Bio Midterm 3 PHENOLOGY / SPECIES / POPULATIONS

Speciation

Process where one species splits into two; increases biodiversity.

Reproductive Isolation

Barriers preventing interbreeding between populations.

Biological Species Concept

Species = group that can interbreed and produce fertile offspring.

Morphological Species Concept

Defines species by structural similarities/differences.

Ecological Species Concept

Defines species by ecological niche and role in environment.

Phylogenetic Species Concept

Defines species as smallest group sharing a common ancestor (based on genetics).

Prezygotic Barrier

Prevents mating or fertilization (e.g., timing, behavior).

Postzygotic Barrier

Occurs after fertilization; hybrids are sterile or nonviable.

Phenology

Timing of biological events (migration, flowering, breeding).

Phenological Mismatch

When species become out of sync (e.g., pollinators vs flowers).

Biodiversity

Variety of life at genetic, species, and ecosystem levels.

Habitat Loss

Main driver of species extinction; caused by human activity.

Climate Change

Shifts habitats and timing; major modern biodiversity threat.

Conservation Biology

Field focused on protecting biodiversity and ecosystems.

Pollination Example (Bees)

Human hand-pollination in China shows value of biodiversity.

Carrying Capacity (K)

Max population environment can support long term.

Population

Group of same species in an area at a given time.

Population Ecology

Study of population size, growth, and interactions with environment.

Population Density

Number of individuals per unit area.

Population Dispersion

Pattern of spacing (clumped, uniform, random).

Clumped Dispersion

Groups around resources or social behavior (e.g., herds).

Uniform Dispersion

Even spacing due to competition or territory.

Random Dispersion

No pattern; independent spacing.

Per Capita Rate of Increase (r)

Birth rate minus death rate per individual.

Exponential Growth

Rapid increase under ideal conditions; J-shaped curve.

Exponential Model Formula

G = rN

Logistic Growth

Slows as resources become limited; S-shaped curve.

Logistic Growth Formula

G = rN((K-N)/K)

Limiting Factors

Environmental conditions that restrict growth.

Density-Dependent Factors

Effects increase with density (competition, disease, predation).

Density-Independent Factors

Unrelated to density (weather, natural disasters).

Intraspecific Competition

Competition among individuals of the same species.

Demographic Transition

Shift from high birth/death rates to low ones with development.

Developed vs Developing

Countries with low vs high population growth rates.

Population Gain

Births + immigration.

Population Loss

Deaths + emigration.

When Birth Rate = Death Rate

Population size is stable.

Human Population Growth

Exponential historically; slowing toward logistic.

G

Population growth per unit time.

r

Per capita rate of increase.

N

Current population size.

K

Carrying capacity.

G = rN

Exponential growth equation.

G = rN((K-N)/K)

Logistic growth equation.

Exponential Curve

J-shaped growth pattern.

Logistic Curve

S-shaped pattern leveling at K.

Mark-Recapture Method

Population estimate based on tagged individuals recaptured.

Density Example

50 rabbits per square kilometer = density measure.

Intraspecific vs Interspecific

Within same species vs between different species competition.

Buffalo Boom Example

Disease removal (rinderpest) increased population exponentially.

Ecosystem Services

Benefits from nature (pollination, water purification).

Habitat Fragmentation

Splitting of habitats; isolates populations.

Conservation Strategies

Protect habitats, create corridors, regulate harvest.

Species Extinction

Permanent loss of species; reduces biodiversity.

n (Symbol)

Haploid number of chromosomes.

2n (Symbol)

Diploid number of chromosomes.

r (Symbol)

Per capita growth rate.

K (Symbol)

Carrying capacity; environmental limit.