2Water and OrganismsWater makes up between % of weight of organisms
3Why is water important to organisms? Water is an important substance for maintaining life. Organisms cannot live without water.Water is a major cell component.
4Importance of Water It acts as: solvent / reaction medium medium for transport (e.g. blood)metabolite (e.g. photosynthesis)others like act as cooling agent (e.g. sweating in hot weather)as supporting agent (e.g. turgidity in young plant)for sexual reproduction
5Water as a Solvent dissolve most organic and inorganic substances needed for all biochemical reactionsremove excretory products such as urea and excess saltsin plants, root hairs absorb mineral salts present in soil in solution form
6As a solventInside an alveolus of the lung: O2 dissolves in water film for diffusionInside a leaf : CO2 dissolves in the water for diffusion to mesophyll cells
7Water as a Medium of Transport human blood plasma consists mainly of water (90%)carry many dissolved substances like excretory wastes, hormones and gases around the bodyin plants, sugar and mineral salts are transported in solution in vascular bundles
8As a medium for transport Human blood plasma consists mainly of water (90%)
9Water as a Metabolitein plants during photosynthesis, carbohydrates are synthesized from carbon dioxide and wateressential in hydrolytic reactions, e.g. digestion
10As a metabolitephotosynthesis: water + carbon dioxide --> carbohydrates + oxygen
11To provide support and to keep shape water keeps plant cells turgid and provides a means of support in plants
12For sexual reproduction Sperms need water to swim to the eggs.
13Ways of Gaining Water in Animals drinkingeatingfrom respiration occurs in cells which the water formed is called metabolic water
14Ways of Losing Water in Animals evaporation from body surfacessweatingexhalationurinationdefaecation
15Ways of losing water in plants: Evaporation from body surface,Transpiration.
16Hypotonic, Hypertonic and Isotonic Solutions Hypotonic solution- a solution has a higher water potential than the reference solution
17Hypertonic solution- solution has a lower water potential than the reference solutionIsotonic solution- a solution has the same water potential as the reference solution
18Water relations of organisms in the cells Osmosis in cellswater will enter the cells if the surrounding fluid is hypotonic ( of higher water potential)water will leave the cells if the surrounding fluid is hypertonic ( of lower water potential)No net water movement will occur when the surrounding fluid is isotonic ( of equal water potential)
19OsmosisThe net movement of water from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.
20Osmosis in animal cell Concentrated saline solution Water Cell swells and eventually burstCell shrinks
21What will happen when water enters and leaves cells? In animal cellswater enter, the cells swell burstwater leaves, the cells shrink.
22Animal Cells Response to Different Solutions water move in by osmosisCells swell and burstin hypotonic solutiontissue cells
23Animal Cells Response to Different Solutions tissue cellsin hypertonic solutionwater move out by osmosiscells shrink
24Investigation 11.1Investigation of the Effects of Different Salt Concentrations on Red Blood Cells
25Tube A: 0.2% sodium chloride solution In A to E 5 test tubes, transfer a drop of the bloodsample and different concentrations of sodiumchloride solution to each of the test tubes.Tube A: 0.2% sodium chloride solutionTube B: 0.6% sodium chloride solutionTube C: 0.8% sodium chloride solutionTube D: 1.6% sodium chloride solutionTube E: 3.2% sodium chloride solution
26Withdraw a drop of liquid from each tube and examine it under the microscope.
27red blood cell swells and is about to burst red blood cell shrinksred blood cell remains unchanged in appearanceIn hypotonic saline solutionIn hypertonic saline solutionIn isotonic saline solutionWhich of the five saline solutions most closely resembles the blood plasma in salt concentration ?Ans: The one in 0.8% saline solution is the most resembles the blood plasma concentration.
28What evidence supports your answer ? red blood cell swells and is about to burstred blood cell shrinksred blood cell remains unchanged in appearanceIn hypotonic saline solutionIn hypertonic saline solutionIn isotonic saline solutionWhat evidence supports your answer ?Ans: Red blood cells in 0.8% saline solution remain unchanged in appearance indicating that the solution is isotonic to blood plasma …
29What evidence supports your answer ? red blood cell swells and is about to burstred blood cell shrinksred blood cell remains unchanged in appearanceIn hypotonic saline solutionIn hypertonic saline solutionIn isotonic saline solutionWhat evidence supports your answer ?Ans: Fewer red blood cells can be observed in 0.6% saline solution and even fewer in 0.2% saline solution. This shows the two solution are hypotonic to the red blood cells …
30What evidence supports your answer ? red blood cell swells and is about to burstred blood cell shrinksred blood cell remains unchanged in appearanceIn hypotonic saline solutionIn hypertonic saline solutionIn isotonic saline solutionWhat evidence supports your answer ?Ans: The 1.6% and 3.2% saline solutions are hypertonic to the red blood cells as a net movement of water out of the red blood cells into the saline solution is noticed.
31Importance of Osmoregulation osmoregulation is the maintenance of correct levels of water in the bodyany excessive gain or loss of water will upset the proper functioning of cells in an organismmetabolic reactions are affected and organisms may die
32The importance of osmoregulation for animal cells Osmoregulation: The process of regulating body fluid to keep it at a constant concentration.In mammals, osmoregulation is achieved by controlling the amount of water and the amount of dissolved substances in the blood.The major organ responsible are the kidneys
35Human Urinary System Inferior vena cava aorta left kidney renal vein renal arteryright kidneyureterssphincter muscleurinary bladderurethraHuman Urinary System
36Human Urinary System - Location of Kidneys mammals have two kidneys which are reddish and bean-shapedthey are situated at one on each side of the vertebral column, below the ribs and are not protected by any part of the skeletal systemrenal artery brings blood to kidney while renal vein takes blood away from it
37Human Urinary System - Ureter carries urine from kidney down to urinary bladder where stores urine temporarilyvalves are present in ureter to prevent urine from flowing upwardsback flow of urine may happen when urinary bladder empties if valves do not close properly.This may lead to infection and damage of kidney
38Human Urinary System - Urinary Bladder a muscular bag situated towards the bottom of the abdominal cavityurethra is led out from iton the top of urethra is surrounded by ring of sphincter muscle
39Urinationnormally, the sphincter muscle is tightly contracted, so no urination occursAdults can control the sphincter muscle but children cannot, it relaxes automatically when the bladder is fullwhen urinary bladder is fullsphincter muscle relaxes wall of urinary bladder contractsurination occurs
40Structure of Mammalian Kidney cortexmedullanephronrenal arterypelvisrenal veinureter
41Structure of Mammalian Kidney made up of three parts: a light outer region - cortex- a dark inner region - medulla- a whitish central region leads to ureter - pelviscontain numerous tiny tubules called nephrons
42Structure of Nephronconsists of a swollen end called Bowman’s capsule which is connected to a narrow tubulethe tubule begins in cortexafter leaving the capsule, it coils up (proximal convoluted tubule)
43It is then descends into the medulla and becomes U-shaped (loop of Henle) It goes back into the cortex and coils up again (distal convoluted tubule)Finally, it drains into a collecting duct which goes through the medulla and down to pelvis
45…... How Nephron is Connected with Blood Vessel afferent arteriole (branches from renal artery)renal arteryenters Bowman’s capsuleGlomerulus (a tightly bunched group of capillaries)efferent arteriole (capillaries join up)…...
46How Nephron is Connected with Blood Vessel leaves Bowman’s capsulecapillaries (spread out and wrap around tubule)venule (capillaries join up)renal vein
47Structure of Nephron first & second convolution Bowman’s capsule (with glomerulus)afferent arterioleefferent arteriolevenuleloop of Henlecollecting duct
48How Nephron Works ?By two ways, one is ultrafiltration and the other is reabsorption
50Capillaries Diffusion It is the smallest blood vessels It is the site of exchange (by diffusion)Thin wall (one cell)NutrientsO2DiffusionCO2Waste
51Ultrafiltrationdiameter of tiny artery leading to the glomerulus is larger than the leaving one so increase in pressure is resulted as blood tries to force its way out of the smaller tubethe high hydrostatic pressure forces small molecules through the walls of capillaries and Bowman’s capsule into the capsular space
52fluid which filtered into the nephron is glomerular filtrate glomerular filtrate has the same composition as that of blood except that it hasn’t got red blood cells, blood proteins & blood platelets
53Reabsorptionreabsorption is the process of absorbing useful substances into capillaries which wrapped around tubuleas in glomerular filtrate, some substances like glucose and amino acid are useful to human so they are absorbed back while fluid travels along the tubule
54those urea which remains in the fluid pass the whole nephron and finally drains into collecting duct which leads to pelvis and form urineurine contains mostly water, with urea and excess mineral salts
55reabsorption of glucose, amino acids and some salts begins in the first convolution and finished when the fluid reaches loop of Henle
56useful substances are reabsorbed by diffusion down the concentration gradient and active transport against concentration gradientin collecting duct, water is mainly reabsorbed by osmosis but the first convolution actually reabsorbs the largest amount of water
57Functions of Kidney kidney mainly has three functions: osmoregulation removal of excess saltexcretion
58Functions of Kidney - Osmoregulation drink a lot of waterblood becomes dilutedsmall proportion of water is reabsorbedMore dilute urine produceAmount of water in blood: CONSTANT
59Functions of Kidney - Osmoregulation after sweatingblood becomes concentratedlarge proportion of water is reabsorbedLess concentrate urine produceAmount of water in blood: CONSTANT
60Functions of Kidney - Removal of Excess Salt after eating a salty mealconcentration of urine is highersalt enters blood, concentration of salt in blood increasevolume of urine increaseman feels thirstydrink water
61Functions of Kidney - Excretion protein cannot be stored in human body, excess protein are broken down in liverremoving of amino groups from amino acids is called deaminationamino groups are incorporated into urea molecules and then excreted in urine
62Kidney Failure and Artificial Kidney some kidney diseases can lead to kidney failure which kidney can no longer function properlytoxic substances will accumulate in blood and patient will die
63artificial kidney is a bulky machine attached to patient which is used to filter and clean patient’s bloodartificial kidney make use of the principle of dialysis. It has a filter made of cellophane which acts as a selectively permeable membrane
64along one side of the membrane is the patient’s blood while the other side is dialysis fluid which has the same contain as plasma except ureaonly urea diffuses from patient’s blood into dialysis fluid through cellophane filterblood without urea will return to patient through his vein
65dialysis fluid flows in direction opposite to that of blood flow to increase the efficiency of diffusion of urea into dialysis fluidother than using artificial kidney, kidney transplant is another possible method but only few people are willing to donate their kidneys after death
66Excretion in Humanmetabolism are reactions take place inside cells of an organismmost of the by-products of metabolism are toxic and should be removed once they are produced by excretionthere are four major excretory organs in human body: Lungs, Kidneys, Liver and Skin
67Excretory Organs - Lungs excrete carbon dioxide which is produced by cells during respiration and is carried by blood to lungscarbon dioxide diffuses out of the blood capillaries surrounding the lungs and passes into the air sacit is excreted when people breathe out. Water is lost during respiration, too
68Excretory Organs - Kidneys deamination (break down of excess amino acids) in liver forms urea and uric acidurea and uric acid are called nitrogenous wastesthe wastes are carried by blood to kidneys which excrete them from the body in form of urine
69Excretory Organs - Liver old red blood cells are destroyed in liver and haemoglobin are releasedhaemoglobin will turned into bile and excreted with bile into small intestinefinally, haemoglobin will expel with faeces and leave the body
70Excretory Organs - Skin skin is the largest excretory organ in human bodyit carries out its function through sweatingsweat contains water, salts and urea, and sweating can excrete these substances from the body
72freely permeable so it lets most of molecules to go through osmosis does not occurcell membranebeneath cell wallselectively permeablecell wall
73 Water Relations of Plant - Turgor plant cell put in distilled water net water movement into the cell by osmosisplant cell contains soluteswater potential lower than pure watervacuole and cytoplasm swells
74cytoplasm is pushed against cell wall turgorturgor is present because:cell wall is rigid and strong, cell bursting is preventedhydrostatic pressure develops inside the cell
75When water potential of cell = water potential of water tendency of the cell to give out water increaseswater potential increasesWhen water potential of cell = water potential of waterTurgor occur (cell cannot take in any water) the cell is turgid
76Water Relations of Plant - Plasmolysis plant cell in concentrated solutionThe whole phenomenon is called plasmolysis and cell is plasmolysednet water movement out of the cell by osmosisflaccidvacuole and cytoplasm shrinkcytoplasm is torn away from cell wall
78Turgidity of Plant Cells cell membrane separatedfrom cell wallcell wallcytoplasmvacuoleenlargedvacuolevery smallsolution here is the sameas the external solutionplasmolysed cell(in hypertonic sol)turgid cell(in hypotonic sol.)
79What will happen when water enters and leaves cells? In plant cellswater enter, the cells become turgid.water leaves, the cells become less turgid flaccid plasmolyzed
80Cells in Different Solutions Solution Concentrationhypotonichypertonicanimal cells(e.g. RBC)haemolysisshrinkplasmolysis(cell is flaccid)plant cellsturgid
81Investigation 11.2To Investigate the Effects of Sucrose Solution and Tap Water on Epidermal Cells of Red Onion Scale Leaf or Rhoeo Discolor Leaf
82fleshy scale leaf of red onion bulb forcepsfilter paperepidermisWhat do you observe when the epidermal strip is placed in the concentrated sucrose solution ?Ans: The coloured cytoplasm shrinks.
84fleshy scale leaf of red onion bulb forcepsfilter paperepidermisExplain your observation.Ans: When the piece of epidermis is placed in concentrated solution, cells lose water by osmosis as the cells have a higher water potential than the sugar solution.
85fleshy scale leaf of red onion bulb forcepsfilter paperepidermisWhat has happened to the cells in tap water ?Ans: The coloured cytoplasm swells and cells become turgid.
87fleshy scale leaf of red onion bulb forcepsfilter paperepidermisExplain your answer.Ans: When the piece of epidermis is placed in tap water, cells gain water by osmosis as the surrounding tap water has a higher water potential than the cells.
88Investigation 11.3Effects of Concentrated Sucrose Solution and Tap Water on Raw Potato Strips
89What has happened to the potato strips ? petri dishwater20% surcose solutionraw potato stripsABWhat has happened to the potato strips ?Ans: Potato strip A increases in both weight and length while potato strip B decreases in both weight and length.
90petri dishwater20% surcose solutionraw potato stripsABExplain your answer.Ans: For potato strip A, it gains water by osmosis so both of its weight and length increase but for potato strip B, it loses water by osmosis so its weight and length decrease.
91Experiment to Show that Water is Given Off During Transpiration Investigation 11.4Experiment to Show that Water is Given Off During Transpiration
92What do you observe in the polythene bags ? Ans: The one enclosing plant A becomes misty while nothing can be noticed in the one enclosing plant B.
93How can you show that it is water ? polythene bagABHow can you show that it is water ?Ans: We can use anhydrous cobalt chloride paper to test it. It will turn the paper from blue to pink or we can use anhydrous copper sulphate. Water will turn it from white to blue.
94What conclusions can you draw from the results ? polythene bagABWhat conclusions can you draw from the results ?Ans: We can conclude that a leafy shoot gives off water during transpiration.
95Transpirationan evaporation of water in form of water vapour from the surface of plant to atmosphere
96it mainly takes place in leaves where there are some openings called stomatamore water loses from the lower surface of the leaf than the upper one as more stomata present on the lower surfaceit also happens in lenticels and cuticle
97How does transpiration take place? How transpiration pull is formedHow transpiration occurs2. Eventually, water is pulled from the xylem, pulling water up the plant.1. Water evaporates into sub-stomatal air space1. Water is lost from the cell surface, this is replaced by water in the cell. Each cell then pulls water from its neighbouring cells( through cell wall through cytoplasm and vacuoles)2. Water diffuses out through stomaLower concentration of water vapourSubstomatal air space with higher concentration of waterHow water lost from leaves causes transpiration and how the transpiration pull is formed.
98Transpiration in Leaves a thin film of moisture is covered with each mesophyll cellthe moisture evaporates from mesophyll cells into intercellular spaces and diffuses out of stomata into atmosphere
99water potential of cells losing water decreases so they draw water from deeper cells in the leaf by osmosis. This in turn, draws water in xylem vessels into leaf to replace the loss
100To Measure the Rate of Transpiration by Using a Simple Potometer Investigation 11.5To Measure the Rate of Transpiration by Using a Simple Potometer
101graduated capillary tube air/water meniscusgraduated capillary tubereservoirleafy shoottapWhat are the environmental conditions under which transpiration occurs quickly ?Ans: It is under dry, warm and windy conditions.
102graduated capillary tube air/water meniscusgraduated capillary tubereservoirleafy shoottapDoes this apparatus give you an accurate measurement of the rate of transpiration ?Ans: No. It is because it only measures the rate of water uptake by the leafy shoot …Ans: In addition, it is too small to fit the whole root system and this may affect the rate of water uptake.
103graduated capillary tube air/water meniscusgraduated capillary tubereservoirleafy shoottapSometimes you may introduce an air bubble into the capillary tube. State the advantage of this method.Ans: Movement of the air bubble is easier to observe than that of air/water meniscus.
104graduated capillary tube air/water meniscusgraduated capillary tubereservoirleafy shoottapSometimes you may introduce an air bubble into the capillary tube. State the disadvantage of this method.Ans: Friction between the capillary wall and the bubble may affect the movement of bubble.
105Environmental Factors Affecting the Rate of Transpiration There are five environmental factors which affect the rate of transpiration. They are:(I) Light Intensity(II) Temperature(III) Humidity(IV) Wind Speed(V) Water Supply
106Light Intensitystomata open in light, so plants can get enough carbon dioxide from atmosphere for carrying out photosynthesislight will increase temperature so increases the rate of transpiration
107Temperature rate of evaporation of water from mesophyll cells relative humidity of air outside leafrate of diffusion of water vapour from intercellular space in leaf to outside
108 Humidity humidity outside rate of transpiration it makes the diffusion gradient of water vapour from moist intercellular space of a leaf to the external atmosphere steeper
109Wind Speed & Water Supply wind blowslack of waterwater vapour around the leaf sweeps awaysoil dries, plant wilts and stomata closetranspiration ratetranspiration rateINCREASESDECREASES
110Stomatastomata are pores in the epidermis which gaseous exchange takes place during photosynthesis (or respiration)find mainly in lower epidermis of dicotyledonous leaves and stems
111Guard Cellseach stoma is surrounded by two guard cells which possess chloroplastsits inner wall is thicker than outer wallit is kidney-shapedstomaguard cell
112Distribution of Stomata in Leaves normal plantsmainly on the lower surface of leavesfloating plantsmainly on the upper surfaceleaves may also have air sacs to keep them afloat so they can carry out gaseous exchange
113submerged aquatic plants no stomata (not required since gaseous exchange can be carried out by diffusion through the leave surface)no cuticle (the primary function of cuticle is to prevent excess water transpiration which is not present in aquatic plants)
114Investigation 11.6Experiment to Investigate Stomatal Distribution in a Leaf by Using Cobalt Chloride Paper
115Obtain a potted plant. Using sellotape stick a small square cobalt chloride papersellotapeObtain a potted plant. Using sellotape stick a small squareof anhydrous cobalt chloride paper onto each surface ofa leaf of the plant. Record the time taken for the cobaltchloride paper on each surface of the leaf to turn pink.
116Which piece of cobalt chloride paper turns pink first? sellotapeWhich piece of cobalt chloride paper turns pink first?Ans: The piece of cobalt chloride paper attached to the lower epidermis of the leaf turns pink first.
117Ans: It is because more stomata are present in the lower epidermis. cobalt chloride papersellotapeExplain your answer.Ans: It is because more stomata are present in the lower epidermis.
118Why is it important to handle cobalt chloride paper with forceps? sellotapeWhy is it important to handle cobalt chloride paper with forceps?Ans: It is because there is moisture on human fingers so the paper may turn pink before sticking onto the surfaces of leaves.
119To Observe the Release of Air Bubbles from Leaves placed in Hot Water Investigation 11.7To Observe the Release of Air Bubbles from Leaves placed in Hot Water
120Which surface has more air bubbles coming off? forcepshot waterleafWhich surface has more air bubbles coming off?Ans: There are more air bubbles appear on the lower surface of the leaf.
121Where does the air come from? forcepshot waterleafWhere does the air come from?Ans: It is in the air spaces between the mesophyll cells in leaf which expands on heating and passes out through stomata of the leaf.
122What does the result show? forcepshot waterleafWhat does the result show?Ans: The result shows that more stomata are present on the lower epidermis of the leaf.
124Structure of Root Root Cap a protective layer at the very tip of root to protect the delicate cells of root from being damaged as the root grows down through the soilEpidermiscover the rest of rootabsence of cuticle so water can enter
125Growing Pointbehind root capcells are capable of active divisionRegion of Elongationmore elongated than cells in growing point and have large vacuoles
126Region of Root Hairlittle way behind root tiproot hair are thin-walled extension of epidermal cells of rootincrease surface area for uptake of water and mineral salts
127Vascular Tissuefurther from the tip of rootcontain xylem and phloemxylem transport absorbed water to every part of plant
128Absorption of Soil Water by Root Hairs soil water is a dilute solution of salts which is more dilute than cell sap and cytoplasm in root hairwater will pass by osmosis into root hair through cell wall and cell membrane
129Transverse Transport of Water to Xylem cytoplasm and cell sap have higher water potential than neighbouring cortical cellsepidermal cells gain water by osmosisNOTE: some water may travel inwards along or between cell walls without entering cytoplasm or vacuole of each cortical cellwater travels by osmosis inwards from cell to cell
131reduction of effective pressure at the top of xylem vessel transpiration occurs in leaves so water is continuously removed from the plantreduction of effective pressure at the top of xylem vesselwater flows upwards from roots continuouslyflow of water through plant: transpiration streamtension produced to draw up water: transpiration pull