Chapter 51-Pop Ecology Flashcards
population
group of individuals from the same species that live in the same area at the same time
Distribution and abundance
ex:Zootoca vivipara lizard
common resident from Ireland in western Europe to Japan in eastern Asia, but can live in many habitats and is cold adapted
Zooming into a local scale, the lizard’s distribution is clumped according to where there is suitable habitat
Population density
number of individuals per unit area - varies throughout the range
Random Distributions
if the position of each individual is independent of the others
Clumped Distributions
patchy habitat or the organisms are social
Uniform Distributions
if organisms have negative interactions that space them evenly
If a species range is small…
it may consist of a single population of interbreeding individuals
If a range is large….
may consist of many populations—sometimes contiguous, and sometimes isolated in space
metapopulation
population of populations connected by migration
-when suitable environments are scattered
Mark–recapture
1: catch individuals and mark them (leg bands, ear tags, etc)
2: release marked animals and allow them to mix well with the unmarked ones in the population
3: catch individuals again - the percentage of marked individuals that were recaptured is recorded
4: marked/total?= marked recaptured/recaptured total
Mark–Recapture assumption (5)
–Individuals are not moving in and out of the study area.
–Individuals mix between captures.
–No bias exists regarding which individuals are caught in each recapture.
–Individuals do not learn to avoid or seek out traps after being caught once.
–Individuals do not change their behaviour, attract and/or deter predators or mates, or die from being handled
Age structure
number of individuals of each age
To predict the future size of a population, you need to know:
–Age structure
–Number of individuals of each age likely to survive to the following year
–Number of offspring produced by females of each age
–How many individuals of different ages immigrate and emigrate each generation
–The average time between a mother’s first offspring and that of her daughter (generation length)
If a population consists of mostly young individuals with high survival and reproductive rates….
should increase
If a population consists of mostly old individuals with low survival and reproductive rates
should decrease
life table
probability that an individual will survive and reproduce in any given time interval over the course of its lifetime
Age class
individuals of a specific age
cohort
group of individuals of the same age that can be followed through time
Survivorship
proportion of offspring that survive, on average, to a particular age
Survivorship curve
plot of the logarithm of the number of survivors versus age
EX: Tyrannosaur Albertosaurus sarcophagus
Had a modified Type II survivorship curve, with low juvenile mortality and increased mortality at reproductive maturity
per capita rate of increase (r)
The difference between the birthrate and death rate per individual
Intrinsic rate of increase, rmax
r is at a maximum when b (birth) is at a maximum and d (death) is at the minimum
Exp growth occurs when…
r is constant
Exp growth is density dependent. Why?
Because population size does not limit growth rate. Exponential growth cannot continue indefinitely, resources are finite and will eventually run out
carrying capacity, K
A population hits its upper limit and switches to logistic growth pattern
Logistic growth is dependent on
pop size
What factors limit population size?
Density-independent factors: weather patterns, are usually abiotic; they change birthrates and death rates irrespective of population size
Density-dependent factors: depend on population size and decrease fecundity or survivorship
metapopulation
collection of populations interacting via dispersal
Pop momentum
- In developing countries, overall population size will increase dramatically over the course of your lifetime
- Part of this increase will be due to increased survivorship
- A paradox – although an average fecundity has decreased, these populations also now have more young women and thus higher m
zero population growth (ZPG)
When fertility at the replacement rate is sustained for a generation
(each woman producing exactly enough offspring to replace herself and her offspring’s father)
The role of fertility rates on pop
Influenced by:
–How much access women have to education and reliable birth control methods
–Overall economic development
–Access to quality health care
Endangered Species survivorship and fecundity
high juvenile mortality, low adult mortality, and low fecundity
–In these species, the fate of a population is sensitive to increases in adult mortality.
–Conservationists can then focus resources on protecting adults rather than eggs or juveniles
The populations within a larger metapopulation are most likely to survive when:
- Have larger population size
- Occupy larger geographical areas
- Are closer to neighbouring populations
- Have higher genetically diversity
Fecundity
# of female offspring produced by each female in pop OR age specific fecundity: specific to each age class of females
Factors that limit pop size:
Density-independent: weather, hurricanes, drought, etc.
Density-dependent: survivorship, fecundity
K varies…
- for different species because some habitats better due to food availability, space, etc
- in time because conditions may be better depending on the season/year
