Ecological Concepts and Principles (Aquatic Ecology) PDF

Ecological Concepts and Principles (AQUATIC ECOLOGY) Levels of Biological Organization Ecology is the study of the complex web of interactions between organisms and their environment at all levels of organization. Principle of Hierarchical Control: As components combine to produce larger function...

Ecological Concepts and Principles (AQUATIC ECOLOGY) Levels of Biological Organization Ecology is the study of the complex web of interactions between organisms and their environment at all levels of organization. Principle of Hierarchical Control: As components combine to produce larger functional wholes in a hierarchical series, new properties emerge. Levels of Organization: Genes: A segment of the DNA molecule that encodes a single enzyme or structural protein unit. Genes are working units of heredity. Individual/Organism: The lowest level of organization in an ecosystem; functions independently, capable of interbreeding and producing fertile offspring. Population: A group of individuals of the same species occupying a common geographical area, consisting of organisms that feed, move, and interbreed among themselves. Community: Two or more populations of different species living and interacting within an ecosystem. Populations compete for space or food, and certain populations serve as food resources for others. Ecosystem: Consists of more than a community of living organisms (biotic factors) and their interaction with non-living ones (abiotic factors). Biosphere: The highest level of ecological organization, encompassing all ecosystems on Earth. Population Dynamics Population Characteristics: Size: The total number of individuals in a population. Density: The number of individuals per unit area or volume, influenced by births, immigration/emigration, and deaths. Distribution/Dispersion: Describes the area over which a population occurs, influenced by suitable environmental conditions. Age Structure: Populations can grow or shrink based on birth and death rates at different ages. Represented through life tables, survivorship curves, and age-sex pyramids. Estimation Methods: Quadrats: Used for determining the population size and density of plants or slow-moving animals.  Mark-Recapture: Used for organisms that move around, such as fish, to estimate population size and density. Life History Strategies Life History / Life Cycle: The pattern of survival and reproduction events typical for a species. Life History Strategy: How members of a species allocate resources among growth, survival, and reproduction. It varies between species based on traits and environmental constraints. Evolutionary Strategies: K-strategist: Few offspring, high probability of survival (e.g., large, long-lived animals). r-strategist: Many offspring with minimal parental care, often in unstable environments. Reproductive Cycles: ○ Semelparity: One-time reproduction with high energy investment. ○ Iteroparity: Multiple reproductive efforts with less energy invested each time. Community Organization Community: A group of species occupying the same geographical area, interacting directly or indirectly. Compete for resources like food, light, space, and water. Communities are defined by species richness, relative abundances, and the nature of species interactions. Biological Structure of a Community: Species Richness: Number of species in a community. Relative Abundance: Percentage contribution of each species to the total. Species Evenness: Equitable distribution of individuals among species. Diversity: Defined by the number of species and their relative abundance. Biodiversity Indices Simpson’s Diversity Index (D): Measures the probability that two randomly selected individuals from a community belong to the same species. D=∑(nN)2D = \sum \left( \frac{n}{N} \right)^2D=∑(Nn​)2, where nnn is the total number  of organisms of a particular species, and NNN is the total number of organisms of all species. Shannon-Weiner Index (H): Measures species diversity, with higher values indicating greater diversity. H=−∑piln⁡piH = -\sum p_i \ln p_iH=−∑pi​lnpi​, where pip_ipi​is the proportion of individuals of species iii in the total sample. Interspecific Interactions Competition: When organisms of two species use the same limited resource, resulting in negative impacts on both. Intraspecific Competition: Among individuals of the same species. Interspecific Competition: Between different species. Resource Partitioning: Allows species with similar requirements to coexist by using resources in different areas, ways, or times. Mutualism: Both species benefit from the interaction. Example: Clownfish and sea anemones. Commensalism: One species benefits, and the other is unaffected. Example: Barnacles on whales. Parasitism: One species benefits at the expense of the other. Example: Cymothoa spp. parasites on fish. Predation: Beneficial to one species, detrimental to another, involving the killing of prey. Example: Sharks as apex predators. Ecological Succession Disturbance: Events that disrupt an ecosystem, leading to ecological succession and ecosystem renewal. Primary Succession: Colonization of newly exposed land. Secondary Succession: Recolonization following a disturbance. Succession Progression: Communities transition from lower to higher species diversity over time.