Question | Answer |
Population Distribution | How individuals are distributed with respect to one another. Either:
Random
Uniform
Clumped |
Density Dependent factors | the size of the population will influence an individual’s probability of survival.
Density-dependent factors include:
For terrestrial plants: water and soil nutrients.
For animals: food, water, and nesting sites. |
Density Independent Factors | the size of the population has no effect on the individual’s probability of survival.
Density-independent factors include:
Hurricanes, tornados, floods, fires, volcanic eruptions, environmental temperatures. |
Growth Rate | the number of offspring an individual can produce in a given time period, minus the deaths of the individual or offspring during the same period. |
Intrinsic Growth Rate | under ideal conditions, with unlimited resources, the maximum potential for growth (denoted as r) for a population |
The Exponential Growth Model | the intrinsic growth rate for a population (r), and
current number of reproducing individuals (N0),
That is, we can use the exponential growth model to estimate a population’s future size (Nt) after a period of time (t) has passed:
Nt = N0ert |
Logistic Growth | when a population whose growth is initially exponential, but slows as the population approaches the carrying capacity. |
Carrying Capacity | is the limit of how large a population can be sustained by the limiting resources, especially food.
(K in equation) |
K-selected Species | the population of a species that grows slowly until it reaches the carrying capacity. |
r-selected species | the population of a species that grows quickly, and is often followed by overshoots and die-offs. |
Species Interactions | Competition
Predation
Mutualism
Commensalism |
Competitive exclusion principle | two species competing for the same limiting resources cannot coexist. This can lead to resource partitioning. |
Predation | the use of one species as a resource by another species. |
True Predators | kill their prey |
Herbivores | consume plants as prey |
Parasites | live on or in the organism they consume. If they cause disease, they are pathogens. |
Parasitoids | lay eggs inside other organisms |
Mutualism | A type of interspecific interaction where both species benefit. |
Commensalism | a type of relationship in which one species benefits but the other is neither harmed nor helped. |
Symbiotic relationships | two species live in close association.
Commensalism, mutualism, and parasitism are all examples of symbiotic relationships. |
Keystone species | : a species that plays a role in its community that is far more important than its relative abundance might suggest; they are in small numbers |
Primary succession | occurs on surfaces that are initially devoid of soil. |
Secondary succession | occurs in areas that have been disturbed but have not lost their soil. |
Aquatic succession | ex: a pond eventually turning into soil |
Factors that determine species richness | Latitude:species richness declines.
Time:older habitats show more variety of species.
Habitat size and distance:size of the habitat and distance from the colonizing species affects the number and types of species. |