Unit 3 Vocabulary and Terms

Marcantonio, 2023-2024.

Specialists

Species with a smaller range of tolerance, or narrower ecological niche makes them more prone to extinction; have specific food requirements; low adaptability.

Generalists

Species with a larger range of tolerance, broader niche makes them less prone to extinction and more likely to be an invasive species; broad food requirements; high adaptability. 

K-selected species

"Quality"; few offspring, heavy parental care to protect them; usually reproduce many times; long lifespan, long time to sexual maturity, low biotic potential, slow population growth rate; more likely to be disrupted by environment change or invasives. 

r-selected species

"Quantity"; many offspring, little to no care; may reproduce only once; shorter lifespan, quick to sexual maturity; high biotic potential; high population growth rate; more likely to be invasive; better suited for rapidly changing environment conditions. 

Biotic potential

Maximum reproduction rate in ideal conditions.

Carrying capacity

The highest population size an ecosystem can support based on limiting resources (food, water, habitat space).

Overshoot

When a population briefly exceeds carrying capacity and results in resource depletion. 

Die-off (die-back)

A sharp decrease in population size when resource depletion (overshoot) which leads to many individuals dying. 

Population characteristics

Size - total number of individuals in a given area at a given time

Density - number of individuals per unit of area

Distribution - how individuals in a population are spaced out compared to each other

Sex Ratio - the ratio of males to females

Density-dependent factors

Factors that influence population growth based on size.  Ex: food, competition for habitat, water, light, disease. 

Density-independent factors

Factors that influence population growth independent of their size.  Ex: natural disasters. 

Age cohorts

Groups of similarly aged individuals.

0-14 = pre-reproductive; 15-44 = reproductive age; 45+ = post-reproductive. 

Extreme pyramid (age structure diagrams)

Represents rapid growth.

Less extreme pyramid (age structure diagrams)

Represents slow, stable growth.

House (age structure diagrams)

Represents stable, little to no growth.

Inverted pyramid (age structure diagrams)

Represents declining population.

Total fertility rate (TFR)

The average number of children a woman in a population will bear throughout her lifetime.

Replacement level fertility

The TFR required to offset deaths in a population and keep population size stable