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What is population ecology?
The study of how and why the number of individuals in aa population change over time
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Demography
- the study of factors that determine size and structure of populations through time
- -analyzing birthrates, death rates, immigration raets, and emigration rates
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Life table
summarizes the probability that an individual will survive and reproduce in any given time interval over the course of its life time.
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Survivorship
the proportion of offspring produced that survive, on average, to a particular age
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Types of surviorship
- 1.Humans:survivorship is high
- 2.Birds: individuals have the same probability of dying in each year of life
- 3.Plants/corals:Extremely high death rates for seeds and seedlings but high survival rates later in life cohort: a group of the same age that can be followed through
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Fecundity
the number of female offspring produced by each female in a population
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Why do fitness tradeoffs occur?
- -because every individual has a restricted amount of time and energy at its diposal..resources are limited..can't have both high fecundity and high survival
- -trade-off between survival and reproduction
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High fecundity individuals
individuals from species with high fecundity tend to grow quickly, reach sexual maturiy at young age, and produce many small eggs Ex. Mustard plant
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Individuals with high surviorship
individuals with high survivorship tend to grow slowly and invest resources in traitts that reduce damage from enemies and increase their own ability to compete for water, sunlight, or foodEx.Coconut palm
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intrinsic rate of increase
- conditions are optimal, meaning birthrates per individual are as high as possible and death rates are low as possibleex.
- fruit flies rmax is highex.
- pandas rmax is low
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exponential growth is ________of population size
- -independent
- (density independent)
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Carrying capacity
the maximum number of individuals in a population that can be supported in a particular habitat over a sustained period of time
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logistic population growth
- changes in growth rate that occur as a function of population size(density dependent)
- 1.Limits to growth(food, space, predators
- 2.More people=more resources used=slower growth
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what is the defining feature of exponential growth?
-the growth rate is constant
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Corridors
allow individuals to move between subpopulations, increasing gene flow and recolonization
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what are population dynamics?
changes in population over time
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Exponential growth equation
- N(t)=Ne^rt
- a.r=intrinsic capacity for growth
- b.N_t=current population size
- c.N_t+1=population size of next generation
- d. Net rate:
- r>1 growth
- r=1 no growth
- r<1 population shrinks
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Logistic growth equation
- N_t+1=N +rN (K-N)/K
- a.r=rate of growth
- b.N=current population
- c.K=carrying capacity
- d.N_t+1=population size in next generation
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Reproductive strategies during logistic growth
- 1. r selection: a lot of offspring produced because a lot die
- 2.K selection: 1 or 2 offspring produced so the population is maintained
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