1. GROWTH RATE

2. By the end of the lesson the students should be able to: (i) Describe absolute (actual) growth curve (ii)Describe absolute growth rate curve 1 Types of Growth Curves Objectives

3. 2 Growth Rate The Types The absolute (actual) growth curve the data obtained from the study of growth in an organism can be analysed by plotting graphs. The absolute growth rate curve

4. 3 Growth Rate The Absolute Growth Curve the most common graph plotted for growth the curve is of sigmoid shape @ S-shaped obtained if any suitable parameter, e.g. dry mass (m), is plotted against time (t) microbe populationlarge plant/animal applicable in the study of growth of microbe population or any large plant/animal

5. 4 Growth Rate The Absolute Growth Curve

6. 5 the overall growth pattern it shows the overall growth pattern and the overall growth period the same for most organisms, the growth pattern are the same initiallyslow  i.e. initially, the growth is slow faster  then, it grows faster finallyslows .finally, it slows down again Growth Rate The Absolute Growth Curve

7. 6 most organisms will continue to grow, able it at the slow rate but for human and other vertebrates, the growth stops when the maximum adult size is achieved Growth Rate The Absolute Growth Curve

8. 7 can be divided into five phases: The lag phase (AB) The log phase (BC) The retardation phase (CD) The stationary phase (DE) The negative growth (EF) Growth Rate The Absolute Growth Curve

9. Lag phase Logarithmic phase Retardation phase Stationary phase Death phase A B C DE F 7 Growth Rate The Absolute Growth Curve

10. AB BC CD DE EF A B C DE F 8 The lag phase (AB) very little growth cell division, enlargement slowly the organism is adapting to the new sources/ environment Growth Rate The Absolute Growth Curve

11. 9 The log phase (BC) AB BC CD DE EF A B C DE F Growth Rate The Absolute Growth Curve the growth accelerates and remains for a certain period of time until the sources become limited @ exponential growth

12. AB BC CD DE EF A B C DE F 10 The retardation phase (CD) @ Linear the growth is limited by: internal factors: organism maturity the growth slows down external factors: food supply  space  competition  Growth Rate The Absolute Growth Curve

13. AB BC CD DE EF A B C DE F 11 The stationary phase (DE) no further growth @ equilibrium / stable nett growth rate = 0 the parameters studied becomes constant the organism matures the rate of cell division = the rate of cell death Growth Rate The Absolute Growth Curve

14. AB BC CD DE EF A B C DE F 12 The negative growth phase (EF) badly deficient in nutrient sources and spaces ageing stage or the ability to get nutrients or to compete for spaces worsens Growth Rate The Absolute Growth Curve growth rate falls drastically

15. 13 Growth Rate The Absolute Growth Rate Curve time obtained by plotting changes/ differences in parameter, dx/dt, against time dx = increase in size dt = the time taken to increase absolute growth rate = total of changes in growth time taken for the overall growth measure of increase in size over a series of equal time intervals.

16. time. Absolute growth rate = dx, dt where: dx = size increased dt = period of time 14 the curve is bell-shaped changes in growth rate it shows the changes in growth rate against time Growth Rate The Absolute Growth Rate Curve

17. 15 absolute growth absolute rate growth i.e. it shows that the highest growth rate in the absolute growth curve is equivalent to the part where the slope is the highest in the absolute rate growth curve Growth Rate The Absolute Growth Rate Curve

18. 16 at the peak of the curve is the inflection point the point where the growth rate begins to decline i.e. the organism is reaching adulthood Inflection point Growth Rate The Absolute Growth Rate Curve

19. 17 Growth Rate The Absolute Growth Rate Curve

20. Types of Growth Curves Example: Growth of Maize Plant parameter = height (cm) # of days after planted height of plant (cm) growth rate for every 10 days 1022 2075 302013 40 20 507535 6011035 7014030 8015010 901555 1001605 1101600 1201600 sigmoid curvebell-shaped curve the growth rate of an organism or a population increase with the time until it achieves a maximum level, after which the growth rate decrease until it become zero. 18

21. 19 Growth Rate The Absolute Growth Rate Curve

22. GROWTH GROWTH UNDER EXTREME CONDITION

23. Objectives To explain and give example of: seed dormancy (legumes) hibernation (polar bear) aestivation (lung fish, insects) diapause (insects )

24.  Occur in animals and plants at certain intervals (temporarily) during their life cycles  during which growth slows or stops  because of extremely low metabolic rate  Resting stage  Can occur in the adult, egg, pupa, spore or seed stage Dormancy 1

25. Purposes unfavorable conditions  organisms able to survive in unfavorable conditions –insufficient food supply, cold weather (winter), hot and dry weather (drought)  It is control by hormones that –Response to physiological in plants and animals –Effecting the behavior in animals 2

26. Seed Dormancy  It is a phenomenon in certain seeds in which they would not germinate if not given an optimal condition ( water, oxygen, optimum temperature ). Can be seen in seeds ( eg: legumes ), buds, spore & food storage organs (tubers). Dormancy 3

27.  due to structure of seed coat - waxy cuticles, suberine layer (cuticle like layer) and lignified sclereids which are impermeable to water; prevent imbibition ( passive uptake ) of water - hard, lignified seed coat which are too strong to allow the penetration of radicle (out of seed) Dormancy in Plants Seed Dormancy 4 Due to many factors include: i.Lack of oxygen ii.Dryness iii.Presence of substances that inhibit germination

28.  Some seeds will not germinate - must undergo certain internal changes - to ensure that premature germination does not occur.  Special mechanism need to ensure germination does not occur before time [inmature seed germination]:-  involve the testa or outer coat – impervious ( impossible to penetrate) to water  also the presence of inhibitor (ABA/ absicic acid) Dormancy in Plants Seed Dormancy 5

29.  in order to break the dormancy, stratification (softening or injury of the seed coat) have to occur  chemical reaction in animal’s digestive tract or by physical abrasion (in order to remove the seed coat) Dormancy in Plants Seed Dormancy 5

30. occur during winter (cold weather) is a state of inactivity (do not consume much energy) which are characterized by lower body temperature, lower metabolic rate (decrease heart rate, respiration), low growth and development. Dormancy in Animal Hibernation to conserve the food stored because of food scarce/ deficiency 6

31. in preparation for hibernating, animals store food as body fat (brown fat) which is utilized during winter pregnant polar bears hibernate in ice dens (similar to igloo); sleep straight through winter Example: polar bear or white bear Dormancy in Animal Hibernation 7

32. other male and non-pregnant polar bears do not sleep straight through winter. they wake up once in a while, walk around and eat before they go back to sleep. Dormancy in Animal Hibernation Others:- small mammals in rodents (ground squirrels, hamster). Some store up food in their nests and feed on them if they wake up when the temperature rises. 8

33. Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo aestivation. Seasonal dormancy; similar to hibernation but, during hot weather increase in temperature and lack of water – drought e.g. lungfish Protopterus and Lipidiseren in Africa and South America Dormancy in Animal Aestivation (summer sleep) 9

34. burying itself in mud formed at the surface of a dried up lake Can continues to live even when the lake has become dry. secretes mucus at its mouth to allow air to enter its lungs becomes inactive (low metabolism – slow breathing and heartbeat rate) Until its water source is back to normal. Dormancy in Animal Aestivation In addition, stored fat and some of the muscle tissues in the bodies of these animals are lost during the aestivation period. 10

35. occur in insects –during winter when the temperature is low and there is no food & water. an insect resting stage during which developmental process is temporarily blocked (at any stage of its life cycle) Dormancy in Animal Diapause 11

36. Dormancy in Animal Diapause caused by the deficiency of certain hormonesInsects diapause is caused by the deficiency of certain hormones –from the brain controlled by external stimuli –the secretion of these hormones is controlled by external stimuli such as drought and long days. 11

37. Dormancy in Animal Diapause The hormones secretion depends on the period of exposure to light, –i.e. it behaves in a photoperiodic manner, similar to the process in plants. When the light period drops below a certain critical level, diapause is initiated. Diapause can be overcome when the light period increases until it exceeds the critical light period. Some insects require a low temperature in order to be released from diapause. 12

38. e.g. some butterflies and moths - diapause occur during larval stage white cabbage butterfly - diapause occur during pupae stage colorado potato beetle - diapause occur during adult Dormancy in Animal Diapause 13

39. Operophtera brumata (L.) Eggs diapause during winter 14

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