Populations: 3.1, 3.2, 3.3, 3.4, 3.5

Specialists

Specialists

Smaller range of tolerance or narrower ecological niche makes them more prone to extinction

-Specific food requirements (bamboo)

-Less ability to adapt to new conditions

Generalists

Large range of tolerance, broader niche makes them less prone to extinction and more likely to be invasive

-Broad food requirement

-High Adaptability

K-Selectect

Few offspring, heavy parental care to protect them, generally have fewer reproductive events than r-strategists, long lifespan, long time to sexual maturity=low biotic potential=slow population growth rates, more likely to be disrupted by environmental change or invasives

r- selected

Many offspring, little to no care, may reproduce only once, generally reproduces many times throughout lifespan, short lifespan, quick to sexual maturity=high biotic potential=high population growth rate, more invasive, better suited for rapidly changing environmental conditions, high chance of adaptation and lower chance of extinction

Survivorship Curve

Line that shows survival rate of cohort (group of same-aged individual) in a population from birth to death

Slower drop in line in survivorship curve

Longer average lifespan

Type I (mostly K-selected)

High survivorship early in life due to high parental care, high survivorship in mid life due to large size and defensive behavior, rapid decrease in survivorship in late life as old age sets

Type II (in between r and K)

Steadily decreasing survivorship throughout life

Type III (mostly r-selected)

High mortality early in life due to little to no parental care, few make it to midlife, slow steady decline in survivorship in mid life, even fewer make it to adulthood, slow decline in survivorship in old age

Carrying Capacity (K)

The maximum number of individuals in a population that an ecosystem can support (based on limiting resources)

Carrying capacity depends on these limiting resources

Food, water, habitat (nesting sites, spaces)

Overshoot

When a population briefly exceeds carrying capacity

Consequence of overshoot

Resource depletion

Die-off

Sharp decrease in population size when resource depletion (overshoot) leads to many individuals dying

Reindeer of St. Paul Island Example

25 introduced in 1910, growth was gradual (10’-30’), then exponential (30’-37’), Carrying Capacity was overshot, sharp die-off lead to population crash as food resources were severely depleted

Size (N)

Total number of individuals in a given area at a give time, Larger = safer from population decline

Density

Number of individuals/ area, high density = higher competition, possibility for disease outbreak, possibility of depleting food source

Distribution

How individuals in population are spaced out compared to each other; Random (ex. Trees), Uniform (Ex. Territorial animals), Clumped (herd/group animals)

Sex ratio

Proportion of males to females, closer to 50:50, the more ideal for breeding (usually), die off or bottleneck effect can lead to skewed sex ratio (not enough females) limiting population growth

Density- dependent factors

Factors that influence population growth based on population size in an area; food, competition for habitat, water, light, and disease limits population growth based on their size; aka small population don’t experience these, large do

Density independent factors

Factors that influence population growth regardless of the population size in an area, ex. Natural disasters, doesn’t matter how big or small a population is, natural disaster limits them both

Biotic potential

Exponential growth, max potential growth rate, no limiting resources; may occur initially, but limiting resources (competition, food, disease, predators) slow growth, and eventually limit population to carrying capacity (k)

Logistic Growth

Initial rapid growth, then limiting factors limit population to K

Inputs that increase population size

Immigration and births

Outputs that decrease population size

Emigration and deaths

Equation for population size

(Immigration + Births) - (Emigrations + Deaths)

What are the two growth factors

Density-Dependent Factors, and Density-Independent Factors

What are the population characteristics

Size (N), Density, Distribution, Sex Ratio