Population Size and Ecosystems

Populations are groups of individuals of the same species living in a particular area at the same time.
Population size is the total number of individuals in a population. It is affected by birth rate, death rate, immigration, and emigration.
The study of how population size changes over time is known as population dynamics.
Population growth can be either exponential, resulting in a J-shaped curve, or logistic, showing an S-shaped curve. The latter accounts for factors like carrying capacity.
The carrying capacity is the maximum population size that an environment can sustain indefinitely, given the available resources.

An ecosystem consists of all the organisms in a particular area and the abiotic factors with which they interact.
Biotic factors are the living parts of an ecosystem, such as plants, animals, and bacteria. These directly impact population size.
Biotic factors like competition, predation, and symbiotic relationships can influence population size and distribution.
Competition within a population can be either intraspecific (between individuals of the same species) or interspecific (between individuals of different species).
Predator-prey relationships influence population sizes in ecosystems, often leading to cyclical fluctuations in numbers.

Abiotic factors are the non-living parts of an ecosystem, like sunlight, temperature, wind, and soil. These factors can limit population size.
Each species has a set of optimal conditions under which it performs well - its preferred range.
If abiotic conditions vary beyond this range, it can become stressful for the species, and may reduce the population size or restrict its distribution.
Climatic factors such as temperature and rainfall define the geographical distribution of certain species, limiting where they can live and reproduce effectively.

Humans cause environmental changes that can reduce biodiversity and alter the size and composition of populations.
Habitat destruction and climate change are primary human-caused threats to population sizes and biodiversity.
Over-exploitation through overfishing and overhunting can lead to drastic declines in population sizes.
Pollution affecting air, water, soil quality or light and noise levels can have a detrimental effect on population sizes.
Conservation measures help to protect biodiversity, restore habitats and manage resources sustainably, thus supporting healthy ecosystems and optimal population sizes.