Introduction to the Biosphere and Ecosystems
The Biosphere
The biosphere encompasses all living organisms on Earth, forming a dynamic system that interacts with the atmosphere, hydrosphere, and Earth’s surface. Living things are open systems, utilizing energy and matter from their environment and returning degraded matter and energy, primarily as heat and work.
Biomass
Biomass represents the total mass of living organisms within a specific area at a given time. Due to its variability, biomass is often measured in dry matter or carbon mass. To estimate the mass of a living organism, a value of approximately 10% of its total mass can be used.
Necromass
Necromass refers to the mass of dead organic matter, serving as an energy source for organisms like scavengers, detritivores, and decomposers.
Populations
A population consists of all organisms of the same species inhabiting a specific area and time, capable of interbreeding and producing fertile offspring. Genetically, individuals within a population share a gene pool, representing the collective genetic material. Genetic exchange occurs between populations through interbreeding and migration, enhancing genetic variability and influencing natural selection.
Biocenosis and Biotope
Biocenosis refers to the collection of populations sharing a geographical area and interacting with each other. The biotope represents the physical environment occupied by the biocenosis.
Ecosystems
An ecosystem comprises the biocenosis, the biotope, and the relationships established between them. It serves as a fundamental unit of study in ecology. Ecosystem boundaries are defined by vegetation, lithology, and other factors, and these boundaries are termed ecotones.
Biodiversity
Biodiversity is a parameter indicating the variety of species and their relative abundance. Biological diversity encompasses the variability among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems. It includes diversity within species, between species, and of ecosystems.
Habitat
Habitat refers to the physical location within an ecosystem that provides the necessary conditions for an organism to live. Each habitat possesses a range of biotic and environmental factors that influence populations. Each environmental factor characterizing a species’ habitat presents a tolerance zone within which the species can survive. This zone includes tolerance limits beyond which an individual dies and an area where growth is optimal.
Tolerance Ranges
- Stenoic Organisms: These organisms tolerate minimal variation in specific environmental factors (e.g., bees).
- Eurioic Organisms: These organisms tolerate a wide range of values for certain environmental parameters (e.g., salmon).
Limiting Factors
Limiting factors are constraints on the growth or distribution of a population.
Ecological Niche
The ecological niche represents the function a species plays within an ecosystem, encompassing various dimensions such as space and food resources. Understanding a species’ role involves examining its way of life, including its diet, reproductive cycle, and habits. While multiple species can share the same habitat, no two species can coexist in the same niche.
Types of Niches
- Fundamental Niche: The niche a species would occupy without considering interactions with other species.
- Realized Niche: The actual niche a species occupies, considering interactions and competition with other species.
Generalists and Specialists
- Generalists: Species capable of feeding in diverse ways and withstanding a wide range of environmental conditions, possessing a more flexible ecological niche.
- Specialists: Species with a restricted ecological niche, limited to specific habitats.
Population Dynamics
Population size in nature fluctuates over time. The growth rate of a population depends on births and immigration, which increase its size, and deaths and emigration, which decrease it. Population dynamics studies these changes using numerical models.
Reproductive Strategies
- R-Strategists: Organisms with high reproductive rates and rapid population growth (e.g., protozoa, bacteria, fish).
- High reproduction rate, low offspring survival.
- Short lifespan.
- Population growth fluctuates significantly.
- Typically generalist species in unstable ecosystems.
- K-Strategists: Organisms with lower reproductive rates and stable populations near carrying capacity (e.g., most animals).
- Low reproduction rate, high offspring survival.
- Most individuals reach adulthood.
- Population size stabilizes around carrying capacity.
- Typically specialist species in stable environments.
Intraspecific Relations
Intraspecific relations occur between individuals of the same species. These relationships can be perennial (lasting a lifetime) or temporal. Examples include:
- Family Associations: Relationships between parents and offspring.
- Gregarious Associations: Groupings for protection, migration, or foraging.
- Colonial Associations: Permanent associations resulting from asexual reproduction.
- State Associations: Hierarchical societies with division of labor.
- Territory: Occupation of a specific area, excluding other individuals of the same species.
- Competition: Occurs when individuals seek the same limited resources.