BIOLOGY 1B Lecture Notes - Lecture 3: Survivorship Curve, Young Life, Exponential Growth
12 Jun 2018
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Lecture 3
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• Concept of population
o Elephant population
▪ Have to capacity for rapid population growth
o A group of individuals of the same species in the same area
o Organism: a living thing
o Species: a population or group of populations whose members can interbreed and
produce viable and fertile offspring
• Demography
o The study of the vital statistics of a population and how they change over time
o 4 things:
▪ birth, death, immigration, emigration
• Birth rate and death rate
o Nt= the number of indivuals in a population at time t
o B= number births till next interval
o D= number deaths till next time interval
o Time interval usually one year for large plant and animal but depends on population
o NT+1= Nt+B-D
• Geometric growth
o Increases by constant fraction
▪ “increases by 20%”
▪ delta N/ delta t= r(delta)N
• Exponential growth
o dH/dt= rN
▪ instantaneous rate of increase
▪ r= intrinsic rate of natural increase
▪ continuous curve that hits discrete points but is smoother representation
▪ if r>o, the population increasing
▪ r=o population not changing
▪ r<0 decreasing
o J shape
• Finite rate of increase
o Carrying capacity
o Stabilized population
• Intrinsic rate of natural increase
o dH/dt= rN
• Linear vs logarithmic y axis for population size and survivorship
o Log y axis- space between intervals shrinking; linear graph
• Cohort life table
o Cohort: a group of individuals born at the same time
o Fieldwork; keeping track of individuals
▪ Tagging animals; Usually one year; Some organisms- might shrink time
▪ Keep track of proportion alive
• Survivorship curve: straight line- fraction dying is same every year
• Survivorship curve
o Type 1: few indiv die throughout young life; aging
o Type 2: same fraction dying every year
o Type 3: lot of death in young, not as much in old
• Age specific fecundity output
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