Population characteristics, growth models, population interactions

1. Population Characteristics

A population is a group of individuals of the same species living in a specific area.
Population density refers to the number of individuals per unit area.
Population dispersion describes the spatial arrangement of individuals (clumped, uniform, random).
Age structure represents the proportion of individuals in different age groups.
Birth rate (natality) is the number of births per unit time.
Death rate (mortality) is the number of deaths per unit time.
Immigration is the arrival of new individuals into a population.
Emigration is the departure of individuals from a population.
Population size is affected by natality, mortality, immigration, and emigration.

Population growth depends on the availability of resources and environmental conditions.
Two major types of population growth models:
- Exponential Growth: Occurs when resources are unlimited, leading to rapid growth.
- It follows the J-shaped curve and is described by the equation: dN/dt = rN, where N = population size and r = growth rate.
- Logistic Growth: Occurs when resources become limited, slowing down growth.
- It follows the S-shaped (sigmoid) curve and is described by the equation: dN/dt = rN (K-N)/K, where K = carrying capacity.
Carrying capacity (K) is the maximum population size that an environment can support.

Populations interact with each other in various ways, influencing ecosystem dynamics.
Major types of population interactions:
- Competition: Occurs when species compete for the same resources, leading to reduced availability.
- Predation: One species (predator) hunts and consumes another (prey), maintaining ecological balance.
- Parasitism: One species (parasite) benefits while harming the host (e.g., tapeworms in humans).
- Mutualism: Both species benefit from the relationship (e.g., bees and flowers).
- Commensalism: One species benefits, while the other is neither harmed nor benefited (e.g., barnacles on whales).
- Amensalism: One species is harmed, while the other remains unaffected (e.g., penicillium fungus inhibiting bacterial growth).

Population ecology studies the characteristics, growth patterns, and interactions of species.
Exponential and logistic growth models describe population expansion.
Different types of interactions regulate ecosystem stability and biodiversity.
Understanding population ecology is crucial for conservation and resource management.