Algemmeine Tiere - 4. Populationsökologie Flashcards
Populationsökologie
population structure, functional charachtaristics and dynamic
life table
survival and productivity ability with age
stochasticity
small populations are in greater risk of extinction
Metapopulations
Same species groups that still have contact (migrating individuals). population might extinct but metapopulation stays stable
Population in narrow sense
homotopic - group of individuals from the species that can repreduce.
Unitary oraganisms
can only develop to specific adult
Modulary oraganisms
the organisem develop, according to envrionmental factors, to many units (Bryozoa)
What can be problematic in defining population size?
- not easy to define living area. size is connected to samples species. several areas shell be compared to define distribution
- its only an evaluation, unrealistic to count.
the distribution might not be random
depends on ones resolution
Mark & recapture
number of marked individuals recaptured is proportional to number of marked individuals in population.
- no births, deaths, immigration during test.
- marking does not affect individual.
Population index (relativ) method in avaluating population size
grid frequency, time intervals, count footprints, kot…
which factors affect population size (equation)?
N = N(t) + births - deaths + immigration - emmigration
Iteroparus species
most of the species - have 1 or more reproduction period in life
Semelpare species
live short, can reproduce once (salmon)
Costs of high reproduction
Limited energy. therefore: less growh (individual), less chances to survive, worse condition for following generation
dynamic life table
a group along a certin period, until the death of the last member.
Cohort: same time interval of birth -> along life
static life table
a group along a certin, predefined amount of time.
Survival curves
survivolshio (log10 Ix) to age. draw the 3 types and give examples
calculate survival rate (Sx - how many of the age x survived)
survivorship I(x)/survivorship I(x-1)
Discrete growth
births - deaths (write proof)
R - individual grouth rate
b per head - d per head
𝝺 - population grouth factor
N(T) = 𝝺TN(0) = (1 + R)T N(0)
𝝺 = 0 : population stays on the same size
𝝺 > 1: exponential growth
0>𝝺 > 1: smaller
Time for duobling the size of the population depends on….
2 x N(0) = N(0) x 𝝺^D 2 = 𝝺D log(2) = log(𝝺^D) log(2) = D * log(𝝺) D = log(2) / log(𝝺) NOT ON ITS CURRENT SIZE
K carrying capacity
How many individuals a species can last for a long time in a limited resouces environment. Mostly births = deaths
Why is a population not growing to infitiny?
- intraspecific copetition
- K
- 𝝺 = 1+R unrealistic: R is smaller when there are less resources.
logistic (s) population growth
Population is stable when N = K (size = carrting capacity)
the right form (not seen in nature as all alrady in platau)
Allee-Effect
copmensation: change in birth or death will have a copmensating reaction. BUT low density population will get even lower (hard finding partners, small group disadvantages) - passanger pigeon
stochasticity - Why do small populations have a large chance to extinct?
- demography - not all that can, reproduce
- genetic factors -mutation fixing, loss of vairance
- many environmental dangers
r/k selection theory
grouth rate / carrying capacity. differences in: fertility, environment stbility, size, generation time, parents caring for children
r strategy
growing exponentially to “conqure” a nisch fast.
frogs, bugs
k strategy
live long, till k. wales, humans
migration
all species
dipersal
individual far from each other (e.g eggs). to avoid incest, small population -> high dispersal
