Lectures 9-12: Life History Evolution & Population Dynamics I-III

Life History

Lifetime pattern of growth, development, and reproduction of a species.

Fecundity

Number of offspring produced per reproductive event.

Reproductive Effort

Total energy and resources devoted to reproduction.

Tradeoff

An evolutionary compromise where improving one trait reduces another.

Resource Allocation

Amount of energy and nutrients devoted to reproduction versus growth.

r-selected Species

Species characterized by many offspring, little parental care, short lifespan, and high mortality.

K-selected Species

Species characterized by few offspring, high parental care, long lifespan, and low mortality.

Phenotypic Plasticity

Ability to change phenotype in response to environmental conditions.

Phenology

Timing of life-history events like breeding or migration.

Survivorship

Probability of surviving through life.

Age-Specific Mortality

Mortality rate varies among age classes.

Iteroparous

Organisms that reproduce multiple times throughout their lifespan.

Semelparous

Organisms that have one major reproductive event followed by death.

Type I Survivorship Curve

High survivorship until old age, typical of mammals, often K-selected.

Type II Survivorship Curve

Constant mortality rate throughout life, typical of many birds.

Type III Survivorship Curve

Very high juvenile mortality, typical of many fish and plants, often r-selected.

Population

Group of individuals of the same species occupying an area and capable of interbreeding.

Population Structure

Abundance, age structure, sex ratio, and gene pool of a population.

Abundance

Total number of individuals in a population.

Age Structure

Number of individuals in different age classes.

Gene Pool

All genetic information in a population.

Distribution

Spatial arrangement of a population.

Random Distribution

Individuals occurring by chance.

Uniform Distribution

Even spacing due to competition or territorial behavior.

Clumped Distribution

Individuals grouped together, most common pattern in nature.

Endemic

Species restricted to a specific geographic distribution.

Ubiquitous

Species found across a wide geographic distribution.

Cosmopolitan

Species found across most of the world.

Fundamental Niche

All physical conditions and resources where a species could survive and reproduce in the absence of biotic interactions.

Realized Niche

Actual conditions and resources occupied after accounting for competition and predation.

Migration

Regular, two-way movement between locations.

Immigration

Movement into a population.

Emigration

Movement out of a population.

Active Dispersal

Organism moves under its own power.

Passive Dispersal

Movement aided by wind, water, or other organisms.

Assisted Dispersal

Humans move a species outside its native range.

Invasive Species

Non-native species established outside their native range causing harm to the ecosystem or economy.

Density

Number of individuals per unit area.

Relative Density and Abundance

Comparison of population size between locations or times.

Ecological Density

Number of individuals per unit of usable or suitable habitat.

Lincoln-Peterson Index

Estimation of total population size using the formula $N = \frac{n \times C}{R}$.

Population Growth Rate

Rate of population change over time, represented as $\frac{dN}{dt}$.

Growth Model: Exponential

Population growth formula: $\frac{dN}{dt} = r_{\text{max}} N$.

Growth Model: Logistic

Population growth formula: $\frac{dN}{dt} = r N \bigg(1 - \frac{N}{K}\bigg)$.

Carrying Capacity (K)

Maximum sustainable population size that the environment can support.

Inflection Point

Point of fastest population growth rate, located at $\frac{K}{2}$.

Density-Dependent Factors

Per capita effects that intensify as population density increases.

Density-Independent Factors

Factors influencing population size regardless of density.

Intraspecific Competition

Competition between individuals of the same species.

Scramble Competition

Intraspecific competition where resources are shared equally among individuals.

Contest Competition

Intraspecific competition where dominant individuals secure resources.

Exploitation Competition

Individuals compete indirectly by consuming shared resources.

Interference Competition

Direct interaction via territorial defense among individuals.

Home Range

Total area traversed by an individual for daily activities.

Territory

Actively defended part of a home range.

Allee Effect

Decreased per capita fitness in small or low-density populations.

Net Reproductive Rate (R_0)

$R_0 = \text{sum of }(l_x b_x)$, indicating population growth.