moves 5. Responds to stimuli 6. Reproduces Where do living things come from? Abiogenesis → theory that states life can be made from non-living things (spontaneous generation) Biogenesis → theory that states life is produced by other living things Francesco Redi questioned spontaneous generation of maggots on meat conducted an experiment on meat 3 treatments: → open air (control) → sealed → screened off Redi’s hypothesis/ → “meat would decay in both jars, but prediction only the jar that allowed contact with flies would produce maggots” Result → only the open air container had meat with maggots Hypothesis was supported! You MUST be able to identify: Manipulated Variable → presence of lid Responding Variable → formation of maggots Do Not Copy The Debate continued…… John Needham believed in abiogenesis boiled chicken broth (sterilized broth) bacteria grew (considers himself victorious) Do Not Copy Lazzaro Spallazani believed in biogenesis repeated Needham’s experiment, but drew off air nothing grew (considers himself victorious) “only proves life needs air” Louis Pasteur designed an experiment to settle the debate boiled nutrient broth 3 treatments: → open → closed → S-neck (open to air, but not atmospheric dust) Pasteur’s hypothesis/ → “believed that micro-organisms prediction would settle in neck of swan-neck flask and, therefore, would not infect the sterile broth” Result → nothing grown in the S-neck flask Hypothesis was supported! concluded there is an active agent in air needed for life, micro-organisms Microscopes and Development of Cell Theory Magnification → enlargement of an image → how many times bigger image is than actual specimen → e.g. 5000X Resolution → microscope’s ability to form clear image → often based on lens quality → how far apart two objects must be in order to appear separate (not blurred together) under microscope → e.g. 10 μm Simple Microscopes → earliest microscopes were similar to magnifying glasses and used one lens Hans and Zacharias Janssen (1595) invented first compound microscope 20 × magnification had two lenses → ocular lens (eyepiece) and objective lens Robert Hooke (1670) compound microscope with three-lens system and magnification of 30x while studying cork, noticed → made of small chambers first to use term ‘cells’ Antony van Leeuwenhoek (1674) used simple microscope but lens was so well made, quality was higher than compound microscopes at the time (up to 500x) first to see and describe unicellular organisms Robert Brown (1833) studying orchids → observes dark spot in cell identifies spot as being important to cell function discovers → nucleus Schleiden and Schwann (1838) Schleiden → all plants made of cells → identifies nucleus as control centre Schwann → all animals made of cells → identifies similarities between animal & plant cells Leads them to propose cell theory Rudolph Virchow (1859) adds to cell theory → cells produced from other cells The Cell Theory all living organisms composed of one or more cells cell → most basic unit of life all cells arise only from pre-existing cells Video – History of Cell Theory https://youtu.be/4OpBylwH9DU Types of Microscopes 1. Modern Compound Microscope series of lenses produces magnified image have several objective lenses of different powers in a revolving nosepiece Human blood smear 400x 2. Dissecting Microscope (Stereoscope) two objectives & two eyepieces produces 3-D visual used to study surfaces of solid specimens, dissections, microsurgery, watch-making, etc PRO: view larger, more opaque objects CON: magnification is much lower 3. Electron Microscopes use beam of e- instead of light stream of e- passes through object and is focused by magnetic field, usually onto a fluorescent or photographic plate far more powerful than ordinary compound microscopes (up to 1.2 million ×) a. Transmission Electron Microscope (TEM) beam of e- pass through very thin section of a fixed & stained sample after passing through, e- hit fluorescent screen of photographic film to produce a 2-D image Mag. 10,000 – 100,000 × Heart tissue infected by a protozoan parasite b. Scanning Electron Microscope (SEM) preferred for surface features, the specimen is “painted” with an e- dense material such as gold e- strike specimen and are reflected, then picked up by sensor that processes a 3-D image Mag. up to 300,000 × Lymphocyte (White Blood Cell) 4. Confocal Laser Scanning Microscope (CLSM) laser beams directed through specimen in planes (like slices), which creates a series of 2-D images images then put together to generate the whole picture (3-D image); good for thick specimens Biofilm Bacteria 5. Scanning Tunneling Microscope (STM) greater magnification than e- microscope e- flow from tip of metal probe to atoms on surface of specimen as probe follows surface contours, info is interpreted by a computer & generates a 3D image DNA What have we discovered? stem cells can divide to produce all other types of specialized cells use of stem cells can lead to development of treatments and cures for many diseases stem cells are found in embryos, and in adult tissue such as bone marrow and cord blood What have we discovered? Do Not Copy genes (molecules of DNA) direct activities of our cells gene sequencing attempts to map the order of the four nitrogenous bases of DNA (adenine, guanine, cytosine, thymine) in the correct order  Do Not Copy this gives us an organism’s genome can be used to study cell activity, determine relationships among organisms, and to develop diagnosing and treating methods for genetic disorders What have we discovered? Do Not Copy cancer → caused by damage to genes tumors → mutations where cells grow uncontrollably scientists study the sequence of cancer-causing genes to learn how they affect cell activity Metastasizing Cancer What have we discovered? Do Not Copy sub-cellular particles not made of cells such as prions and viruses have been discovered. Are they living? a virus is genetic material in a protein coat that takes over cells’ reproductive machinery (ie. cold, flu, polio) a prion is a protein that converts into harmful particles that cause deadly disease (ie. BSE or “mad cow disease”) HIV Virus Mouse prion  Ocular Lens Revolving Nosepiece Arm Objective Lens Stage Clips Stage Diaphragm Coarse Adjustment Light Source Fine Adjustment Base Working with the Compound Microscope 1. ALWAYS carry with two hands 2. Store the microscope on the LOWEST power objective lens 3. Clean with lens paper 4. NEVER use the coarse adjust knob on anything but lowest magnification To focus on a specimen 1. Always start on LOW power, stage down 2. Place specimen on stage (secure with clips) 3. Viewing from the side, raise the stage so the slide almost touches the lens 4. Look through ocular lens, lower the stage using COARSE adjustment knob until the image focuses → DO NOT TOUCH coarse adjustment again 5. Sharpen the image using FINE adjustment knob 6. You can increase magnification by changing the objective lens 7. Focus with FINE adjustment 8. You may want to adjust light using the DIAPHRAGM in order to improve contrast 9. To change slides, switch to LOW power, LOWER stage and change slide How to prepare and stain a Wet Mount Slide 1. Place the specimen on the slide 2. Cover the specimen with 1 drop of distilled water 3. Hold the cover slip at 45o and slowly lower it with a dissecting needle 4. Put a drop of stain on one side of the slide 5. Draw the stain across the specimen using a paper towel placed on the other side of the slide  Wet mount protect sample from drying out and contacting objective lens Staining improves contrast to enable visualization of transparent sample, especially cell organelles, and can help differentiate between different cell types Magnification Images Images are inverted and flipped e.g. The letter p when inverted is b and then flipped would be viewed under the microscope as d Images appear to move opposite direction of slide e.g. move slide towards you, image moves away Microscope Calculations Total Magnification Microscope Mag = Ocular power × Objective power Ocular power = 10× (unless stated otherwise) Objective power: Low power = 4× Medium power = 10× High power = 40× Example B1 If a student views a paramecium under medium power with an ocular lens of 10×, what is the total magnification of his microscope? Microscope Mag = Ocular power × Objective power = (10x)(10x) = 100x Field of View Measurement of diameter of circular area visible through lens Low power = 4.0 mm = 4000 μm Medium power = 1.6 mm = 1600 μm High power = 0.40 mm = 400 μm Magnification & Field of View Objective magnification x Field of view = Constant (Field of View 1) x (Magnification 1) = (Field of View 2) x (Magnification 2) Power Magnification Field of View Product Low 4x 4.0 mm 16 Medium 10x 1.6 mm 16 High 40x 0.40 mm 16 Magnification & Field of View Determine the missing values Power Magnification Field of View Product Low 4x 7 mm 28 Medium 10x 2.8 mm 28 High 40x 0.70 mm 28 Estimating the Size of the Object if you know the size of the FOV and how many objects fit across that FOV, you can calculate the size of one of the objects look at ONE specimen on your slide how much of your FOV does it take up? 1/5? (fit # = 5) Actual Size = field of view fit number More on Fit Number Fit number equals the reciprocal of the fraction of the FOV covered by object e.g. if one object covers 2/3 of FOV, then fit # is 3/2 If difficult to estimate fit #, then can measure image of object and of FOV to determine precise fit # Fit # = 60 mm/26 mm = 2.3 Example B2 The image of the amoeba is seen under medium power. What is its actual size? Field of view 1.6 mm Actual size= = = 0.64 mm Fit number 2.5 Estimating the Size of a Drawing rules exist for formal biological drawings must record the scale on your drawing Scale calculation = drawing size actual size measure your drawing lengthwise values must be in the same units Example B3 Sarah makes a drawing of her bacterium and measures it to be 5.6 cm across. Two bacteria will fit across her field of view when she is viewing it under high power. Calculate the scale of her drawing. Drawing size = 5.6 cm = 56 mm; Fit number = 2; Field of view = 0.40 mm Field of view 0.40 mm Actual size= = = 0.20 mm Fit number 2 Drawing size 56 mm Drawing scale= = = 280 Actual size 0.20 mm Prokaryotic vs. Eukaryotic Cells Prokaryotes → lack membrane bound organelles & nucleus Ex. bacteria & some algae Eukaryotes → contain organelles to complete life functions, just like your body has organs to help you survive Ex. most plant & animal cells Analogy → comparison between two similar things → helps to clarify new ideas organelles vs. organs vs. activities (world around us) all open systems exchanging matter & energy  to view organelles, must use an electron microscope bc → so small organelles are located in cytoplasm, which is fluid inside the cell Nucleus controls all activities of cell (ie brain or city hall) contains DNA surrounded by nuclear envelope Nucleolus in center of nucleus synthesizes ribosomes Ribosomes turn DNA into protein (for growth and reproduction) Mitochondrion cell’s powerhouse uses oxygen to make cell energy (ATP) performs cellular respiration Lysosome vesicle that contains enzymes breaks down particles disposes of waste Vacuole stores food and water involved in transport → plants have 1 large vacuole (important for structure) → animals have several small vacuoles Endoplasmic Reticulum & Ribosomes attached to nucleus rough ER (RER) has ribosomes → transports DNA smooth ER (SER) has no ribosomes → synthesizes lipids (fats) required by the cell Golgi Apparatus modifies and repackages fats disposes of waste products Centrioles involved in cell division like reproductive system Cytoskeleton (animal cells only) supports structure of cell facilitates transport intricate network of fibre-like structures Cell Membrane protective barrier around cell semi-permeable (brings in wanted things, keeps out, or kicks out, unwanted things) both plants and animal cells have cell membranes Cell Wall plant cells, some fungi and bacteria (i.e. prokaryotic and eukaryotic) rigid, supportive, shaping cellulose encloses membrane acts like skeleton for plant cells (along with large vacuole) Chloroplasts (plant cells only) site of photosynthesis (solar energy converted into chemical energy) in plant cells made up of two membranes contains chlorophyll The Cell Membrane (Plasma Membrane) Why is a cell considered an open system? In order to maintain homeostasis, a cell must: → obtain or make all materials needed → obtain energy from the environment → control the movement of matter and energy in and out of the cell The Cell Membrane (Plasma Membrane) makes up cell membranes and organelle membranes semi-permeable made of phospholipids, proteins, carbohydrates and cholesterol role is to maintain equilibrium  channel carrier phospholipid protein protein carbohydrate cholesterol transport/transmembrane proteins integral protein hydrophilic head hydrophobic tail Phospholipid Bilayer phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) fatty acid tail causes phospholipids to arrange in bilayers (heads facing towards extracellular fluid and cytoplasm) Fluid-Mosaic Model of the Cell Membrane Fluid → made of small, movable, components → flexible Mosaic → made of different parts ○ phospholipids are the main structure ○ carbohydrates act to recognize & bind substances ○ proteins help transport materials, and are receptors ○ cholesterol keeps the fatty acids mobile Particle Theory of Matter All matter made of small particles that are constantly randomly moving (Brownian motion) o Speed of particles (EK) increases with temperature ▪ e.g. smell of garbage in summer vs. winter Transport across the Cell Membrane concentration gradient → difference in concentration ([ ]) across a membrane dynamic equilibrium → equal [ ] on either side → substances moving back & forth across membrane at equal rates, Equilibrium, but NO NET A GRADIENT no gradient. System is movement exists BALANCED Transport across the Cell Membrane Also depends on size and polarity of substance Passive Transport is ALWAYS DOWN the concentration gradient (move from area of high [ ] to area of low [ ]) doesn’t cost any energy NO ATP (energy) NEEDED 3 types 1. Diffusion net movement of particles from an area of high [] to low [] particles move randomly (Brownian Motion), so diffusion driven entirely by EK the molecules possess non-polar, small molecules (O2, CO2) 2. Osmosis net movement of water from high [ ] to low [ ] water moves when solute can’t 3. Facilitated Diffusion many polar molecules & ions diffuse passively with help of transport proteins still passive because down a [ ] gradient a. Channel Proteins – have hydrophilic channels that allow molecules/ions to cross membrane ex. aquaporins – allow entry of up to 3 billion water molecules per second (in the kidneys – if we didn’t have aquaporins, we would have to drink 50 gallons of water a day!!) b. Carrier Proteins – undergo change in shape to pass molecule through membrane ex. glucose transporter – C6H12O6 passes through 50,000 × faster than if diffusing on its own What happens when cells are placed in solution? Must compare [ ] in solution to [ ] in cell’s cytoplasm Water will move from area with higher [H2O] & lower [solute] to area with lower [H2O] & higher [solute] Hypotonic → relatively lower [solute] & higher [H2O] Hypertonic → relatively higher [solute] & lower [H2O] Isotonic Solution → equal [H2O] & [solute] → water will flow at same rate in both directions Tonics and Animal Cells Tonics and Plant Cells Dialysis passage of material across semi-permeable membranes (dialysis tubing) address solute imbalances resulting from damaged kidney machine pumps blood out alongside membranes bathed in H2O and other solute mixtures waste material diffuses out, blood returned to the body. done multiple times a week Dialysis Diffusion & Osmosis Examples A beaker contains a sealed pouch made of dialysis tubing. The tubing is permeable to water, but not to solutes. Identify: a. the missing % concentration in the bag b. the missing % concentration in the beaker c. whether the tube is hyper, hypo or isotonic to the surrounding solution d. indicate the flow of water a. 85% H2O in bag initially b. 50% H2O in beaker initially c. The bag is hypotonic compared to the surrounding solution d. Water would flow from the bag into the surrounding solution Diffusion & Osmosis Examples A B The U-tube has sides A and B separated by a semipermeable membrane, m. The volumes of A and B are equal initially for each situation. Assuming that m is impermeable to starch, determine the % concentrations for the equilibrium state. m Initial At Equilibrium Side A: 6% glucose, 2% Starch Side A: Glucose _____, 2% 4% Starch ______ Side B: 2% glucose, no starch Side B: Glucose _____, 4% Starch ______ 0% Diffusion & Osmosis Experiments Iodine Diffusion via Egg Mass Change Potato Length Change Dialysis Tubing via Osmosis via Osmosis (Video) (Video) (Video) Active Transport requires the cell to expend energy (uses ATP) solute may be “pumped” against (up) a [ ] gradient (from low to high [ ]) done by carrier proteins allows cells to maintain internal environment of solutes that differs from external environment 1. Protein Pumps each solute has its own pump a. Sodium-Potassium Pump animal cells NEED high [ ] of K+ and low [ ] of Na+ membrane helps keep these gradients by pumping Na+ OUT of the cell and K+ INTO the cell pumps 3 Na+ out for every 2 K+ in b. Proton Pump actively transports H+ out of the cell co-transport → substance that has been pumped out can do work as it moves back across (H+ can couple with sucrose and bring it back into cell) 2. Exocytosis (Bulk Transport) cells excrete molecules using vesicles (small membrane sacs) that fuse with membrane and release contents outside cell membrane, Golgi and ER can all form vesicles 3. Endocytosis cells take in molecules by forming new vesicles from cell membrane a. Phagocytosis (cell “eating”) used to bring in large materials to be digested white blood cells (macrophages) swallow bacteria b. Pinocytosis (cell “drinking”) cells take in droplets of fluid and small solutes c. Receptor Mediated Endocytosis uses protein receptors in membrane to identify, bind and bring specific materials into the cell Do not copy - rate at which a substance moves in a cell is 0.02 μm/s - how long for it to move halfway across a cell that is 100 μm in diameter? (2 500 s or 42 min) - how long for it to move halfway across a cell that is 0.25 m in diameter (e.g. basketball)? (6 250 000 s or 72 days!) - What’s the problem? Cell Size and Function once inside the cell, all materials move by diffusion diffusion over long distances is slow & inefficient o risk of cell death if cannot quickly remove waste from and bring nutrients into cell there is an upper limit on cell size o address via cell shape and division Surface Area and Volume HIGH surface area means lots of places for materials to enter and leave LOW volume, means that once inside, nutrients get to where they are needed quickly Surface Area to Volume Ratio ratio of external surface area to volume (SA:VOL) S.A. V higher the number, more efficient the cell, greater chances for survival SA:VOL & Cell Shape high SA:VOL for cells with o flattened shapes (i.e. not a sphere) o lots of folding of membrane (i.e. wavy, reticulated) SA:VOL & Cell Size/Number  many smaller, flatter, wavy cells is more efficient than a few larger, round cells examples → villi line the intestines for nutrient absorption → plant roots have root hairs Calculating SA to Vol Ratio SA for a cube: (L x W) x 6 Volume for a cube: (L x W x H) divide SA by Vol to compare cells with different proportions SA increases with L2, while V increases more rapidly with L3 Example Determine the surface area to volume ratio of a rectangular prism cell with a length of 13.0 μm, a width of 12.0 μm, and a height of 11.0 μm. SA = 2(13x12) + 2(13x11) + 2(12x11) = 862 μm2 Volume = 13x12x11 = 1716 μm3 SA:V = 0.502 Specialization limits placed on size b/c as ↑ size, SA:Vol ↓ large, multicellular organisms solve this in 3 ways: 1. make cells smaller (↑ SA:Vol) 2. cells specialized for particular jobs 3. interdependence – cells support each other in survival  Do not copy Organization whole organisms are organized into a hierarchy of structure (organizes and streamlines life functions)  Do not copy Cells → Tissues → Organs → Organ Systems → Organisms Organism living entity made of interacting inter-dependent systems  Do not copy Organ Systems group of interacting organs that work together to accomplish specific function for the plant Plant Organ Systems 1. shoot system – everything above ground, captures energy 2. root system – mostly below ground – obtains water, nutrients & anchors plant Organs Do not copy groups of tissues working together to accomplish a specific task Plant Organs Flowers: reproduction Stem/Shoot: support, transport, energy capture Leaves: gas exchange, energy capture/photosynthesis Roots: obtain water, nutrients, support Tissues groups of cells working together to perform the same function Leaf Tissues be able to identify tissue from image (e.g. text p 321 & 325) and describe its function Dermal → outer layer of non-woody plants → one cell layer thick → protective layer that is transparent to transmit light → waxy cuticle limits from water loss Palisade Mesophyll → packed vertically/tightly, many chloroplasts, primary site of photosynthesis Spongy Mesophyll → round and loosely packed, gas exchange Meristem → specialized growth tissue, site of cell division Vascular → transport tissue, tube-like veins transport water & nutrients (present in roots, stems and leaves) Cells (Specialized Cells in the Leaf) plants photosynthesize (not animal cells) 6 CO2 (g) + 6 H2O (l) + energy → C6H12O6 (s) + 6 O2 (g) plants also undergo cellular respiration (as do animal cells) C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) + energy Stomata → holes on underside of leaf where CO2, H2O and O2 enter and exit leaf → open or close to regulate water loss and gas exchange → typically open during day, closed at night Guard Cells → open or close stomata → lots of water in guard cells (turgid) causes them to swell and stomata to open → less water in guard cells (flaccid) causes them to deflate and stomata to close Turgor Pressure → pressure applied by water in a cell Specialized Cells in the Plant Xylem → non-living cells at maturity → conducts water & minerals from root to leaves → one-way transport Phloem → formed from long sieve tubes (no nuclei) which are connected to companion cells (nuclei) → transports sugary sap and water from leaves to other parts of plant Do not copy Other Specialized Structures Lenticels → plants with bark have lens shaped pores Root Hairs → growths on root to ↑ SA and ↑ absorption Pollen → male gametes (reproductive cells) of plant Seeds → embryonic plant enclosed in protective coating Needles → retain H2O in coniferous tree Transport in Plants plants must be able to move nutrients from the SOURCE (where they originate) to the SINK (where needed) Movement in the Xylem H2O moves by “pushing” and “pulling” Root Pressure minerals are actively transported into the roots H2O follows and increases pressure in the xylem this positive pressure (root pressure) pushes H2O up to small heights in the xylem Transpiration evaporation of H2O through leaf stomata & bark lenticels creates a transpiration pull of water and dissolved minerals up the xylem dependent on temp ↑ temp ↑ evaporation ↑ movement in xylem Cohesion attraction of H2O to each other (due to H bonding) Adhesion attraction of H2O molecules to other substances (like the inside of the xylem) → cohesion & adhesion help H2O pull itself up the plant From Source to Sink – Transport in the Phloem leaves (site of photosynthesis) are the source places where sugars are used are known as the sink phloem tissue is essential to transport of sugar from leaves to rest of plant for cellular respiration Pressure Flow Theory Do not copy in leaf, phloem becomes loaded as companion cells use carrier proteins & active transport to take in sugar from photosynthesis water moves into sieve cells by osmosis ↑ water pressure inside sieve cells pushes water & sugars through phloem to rest of plant Do not copy Plant Adaptations features / structures / behaviors of organisms to help them survive (and reproduce) in their env’t Larger leaves → ↑ SA to capture more light Darker leaves → absorb more light; whereas leaves lighter in colour will reflect more light To reduce Water Loss: - Waxy Cuticle - Lower SA - Thick Epidermis - Hairs ▪ Create a mini-windbreak that allows for a thick boundary layer of water vapor adjacent to plant Tropisms directional growth of a plant as determined by an environmental factor Positive tropism → grow toward the stimulus Negative tropism → grow away from the stimulus Types of Tropisms Phototropism: response to light Gravitropism: response to gravity Hydrotropism: response to water Thigmotropism (Nastic Response): response to contact tropisms are control systems to ensure survival Investigations of Phototropism Darwin & Darwin tip of plant was responsible for detection of light Boysen-Jensen proposed a chemical moving from tip is what allowed communication with area of elongation cut tip and placed gelatin (allowed chemical to flow) cut tip and inserted mica (did not allow chemical to flow) Went isolated the chemical – auxin auxin is a hormone – a chemical compound made in one area and transported to another  auxin causes cells on side away from light to elongate Gravitropism roots grow toward gravity→ positive tropism shoots grow against gravity→ negative tropism Thigmotropism (Nastic Response) plants attaching to a support (ex fence) to aid growth