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General Ecology > Lecture 9: Populations: Population growth & regulation > Flashcards

Lecture 9: Populations: Population growth & regulation Flashcards

1
Q

per-capita phenomenon

A

Population growth via births and deaths

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2
Q

Total population growth

A

the individual reproductive rate multiplied
by the population size

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3
Q

the bigger the population size, what gets greater?

A

the numerical growth

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4
Q

what is an appropriate and convenient way to view growth?

A

in discrete time steps (generations, years)

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5
Q

when counting a population when should they be taken and why?

A

it needs to be taken at the same time each time step, to be sure that the same birth and death cycles are included

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6
Q

Geometric growth

A
  • Growth via discrete time steps
  • Population size is a function of starting population size, per capita growth factor, and number of time steps
  • lines on the graph do not represent anything, data is only present on the dots
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7
Q

geometric growth formula

A

Nt = (N0)(λ^t)

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8
Q

explain the variables in the geometric growth formula

A
  • N = Number of individuals
  • λ (lambda) = Geometric growth factor
  • t = Number of discrete time steps.
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9
Q

what is the geometric growth factor (λ)

A
  • it is a multiplier
  • ratio of population size/population size the previous year
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10
Q

what happens to organisms with a continuous growth?

A

they reproduce and die at a relatively steady rate at all times

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11
Q

what is exponential growth

A

-Growth (positive or negative) at a continuous rate that is a proportion of the total number of individuals at any given time.
-Population size is a function of starting population size, the growth rate, and the time that has elapsed
- lines on the graph represent the data

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12
Q

exponential growth formula

A

Nt = (N0)(e^rt)

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13
Q

explain the variables for the exponential growth formula

A
  • r = Exponential growth rate.
  • e = the exponential constant.
  • N = Number of individuals
  • t = Time elapsed.
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14
Q

what is e^r in the exponential growth formula replacing and why

A
  • it replaces λ
  • to describe that all individuals have a chance of reproducing at any time, not just at a discrete time step
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15
Q

geometric growth (λ) - decreasing population size

A
  • 0 < λ < 1
  • λ is in between 0 and 1, not inclusive
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16
Q

geometric growth (λ) - constant population size

A

λ = 1

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17
Q

geometric growth (λ) - increasing population size

A

λ > 1

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18
Q

exponential growth (r) - decrease in population size

A

r < 0

19
Q

exponential growth (r) - constant population size

A

r = 0

20
Q

exponential growth (r) - increase in population size

A

r > 0

21
Q

if λ<1 or r<0, what does the graph look like?

A

it will be a negative exponential shaped graph

22
Q

if λ=1 or r=0, what does the graph look like?

A

it will be a horizontal line

23
Q

if λ>1 or r>0, what does the graph look like?

A

it will be a positive exponential shaped graph

24
Q

what do we do when birth and death rates vary with age

A

we have to account for the growth rate/factor or each age class for accurate calculations

25
Q

why is identifying age structures important

A

populations with the same birth and death rates but different age structures will grow at different rates

26
Q

how is population growth shaped in a population with age structures

A

it will have different birth and death rates for different age classes

27
Q

rapid and slow maturation in population growth

A

-Rapid maturation: limits age-class bias
-Slow maturation and bias in fecundity: maximizes age-class bias

28
Q

what is a life table

A

it is used to organize the information for age structured populations and to calculate growth.

29
Q

who does the life table typically track

A

-it tracks females and number of female offspring per reproductive female
-contribution of individual males are hard to track

30
Q

Cohort tracking approach

A

follows a group of individuals from birth through to death

31
Q

Cohort tracking approach - what it requires

A

requires that all individuals can to be marked and tracked for their whole life

32
Q

Cohort tracking approach - pros and cons

A
  • pros: provides rich data
  • cons: no replication for strange years because age is confounded by time
33
Q

Static age structure approach

A

Quantifies the survival and fecundity of all individuals of all ages in a population at a single time interval

34
Q

Static age structure approach - what it requires

A

Requires a way to assess survival and fecundity within a single time interval.

35
Q

Static age structure approach - pros and cons

A
  • pros: All age classes face the same environment at the time of census, so age not confounded by time
  • cons: it is unclear if the data is generalizable across years
36
Q

general patterns of survivorship - type I

A

High initial survival, followed by age-specific mortality in later age classes (ex: big mammals)

37
Q

general patterns of survivorship - type II

A
  • Constant survival – organisms of all ages face the same likelihood of dying (small mammals)
  • graph is negative and linear
38
Q

general patterns of survivorship - type III

A
  • High mortality early in life then escape major sources of mortality(ex: plants and invertebrates)
  • graph is negative and exponential shaped
39
Q

define fecundity

A

the amount of offspring an organism produces

40
Q

consequences of age structured populations: example of fisheries

A
  • fishing practices selectively target the most important age class of population stability
  • results in the collapse of many fisheries worldwide
41
Q

how were fishing practices selectively targeting the important age class

A
  • edible fish have reproductive bursts later in life
  • fisheries get paid more for catching bigger (older) fish
  • these fisheries ended up catching the oldest class of large, reproductively mature fish that were responsible for the reproductive output of the population
42
Q

what are cultural shifts in humans that slow population growth

A
  • Fewer children: lower fecundity rate reflecting very high childhood survival
  • Later reproduction: slower generation time reduces per capita growth rate per year, similar to later age of reproductive maturity
43
Q

what factors constitute to human population growth

A
  • Survival at all life stages is greatly improved globally.
  • Fecundity rates in many parts of the world are unchanged from a historical time when many children died and adult life expectancy was much shorter.

General Ecology (23 decks)

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