BIOL215 Lecture 20 Notes
Review:
Population: a group of individuals from one species that occupy the same space at the same time
In population biology, population will grow as a function of birth and immigration while population
will decrease as a function of death and emigration
A variety of equations that allow you to move from move the size of a population at time t to the size
of a population at t+1
What is survivorship and reproduction? Examine different types of species with different survivorship
patterns (Type 1, 2, 3). Different ways of summarizing the population vital statistics which are
survivorship and reproduction
Distinction between cohort table (all the individuals born at the same time and follow them through
time) and static table (going into a population at one time and trying to understand the birth and
death of that population based on what you see at that one moment)
Equations for net reproductive rate, generation time, instantaneous rate of increase, and geometric
growth
Understand the impact of net reproductive rate on the growth of a population will depend on the
generation time (the time it takes between two generations). Those two equations allow us to
calculate the instantaneous rate of increase in a population
Geometric growth and exponential growth has the same curve shape, but in geometric growth, you
have discrete episode of reproduction like in annual plants, they reproduce in one year, everyone dies
and then the next year, a new generation is born. In exponential growth, it is continuous reproduction
but that yields the same sort of growth form
The prairie chicken is a good example of a declining population
One of the most important reasons why we looked at applications of demography is because it is
important in conservation and allows us to make diagnostic about populations that are declining and
to help us better manage those populations
For geometric/exponential growth, it will apply to populations that will keep growing and growing
without stopping
In realistic terms, populations will follow the logistic growth where the size of a population will reach
a plateau where it reaches a carrying capacity (the moment where the population stops growing)
Growth: the change of individual over time
Population size: the number of individual at a given time
Carrying capacity: the number of individual where the environment cannot sustain anymore individual
At carrying capacity, the population number stops, population number stabilizes, and growth stops.
Population growth rate is maximum when the size of population is equal to carrying capacity divided
by two. This application has been used to manage fishery and the challenges associated with the
fishing industry
From deterministic to probabilistic models. The models studied so far are predicting one exact
outcome. Biological systems are probabilistic
Species interaction competition - the interaction between different species. This is the realm of
community ecology.
Community: looks at many species that cohabit in the same space at the same time Intraspecific competition - why do species keep growing if we're looking population under logistic
equation? It is because individual of the same species are fighting for the same resources
Interspecific competition: competition between two different species fighting for resources
In competition, we examined different ways of avoiding competition. Example is wobbler that forage
in different places in different trees. We also looked at the fact that competition is a structuring factor
in competition
A second type of interaction between species is predation. Understand coupled models of predator-
prey and the cycling of the model (abundance of prey controls abundance of predators)
To cope with predation, we know species take refuge via shelters, numbers, size, aposematic
coloration such as the "Batesian" mimics in snakes
Different types of interactions such as mutualism, parasitism, and herbivory and make relationship
between these and earlier interactions
Understand density-dependence: the more abundant the individual, the stronger the interaction
between individuals. Density-dependence is something that plays in population, that will

More
Less