Population Ecology Concepts

Study Notes

A population is a group of organisms of the same species living in the same place at the same time, capable of interbreeding.
Density measures the number of individuals per unit area.
Age structure describes the proportion of individuals in different age groups.
Population growth is determined by births, deaths, and migrations.

Demography studies vital statistics like age structure, density, birth rates, deaths, growth, and reproduction.
Population genetics focuses on the breeding structure and genetic composition of a population.
Ontogeny describes the development of an organism from its origin to maturity, considering whether it is a unitary organism or modular organism.

Organisms can reproduce through unitary or modular mechanisms.
Unitary organisms develop from a single zygote and grow into a defined adult form, like a deer.
Modular organisms can produce new individuals (ramets) from buds or stems, like a tree.

A population consists of interbreeding organisms sharing a common gene pool.
Gene flow is the exchange of genetic information between populations.
Populations can evolve over time through changes in gene frequency within their gene pool.
Selective pressures from the environment can influence these changes, leading to adaptations.
Populations can further be divided into subpopulations or 'demes' with varying population densities.

Random distribution occurs when individuals are dispersed independently of each other, common in uniform environments with no interaction among individuals.
Uniform distribution involves evenly spaced individuals, often due to competition for resources.
Clumped distribution is the most common, where individuals cluster together due to shared resources or social interactions.
Temporal dispersion describes the distribution of individuals within a population over time.
It can be influenced by daily light-dark cycles, seasonal changes, and other environmental factors.

Dispersal is the movement of organisms away from their birth site.
Active dispersal occurs when organisms move under their own power.
Passive dispersal relies on external forces like wind or water currents.
Dispersal is vital for species survival, allowing colonization of new areas, expansion of species range, and gene flow.
Four types of dispersal:
- Immigration is movement into a new habitat.
- Emigration is movement out of a habitat.
- Migration involves seasonal movement between habitats.
- Nigration is one-way movement without return to the original habitat.