Palaeoecology - Lecture 6 Flashcards
The equation for exponential growth is dN/dt=rN. In this equation what does the N, t, dN/dt and the r represent?
N= size of population at time, t= time, dN/dt= change of N through time, r= reproductive success (population growth rate)
Which two communities particularly prosper when resources become abundant?
Pioneering communities and microbial communities
What limits exponential growth?
With growing population numbers competition for resources increases
Each environment has a specific carrying capactiy. What is the symbol for this?
K
What does carrying capacity mean?
The maximum population size that a species can maintain indefinitely in an environment based on the available resources of the habitat
Which relationship must exist between population size N and carrying capacity K for continuous population increase?
N<K
What happens to population growth if N exceeds K?
Population decrease
The formula for logistic growth is dN/dt=rN (1-N/K). What do ‘r’ and ‘K’ reflect?
‘r’ reflects reproductive performance and ‘K’ reflects the resources avaliable
The ‘r-selction’ occurs below the inflection point 1/2 K. This operates well below the carrying capacity. What characteristics to organisms here possess?
Large numbers of young, small body size and early maturity e.g. many insects, bacteria or grasses
The ‘K-selection’ operates near or at carrying capacity. What kind of characteristics do organisms here possess?
Small numbers of young, large body size, long life expectancy and slow population growth e.g. large animals or trees
What kind of fossil assemblages are expected for ‘r-selection’ and ‘k-selection?’
r-selective= high abundance, ow diversity. K-selective= high diversity, uneven spread
Define the term ‘Niche?’
An organisms role in a community
