Lecture 8-Births, deaths and survival: Life history and life tables Flashcards Preview

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Flashcards in Lecture 8-Births, deaths and survival: Life history and life tables Deck (30)
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1
Q

What does the equation Nt+1= Nt+B-D+I-E assume?

A

-that all individuals have same birth and death rates, same probability of dying -in reality, these things change with age of the individual, population density and e.g. weather -so quantify the lifecycle of the species and transitions from one life stage to the next

2
Q

What should we consider into the equation for Nt?

A

-How long lived the organisms are. -When are they active (winter/summer) -how often do they reproduce -how long is each stage in the lifecycle = how do all these vary between species, environments, densities…

3
Q

What does semelparous mean?

A

-grow, reproduce, die -big bang reproduction (lot of offspring) (salmon)

4
Q

What does iteroparous mean?

A

-grow, reproduce again and again and eventually die= humans

5
Q

What is ephemeral?

A

-they take advantage of special conditions, only grow in water, winter or summer etc.

6
Q

What do annuals do?

A

-active throughout the year

7
Q

What are life tables used for?

A

-Life tables are used to describe age-specific mortality and survival rates for a population. When this information is combined with fecundity data, life-tables can be used to estimate rates of population change -shows for each age the probability that the individual will die before the next birthday, probability of one surviving to particular age -remaining life expectancy for individuals at different ages

8
Q

What are the three types of life tables? (name only)

A
  • cohort or age-specific
  • static= time specific
  • composite=both
9
Q

What is a cohort or age specific life table(dynamic)?

A
  • data are collected by following a cohort throughout its life. This is rarely possible with natural populations of animals.
  • horizontal, age specific
10
Q

What is a cohort?

A

-a cohort is a group of individuals all born during the same time interval.

11
Q

What is a static or time specific life table?

A
  • age-distribution data are collected from a cross-section of the population at one particular time or during a short segment of time, such as through mortality data. Resulting age-specific data are treated as if a cohort was followed through time (i.e., the number of animals alive in age class x must be less than alive in age class x-1). Because of variation caused by small samples, data-smoothing techniques may be required -show the probability of death in the current year -assume that the death rate is constant= big assumption
  • vertical, time specific
12
Q

What is a composite life table?

A

-data are gathered over a number of years and generations using cohort or time-specific techniques. This method allows the natural variability in rates of survival to be monitored and assessed

13
Q

What’s the first column in a life table?

A

-a list of the age classes (some cases= life stages)

14
Q

What is the second column in a life table?

A

-the raw data collected for how many individuals survive to the beginning of each age class

15
Q

What is in the third column of a life table?

A

lx -the proportion of the original cohort surviving to the beginning of that age class -shown as proportion or percentage

16
Q

How do you calculate lx?

A

-take the number surviving in the age class and divide by the whole cohort (the original number started with) -if we had 100 individuals in the beginning and in this age class 10 survived= 10/100= 0.1 or 10%

17
Q

What is the fourth column of a life table?

A

dx -the percentage of originals dying

18
Q

How do you calculate dx?

A
  • lets say have 843 in class 1 and 722 in class 2 -the number of individuals who died= 843-722=121 -the percentage of dying= 121/843= 14.3 -this dx goes into the line where we have 843 individuals as it’s out of those these died and it shows how many out of each class die
19
Q

What is in the fifth column of a life table?

A

-qx -mortality rate -the proportion of individuals dying out of the population not the originals!

20
Q

How do you calculate qx?

A

-lets say we have 722 individuals in class 1 and 527 in class 2 -722-527= 195 individuals died - 195/722= 0.271 = the proportion of individuals from the population dying - the number qx goes in the line where 722 individuals are as it is the proportion of thos that died

21
Q

What is in the sixth column of a life table?

A

-fecundity -bx or mx

22
Q

How do you get bx or mx?

A
  • it is the number of offspring per individual
23
Q

What is this equation?

A

-finite rate of increase

Nt= number of individuals

Nt+1= number of individuals at time +1

-can calculate if have two points on a graph to compare the poulation growth

24
Q

What is this equation?

A
  • Fundamental net reproductive rate
  • maximum rate of increase in that habitat
25
Q

What is a possible problem with cohorts?

A

-living for a long time, longer than funding, or scope

26
Q

What are survivorship curves for?

A
  • show how the proportion of the original group surviving changes over time
  • hence (if using a log scale) how survival probability changes over time
  • if a straight line= rate of decline is constant over time
27
Q

Explain:

A
  • three types of survivorship curves
  • Type I= humans, stable then steep decline
  • Type II= birds, constant decline
  • Type III= oaks, many die young and not many die later
28
Q

What does a fecundity schedule look like for animals?

A
  • low at first, reaches high and then decreases with age
  • same for most species (animals)
  • the peak can move (humans= postponing having children)
29
Q

How can fecundity change in fisheries?

A
  • we catch the big ones often before reproduction
  • they adapt, start reproducing at smaller size
30
Q

What does a fecundity schedule look like in plants?

A
  • not as typically shaped curves
  • varies