Cell Biology: Prokaryotic vs Eukaryotic Cells & Transport

CELLS AS A BASIS FOR LIFE – MODULE 1 Inquiry Question: What distinguishes one cell from another? ● investigate different cellular structures, including but not limited to: – examining a variety of prokaryotic and eukaryotic cells Prokaryotes  Unicellular, smaller, less complex, not membrane bound Prokaryotes include: - Bacteria - Archaea Genetic material stored in singular DNA chromosomes contained in nucleoid. Cell membrane surrounded by cell wall.  Many have a capsule outside the wall to protect from damage, dehydration, and engulfment from eukaryotic cells Move around using flagellum, many use pili to allow movement       1. Bacteria Can survive in almost any environment Gain energy from either photosynthesis or reducing inorganic compounds Contribute to ecosystem as they break down plants and animal waste products 2. Archaea Extremophiles – survive in many kinds of extreme conditions - High and low temperatures - Oxygen deprived environments Have cell wall, live in extreme conditions because of unique cell membrane (made of lipids) and set of genes Flexible membrane allows them to respond to external conditions and allow for proteins, rather than denature Eukaryotes  Have cell wall to provide structure and support, animal cells do not  Plant cells have a permanent vacuole that stores wastes minerals and nutrients (saps) – also gives structure by keeping cell turgid - animal cells have smaller, multiple vacuoles but they do not provide support  have chloroplasts which are site of photosynthesis Describe two differences between prokaryotic and eukaryotic cells: Eukaryotic cells have membrane bound organelles, meaning that organelles such as the nucleus and mitochondria are surrounded by a lipid bilayer membrane, whereas prokaryotic cells do not have membrane bound organelles. Eukaryotic cells have a nucleus for the DNA, however prokaryotic cells have their DNA distributed throughout the cell. Compare and contrast plant and animal cells: Plant and animal cells are both eukaryotic, so both have a nucleus and membrane bound organelles. Plant cells have a cell wall and vacuoles to provide support, however animal cells do not have cell walls, and have small vacuoles that do not provide support. Also, plant cells have chloroplasts for photosynthesis, but animal cells do not. – describe a range of technologies that are used to determine a cell’s structure and function Function of microscopes 1. To enlarge a microscopic specimen to be studied (magnification) 2. To observe the microscopic specimen’s features in clarity (resolution) Light microscope  Contemporary light microscopes can magnify objects up to about a thousand times  Only organelles that can be observed are nuclei, chloroplasts, and mitochondria  Not sufficiently powerful to reveal finer details of cell structure Electron microscope  Can achieve greater resolution because wavelength of electrons is shorter than that of light  Must be performed in vacuum to keep electrons travelling in a beam ● investigate a variety of prokaryotic and eukaryotic cell structures, including but not limited to: – comparing and contrasting different cell organelles and arrangements Nucleus – stores the cell’s DNA, nucleus produces ribosomes Mitochondrion – respiration occurs here, glucose and oxygen are used to produce energy (ATP) Chloroplast – where photosynthesis occurs, granum (stacked discs of thylakoids) increases the surface area for light reaction, stroma (liquid part where dark reaction occurs) Endoplasmic reticulum and ribosomes – rough endoplasmic reticulum (have ribosomes) and smooth endoplasmic reticulum, transports proteins throughout the cell Golgi body and lysosomes – Golgi bodies sort and process substances for packaging and transporting out of the cell, lysosomes break down and remove waste from cell (contains digestive enzymes) Cell membrane and cell wall – transports nutrients into the cell and waste from cell, cell wall provides support and protection for the cell with cell walls on outside of cell membrane  cell walls are only found in plant cells Vacuole – sac-like structure that stores materials such as water, ions, wastes and proteins  found in both but have one permanent vacuole in plants – modelling the structure and function of the fluid mosaic model of the cell membrane Cell membrane  forms barrier around outside of cell – semi-permeable i.e., smaller compounds such as water easily move but large compounds (starch) cannot  help with transporting molecules in and out of cell, cell recognition and communicate with other cells  consist of phospholipid bilayer, proteins, carbohydrates, cholesterol Fluid mosaic model - Trans-membrane - Integral membrane - Peripheral membrane Proteins embedded in the phospholipid bi-layer form channel that allow certain substances to pass across the membrane in either direction Fluidity of cell membrane  Phospholipids and proteins can move with some crossing on to other side of membrane Phospholipids  Have polar hydrophilic heads and non-polar hydrophobic tails  Makes them impermeable to water particles, ions, and polar molecules  Protein channels control movement Cholesterol  Provides membrane with stability without affecting fluidity  Ensures fluidity of membrane will be maintained in high and low temperatures Proteins  Integral proteins are a permeable part of the membrane  Perform important cellular and inter cellular activities   Peripheral proteins are temporary part of membrane and bind to integral proteins Help with transportation of materials using facilitated transport Carbohydrates  Linked to producing proteins (glycoproteins) or lipids (glycolipids)  Allow recognition and adhesion between cells and of antibodies, hormones, and vitamins by cells Inquiry question: How do cells coordinate activities within their internal environment and the external environment? ● investigate the way in which materials can move into and out of cells, including but not limited to: – conducting a practical investigation modelling diffusion and osmosis Cell membrane permeability Many substances made of molecules need to be brought into a cell and then excreted. The permeability (a measure of the ability of a substance to pass through the membrane) of a membrane to molecule depends on: a) size b) electrical charge c) lipid solubility   small molecules move across membranes fast hydrophilic molecules have difficulty penetrating a membrane  lipid-soluble molecules can easily penetrate the membrane – e.g., urea and ethanol have high permeability  electrically charged molecules have low membrane permeability  neutral molecules e.g., carbon dioxide, oxygen have high permeability  molecules that have low permeability rely on carrier proteins to transport them across membrane in cells, known as active transport Diffusion and osmosis   Diffusion is movement of particles from high concentration to low concentration No energy required therefore passive process Simple diffusion refers to movement of particles across a semi-permeable membrane. Factors that affect this include: - Concentration (greater the gradient, faster the diffusion) - Temperature (higher, faster) - Particle size (smaller the particle, faster it moves) Facilitated diffusion occurs when particles move down the concentration gradient  protein channels in cell membrane allow for movement of particles - More specific about what particles are transported - Channel proteins are found in membranes are specific for substances Importance of diffusion  Used in transporting food, waste products in and out of cells  When oxygen is used up, the concentration lowers so oxygen will diffuse through cell membrane  When living cells produce carbon dioxide as a waste product, the surrounding concentration is lowered and so carbon dioxide will diffuse out of the cell into the surroundings Osmosis  Type of diffusion that refers to net diffusion of water molecules from high to low concentration  Water will enter the cell until the osmotic gradient is equal  Movement of war occurs when there is more water outside than in How does osmosis affect red blood cells? When red blood cells are in a hypertonic solution, water flows out of the cell faster than it comes in. this results in crenation of the blood cell. On the other extreme, a red blood cell that is hypotonic will result in more water flowing into the cell than out. This results in swelling of the cell and potential haemolysis of the cell. In an isotonic solution, the flow of water in and out of the cell is happening at the same rate. ● investigate the way in which materials can move into and out of cells, including but not limited to: – conducting a practical investigation modelling diffusion and osmosis examining the roles of active transport, endocytosis, and exocytosis Endocytosis  Cells take in materials in bulk by forming new vesicles from the cell membrane  Materials near the membrane are enclosed by it  The vesicle transports the substance to its required location in the cell Exocytosis  The secretory vesicle membrane and cell membrane touch, some proteins alter the arrangement of phospholipids  Membranes fuse and contents of secretory vesicle are released  Vesicle membrane becomes a permanent part of the cell membrane Active transport  The movement of molecules from an area of low concertation to an area of high concentration Active transport requires carrier proteins that spans the membrane to actively move chemicals from a low to high concentration, using cellular energy in the form of ATP. e.g., glucose and amino acids are reabsorbed by kidney cells so that they are not lost in urine or when the end products of digestions are loaded from the small intestine into the bloodstream. ● investigate the way in which materials can move into and out of cells, including but not limited to: – relating the exchange of materials across membranes to the surface-area-to-volume ratio, concentration gradients and characteristics of the materials being exchanged Surface area to volume ratio - surface area of cell membrane effects rate of exchange between cell and its environment  larger cells have greater metabolic needs, so need to exchange more materials  smaller cells can exchange matter more efficiently As the size increases, the surface area to volume ratio decreases Survival  Cells must constantly interact with their surrounding environment  Gases and food molecules dissolved in water must be absorbed and waste products must be eliminated  Raw materials (for metabolism) enter through cell membrane  the greater the surface area, the larger the amount of raw matter that can enter at only one time  but if a cell’s volume is too large, the organelles in the centre are too far away for diffusion of nutrients to effectively occur The volume increases more rapidly than the surface area, and so the relative amount of surface area available to pass matter to a unit volume of the cell steadily decreases What is the significance of the diagram on the right in terms of cell survival? The cube with the highest surface area: volume ratio is best for cell survival as diffusion can effectively occur to get nutrients to the centre of the cell. The cube with the lowest ratio would not survive as easily since it is too difficult for nutrients to reach the centre. ● investigate cell requirements, including but not limited to: – suitable forms of energy, including light energy and chemical energy in complex molecules – matter, including gases, simple nutrients, and ions – removal of wastes Cell requirements: energy  Autotrophs make their own organic compounds from inorganic compounds in soil and atmosphere  carbon fixation - Producers, include plants who carry out photosynthesis  Heterotrophs gain organic compounds by consuming other organisms - Consumers, include animals and fungi Cell requirements: matter  The elements found on earth are found in all types of cells  These atoms are organised into larger compounds in living things Inorganic compounds  Water (H2O) is a solvent and transport medium - Chemical reactions in cells take place in a water-based fluid (cytosol)  Oxygen (O2) is needed for energy and is achieved through cellular respiration - Terrestrial organisms take it in by gas, and aquatic organisms take it in solution  Nitrogen (N) is part of amino acids that link to form protein molecules - Consumers get nitrogen from plants that are added to the soil from the N2(g) in the air  Minerals build many enzymes and vitamins, for example:  Calcium (bones and teeth)  Sodium and potassium (nervous system)  Magnesium (muscle function)  Iron (haemoglobin production) Organic compounds Carbohydrates are important for energy and structure of organisms  Glucose  Sucrose  Starch  Cellulose  Lipids are important in cell membranes - Good for energy storage and help maintain structure of the membrane  Proteins are composed of amino acids - Have many functions including enzymes, hormones, antibodies, or carrier molecules (haemoglobin) - Proteins are a part of the cell membrane  Nucleic acids carry genetic information. DNA and RNA are made of long chains of nucleotides, sugars, and phosphates  DNA carries information required to assemble proteins from amino acids  RNA helps with the manufacturing of proteins in the cell Chemical Nucleic acids Chloride ions Lignin Elements they are composed of Elements in DNA and RNA Chlorine Carbon, hydrogen, and oxygen Parts of the cell Nucleus Cell membrane Plant cell wall Carbohydrate: Glucose Carbon, hydrogen, and oxygen Mitochondria Carbohydrate: Starch Carbohydrate: cellulose Carbon, hydrogen, and oxygen Carbon, hydrogen, and oxygen Chloroplast Cell wall Lipids Carbon, hydrogen, and oxygen Cell membrane proteins Carbon, hydrogen and oxygen, nitrogen Organelles and cell membrane, enzymes Use or function Carry genetic information Electrochemical signalling Strengthen cell wall, provide rigidity Used in respiration for ATP production Storage of glucose for later use Strengthen cell wall, provide rigidity Form a ‘waterproof’ barrier between the cell and the outside world Speed up chemical processes, structure of most parts of the cells Cell requirements: waste removal Autotrophs and heterotrophs have waste products from their metabolisms known as excretion - Carbon dioxide from cellular respiration - Nitrogenous wastes from the breakdown of proteins and nucleic acids ● investigate the biochemical processes of photosynthesis, cell respiration and the removal of cellular products and wastes in eukaryotic cells Photosynthesis in eukaryotic cells Plants require light, water, and carbon dioxide to make glucose (C6H12O6) which is produced in green tissues (leaves). They trap the energy from sun and convert it into chemical energy, which is stored in bonds between the glucose molecules. Carbon dioxide + water  glucose + oxygen 6CO2 (g) + 6H2O(l)  C6H12O6 (s) + 6O2 (g) Photosynthesis in the ecosystems: 1. Photosynthesis transforms radiant head from sun into chemical energy in organisms. Autotrophs therefore begin food chains where energy is passed from one trophic level to the next 2. Photosynthesis releases gaseous oxygen and removes carbon dioxide from the atmosphere Importance of leaves  Main location where photosynthesis occurs  Broad and flat to capture as much sunlight as possible Leaf surface  Upper and lower surfaces are only one cell thick – epidermis  Transparent to allow sunlight to reach cells inside leaf   Epidermis covered with waxy layer (cuticle) to protect leaf from harsh weather conditions and drying out Gases from air (carbon dioxide and oxygen) can enter through small openings on underside of leaf  Guard cells allow stomata to open and close  Water can evaporate through stomata which draws water up from roots to leaves through xylem tubes (transpiration) - Stomata would be open when photosynthesis is occurring Stomata would close on hot days to prevent water loss Inside the leaf  Upper layers of cells are palisade cells, tightly packed and contain chloroplasts for photosynthesis  Lower layers are mesophyll cells, loosely packed and contain chloroplasts  Air spaces for gases to move easily between cells  Water supplied to leaves through xylem cells  Phloem cells take glucose away from leaves to rest of the plant Chloroplasts  Site of photosynthesis - Light energy converted into glucose and oxygen is released   Leaves and stems (sometimes) are green due to chlorophyll pigment Chlorophyll absorbs light energy  Chloroplasts found in mesophyll at upper surface of leaf (more sun exposure)  increases rate of photosynthesis   Inside each chloroplast are flattened membranes called grana Grana holds thylakoids where chlorophyll is made  Inner membrane is permeable and surrounded by a stroma (contain enzymes, DNA, and ribosomes) Photosynthesis occurs in two stages:   1. Light dependant reactions Chlorophyll captures solar energy to produce ATP Water split into hydrogen ions and oxygen gas – these reactions take place in grana (where chlorophyll is located) Water  hydrogen ions + oxygen + ATP 2. Light independent reactions  Stroma then use hydrogen ions and carbon dioxide to produce glucose (do not require solar energy)  ATP from stage 1 provides energy for stage 2  This energy allows carbon dioxide and hydrogen ions to form glucose and water Hydrogen ions + ATP + carbon dioxide  glucose + water + ADP (Water is then used to feed back into stage 1) Atmosphere  stomate opening  sub-stomal cavity  air spaces  palisade cells Cellular respiration A chemical reaction that occurs in living cells using glucose and oxygen to produce energy, with carbon dioxide and water as waste products Adenosine triphosphate (ATP)  Immediate source of energy for cells  Unstable energy of ATP is contained in phosphate bonds - Cycling of ATP and ADP means energy is always available   Cellular respiration occurs in mitochondrion Folds in the inner membrane are cristae, which increase surface area for reaction to take place Photosynthesis Location Chloroplast Cellular Respiration Aerobic Mitochondria Reactants Carbon dioxide and water Glucose and oxygen Glucose and an electron acceptor (not oxygen) Products Glucose and oxygen Carbon dioxide, water, and ATP Carbon dioxide, ATP, reduced species Anaerobic Cytoplasm 1. In photosynthesis, what are the two major reactions that take place? Light dependent and light independent 2. Where do each of these reactions take place? Light dependent occurs in the thylakoids in the chloroplasts. Light independent occurs in the stroma, in the chloroplasts. 3. In aerobic cellular respiration, what three major steps are involved? Glycolysis, Kreb’s Cycle/TCA, electron transport chain 4. Where do each of these three major steps take place (for eukaryotes)? - Cytoplasm - Mitochondria Chloroplasts  Contain pigment to capture light energy  Oxygen gas production occurs  Found in plant cells  Glucose production occurs within  Sometimes found within photosynthetic protist  Contains chlorophyll  Calvin Cycle occurs ● ● Mitochondria  Main goal to produce ATP energy  Can be found in plant or animal cells  Carbon dioxide gas production occurs  Would be in muscle cells  Water production occurs  Sometimes found within photosynthetic protist  Site of aerobic cellular respiration  Krebs and Electron Transport Chain occurs conduct a practical investigation to model the action of enzymes in cells investigate the effects of the environment on enzyme activity through the collection of primary or secondary data Enzymes  Proteins that act as biological catalysts Features:  Specificity of some enzymes  Only bind to one substrate which catalyses one specific reaction  But some bind to many and catalyse multiple reactions  Not consumed during a reaction, and can therefore be reused multiple times Active site When an active site binds to a substrate it is called an enzyme-substrate complex. Enzyme interaction models 1. Lock and key models  How the active site and specific substrate fit together like a lock and key (highly specific)  If it does not fit into active site, no reaction occurs    2. Included fit model When a substrate binds to the active site, the AS can slightly change to accommodate More accurate than lock and key Active sites are capable of changing shape to achieve a tight fit Maintenance of a constant internal environment for optimal metabolic efficiency - Enzymes control all metabolic processes in the body - Work optimally in an environment where temperature and pH conditions are met - At temperature and pH values other than the optimum, enzymes will not work as efficiently or not at all Factors affecting enzyme activity  Sensitive to temperature and pH (acidity or alkalinity of a substance)      a) Temperature sensitive Enzymes within cells function best at temperature of the living organism in which they occur Function normally at temperatures up to 40°C Above this, their efficiency decreases Molecules denature above 60°C Excessive cold also causes it to change shape and slow or stop functioning b) pH sensitive Each enzyme has its own narrow range of pH within which it functions most efficiently  related to the concentration of hydrogen ions in a solution    Alkalinity or acidity outside of optimum pH can alter shape or slow/stop is functioning Most enzymes function at or near neutral Enzymes in the digestive tract function in an acidic or alkaline medium    c) Effect of substrate concentration on enzyme activity Increasing substrate concentration increases the rate of reaction This is because more substrate molecules will collide with enzyme molecules so more products will be forms The reaction should occur quicker BUT    An enzyme only contains one active site If substrate concentration increases, then after a while all active sites will be ‘taken’ (saturation) Increasing the concentration of the substrate no longer has an increasing effect on the reaction rate Denaturing of enzymes  Shape of active site is affected by pH and temperature  Increasing the temperature to 40°C will cause permanent change to the shape of the active site  This is why enzymes top working when they are heated  denature Role of catalase in breaking down hydrogen peroxide in cells  Hydrogen peroxide is often formed because of reactions in all plant and animal cells  Build up = hazardous  Catalase enzymes found in all plant and animal cells break down hydrogen peroxide into water and oxygen ORGANISATION OF LIVING THINGS – MODULE 2 Inquiry question: How are cells arranged in a multicellular organism? ● compare the differences between unicellular, colonial, and multicellular organisms by: – investigating structures at the level of the cell and organelle – relating structure of cells and cell specialisation to function  ORGANISATION OF CELLS: unicellular vs. multicellular Unicellular organisms – so small that their surface area to volume ratio means they rely on diffusion to supply oxygen for cellular respiration and to remove waste products such as carbon dioxide Multicellular organisms – bigger in size and so total surface area to volume ratio is smaller. Cells at the centre of the organisms would be too far away from the surface for substances from the outside environment to reach them effectively Colonial organisms (link between uni and multi) – first step from single celled to multicellular organisms. All individual cells of a colonial organisms can carry out functions necessary for life, so they could all be seen as a single organism e.g., volvox consist of green algae cells that form spherical colonies of up to 50,000 cells, they live in a variety of freshwater habitats Complexity Multicellular organisms need specialised organ systems, whereas all the life processes in a unicellular organism take place in one cell. Multicellular organisms need organ systems to carry out functions such as: - Communication between cells, e.g., nervous system and circulatory system - Supplying the cell with nutrients, e.g., digestive system - Controlling exchanges with the environment, e.g., respiratory system and excretory system ● investigate the structure and function of tissues, organs and systems and relate those functions to cell differentiation and specialisation  ORGANISATION IN MULTICELLULAR ORGANISMS: specialised cells to systems Cell differentiation and specialisation - division of labour in multicellular organisms become structurally suited to carry out functions - increases their efficiency in carrying out their functions - some cells obtain nutrients and other tissues function in movement, growth, and excrement - embryonic cells require protection and nutrients, only when they mature and develop structural changes so they can carry out specialised functions when cells become specialised to perform a particular function they differentiate they develop suitable structural features which makes them structurally different from other cells and from the embryonic cells they arose from a group of cells that are similar in structure and work together for common functions is called a tissue Explain why cell differentiation is necessary for multicellular organisms: Multicellular organisms are very large and have lots of cellular requirements for nutrient transfer and waste being excreted. Differentiation increases efficiency by different cells having different functions so that the organism can perform all required tasks. Organelles (membrane-bound structures that have specific roles in the cell) e.g., mitochondria, nucleus Cells (basic structural and functional unit of living organisms) e..g, cardiac muscle cells Tissues (cells that perform similar functions) e.g., cardiac muscle tissue Organs (different tissues grouped together to perform a specific function) e..g, heart Organ systems (organs grouped together to carry out particular function) e.g., cardiovascular system Organism (a living thing made up of many interrelated components that work together) e.g., human Inquiry question: What is the difference in nutrient and gas requirements between autotrophs (plants) and heterotrophs (animals)? investigate the function of structures in a plant, including but not limited to: – dissected plant materials – microscopic structures  NUTRIENT AND GAS REQUIREMENTS Autotrophs – plants are autotrophs/producers, manufacture food by photosynthesis, and are carry out cellular respiration 24/7 through vascular tissues (xylem and phloem) Xylem tissues carry water and dissolved minerals from the roots upwards, through the stems and to the leaves. Phloem vessels carry food such as glucose dissolved in water and amino acids from the leaf to all other cells. Energy + chlorophyll Water + carbon dioxide  glucose + oxygen 1. Xylem vessels  Water and dissolved nutrients move from the soil into roots through epidermal cells via root hair  Water then moves to root tissues from outer epidermal layer to transport tissue in cells of root  When cells specialise to become xylem vessels, their transverse walls break down, so cells are stacked on top of each other and become continuous tubes 2. Transpiration-Cohesion-Tension Theory  Sap is mainly pulled by transpiration rather than pushed by root pressure Cohesion – attraction between water molecules allows a continuous stream of molecules from leaves to roots Adhesion – attraction between two types of molecules where water molecules adhere to the cell molecules in the walls of the xylem. As water molecules are removed by transpiration, the next molecule moves upwards to take its place, pushing the stream of molecules continuously along (passive transport) - Roots cells absorbing water - Transpiration stream carrying water through the xylem - Cohesion and adhesion ● investigate the function of structures in a plant, including but not limited to: tracing the development and movement of the products of photosynthesis Movement of products of photosynthesis through phloem vessels Phloem vessels – specialised tissue that transports substances (produced by photosynthesis from leaves to rest of plant to feed each cell)  Unlike xylem vessels, sieve tube elements are cells with living contents (cytoplasm) but do not have nucleus or other organelles besides mitochondria Companion cells – small cells associated with each sieve tube element and responsible keeping sieve tubes aligned  Organic nutrients (sugars), produced by photosynthesis, move up or down the plant through sieve tube elements, known as translocation  Sap flows from one cell to the next through perforated transverse walls known as sieve plates Source to sink theory 1. Sugar loaded into phloem tube from sugar source e.g., the leaves active transport - Needs to be transported from low to high concentration and active transport is required to move against concentration gradient 2. Water enters by osmosis due to high solute concentration in the phloem tube where water pressure is raised - Water moving from an area of high to low concentration of water is passive transport 3. At sugar sink, where sugar is taken to be used or stored, it leaves the phloem tube. Water follows the sugar leaving by osmosis and the water pressure in the tube drops 4. Building up of pressure at the source end, and reduced at sink end, causes water to flow from source to sink. As sugar is dissolved in the war, it flows at same rate. Sieve tubes between phloem cells allow movement of phloem sap to continue ● investigate the gas exchange structures in animals and plants through the collection of primary and secondary data and information, for example: – microscopic structures: alveoli in mammals and leaf structure in plants – macroscopic structures: respiratory systems in a range of animals  GAS REQUIREMENTS IN ANIMALS System involved respiration, breathing and gas exchange Respiration is a biochemical process occurring in all cells: glucose + oxygen  water + carbon dioxide + energy Breathing – process that allows an animal to inhale and exhale and uses muscles and skeletal system - helps increase the amount of gaseous exchange that can occur across a gas exchange surface Gas exchange – a physical process in living organisms where gases move by diffusion across cell membranes - gases required by organisms for their normal functioning move into cells and gases are expelled Externally: 1. oxygen required for respiration moves from the air into the alveoli of the lungs 2. oxygen moves across the surface of the air sacs, into bloodstream 3. Carbon dioxide moves out of bloodstream into the air sacs 4. Carbon dioxide moves out of the lungs Internally: 1. Oxygen moves from the blood stream out of capillaries into surrounding cells 2. Carbon dioxide moves from the cells into the blood vessels Structure Waxy cuticle Location Top of leaf Function Reduces water loss from the leaf and protects from cold weather, fungal and bacterial invasion Allows light to reach lower cell layers Upper/Lower epidermis Top and bottom of leaf Palisade mesophyll Middle of lead, leaf below cuticle and upper epidermis Below palisade mesophyll Middle of leaf Contain chloroplasts and is where photosynthesis can occur Next to xylem cells Carry glucose from leaf to the rest of the cells in the plant Bottom of leaf next to stomata Underside of the leaf Change the shape or open/close stomata Spongy mesophyll Vascular tissue: Xylem cells Vascular tissue: Phloem cells Guard cells Stomata Allows for gas exchange to enable photosynthesis to occur Supply water to the leaf from the roots of the plant Allow gases to pass in and out of the leaf. Water loss occurs here. Stomates (stomata)      ● ● Most gaseous exchange in plants occurs through stomata in leaf Stomates are in epidermis of leaves, bordered by guard cells When stomates are open, gases can diffuse through them but when closed no gases are transported When guard cells fill with water and become turgid, the thing outer walls stretch but the thick inner walls do not bulge so are pulled apart and the pore between them widens When stomates lose water, the out walls no longer budge so the inner walls move and close the pore interpret a range of secondary-sourced information to evaluate processes, claims and conclusions that have led scientists to develop hypotheses, theories and models about the structure and function of plants, including but not limited to:  photosynthesis Complete Blitzing Biology pages 145 -149 – transpiration-cohesion-tension theory (covered later in this module) trace the digestion of foods in a mammalian digestive system, including: – physical digestion – chemical digestion – absorption of nutrients, minerals, and water – elimination of solid waste  NUTRIENT REQUIREMENTS IN ANIMALS: THE DIGESTIVE SYSTEM The process by which food is broken down into smaller, soluble molecules that can be easily absorbed. To maintain human metabolism, the following chemical substances are needed:  Oxygen  Water  Minerals     Vitamins Carbohydrates Proteins Lipids 1. Mechanical digestion  Physical breakdown of food  Occurs in stomach, where muscles churn food  Teeth used to break down food to be able to be swallowed  Teeth increase surface area of food which allows greater exposure to digestive enzymes 2. Chemical digestion  Specialised proteins (enzymes) in mouth, stomach, and small intestines  Along with other chemicals (e.g., hydrochloric acid), break down complex molecules into simple molecules a) Amylase – break down carbohydrates e.g., starch into glucose b) Protease – protein into amino acids c) Lipase – lipids (fats) into fatty acids and glycerol The process of absorption of nutrients, minerals, and water Mouth and oesophagus  Food is ground up by teeth and moistened with saliva  Enzyme amylase in saliva beings breaking down carbohydrates into simple sugars  Once swallowed, muscular contractions (peristalsis) of the oesophagus move the food into stomach Stomach  Food passes through a sphincter into stomach  Mixed with gastric juices including hydrochloric acid and enzyme protease  Churns food to mechanically and chemically  Then squeezed through second sphincter to part of small intestine, duodenum Small intestine  Food is mixed with digestive enzymes from pancreas and bile from liver  Bile to emulsify fat (break down lipids into small molecules)  Nutrients absorbed from ileum, lined with villi – increase surface area for food absorption  Each villus is connected to capillaries  how nutrients pass into bloodstream Pancreas  Secrets hormone insulin, which regulates sugar in the blood  diabetes is a condition caused by problems with insulin production Liver  Breaks down fat using file stored in gall bladder  Processes proteins and carbohydrates  Filtering and processing impurities, drugs, and toxins  Generation of glucose for short-term energy needs Large intestine  Once all nutrients absorbed, waste moved into large intestine  Water is removed and faeces stored in rectum Inquiry Question: How does the composition of the transport medium change as it moves around an organism? ● investigate transport systems in animals and plants by comparing structures and components using physical and digital models, including but not limited to: – macroscopic structures in plants and animals – microscopic samples of blood, the cardiovascular system and plant vascular systems ● investigate the exchange of gases between the internal and external environments of plants and animals ● compare the structures and function of transport systems in animals and plants, including but not limited to: – vascular systems in plants and animals Cells of multicellular organisms need to be supplied with nutrients and have wastes removed from them. To do this efficiently, specialised tissues organised into transport systems are needed. Plants: vascular system  interconnecting tube-shaped cells throughout roots, stem, and leaves Vessels include  Root hair cells  Xylem  Phloem Describe the process that transports sugars through a plant Sugars produced in the leaves are transported into the phloem by active transport. Water from the xylem then follows by osmosis, which increases the pressure in the phloem. This creates a pressure gradient in the phloem allowing the sugar to move up or down the plant. At the sink, sugars are removed actively.  TRANSPORT SYSTEMS IN ANIMALS: CIRCULATORY SYSTEM Role of the circulatory system: - Transport of gases (carbon dioxide and oxygen), nutrients, waste products, hormones, and antibodies - Maintenance of constant internal environment (pH, ions, blood gases, osmotic pressure) - Removal of toxins and pathogens Structure of arteries, capillaries, and veins in relation to function  Arteries carry blood away from heart under high pressure and must be able to withstand this  Thin but elongated walls made of endothelium (lining), smooth muscle (to contract vessel), and connective tissue (for expansion)       Veins carry blood towards heart Carry same quantity of blood as arteries but not at same high pressure Have same three layers however layers are not as thick Veins also contain valves that prevent backflow of blood Capillaries have one cell thick walls to allow diffusion of materials To reach the cells found in the tissues in which the capillary is located Main changes in chemical composition of blood as it moves around the body Pulmonary system  Blood flows from heart to lungs then back to heart  Travels in pulmonary arteries from right ventricle to left where carbon dioxide is realised into alveoli of lungs  Ultimately released out of the body  Oxygen picked up from alveoli and diffused into red blood cells to be taken back to heart  via the pulmonary system, carbon dioxide is decreased, and oxygen levels increase Systemic system  Blood flows from heart to rest of body except lungs, and returns  Left ventricle pumps oxygenated blood to rest of body  As this blood circulates in capillaries, oxygen is delivered to the cell and carbon dioxide is picked up  Other waste products, like urea, are also picked up from liver and transported in blood to kidneys  Blood slowing to small intestines collects products of digestion and transports them to liver  Glucose is circulated in blood stream to all cells for respiration  Deoxygenated blood returns to the heart via the inferior and superior vena cava BIOLOGICAL DIVERSITY AND ECOSYSTEM DYNAMICS – MODULE 3 & 4 1. Population Dynamics (and Effects of the Environment on Organisms) (from Module 3) Inquiry question: How do environmental pressures promote a change in species diversity and abundance? predict the effects of selection pressures on organisms in ecosystems, including: - biotic factors (from Module 3) - abiotic factors (from Module 3) Inquiry question: What effect can one species have on the other species in a community? ● investigate and determine relationships between biotic and abiotic factors in an ecosystem, including: – the impact of abiotic factors Effects of the environment on organisms Ecosystems are controlled by: a) abiotic factors of the environment e.g., climate, light, temperature, wind speed, sunlight, water, altitude b) biotic (living) factors e.g., source of food, number of predators etc., competition between/within species Abiotic and biotic factors determine the following: 1. Distribution of organisms – where they are found in the ecosystem 2. Diversity of organisms – different types of organisms 3. Abundance of organisms – how many are present Environmental pressures affecting diversity and abundance: ABIOTIC Amount of light Amount and strength of mind and rainfall Temperature: daily and seasonal variations Effect of topography, altitude, and depth Strength of ties, currents, and waves Amount, salinity, pH, and availability of water Type and availability of substrate Availability of space and shelter Availability of oxygen ● BIOTIC Number of predators Number of mates available Number and variety of disease-causing organisms Availability and amount of food Number of competitors for food/shelter (same or diff species) investigate and determine relationships between biotic and abiotic factors in an ecosystem, including: – the impact of biotic factors, including predation, competition, and symbiotic relationships What is an ecosystem? All the living and non-living factors in a defined area that interact and exchange materials, e.g., pond, rainforest, desert, marine rock platform. What is a community? A group of different species living together and interacting with one another in a particular habitat. All ecosystems have: 1. Sun as the source of energy (not recycled in an ecosystem) 2. Nutrients as in food (matter that is continuously recycled in natural ecosystems) 3. Organisms. Including:  Producers:  Make or produce their own food using simple substances and energy from sun  Known as autotrophs  Consumers:  Depend on other organisms for food  Known as heterotrophs  Decomposers:  Break down waste products and dead bodies of organisms  Release simple chemical substances into environment  Can be recycled and used by other organisms  Fungi and bacteria are common decomposers 1. Explain the role of a plant in an ecosystem Plants turn light energy from the sun into chemical energy via photosynthesis to create glucose. Plants are producers, and they can be eaten by consumers such as animals, which are then eaten by other consumers. Without producers, the ecosystem would be unable to function as there would not be any available food. 2. Explain the role of bacteria in an ecosystem Bacteria are decomposers. They break down waste products and dead bodies of other organisms, releasing chemical substances back into the environment. They are essential to recycle nutrients in the ecosystem. Environment – both biotic and abiotic surrounds of an organism Biome – large regional system characterised by a major vegetation type e.g., desert Population – group of organisms of the same species living in the same area at a particular time Niche – place of a species within a community involving relationships with other species Ecosystem – a community with its environment; any environment containing biotic and abiotic parts that interact Species – groups of similar individuals that can reproduce fertile offspring Community – groups of different populations in an area or habitat Ecology – study of the relationships living organisms have with each other and their environment – – the impact of biotic factors, including predation, competition, and symbiotic relationships predicting consequences for populations in ecosystems due to predation, competition, symbiosis, and disease RELATIONSHIP Mutualism DESCRIPTION Both species benefit Commensalism One species benefits and one is not affected Parasitism One species benefit and one is harmed Predation Competition Where prey is eaten by a predator Where organisms compete for access to food or other resources EXAMPLE Acacia tree ants use the acacia tree for habitat and the ants defend the tree from predators Barnacles attach to whales, which gives barnacles habitat and access to food while the whale is not affected Ticks living on a dog harms the dog while the tick uses the dog’s blood for nutrients Mouse is eaten by a snake Lions and cheetahs both eat deer and zebra, so compete for this food Competition for resources Means that there is ‘struggle’ between two or more organisms from either same or different species for resource that is in limited supply  competition between members of the same species is intraspecific competition e.g., two rabbits  competition between members of different species is called interspecific competition e.g., rabbits and bilbies interspecific competition is usually less intense – same species have far more resource needs in common to compete for Plants compete for growth space, sunlight, and water. Many species have fast growing seeds as the tallest to spread its leaves receive the most sunlight.  Some plants secrete allopathic chemicals into soil to inhibit the growth of plants next to them Describe the distribution of the two barnacle species and suggest an explanation (include intraspecific and interspecific) When Chthalamus is on their own, they only have intraspecific competition for resources, so can have a larger distribution across the habitat. When Semibalanus live in the same habitat there is interspecific competition for resources, which changes the distribution of Chthalamus, forcing them into a smaller niche. – the ecological niches occupied by species Ecological niches – relationships between organisms in an ecosystem are important to maintain the ecosystem  The role of particular species in an ecosystem is called its ecological niche Consists of all physical and biological conditions which determine the organism’s survival and reproductive prospects An ecological niche comprises of: - Habitat in which an organism lives - Activity patterns of the organism e.g., periods of during which it is active - Resources it obtains from the environment e.g., food sources, territorial boundaries etc. - Interactions that occur with other species in the community e.g., predator-prey relationships, competitors etc.  Two species cannot survive indefinitely in the same habitat if their niches are identical  if two distinct species share an identical niche, there will be interspecific competition for space and resources   Competition between two species will result in fitness of one being lowered The less well-adapted species will struggle to survive and reproduce  it will eventually be eliminated from the niche Interspecific competition within a shared niche will prompt two responses: 1. Competitive exclusion – one species uses the resources more efficiently, driving other to extinction 2. Resource partitioning – both species alter use of habitat to divide resources (i.e., niche separation) – measuring populations of organisms using sampling techniques Sampling techniques  Study of natural communities is extremely complex  Impossible in a reasonable time, undesirable to investigate entire area covered by community  Techniques in smaller areas chosen at random to determine abundance and distribution of organisms in ecosystem       1. Quadrats Large areas investigated by sampling smaller sections with quadrats Square of unknown dimensions placed/marked out at random within an area Information gained by numerous quadrats in different and smaller areas can be averaged Estimate percentage can be used 2. Line transect Placing a line along the area to be studied Species touching the line can be recorded via continuous sampling or quadrats placed at various intervals with the number, position, and distribution of species recorded  3. Timed observations Timed observations of organisms e.g., observation of birds should be repeated at regular intervals   4. Spotlighting To observe nocturnal animals, a strong torch is used to look for eye shine in treetops and ground cover Red filter should be fitted over beam to reduce disorientation or frightening animals    5. Capture recapture Used to estimate populations where the individuals are moving Tagging or marking a sample of population then releasing back Subsequent recapturing and calculation of the proportion of tagged animals in recaptured sample can give reasonable estimate of the total population Mass extinctions over history of the earth  Understanding causes of past extinction events help prevent further extinctions and loss of biodiversity  Scientists have identified 5 mass extinctions which each led to a loss of more than 75% of animal species  Thought that mass extinction events were due to natural causes (e.g., volcanic activity, asteroid impact, climate change etc.)  Human activity is changing the environment by applying pressure on other species  This is a threat to biodiversity Explain what caused the Tasmanian Tiger (thylacine) to become extinct It is thought that humans killed the thylacine, assuming they were responsible for sheep killings. The Tasmanian government introduced a bounty for killing the tigers, and at least 3,500 were killed. In addition to competition with dingoes, habitat loss, and disease, caused the species to decline rapidly. Together, these factors likely caused the Thylacine to become extinct. Inquiry question: How do selection pressures within an ecosystem influence evolutionary change? ● ● investigate and analyse past and present technologies that have been used to determine evidence for past changes, for example: – radiometric dating – gas analysis analyse palaeontological and geological evidence that can be used to provide evidence for past changes in ecosystems, including but not limited to: – Aboriginal rock paintings – Rock structure and formation Aboriginal rock paintings  First Indigenous people reached Australia 60,000 years ago  Thylacine species well known to Aboriginal people and co-existed for thousands of years before its disappearance from mainland (between a few thousand years to mid-1800s)  Some pictographs undoubtedly represent thylacine, some may illustrate other striped marsupials Rock structure and formation  Abiotic factors provide evidence to show changes in climate, volcanic activity, atmospheric oxygen, sea levels  Igneous rocks tell of past volcanic episodes and can also be used to age date periods  Sedimentary rocks record past depositional environments (e.g., deep ocean, shallow shelf, fluvial) and contain fossils from past ages  Metamorphic rock informs on plate tectonic movements and how continents were together and apart  Biotic factors (fossils) show evolution and organisms over geological time Ice core drilling and gas analysis  Gas bubbles trapped in ice cores can be analysed to give data about the past composition of the earth’s atmosphere Ice cores drilled, ice is crushed in a vacuum, gas bubbles released, gas bubbles analysed by a mass spectrometer ● ● analyse evidence that present-day organisms have evolved from organisms in the past by examining and interpreting a range of secondary sources to evaluate processes, claims and conclusions relating to the evolution of organisms in Australia, for example: – small mammals – sclerophyll plants investigate the reasons for changes in past ecosystems, by: - interpreting a range of secondary sources to develop an understanding of the changes in biotic and abiotic factors over short and long periods of time - e - valuating hypotheses that account for identified trends Break up of Pangea Describe the breakup of Pangea and explain why the climate of Australia has changed over millions of years 250 million years ago, Pangea was one large mass. Throughout the Triassic, Jurassic, and Cretaceous periods, it slowly spread apart, due to convection currents causing continental drift. Eventually the continents were separated to present day formation. Australia moved further north, from its position in Pangea to present day, which resulted in a warmer and drier climate. Fossil evidence to support theory of continental drift Use the diagram to describe how fossils support the theory of continental drift Fossils have been found across now separated continents, suggesting that the continents were once connected, so that the organism could freely roam across the land mass. When the continents separated, the organisms stayed on the land, and eventually became fossils. An example is the plant shown by the green line, that has been found in all continents. Current evidence of evolutionary change  Scientists examine current ecosystems and living parts of organisms to gain insight into changes  They compared existing present-day animals and plant species with extinct ancestors to inform how the climate and environment has changed  Until 100 million years ago, the Australian continent was connected to Gondwana  This included Australia, New Zealand, Antarctica, India, South America, and Africa  The supercontinent was located much further south so environmental conditions were very different  About 85 million years ago, Australia began to separate from Antarctica  Since then, Australia has been moving north at 8cm per year As Australia moved north the climate became warmer, much drier, and many plants and animals that were previously adapted to a colder climate became extinct. Other plant and animal species evolved, and their adaptations allowed them to survive in the warmer, drier conditions. Increased temperature caused more hardy plants such as eucalypts to evolve – abiotic Rain become seasonal causing more hardy plants to evolve, and marsupials move from rainforest environments to dry, open sclerophyll desert – abiotic Nutrient deficient soil, fire – abiotic Inquiry question: How do environmental pressures promote a change in species diversity and abundance? ● predict the effects of selection pressures on organisms in ecosystems, including: – biotic factors – abiotic factors Biodiversity comes from two words Bio meaning life and diversity meaning variability. Biodiversity is the variety of all living things; the different plants, animals and micro-organisms, the genetic information they contain and the ecosystem they form. (See module 4 for details on biotic and abiotic factors) Adaptations Inquiry question: How do adaptations increase the organism’s ability to survive? Note: This was covered in your depth study. ● conduct practical investigations, individually or in teams, or use secondary sources to examine the adaptations of organisms that increase their ability to survive in their environment, including: – structural adaptations – physiological adaptations – behavioural adaptations   An adaptation is any feature which helps an organism survive in its environment Environmental pressures that affect an organism’s survival include predators, water availability, temperature  Adaptations determine the biological success of a species Organisms have certain features related to the ecosystem they exist in Adaptations are inherited and these features have developed over time, enabling the organism to better suit its environment   For a characteristic to be an adaptation it must be: 1. Inheritable 2. Assumed that the organism has existed in the same environment for a period Structural – physical features that help an organism survive in its environment e.g., webbed feet on platypus help it swim. Behavioural – adaptations caused by an animal responding to an external stimulus e.g., penguins huddle during winter Physiological – related to how the organism functions (usually involving metabolism and physiology) that help it survive e.g., marsh crabs have gills and kidneys that excrete excess salt Inquiry question: What is the relationship between evolution and biodiversity? Investigate, through secondary sources, the observations and collection of data that were obtained by Charles Darwin to support the Theory of Evolution by Natural Selection, for example: – finches of the Galapagos Islands – Australian flora and fauna Variation in a species  Survival of any species depends on individuals producing offspring  No two plants or animals are genetically identical in a population  Those that survive will have the most favourable characteristics that will be passed to their offspring  Variation allows a species to better survive in its environment  natural selection Theory and theories of evolution What is evolution? The process by which living organisms are believed to have developed from earlier forms during the history of the earth Jean-Baptiste Lamarck (1744-1829)  French biologist known for Theory of Inheritance of Acquired Characteristics presented in 1801  Believed that evolution was ‘acquired traits’ of a species that is inherited by its offspring  If an organism continually used a structure to carry out a task, the structure would become physically modified to make the task easier For example: if a giraffe continually stretches out its neck to reach high leaves, it would become longer over time Charles Darwin (1809-1882)  Theory of evolution through Natural Selection or ‘Survival of the Fittest’  Organisms, even of same species, are different and over time they adapt to survive  Those organisms who do not adapt to changing environments do not live to breed and pass on their genes  Concluded that there was a variety of physical and behavioural features within a species  Organisms which had features that helped them adapt to environment and circumstances would likely survive  Offspring inherited the ‘successful’ features  Suggested that same species living in different environments will evolve differently until they become separate species  Darwin believed that all species of life on earth are related and have a common ancestor Natural selection 1. Individuals in a species show variation because of differences in their DNA 2. Individuals with characteristics which suit the environment are more likely to survive and reproduce 3. DNA from these individuals are passed onto the next generation Mutation and adaptation  Offspring are produced to look similar to their parents  Most successful individuals pass on their characteristics through DNA  Mutations are detrimental to survival of individuals as they make them less suited to their environment  Mutations create variation within a species that increase their change of survival For example: a change in colour may make a bird more camouflaged  Variation increases the chance of a species to adapt  More variation makes a species less vulnerable to environmental changes  Environmental pressures (predation) eliminate individuals less fit for survival and favourable genetic variations will have a greater chance of survival  The variation coded by the DNA will become more common through population ● explain, using examples, how Darwin and Wallace’s Theory of Evolution by Natural Selection accounts for: – convergent evolution – divergent evolution   Darwin/Wallace theory outlines favourable characteristics for reproduction and survival of organisms Adaptive radiation refers to the variety of different species that evolve from an ancestral line because of migration and isolation  Theory of natural selection and isolation provide mechanism for adaptive radiation  If populations become isolated, they will likely encounter differing selective pressures as each environment evolves independently Eventually, the populations may have changed sufficiently that they become different species  e.g., evolution of Darwin’s finches came about due to selective pressures operating on each island resulting beak specialisation Unique biodiversity of flora and fauna in Australia is a result of adaptive radiation When the continent of Gondwana separated, the organisms evolved due to selective pressures from the changing environment    Divergent evolution  Occurs when closely related species experience different environments so different characteristics are selected  Species will evolve differently and will eventually appear quite different  e.g., elephants are large plain-dwelling animals that are closely related to guinea-pig animals called a hyrax Convergent evolution  When two relatively unrelated species develop similar structures, physiology, or behaviours in response to similar selective pressure from similar environments  e.g., communal social behaviour has developed independently in ants, termites, and bees Explain the difference between divergent evolution and convergent evolution Divergent evolution is when organisms have a common ancestor but have adapted to suit different environments. The organisms have homologous structures that suit this environment but have similar fundamental structures. Convergent evolution is when organisms have different ancestors but share similar features (analogous structures) because they have adapted to the same environment. A virus was used to kill rabbits in Australia. After first release of the virus nearly all rabbit were killed, but over time the numbers recovered. Outline how Darwin/Wallace’s theory of evolution could be used to explain the recovery of rabbit numbers. Initially, the virus would kill most rabbits, but a small amount would have a mutation that makes them resistant to the virus. Those rabbits would be able to survive and reproduce, passing on the mutated genes to their offspring. Some of their offspring would be resistant to the virus too, and these rabbits would continue to survive and reproduce until the population is filled with rabbits that are resistant to the virus, so their numbers could recover. Therefore, Darwin/Wallace’s theory of survival of the fittest can explain rabbit numbers increasing.  explain how punctuated equilibrium is different from the gradual process of natural selection Punctuated equilibrium The Theory of punctuated equilibrium proposes that evolution occurs in short bursts of rapid change, followed by long periods of stability within populations. - Proposed in 1970s by Stephen Jay Gould based on fossil evidence  Suggests that evolutionary change is gradual, and could be predicted by fossil remains showing these gradual changes  Darwinists use transitional forms to support idea of ‘gradualism’ – a gradual change over long period of time  Many fossilised remains show millions of years going without noticeable evolutionary change to most species  e.g., soft-bodied organisms dominated seas for hundreds of millions of years and then (within few million years) disappeared and were replaced by organisms with shells and skeletons     Horseshoe crabs have remained unchanged for 200 million years Supporters of punctuated evolution argue that if evolution occurs gradually, there should be greater division among living things than what exists Fossil record is inconclusive, difficult to agree on rate of evolutionary change Theory of punctuated equilibrium does not contradict basis of Darwin-Wallace theory (that it occurs by natural selection, and the question is whether in short bursts of rapid change, or gradually over a long period of time) Explain how punctuated equilibrium is different to gradual process of natural selection Punctuated equilibrium is the theory that evolution occurs in short, rapid bursts, between long periods of no obvious changes. The gradual process of natural selection, however, is the theory that evolution occurs more gradually over a long period of time. Inquiry question: What is the evidence that supports the Theory of Evolution by Natural Selection? ● investigate, using secondary sources, evidence in support of Darwin and Wallace’s Theory of Evolution by Natural Selection, including but not limited to: – biochemical evidence, comparative anatomy, comparative embryology, and biogeography – techniques used to date fossils and the evidence produced For any theory to be generally accepted by scientists, substantial evidence must be collected to support it. The following evidence shows certain interferences to be drawn which have allowed the current theory of evolution to be accepted as an underlying concept of biology.     a) Palaeontology – study of fossils Fossils are preserved traces of past life found in sedimentary rocks Can include preserved body parts, molds, and casts of decayed organisms, and imprints of footprints in mud Fossil record provides a timeline of evolution of life in rock layers Some parts show gradual change in life forms over millions of years Transitional forms  Transitional fossils have characteristics belonging to ancestors and descendant groups  EXAMPLE 1: reptiles to birds  Most famous transitional form is archaeopteryx  Fossil first thought to be therapsid reptile  Reptilian features include teeth and reptilian-like skeleton  Archaeopteryx also had feathers and wishbone sternum for flight muscles  Provides evidence of an evolutionary pathway from dinosaurs to birds  EXAMPLE 2: fish to amphibians  Fossils of lobe-finned fish (crossopterygian) show bones in their paired fins that may have allowed them to drag themselves over land from one pond to the next when the environment changed  Fins thought to represent the ancestral limbs of terrestrial vertebrates  EXAMPLE 3: terrestrial to aquatic  Whales are aquatic mammals not fish  Thought to have evolved from terrestrial mammal ancestor  Remains of two transitional forms, ambulocteus and rhodocetus, have hind limbs that became smaller until they were lost  This resulted in whales with no hind limbs but have remnants of a skeletal pelvis  b) Biogeography – study of geographical distribution of organisms both living and extinct Darwin-Wallace theory proposed that for new species to arise, a group of individuals must be isolated Isolation is necessary for new species to arise from an original species. New species should resemble species with which they shared a habitat e.g., they will be more similar to: 1. Species that lived close by then to species found far away 2. Species that live in a common area before it split apart e.g., Gondwana Evidence: Darwin studied and compared numerous animals (including Darwin’s finches on islands such as the Galapagos) Wallace noted that north-western Indonesian islands (including Bali), had bird species most similar to closer Asian mainland, whereas islands in the south-east (including Lombok) had birds like those in Australia.  Darwin and Wallace concluded that the island forms may have evolved from mainland forms which became isolated.         Biogeographical evidence supports evolution of flightless birds (ratites) and continental drift Present-day distribution suggests that the birds originated from a common ancestor and that the populations evolved on isolated continents as they drifted apart Resulted in distribution of emus in Australia, ostriches in South Africa, kiwis in New Zealand, and rheas in South America, which share similarities suggesting a common ancestor c) Comparative embryology Similarities between embryos of fish, amphibians, reptiles, birds, and mammals Comparison of embryos of vertebrates shows they all have gill slits even though they do not remain aquatic (- fish) Indicates fundamental step that is common to vertebrates and supports common ancestor Suggests that all vertebrates begin their development with fish-like structures  e.g., all possess pharyngeal (throat) pouches at some stage of embryonic development Likely inherited from common aquatic ancestor as all life began in aquatic environment d) Comparative anatomy Anatomical structures on different organisms that have same basic plan but perform different functions are called homologous structures  evidence for evolution - Shared by related species because inherited from common ancestor The Pentadactyl limb  Example of homologous structure found in amphibians, reptiles, birds, and mammals  Basic plan of one bone in upper limb, two in lower, leading to five fingers or toes     Vestigial organs are homologous structures that have little importance  e.g., modern whales lack hind limbs but have vestiges of pelvis and leg bones Other vestigial organs include remains of limbs of snakes, appendix of humans Vestigial organs provide evidence for evolution as it would be wasteful to continue providing blood, nutrients and space to an organ that has no major function Natural selection would favour individuals with reduced versions of these organs and will phase out obsolete structures e) Biochemistry  Advancements have allowed comparisons of organisms on a molecular basis rather than comparison of structures  Previously impossible between distantly related organisms - Biochemistry is the study of chemicals found in cells and includes molecular biology and genetics  Study of amino acid sequences show closely related species share more common sequences than unrelated species  Evidence derived from amino acid sequences in haemoglobin show humans and rhesus monkeys share 8 amino acid sequences whereas there are 125 amino acid differences between humans and lampreys   This supports the fossil, embryological, and anatomical evidence that humans are more closely related to rhesus monkeys than they are to lampreys Similarities in biochemistry among living organisms is evidence for descent from a common ancestor ● explain modern-day examples that demonstrate evolutionary change, for example: – the cane toad - antibiotic-resistant strains of bacteria Role of antibiotics in management of infectious diseases (as an example of microevolution)  Antibiotics discovered by Alexander Fleming in 1928  Naturally occurring compounds produced by one organism to prevent the growth of bacteria Microevolution – change in gene frequencies that occurs over time within a population Antibiotic resistance  Overuse of antibiotics has led to selection of more virulent bacteria that are resistant to antibiotics  When first introduced, had dramatic effect on pathogens that cause disease  Over time became less potent because of drug resistance in pathogen  Each time an antibiotic is used, there may be individual pathogens that have a natural resistance to the drug  Naturally resistant individuals are left to breed next generation and pass on genetic information that made them resistant so the next time the drug is used, it will have less effect   Overuse of antibiotics resulted in ‘superbugs’ These strains are resistant to antibiotics and include vancomycin resistant golden staph (staphylococcus aureus) and are not destroyed by even strongest antibiotics Use the diagram above to explain antibiotic resistance If a population of non-resistant bacteria exists, they will continue to reproduce and multiply. Over time, some of these offspring will mutate and have resistance to the antibiotics. This is shown in the second image (the resistant bacteria are coloured yellow). When the antibiotic is applied, the drug resistant bacteria will survive, seen in image 3, while the rest die. The drug resistant bacteria can survive and will reproduce until the whole population is resistant.

Cell Biology: Prokaryotic vs Eukaryotic Cells & Transport

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