BIO 209 cont.

Population

A group of individuals of a single species inhabiting a specific area.

Fundamental Niche

The full range of environmental conditions (physical and chemical) under which a species can survive and reproduce.

Realized Niche

The actual niche occupied by a species; it is restricted by biotic interactions such as competition, predation, and disease.

Density-Body Size Relationship

Generally, there is an inverse relationship where smaller organisms live at higher population densities than larger organisms.

The 3 Aspects of Rarity

(1) Geographic Range (extensive vs. restricted), (2) Habitat Tolerance (broad vs. narrow), and (3) Local Population Size (large vs. small).

Survivorship Curve Type I

High survival of young; most mortality occurs among the elderly (e.g., humans, large mammals).

Survivorship Curve Type II

Constant rate of survival/mortality throughout the lifespan (e.g., birds, many reptiles).

Survivorship Curve Type III

Extremely high mortality for the young, followed by high survival for the few that reach adulthood (e.g., many fish, perennial plants, marine invertebrates).

lx (Survivorship)

The proportion of the original cohort surviving to age x.

mx (Fecundity)

The average number of offspring produced by an individual of age x.

R0 (Net Reproductive Rate)

The mean number of offspring produced by an individual in its lifetime.

T (Generation Time)

The average age of reproduction.

r (Per Capita Rate of Increase)

Used for overlapping generations. Calculation: r = ln(R0) / T

Geometric Growth

Used for populations with non-overlapping generations (e.g., annual plants or insects with one pulse of reproduction).

Exponential Growth

Used for populations with overlapping generations in an unlimited environment.

Density-Dependent Factors

Biotic factors that change in intensity based on population size (e.g., disease, competition, predation).

Density-Independent Factors

Abiotic factors that affect population regardless of size (e.g., floods, extreme temperature).

r-selection

High per capita growth rate. Favors unpredictable environments, small body size, rapid development, and many small offspring (Type III survivorship).

K-selection

Favors competitive ability and efficiency. Found in stable environments, large body size, slow development, and few large offspring (Type I or II survivorship).

Competitive Exclusion Principle

Two species with identical niches cannot coexist indefinitely.

Parasites vs. Parasitoids

Parasites usually don't kill their host immediately; parasitoids always kill the host (usually insects).

Mutualism (+/+)

Both species benefit (e.g., pollinators and plants).

What is a population?

A group of individuals of a single species inhabiting a specific area at the same time.

What are common measures of population abundance?

Common measures include population density (individuals per unit area), total count, and relative abundance indices.

What is the density-body size relationship?

Generally, population density decreases as the average body size of the individuals in the population increases.

What is the difference between a fundamental and a realized niche?

The fundamental niche is the full range of environmental conditions under which a species can survive and reproduce; the realized niche is the actual range of conditions occupied by the species after accounting for biotic interactions like competition.

What are the three patterns of distribution?

Random, regular (uniform), and clumped.

What are the three aspects of rarity?

Geographic range (narrow vs. wide), habitat tolerance (narrow vs. broad), and local population size (small vs. large).

What are survivorship curves?

Graphs showing the number or proportion of individuals surviving to each age for a given species. Type I: high survival until old age (humans); Type II: constant mortality rate (birds); Type III: high juvenile mortality (fish/plants).

What is the net reproductive rate (R0)?

The average number of offspring produced by an individual during its lifetime; calculated as the sum of lxmx.

How do you determine if a population is growing, stable, or shrinking using r?

If r > 0, the population is growing; if r = 0, it is stable; if r < 0, it is shrinking.

What is the difference between exponential and logistic growth?

Exponential growth occurs in an unlimited environment (J-curve); logistic growth accounts for environmental resistance and carrying capacity (S-curve).

What is carrying capacity (K)?

The maximum population size of a species that a specific environment can sustain indefinitely.

What is r-selection vs. K-selection?

r-selection favors high growth rates in unstable environments (many offspring, little care); K-selection favors efficient resource use in stable environments (few offspring, high care).

What is phenology?

The study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life.

What is the principle of competitive exclusion?

Two species with identical niches cannot coexist indefinitely; the more efficient competitor will eventually exclude the other.

What is the difference between exploitative and interference competition?

Exploitative competition occurs indirectly through the depletion of shared resources; interference competition involves direct aggressive interaction between individuals.

What are the types of exploitative interactions?

Predation, herbivory, parasitism, and parasitoidism.

What is the difference between parasites and parasitoids?

Parasites typically live on or in a host without killing it immediately; parasitoids are insects whose larvae consume and eventually kill their host.

What are prey-predator cycles?

Oscillations in population size where predator numbers follow prey numbers with a time lag, often modeled by Lotka-Volterra equations.

What is mutualism?

An interspecific interaction where both participating species receive a fitness benefit.

What are the types of mutualism?

Obligate (required for survival) and facultative (beneficial but not required).

What is a community?

An association of interacting species living in a particular area.

What is the formula for exponential population growth?

Nt = N0 * e^(rt)