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Water and Organisms – –Water makes up between 60 - 95% of weight of organisms.

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Presentation on theme: "Water and Organisms – –Water makes up between 60 - 95% of weight of organisms."— Presentation transcript:



3 Water and Organisms – –Water makes up between 60 - 95% of weight of organisms

4 Why is water important to organisms? Water is an important substance for maintaining life. Organisms cannot live without water. Water is a major cell component.

5 Importance 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

6 Water as a Solvent dissolve most organic and inorganic substances needed for all biochemical reactions remove excretory products such as urea and excess salts in plants, root hairs absorb mineral salts present in soil in solution form

7 As a solvent Inside an alveolus of the lung: O 2 dissolves in water film for diffusion Inside a leaf : CO 2 dissolves in the water for diffusion to mesophyll cells

8 Water 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 body in plants, sugar and mineral salts are transported in solution in vascular bundles

9 As a medium for transport Human blood plasma consists mainly of water (90%)

10 Water as a Metabolite in plants during photosynthesis, carbohydrates are synthesized from carbon dioxide and water essential in hydrolytic reactions, e.g. digestion

11 As a metabolite photosynthesisphotosynthesis: water + carbon dioxide --> carbohydrates + oxygen

12 To provide support and to keep shape water keeps plant cells turgid and provides a means of support in plants

13 For sexual reproduction Sperms need water to swim to the eggs.

14 Ways of Gaining Water in Animals drinking eating from respiration occurs in cells which the water formed is called metabolic water

15 Ways of Losing Water in Animals evaporation from body surfaces sweating exhalation urination defaecation

16 Ways of losing water in plants: Evaporation from body surface, Transpiration.

17 Hypotonic, Hypertonic and Isotonic Solutions Hypotonic solution - a solution has a higher water potential than the reference solution

18 Isotonic solution - a solution has the same water potential as the reference solution Hypertonic solution - solution has a lower water potential than the reference solution

19 OsmosisOsmosis in cellsOsmosis – –water 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) Water relations of organisms in the cells

20 Osmosis The net movement of water from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.

21 Osmosis in animal cell Cell swells and eventually burst Cell shrinks Water Concentrated saline solution

22 In animal cells – – water enter, the cells swell burst – – water leaves, the cells shrink. What will happen when water enters and leaves cells?

23 Animal Cells Response to Different Solutions tissue cells water move in by osmosis in hypotonic solution Cells swell and burst

24 tissue cells water move out by osmosis in hypertonic solution cells shrink Animal Cells Response to Different Solutions

25 Investigation of the Effects of Different Salt Concentrations on Red Blood Cells

26 In A to E 5 test tubes, transfer a drop of the blood sample and different concentrations of sodium chloride solution to each of the test tubes. Tube A: 0.2% sodium chloride solution Tube B: 0.6% sodium chloride solution Tube C: 0.8% sodium chloride solution Tube D: 1.6% sodium chloride solution Tube E: 3.2% sodium chloride solution

27 Withdraw a drop of liquid from each tube and examine it under the microscope.

28 Which 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. red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution

29 What 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 … red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution

30 What 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 … red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution

31 What 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. red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution

32 Importance of Osmoregulation osmoregulation is the maintenance of correct levels of water in the body any excessive gain or loss of water will upset the proper functioning of cells in an organism metabolic reactions are affected and organisms may die

33 The 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

34 The kidneys role in osmoregulation

35 Human Urinary System kidney ureter urinary bladder urethra

36 Human Urinary System aorta renal artery ureters urinary bladder left kidney renal vein right kidney sphincter muscle urethra Inferior vena cava

37 Human Urinary System - Location of Kidneys mammals have two kidneys which are reddish and bean-shaped they are situated at one on each side of the vertebral column, below the ribs and are not protected by any part of the skeletal system renal artery brings blood to kidney while renal vein takes blood away from it

38 Human Urinary System - Ureter carries urine from kidney down to urinary bladder where stores urine temporarily valves are present in ureter to prevent urine from flowing upwards back flow of urine may happen when urinary bladder empties if valves do not close properly.This may lead to infection and damage of kidney

39 Human Urinary System - Urinary Bladder a muscular bag situated towards the bottom of the abdominal cavity urethra is led out from it on the top of urethra is surrounded by ring of sphincter muscle

40 Urination normally, the sphincter muscle is tightly contracted, so no urination occurs when urinary bladder is full sphincter muscle relaxes + wall of urinary bladder contracts urination occurs Adults can control the sphincter muscle but children cannot, it relaxes automatically when the bladder is full

41 Structure of Mammalian Kidney cortex medulla renal artery renal vein ureter pelvis nephron

42 Structure 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 - pelvis contain numerous tiny tubules called nephrons

43 Structure of Nephron consists of a swollen end called Bowmans capsule which is connected to a narrow tubule the tubule begins in cortex after leaving the capsule, it coils up (proximal convoluted tubule)

44 It 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 Nephron renal artery renal vein proximal convoluted tubule (first convolution) capillaries around nephron Loop of Henle afferent arteriole glomerulus efferent arteriole collecting duct distal convoluted tubule (second convolution) Bowmans capsule

46 How Nephron is Connected with Blood Vessel renal artery enters Bowmans capsule Glomerulus (a tightly bunched group of capillaries) afferent arteriole (branches from renal artery) efferent arteriole (capillaries join up) …...

47 How Nephron is Connected with Blood Vessel leaves Bowmans capsule capillaries (spread out and wrap around tubule) venule (capillaries join up) renal vein

48 Bowmans capsule (with glomerulus) afferent arteriole efferent arteriole loop of Henle Structure of Nephron collecting duct first & second convolution venule

49 How Nephron Works ? By two ways, one is ultrafiltration and the other is reabsorption


51 Capillaries It is the smallest blood vessels It is the site of exchange (by diffusion) Diffusion Thin wall (one cell) CO 2 Waste Nutrients O2O2

52 Ultrafiltration diameter 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 tube the high hydrostatic pressure forces small molecules through the walls of capillaries and Bowmans capsule into the capsular space

53 fluid which filtered into the nephron is glomerular filtrate glomerular filtrate has the same composition as that of blood except that it hasnt got red blood cells, blood proteins & blood platelets

54 Reabsorption reabsorption is the process of absorbing useful substances into capillaries which wrapped around tubule as 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

55 those urea which remains in the fluid pass the whole nephron and finally drains into collecting duct which leads to pelvis and form urine urine contains mostly water, with urea and excess mineral salts

56 reabsorption of glucose, amino acids and some salts begins in the first convolution and finished when the fluid reaches loop of Henle

57 useful substances are reabsorbed by diffusion down the concentration gradient and active transport against concentration gradient in collecting duct, water is mainly reabsorbed by osmosis but the first convolution actually reabsorbs the largest amount of water

58 Functions of Kidney kidney mainly has three functions: osmoregulation removal of excess salt excretion

59 Functions of Kidney - Osmoregulation drink a lot of water blood becomes diluted More dilute urine produce small proportion of water is reabsorbed Amount of water in blood: CONSTANT

60 after sweating blood becomes concentrated large proportion of water is reabsorbed Less concentrate urine produce Amount of water in blood: CONSTANT Functions of Kidney - Osmoregulation

61 Functions of Kidney - Removal of Excess Salt after eating a salty meal salt enters blood, concentration of salt in blood increase volume of urine increase concentration of urine is higher man feels thirsty drink water

62 Functions of Kidney - Excretion protein cannot be stored in human body, excess protein are broken down in liver removing of amino groups from amino acids is called deamination amino groups are incorporated into urea molecules and then excreted in urine

63 Kidney Failure and Artificial Kidney Kidney Failure and Artificial Kidney some kidney diseases can lead to kidney failure which kidney can no longer function properly toxic substances will accumulate in blood and patient will die

64 artificial kidney is a bulky machine attached to patient which is used to filter and clean patients blood artificial kidney make use of the principle of dialysis. It has a filter made of cellophane which acts as a selectively permeable membrane

65 along one side of the membrane is the patients blood while the other side is dialysis fluid which has the same contain as plasma except urea only urea diffuses from patients blood into dialysis fluid through cellophane filter blood without urea will return to patient through his vein

66 dialysis fluid flows in direction opposite to that of blood flow to increase the efficiency of diffusion of urea into dialysis fluid other than using artificial kidney, kidney transplant is another possible method but only few people are willing to donate their kidneys after death

67 Excretion in Human Excretion in Human metabolism are reactions take place inside cells of an organism most of the by-products of metabolism are toxic and should be removed once they are produced by excretion there are four major excretory organs in human body: Lungs, Kidneys, Liver and Skin

68 Excretory Organs - Lungs Excretory Organs - Lungs excrete carbon dioxide which is produced by cells during respiration and is carried by blood to lungs carbon dioxide diffuses out of the blood capillaries surrounding the lungs and passes into the air sac it is excreted when people breathe out. Water is lost during respiration, too

69 Excretory Organs - Kidneys Excretory Organs - Kidneys deamination (break down of excess amino acids) in liver forms urea and uric acid urea and uric acid are called nitrogenous wastes the wastes are carried by blood to kidneys which excrete them from the body in form of urine

70 Excretory Organs - Liver Excretory Organs - Liver old red blood cells are destroyed in liver and haemoglobin are released haemoglobin will turned into bile and excreted with bile into small intestine finally, haemoglobin will expel with faeces and leave the body

71 Excretory Organs - Skin Excretory Organs - Skin skin is the largest excretory organ in human body it carries out its function through sweating sweat contains water, salts and urea, and sweating can excrete these substances from the body

72 Plants Cell cell wall cytoplasm cell membrane vacuole

73 cell wall freely permeable so it lets most of molecules to go through osmosis does not occur cell membrane beneath cell wall selectively permeable

74 Water Relations of Plant - Turgor plant cell put in distilled water plant cell contains solutes water potential lower than pure water net water movement into the cell by osmosis vacuole and cytoplasm swells

75 cell wall is rigid and strong, cell bursting is prevented turgor is present because: turgor hydrostatic pressure develops inside the cell cytoplasm is pushed against cell wall

76 tendency of the cell to give out water increases water potential increases When water potential of cell = water potential of water Turgor occur (cell cannot take in any water) the cell is turgid

77 Water Relations of Plant - Plasmolysis plant cell in concentrated solution net water movement out of the cell by osmosis vacuole and cytoplasm shrink cytoplasm is torn away from cell wall flaccid The whole phenomenon is called plasmolysis and cell is plasmolysed

78 Plasmolysed cells

79 Turgidity of Plant Cells turgid cell (in hypotonic sol.) plasmolysed cell (in hypertonic sol) cell wall cytoplasm vacuole enlarged solution here is the same as the external solution cell membrane separated from cell wall vacuole very small

80 In plant cells – –water enter, the cells become turgid. – –water leaves, the cells become less turgid flaccid plasmolyzed What will happen when water enters and leaves cells?

81 Cells in Different Solutions Solution Concentration animal cells (e.g. RBC) plant cells hypotonichypertonic haemolysis turgid shrink plasmolysis (cell is flaccid)

82 To Investigate the Effects of Sucrose Solution and Tap Water on Epidermal Cells of Red Onion Scale Leaf or Rhoeo Discolor Leaf

83 fleshy scale leaf of red onion bulb forceps filter paper epidermis What do you observe when the epidermal strip is placed in the concentrated sucrose solution ? Ans: The coloured cytoplasm shrinks.

84 Plasmolysis of red onion epidermal cells (400X)

85 Explain 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. fleshy scale leaf of red onion bulb forceps filter paper epidermis

86 What has happened to the cells in tap water ? Ans: The coloured cytoplasm swells and cells become turgid. fleshy scale leaf of red onion bulb forceps filter paper epidermis

87 Fully turgid red onion epidermal cells (400X)

88 Explain 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. fleshy scale leaf of red onion bulb forceps filter paper epidermis

89 Effects of Concentrated Sucrose Solution and Tap Water on Raw Potato Strips

90 What 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. petri dish water 20% surcose solution raw potato strips AB

91 Explain 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. petri dish water 20% surcose solution raw potato strips AB

92 Experiment to Show that Water is Given Off During Transpiration

93 What 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. polythene bag AB

94 How 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. polythene bag AB

95 What conclusions can you draw from the results ? Ans: We can conclude that a leafy shoot gives off water during transpiration. polythene bag AB

96 Transpiration an evaporation of water in form of water vapour from the surface of plant to atmosphere

97 more water loses from the lower surface of the leaf than the upper one as more stomata present on the lower surface it also happens in lenticels and cuticle it mainly takes place in leaves where there are some openings called stomata

98 How does transpiration take place? How water lost from leaves causes transpiration and how the transpiration pull is formed. How transpiration occurs 1. Water evaporates into sub-stomatal air space 2. Water diffuses out through stoma How transpiration pull is formed 1. 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. Eventually, water is pulled from the xylem, pulling water up the plant. Substomatal air space with higher concentration of water Lower concentration of water vapour

99 Transpiration in Leaves a thin film of moisture is covered with each mesophyll cell the moisture evaporates from mesophyll cells into intercellular spaces and diffuses out of stomata into atmosphere

100 water 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

101 To Measure the Rate of Transpiration by Using a Simple Potometer

102 What are the environmental conditions under which transpiration occurs quickly ? Ans: It is under dry, warm and windy conditions. air/water meniscus graduated capillary tube reservoir leafy shoot tap

103 Does 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. air/water meniscus graduated capillary tube reservoir leafy shoot tap

104 Sometimes 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. air/water meniscus graduated capillary tube reservoir leafy shoot tap

105 Sometimes 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. air/water meniscus graduated capillary tube reservoir leafy shoot tap

106 Environmental 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

107 Light Intensity stomata open in light, so plants can get enough carbon dioxide from atmosphere for carrying out photosynthesis light will increase temperature so increases the rate of transpiration

108 Temperature temperature relative humidity of air outside leaf rate of evaporation of water from mesophyll cells rate of diffusion of water vapour from intercellular space in leaf to outside

109 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

110 Wind Speed & Water Supply wind blows water vapour around the leaf sweeps away transpiration rate INCREASES lack of water soil dries, plant wilts and stomata close transpiration rate DECREASES

111 Stomata stomata are pores in the epidermis which gaseous exchange takes place during photosynthesis (or respiration) find mainly in lower epidermis of dicotyledonous leaves and stems

112 Guard Cells each stoma is surrounded by two guard cells which possess chloroplasts its inner wall is thicker than outer wall it is kidney-shaped guard cell stoma

113 Distribution of Stomata in Leaves normal plants mainly on the lower surface of leaves floating plants mainly on the upper surface leaves may also have air sacs to keep them afloat so they can carry out gaseous exchange

114 submerged 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)

115 Experiment to Investigate Stomatal Distribution in a Leaf by Using Cobalt Chloride Paper

116 cobalt chloride paper sellotape Obtain a potted plant. Using sellotape stick a small square of anhydrous cobalt chloride paper onto each surface of a leaf of the plant. Record the time taken for the cobalt chloride paper on each surface of the leaf to turn pink.

117 Which 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. cobalt chloride paper sellotape

118 Explain your answer. Ans: It is because more stomata are present in the lower epidermis. cobalt chloride paper sellotape

119 Why 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. cobalt chloride paper sellotape

120 To Observe the Release of Air Bubbles from Leaves placed in Hot Water

121 Which surface has more air bubbles coming off? Ans: There are more air bubbles appear on the lower surface of the leaf. forceps hot water leaf

122 Where 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. forceps hot water leaf

123 What does the result show? Ans: The result shows that more stomata are present on the lower epidermis of the leaf. forceps hot water leaf

124 Structure of Root

125 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 soil Epidermis cover the rest of root absence of cuticle so water can enter

126 Growing Point behind root cap cells are capable of active division Region of Elongation more elongated than cells in growing point and have large vacuoles

127 Region of Root Hair little way behind root tip root hair are thin-walled extension of epidermal cells of root increase surface area for uptake of water and mineral salts

128 Vascular Tissue further from the tip of root contain xylem and phloem xylem transport absorbed water to every part of plant

129 Absorption 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 hair water will pass by osmosis into root hair through cell wall and cell membrane

130 Transverse Transport of Water to Xylem epidermal cells gain water by osmosis NOTE: some water may travel inwards along or between cell walls without entering cytoplasm or vacuole of each cortical cell cytoplasm and cell sap have higher water potential than neighbouring cortical cells water travels by osmosis inwards from cell to cell


132 transpiration occurs in leaves so water is continuously removed from the plant flow of water through plant: transpiration stream tension produced to draw up water: transpiration pull reduction of effective pressure at the top of xylem vessel water flows upwards from roots continuously

133 ~ End ~ ~ End ~

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