2nd Half - Exam Review

The max rate at which a population can grow under ideal conditions - r in exponential - Lambda geometric model

• Simplify complexity • Make (quantitative) predictions • Explore various scenarios • Test hypothesis and mechanisms • Communicate between disciplines • To criticize models and decide if assumptions are realistic

Populations grow geometrically when reproduction occurs at regular time intervals Population Increases - By a fixed proportion - lambda - Constant ratio of change from one time to the next - Over discrete, non overlapping time intervals - The larger the population becomes, the faster it grows - Used to model populations with discrete breeding seasons or generations.

Populations grow exponentially when reproduction occurs continuously - at a rate proportional to its current size - continuously - Larger the population becomes the faster it grows - Used to model populations that grow continuously (rather than discrete intervals)

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0

No growth or change in population size

Similarities: 1. Both show rapid growth due to multiplication 2. Both involve some intrinsic rate of increase Differences 1. Geometric growth is discrete, exponential growth is continuous 2. Different interpretation of growth rates

The rate of biological process is limited by the factor in least amount relative to the organism’s requirements - some factor is limiting

1.Density dependant factors - become more important as the population size increases - lead to carrying capacity - often due to increased infraspecific competition at higher population • Density independent factor - affect the population size regardless of its density

The max number of individuals of a species that can be supported by the available resources in a particular environment

• decrease in birth rate • increase in death rate • both

• When the relationship between r max and density is -ve • Due to intraspecific competition

If population exceeds carrying capacity - decrease in birth rates - increase in death rate - both Leads die off

The growth rate or survival of population increases as the population density increase Due to: - finding mate - cooperative behaviours - predator satiation - resource availallity (niche construction)

The common model for negative density dependence - S-shaped - Inflection point - Exponential phase before inflection point - Logistic phase after inflection K = carrying capacoty

• Births • Immigration - individuals moving into the population • Deaths • Emigration - The movement of individuals out of the population to other areas

• Regular - tied to seasonal changes in environment • Irregular - not tied to seasonal changes • Cyclical - Intrinsic factors, result in a regularish pattern in the species, species interactions

A smooth approach to carrying capacity

Regular fluctuations that that decrease overtime

Regular fluctuations that is consistent over time

Complex, unpredictable and irregular fluctuations

Due to stochasticity (conditions are changing in complex ways), typically unpredictable events - Disease outbreaks (biotic), new disease not present (disease can be density dependant) - Natural disasters (abiotic) - Human disturbances

• Stability - The maintenance of a relatively constant population size over time within a given geographic area (in terms of population). • Fluctuations can lead to periods of low population size • Small populations are more vulnerable to environmental changes and stochastic events • Small populations are thus at much greater risk of extinction than large populations