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Biol 150 final notes.docx

Course Code
Rebecca Rooney
Study Guide

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Lecture 1 – Population Ecology
- # of individuals present in pop’n depends on; birth, death, immigration and emigration.
- is the study of factors (including these) that determine the size and structure of pop’ns over time.
- to make predictions need to understand:
ohow many individuals of each age are alive
ohow likely individuals of each age are to survive to the following year
ohow many offspring are produced by females of diff. ages.
- also need to know how many individuals of diff ages migrate each generation
ogeneration: mean age at which parents produce offspring (can be calculated from life table
Life Table
- summarizes probability that an individual will survive and reproduce in any given year of its entire lifetime.
- produces a value called “survivorship”.
- also produces a value called “fecundity”.
- data of these two values allows for calculation of growth rate of population
- proportion of indiv. remaining alive from one age class to next.
-survivorship curve: plot of the logarithm of the number of survivors versus age.
- 3 types of curves: Type I, Type II, Type III.
oType I: (humans), relatively low juvenile and young adult mortality, most deaths occur at end of
life span (in oldage).
oType II: (most birds), constant risk of mortality throughout life (steady and straight linear line).
oType III: (trees), very high mortality in early life (seeds and saplings for trees), low mortality in

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- # of [female] offspring produced by each female in the population.
-Age-specific F: average # of [female] offspring produced by a female in a given age class (group of
individuals of a specific age)
oHuman females: age-specific F is ZERO after menopause.
Life History, Survivorship and Fecundity
-Fitness Trade-offs: happen b/c every indiv. has a restricted amount of time and energy and its
disposal and its resources are limited.
-Life History of indiv. consists of how the organism allocates its resources to growth, reproduction and
activities related to survival.
- Life history trade-offs are universal.
- Trade-off between survival and reproduction:
oBlue birds that have a greater clutch size are more likely to reproduce but less likely to survive
following year.
- organisms with high fecundity tend to grow quickly, reach sexual maturity at a young age and produce many
small eggs or seeds  low survivorship
- other organisms grow slowly, invest their energy and time in traits that reduce damage from enemies and
increase own ability to compete, reach sexual maturity at an older age, and produce fewer, larger eggs or
seeds  high survivorship
- Overall want to maximize fitness
- life-history changes caused by changes in conditions that affect a populations growth rate.
- Trade-off and plasticity: Arctic Lake trout (slow growing and iteroparous)
oTrade off between growth (Sea Run) and reproduction (Freshwater).
oSea Run: matures later and reach a larger size (larger fish produce more and larger eggs).
older age-at-maturity, likely fewer spawning events over lifetime BUT greater number of
eggs that a larger.
oFreshwater: matures earlier and reach a small size (smaller fish produce fewer and smaller eggs.)

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more reproductive events BUT eggs are smaller and/or fewer.
Lecture 2: Population Growth
Population Growth
- PG rate is the change in # of indiv. in pop’n (N) per unit time (t).
- No migration: PGR = N x r
-per-capita rate of increase (r) is the difference b/w the birth rate and death rate: r= b – d.
- If PC birth rate > PR death rate, then r is positive and pop’n is growing.
- if PC birth rate < PC death rate, then r is negative and pop’n is declining.
-Birth rate = # of newborns/total pop’n [per unit time]
-Death rate = # of deaths/total pop’n [per unit time]
- make sure to choose an interval for time appropriate to the life history of organism/
-r-value: population birth rate – population death rate (If NO migration)
or <0: pop’n decling, death>birth
or=0: pop’n stable, birth=death
or>0: pop’n growing death<birth
-Intrinsic rate of increase: when birth rates are high as possible and death rate low as possible, rmax.
oWhen this occurs: pop’n growth rate is expressed as: N/t = rmaxN
oIROI does not change, but at any given time PCROF (r) is much lower than rmax..
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