Recap Infomation (Week 1) Flashcards
What is population dynamic
the pattern and processes of change in populations
What is a population?
a population consists of - individuals of a species that interact with one another within a given area at a particular time
What is Demography?
the study of population processes
What are Life History Strategies/ Traits?
A way of describing how time and energy is allocated among various activities throughout an organisms life - They vary dramatically - The variations determine how fast populations grow
Environmental conditions affect life history strategies. what is the simplest population model?
Intrinsic rate of increase (r) r = births - deaths
Intrinsic Rate of Increase: What happens when births exceed deaths (r>0)?
The population grows
Intrinsic Rate of Increase: What happens when deaths exceed Births (r<0)?
The population declines
Intrinsic Rate of Increase: What happens if r=0?
the population is stable
which traits are most commonly influenced by environmental changes?
Age at Reproduction (generation time) Number of broods per female Number of offspring per brood
What are iteroparous species?
Species which reproduce multiple time during their life - typical of organisms whose survival chances are initially low, but increase once they reach maturity. - E.g. Social insect nests are very stable environments (iteroparity is common) Examples include Northern Gannets
What are Semelparous species?
species which reproduce once - Typically produce more offspring at once - Typical of organisms with low survivorship (E.g. some fishes, many insects, all annual plants, Rusty Tussock Moth
Give an example where predation influences Life history strategy.
Guppies (Poecilia reticulata) - Trinidad - Predator fish are excludes by waterfalls and the guppies have a lower mortality rate - Lab: Compare LHS of guppies in high vs. Low predation sites High predation sites: - Mature early, produces more offspring per brood, more eggs compared with low predator guppies Conclusion: adaptation to predation due to natural selection of life history traits
What is expotential growth?
when growth rate remains constant - as population size increases, number of new individuals added per time unit increase
what is the mathmatical equation for Expotenial population Growth?
^N/^t = b-d Change in no. over time = births-deaths dN/dt=(b-d)N dN/dt defines the rate of change in potenial size over time dN/dt = rN Intrinsic rather of increase (rN is sometimes called the biotic potential of a population)
Is exponential populations growth unsustainable?
yes. for short periods of time some populations may grow at an exponential rate usually followed by a population crash. E.g. Reindeer
What factors limit population densities?
Resources become scares/depleted, birthrates drop and death rates increase
How are populations limited?
Carrying Capacity (K): - Number of individuals of a species that can be supported by an environment (Key for sustainablilty)
What happens to a population when it nears the carrying capcity?
It slows down (logisitc growth) which makes an S shape on a graph E.g. sawtoothed grain beetle
What is environmental resistance?
The reduction in population growth due to a known reduction in resources
what is the formula of logistic growth when incoperating carrying capacity?
dN/dt= rN K-N/K r = Intrinsic growth rate N = Population size K = Carrying capacity
what is the Allee effect?
Individuals have a more difficult time surviving or reproducing if the population size is too small E.g. meerkats (Suricatta suricatta)
density-independent factors are:
Abiotic E.g. Deserts, Storms, cold periods of time
Density-dependent factors are:
Biotic E.g. availability of food, predation, disease and migration
What is associated with unpredictable habitats?
High fecundity High intrinsic rate of increase r- strategists
