Individuals, populations,communities and ecosystems

Ecology - the study of organisms in their environment

Species - a group of organisms that share common characteristics and that interbred to produce fertile offspring.

Taxonomists use a variety of tools to identify an organism. One such tool is the dichotomous key. It is a tool consisting of questions with two choices in each step and answering the questions leads the user to the right identification.

Individual - a single organism of one species.

Ecosystem - a biological community of interacting organisms and their physical environment.

Population - all the individuals of the same species within a community. (Interbreeding unit)

Abiotic factors - the non living components of an ecosystem e.g., temperature, sunlight, pH, salinity, soil, atmosphere, water.

Biotic factors - the living components of an ecosystem and the interactions between them e.g., producers, consumers, detrivores, predation, mutualism.

Population interaction:

• Predator - prey relationship: oscillating populations where an increase in predators leads to a decrease in prey followed by a decrease in predators due to a lack of food.

• Mutualism: relationship between two species in which both of them benefit.

• Parasitism: relationship between parasite and host.

• Herbivore: the consumption of plant materials between animals.

Population size is regulated by density-dependent factors and negative feedback mechanisms. Density-dependent population limiting factors like disease tend to regulate the population more significantly.

Population size would significantly decline as a result of disease outbreaks if the population size is large rather than small.

Carrying capacity - the maximum number of organisms an area can support without environmental degradation.

Density-dependent factors significantly determine is a population reaches carrying capacity or not. Limiting factors of human population growth have been increasingly eliminated, resulting in unsustainable ecosystems. These factors have been eliminated through technological and health advancements, education and infrastructure development.

• S-curve (Logistic Growth):

  • Characterized by slow initial growth, followed by rapid growth, and then levelling off as the population approaches carrying capacity.

  • Typical of populations in stable environments with limited resources.

• J-curve (Exponential Growth):

  • Shows rapid, unrestricted growth.

  • Occurs when resources are abundant and there are no significant limiting factors.

Community - a group of interacting species living within the same ecosystem ( does not include abiotic factors)

Habitat - the environment in which a species normally lives (e.g., habitat of african elephant includes savannahs, woodlands, deserts and marches). They can change over time due to migration.

Ecological niche - the particular set of biotic abiotic conditions and resources upon which an organism or population depends. Includes space utilization, food consumption, temperature range, moisture requirements. Essentially the role a species carries out in their ecosystem.

A habitat is like an address, a niche is an organisms habitat and what it does there.

1. Fundamental Niche: This represents the full range of conditions and resources in which a species could potentially survive and reproduce if there were no competition or other limiting factors.

2. Realized Niche: This is the actual set of conditions and resources that a species utilizes in the presence of other species and environmental constraints.