Glossary
Biotic potential
The maximum reproductive capacity of a population under ideal environmental conditions, representing the highest possible growth rate.
Example:
A single bacterium, under perfect conditions, has an immense biotic potential, capable of producing millions of descendants in just a few hours.
Carrying capacity
The maximum population size of a biological species that can be sustained indefinitely by a given environment, considering the available resources.
Example:
The deer population in a national park will eventually stabilize around its carrying capacity as food and habitat become limiting factors.
Ecological Succession
The gradual process of change in the species structure of an ecological community over time, often following a disturbance or in newly formed habitats.
Example:
After a forest fire, the regrowth of vegetation from grasses to shrubs and eventually trees is an example of ecological succession.
Exponential growth
Population growth that occurs when a population's per capita growth rate remains constant, resulting in a rapid, accelerating increase in population size over time, often seen in r-selected species.
Example:
In a lab setting with unlimited nutrients, a bacterial colony can exhibit exponential growth, doubling its numbers at a fixed rate.
Invasive species
A non-native species whose introduction to an ecosystem causes or is likely to cause environmental or economic harm, often characterized by r-selected traits.
Example:
The zebra mussel is an invasive species in North American waterways, outcompeting native mussels and clogging pipes.
K-selected species
Species characterized by a low reproductive rate, few large offspring, extensive parental care, and long lifespans, typically found in stable, competitive environments near their carrying capacity.
Example:
The long gestation period and intensive maternal care of a grizzly bear exemplify a K-selected species focused on the survival of a few high-quality offspring.
Late-successional species
Species that dominate the later stages of ecological succession, typically K-selected, characterized by slower growth, longer lifespans, and strong competitive abilities.
Example:
Large, shade-tolerant redwood trees are late-successional species that thrive in mature, stable forest ecosystems.
Pioneer species
The first species to colonize newly disturbed or barren environments, often r-selected due to their rapid reproduction and dispersal abilities.
Example:
Lichens are classic pioneer species that can grow on bare rock, slowly breaking it down to create soil for other plants.
Reproductive Strategies
Different approaches species adopt to maximize their survival and the passing on of their genes, typically categorized along a spectrum from r-selected to K-selected.
Example:
An organism's reproductive strategy determines whether it produces many offspring with little care or few offspring with extensive parental investment.
Survivorship Curve
A graph that illustrates the number or proportion of individuals surviving at each age for a given species or group, revealing patterns of mortality over a lifespan.
Example:
By analyzing a population's survivorship curve, ecologists can understand if most individuals die young, live to old age, or have a constant mortality risk.
Type I Survivorship Curve
A survivorship curve characterized by high survival rates throughout most of the lifespan, with mortality increasing sharply in old age, typical of K-selected species.
Example:
Modern human populations often display a Type I Survivorship Curve, where most individuals survive well into adulthood due to healthcare and stable conditions.
Type II Survivorship Curve
A survivorship curve characterized by a relatively constant mortality rate throughout the lifespan, meaning individuals are equally likely to die at any age.
Example:
Many bird species exhibit a Type II Survivorship Curve, facing a consistent risk of predation or disease regardless of their age.
Type III Survivorship Curve
A survivorship curve characterized by very high mortality rates early in life, with much lower mortality for those few individuals who survive to adulthood, typical of r-selected species.
Example:
A sea turtle laying hundreds of eggs, most of which will not survive to maturity, demonstrates a classic Type III Survivorship Curve.
r-selected species
Species characterized by a high reproductive rate, many small offspring, little to no parental care, and short lifespans, often thriving in unstable or newly disturbed environments.
Example:
A sudden outbreak of mosquitoes after heavy rainfall is typical of an r-selected species, rapidly exploiting temporary abundant resources.