Life Histories, Strategies, and Tables

ZF
by Zubeyr Farah1 view·Updated Jun 2, 2022
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  1. this recording will focus on life histories.
  2. Life histories are a combination of traits that
  3. help maximize an individual survival and reproductive success.
  4. It consists of the following uh factors which is few Kennedy
  5. maturity
  6. parity and aging,
  7. aging is is simply defined as the time of death or termination of life
  8. parody
  9. is defined as the
  10. number of reproductive episodes, maturity is the age of reproduction
  11. and free content. It is defined as
  12. the number of offspring that are born in a tree productive episode.
  13. There are many trade offs that exists uh that we actually see,
  14. but we don't really process in our brains.
  15. Uh We see energy resources and time
  16. um
  17. being traded for growth, reproduction and survival.
  18. And depending on the organism, these factors are
  19. traded differently.
  20. So for example, some organisms have low survival rate
  21. but they have many offspring. Uh and they have early age of maturity.
  22. While organisms that reproduce slowly,
  23. they usually reach reproductive age later in their life.
  24. Uh They have few large offspring and theirs
  25. a significant amount of parental investment and they have a high survival rate.
  26. Specifically, these two types of organisms differ and their uh
  27. ah
  28. type of survivorship
  29. life history strategies.
  30. Uh There are two episodes specific episodes of reproduction.
  31. There's similar pairs. And video paris summer paris usually only
  32. I have only one reproductive episode and
  33. they usually die after that reproductive episode.
  34. While radio paris usually uh have reproductive episodes
  35. throughout the year and throughout their lifetime.
  36. There are two types of species case selected and are selected.
  37. Uh R selected species follow similar paris reproduction
  38. while case selected follow video paris uh reproduction.
  39. The K.
  40. Selected species usually live near the carrying capacity
  41. and they follow a type on survivorship.
  42. While r selected species usually live
  43. significantly below the carrying capacity and
  44. therefore have a large R value or intrinsic rate of increase.
  45. They also follow a Type three survivorship where a significant uh
  46. juvenile mortality is observed.
  47. Well, in uh type one survivorship,
  48. many individuals die later on in their life
  49. due to sickness or predation or disease.
  50. Uh The professor had asked a very interesting
  51. question uh in one of his lecture videos where
  52. he asked us what conditions conditions would you expect
  53. each of these strategies to be most successful?
  54. Um With the knowledge that I have, I would assume that the K.
  55. Selected species would uh do far better in environments that are not disturbed
  56. because of the time that it takes for K.
  57. Selected species to reproduce and the little amount of
  58. offsprings that they produce for each reproductive episode.
  59. Um An environment that has a significant amount of disturbances will
  60. may lead to the extinction of such species.
  61. Well, r selected species, I would assume to be
  62. in uh conditions where or environmental conditions
  63. where a lot of disturbances are present.
  64. Um
  65. And
  66. they're simply able to survive due to their
  67. large uh intrinsic rate of increase or population growth
  68. life tables. Uh
  69. They will be uh
  70. relaxing another assumption of the exponential growth equation model.
  71. This time they're relaxed at this time. Uh This this
  72. this factor is relaxing the
  73. assumption of equivalent individuals,
  74. no genetic age or size structure difference.
  75. And it is used to calculate the population growth in a given age class.
  76. And it consists of the following variables
  77. X. Which represents H. Class
  78. Alex which represents the proportion of individuals that are surviving
  79. Mx. Which is the fecundity
  80. annex.
  81. Which is the number of number of surviving individuals in that specific age class.
  82. Uh P. X. Is the survival probability. Uh
  83. And fx's fertility and Alex Mx is the survival of justice fecundity.
  84. Uh This value actually when we when you add all the values together will give
  85. us the net reproductive rate or the number
  86. of female offspring produced by per female.
  87. And we will be using this uh significantly in the
  88. next slide when we are are doing a problem set
  89. ah
  90. Question.
  91. Now the net reproductive rate. Uh
  92. It's a bit similar to the finite rate of increase
  93. in terms of what we consider a population that is increasing
  94. or decreasing.
  95. When are some not is greater than one.
  96. We are we are going to observe an increase in population.
  97. Well if it's equal to zero equal to one uh it's at an equilibrium.
  98. And if it's under one of the population will eventually go extinct.
  99. Now the problem said uh this uh it asks us to complete to the following uh
  100. I guess variables the network, productive rate,
  101. generation time and the entrance to creative increase by completing the table.
  102. Uh So the fecundity rate is usually given to us.
  103. Uh The population size in each specific age
  104. class is also something that's provided to us.
  105. The Alex is uh or the probably probably the probability of individuals surviving.
  106. It's something that we have to calculate for. And we calculate despite dividing
  107. the number of individuals in that specific age class
  108. by the original amount of individuals. So let's say in the age class. Uh The second
  109. age class number two,
  110. we have
  111. 500 individuals. We do 500 divided by 4000 is the initial amount of the population.
  112. And we get a value of .25.
  113. We use the proportion of individuals surviving. And we multiply that uh
  114. by the if you couldn't rate and uh this these values when we add
  115. them together like I have stated previously will give us the net reproductive rate.
  116. And as you can see that that reproductive rate we added 01.51.5 and .375.
  117. And we've got a value of 3.38.
  118. And because this value is above one,
  119. we're expecting this population to increase uh to calculate for a generation time.
  120. Now that we have are are some not. We can basically plug this into the calculation
  121. ah
  122. calculate for the numerator. We have to use the Alex mx values the survival.
  123. Uh The individuals surviving in each age class multiplied by difficulty rate.
  124. And we also have to multiply this by the age class.
  125. We will sum all these values together.
  126. And when we get zero plus 1.5 plus three plus 1.1
  127. 25.
  128. Uh and we divide that by the are some not which is 3.38.
  129. And we get a generation time of 1.67.
  130. Now that we have both the generation time and the net reproductive rate.
  131. We can use this to calculate for the intrinsic rate of increase. Uh And
  132. this equation is natural log
  133. multiplied by are some not
  134. divided by the generation time.
  135. Ellen of 3.375.
  136. That's supposed to be 3.83 point 3 to 8.
  137. And said I forgot to round that up divided by 1.67 which is the generation time.
  138. Uh And when we when we do this calculation we
  139. get a value of 0.73 which is easily above zero.
  140. And this indicates population
  141. increase.