Population Ecology and Community Dynamics

Comprehensive vocabulary flashcards covering population parameters, estimation techniques, growth forms, community interactions, ecological succession, and human population demographics.

Population

A group of organisms of the same species living in the same area that can interbreed.

Species

A group of organisms that share characteristics and can interbreed

Natality

The birth rate or rate of seed production in a population.

Mortality

The death rate within a population.

Immigration

The process of individuals moving into a population.

Emigration

The process of individuals leaving a population.

Direct Methods of Population Estimation

When organisms can be seen + stationary or slow-moving & the area is small (aerial photographs, censuses, helicopters)

Mark-Recapture Method

An indirect estimation method = individuals are captured, marked, and released ($M$), (marking don’t harm) and a second sample ($C$) is caught after a short time to record the marked recaptured ($R$)

$P = \frac{M \times C}{R}$,

Quadrat Method

(no. in sample size x size of habitat) ÷ quadrat size

1. measure total area

2. quadrat distributed randomly (10)

3. count individuals in each quadrat

Limiting Factors

Environmental factors that regulate population size (stop growing indefinitely)

Density-Dependent Factors

Factors that have a progressively greater effect as population density increases, such as competition, disease, and predation.

Density-Independent Factors

Abiotic environmental events that impact a population regardless of its density.

Environmental Resistance

The total factors in an environment that prevent a population from maximum reproduction.

Geometric Growth Form (J-Shaped Curve)

A growth form characterized by a rapid increase in population size until unfavourable environmental conditions cause an abrupt stop or population crash.

Logistic Growth Form (S-Shaped Curve)

A= growth slow as individuals adapting to environment or not reproductive age

B= no resistance = rapid growth

C= rate of reproduction decreases due to resistance

D= BR = DR

Carrying Capacity

The maximum number of individuals of a species that an environment can sustain without degradation.

Predation

An interaction where one species (the predator) kills and feeds on another species (the prey) = regulate population size + keep prey genetically fit

Intraspecific Competition

Competition between individuals of the same species for resources such as mates and food.

Interspecific Competition

Competition between individuals of different species competing for the same resources.

Ecological Niche

Abiotic and biotic conditions that an organism needs to survive and reproduce.

Competitive Exclusion Principle

When two species compete for same resource in an ecological niche, one will outcompete the other = local extinction.

Resource Partitioning

Species with similar requirements living in the same habitat divide resources by using them at different times, areas, or parts of a plant.

Social Organisation

Division of tasks and resources in group = improves individual survival and reproductive success by predator avoidance, cooperative hunting, or mate finding.

Dilution Effect

A predator avoidance in herds/flocks = higher no of individuals decreases the probability of individual being captured.

Caste System

A division of labour among non-breeding and breeding individuals (eusocial species, naked mole-rats)

Dominant queen suppresses reproduction with pheromones while fertile males fertilize

Sterile males defend & sterile females work.

Ecological Succession

The pattern of gradual changes in the species composition of a community after an environmental disturbance.

Primary Succession

Succession that begins on barren places without prior plant life or soil, beginning with pioneer species (lichens/moss)

Secondary Succession

Succession in areas where an environmental disturbance has removed existing species but left the soil intact (annual weeds)

Pioneer Species

Hardy and resistant species that are the first to colonize a disturbed area

Break down rocks to form soil and add organic matter/humus to the soil = improve soil conditions for other plants to grow.

Climax Community

The final stage of succession = endpoint is determined by factors such as rainfall, overgrazing, wetland drainage, or invasive alien species.

Population Pyramid

Dependency Ratio

Economically dependent ( $0\text{--}15\,\text{years}$ and $65+\,\text{years}$) compared to the economically active($18\text{--}65\,\text{years}$).

Factors Altering Population Makeup

HIV/AIDS, incoming young immigrants, emigration, war-related deaths among males, and reduced birth rates.