Tag Archives: ecology

Environment & Ecology

Ecological Succession

Biogeochemical cycles, also known as nutrient cycles, describe the movement of chemical elements through different media, such as the atmosphere, soil, rocks, bodies of water, and organisms. Biogeochemical cycles keep essential elements available to plants and other organisms. The biogeochemical cycles of four elements—carbon, nitrogen, phosphorus, and sulfur—are discussed below. The cycling of these elements is interconnected with the Water Cycle For example, the movement of water is critical for the leaching of sulfur and phosphorus into rivers, lakes, and oceans.

The Carbon Cycle Carbon is the basic building block of all organic materials, and therefore, of living organisms. The carbon cycle is actually comprised of several interconnected cycles: one dealing with rapid carbon exchange among living organisms and the other dealing with the long-term cycling of carbon through geologic processes.

Carbon dioxide in the atmosphere is converted to organic carbon through photosynthesis by terrestrial organisms (like trees) and marine organisms (like algae).

Respiration by terrestrial organisms (like trees and deer) and marine organisms (like algae and fish) release carbon dioxide back into the atmosphere. Additionally, microbes that decompose dead organisms release carbon dioxide through respiration.

Weathering of terrestrial rocks also brings carbon into the soil. Carbon in the soil enters the water through leaching and runoff. It can accumulate into ocean sediments and reenter land through uplifting. Long-term storage of organic carbon occurs when matter from living organisms is buried deep underground and becomes fossilized. Volcanic activity and, more recently, human emissions stored carbon back into the carbon cycle.

The Nitrogen Cycle

All organisms require nitrogen because it is an important component of nucleic acids, proteins, and other organic molecules. Getting nitrogen into living organisms is difficult. Plants and algae are not equipped to incorporate nitrogen from the atmosphere (where it exists as tightly bonded, triple covalent N2) although this molecule comprises approximately 78 percent of the atmosphere. Because most of the nitrogen is stored in the atmosphere, the atmosphere is considered a reservoir of nitrogen.

In the nitrogen cycle, nitrogen-fixing bacteria in the soil or legume root nodules convert nitrogen gas (N2) from the atmosphere to ammonium (NH4+).

  • Nitrification occurs when bacteria convert ammonium to nitrites (NO2-) and then to nitrates (NO3-). Nitrates re-enter the atmosphere as nitrogen gas through denitrification by bacteria.
  • Plants assimilate ammonium and nitrates, producing organic nitrogen, which is available to consumers.Three processes are responsible for most of the nitrogen fixation in the biosphere. 
  • Decomposers, including aerobic and anaerobic bacteria and fungi, break down organic nitrogen and release ammonium through ammonification.
    • The first is atmospheric fixation by lightning. The enormous energy of lightning breaks nitrogen molecules and enables their atoms to combine with oxygen in the air forming nitrogen oxides. These dissolve in rain, forming nitrates, that are carried to the earth. Atmospheric nitrogen fixation probably contributes some 5-8% of the total nitrogen fixed.
    • The second process is industrial fixation. Under great pressure, at a temperature of 600°C (1112°F), and with the use of a catalyst (which facilitates chemical reactions), atmospheric nitrogen and hydrogen can be combined to form ammonia (NH3). Ammonia can be used directly as fertilizer, but most of it is further processed to urea and ammonium nitrate (NH4NO3).
    • The third process is biological fixation by certain free-living or symbiotic bacteria. Some form a symbiotic relationship with plants in the legume family, which includes beans, peas, soybeans, alfalfa, and clovers . Some nitrogen-fixing bacteria even establish symbiotic relationships with animals, e.g., termites and “shipworms” (wood-eating bivalves).

    Nitrogen-fixing cyanobacteria are essential to maintaining the fertility of semi-aquatic environments like rice paddies. Although the first stable product of the process is ammonia, this is quickly incorporated into protein and other organic nitrogen compounds.

Ammonium is converted by bacteria and archaea into nitrites (NO2−) and then nitrates (NO3−) through the process of nitrification. Like ammonium, nitrites and nitrates are found in water and the soil. Some nitrates are converted back into nitrogen gas, which is released into the atmosphere. The process, called denitrification, is conducted by bacteria. Plants and other producers directly use ammonium and nitrates to make organic molecules through the process of assimilation. This nitrogen is now available to consumers. Organic nitrogen is especially important to the study of ecosystem dynamics because many processes, such as primary production, are limited by the available supply of nitrogen. Consumers excrete organic nitrogen compounds that return to the environment. Additionally dead organisms at each trophic level contain organic nitrogen. Microorganisms, such as bacteria and fungi, decompose these wastes and dead tissues, ultimately producing ammonium through the process of ammonification.

The Phosphorus Cycle Several forms of nitrogen (nitrogen gas, ammnoium, nitrates, etc.) were involved in the nitrogen cycle, but phosphorus remains primarily in the form of the phosphate ion (PO43-). Also in contrast to the nitrogen cycle, there is no form of phosphorus in the atmosphere. Phosphorus is used to make nucleic acids and the phospholipids that comprise biological membranes.

Phosphate enters the atmosphere from volcanic aerosols, which precipitate to Earth. Weathering of rocks also releases phosphate into the soil and water, where it becomes available to terrestrial food webs. Some of the phosphate from terrestrial food webs dissolves in streams and lakes, and the remainder enters the soil. Phosphate enters the ocean via surface runoff, groundwater flow, and river flow, where it becomes dissolved in ocean water or enters marine food webs. Some phosphate falls to the ocean floor where it becomes sediment. If uplifting occurs, this sediment can return to land.

The Sulfur Cycle Sulfur is an essential element for the molecules of living things. As part of the amino acid cysteine, it is critical to the three-dimensional shape of proteins.

Atmospheric sulfur is found in the form of sulfur dioxide (SO2), which enters the atmosphere in three ways:

  • first, from the decomposition of organic molecules;
  • second, from volcanic activity and geothermal vents; and,
  • third, from the burning of fossil fuels by humans.

Sulfur dioxide (SO2) from the atmosphere is dissolved in precipitation as weak sulfuric acid or falls directly to Earth as fallout. This releases sulfates (SO42-) into the soil and water. Soil sulfates can be carried as runoff into the water. Marine sulfate can form pyrite, and this can break down to release soil sulfates.

Organisms in terrestrial and marine ecosystems assimilate sulfate, adding sulfur to organic molecules, such as proteins (not shown). Decomposition of these organisms returns sulfates to the soil. Microorganisms can convert sulfates to hydrogen sulfide (H2S) and vice versa. Decomposition, volcanic eruptions, and human activities (including burning fossil fuels) can release hydrogen sulfide (H2S) or sulfur dioxide into the atmosphere.

Ecological succession 

Ecological succession is the gradual and sequential replacement of one community by the other in an area over a period of time. According to E.P. Odum (1971), the ecological succession is an orderly process of community change in a unit area. It is the process of change in species composition in an ecosystem over time.

Process of Ecosystem Succession The ecological succession is a complex process and it may take thousands of years. Frederic Clements in 1916 for the first time proposed the sequential phases of an ecological succession.

Different Types of Ecological Succession

Primary succession is initiated when a new area that has never previously supported an ecological community is colonized by plants and animals. This could be on newly exposed rock surfaces from landslides or lava flows.

Secondary succession occurs when an area that has previously had an ecological community is so disturbed or changed that the original community was destroyed and a new community moves in. This is more common than primary succession and is often the result of natural disasters, such as fires, floods, and winds, as well as human interference, such as logging and clear-cutting.

Stages of Succession

Nudation/Bare Area: The creation of a lifeless area, whether from a disturbance or new habitat formation.

Migration: The dispersal of seeds, spores, and other propagules from existing communities into the bare area by wind, water, or animals.

Ecesis: The successful establishment and growth of the colonizing species as they adapt to the new environment.

Aggregation: The growth in population of these initial species, leading to a denser and more complex community.

Competition and Co-action: As populations grow, species begin to interact and compete for resources, influencing the community’s structure.

Reaction: The development of new environmental conditions by the existing community that may hinder its own survival but facilitate the establishment of new species.

Stabilization/Climax Community: A stable, mature community that is relatively well-adapted to its environment, with high biodiversity and a balanced species composition.

Environment & Ecology

Ecosystem Functions

Photosynthetic and Chemosynthetic organisms

Photosynthetic and chemosynthetic organisms are autotrophs, which are organisms capable of synthesizing their own food (more specifically, capable of using inorganic carbon as a carbon source).

Photosynthetic autotrophs (photoautotrophs) use sunlight as an energy source, and chemosynthetic autotrophs (chemoautotrophs) use inorganic molecules as an energy source. Autotrophs are critical for ecosystems because they occupy the trophic level containing producers. Without these organisms, energy would not be available to other living organisms, and life would not be possible.

Photoautotrophs, such as plants, algae, and photosynthetic bacteria, are the energy source for a majority of the world’s ecosystems.

Photoautotrophs harness the Sun’s solar energy by converting it to chemical energy.

Chemoautotrophs are primarily bacteria and archaea that are found in rare ecosystems where sunlight is not available, such as those associated with dark caves or hydrothermal vents at the bottom of the ocean . Many chemoautotrophs in hydrothermal vents use hydrogen sulfide (H2S), which is released from the vents, as a source of chemical energy. This allows them to synthesize complex organic molecules, such as glucose, for their own energy and, in turn, supplies energy to the rest of the ecosystem.The feeding positions in a food chain or web are called trophic levels. The different trophic levels are defined in the Table below. Examples are also given in the table. All food chains and webs have at least two or three trophic levels. Generally, there are a maximum of four trophic levels.
Many consumers feed at more than one trophic level. Humans, for example, are primary consumers when they eat plants such as vegetables. They are secondary consumers when they eat cows. They are tertiary consumers when they eat salmon.

Trophic Levels

The feeding positions in a food chain or web are called trophic levels. The different trophic levels are defined in the Table below. Examples are also given in the table. All food chains and webs have at least two or three trophic levels. Generally, there are a maximum of four trophic levels. Many consumers feed at more than one trophic level. Humans, for example, are primary consumers when they eat plants such as vegetables. They are secondary consumers when they eat cows. They are tertiary consumers when they eat salmon.

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Environment & Ecology

What is Ecology

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The word ecology is a combination of the Greek ‘oikos,’ for house, and ‘logy’ for knowledge. Literally translated, ecology means ‘the study of our house.’ Our house is planet Earth. Ecology is the study of every living thing in every environment, at every scale, from the bacteria living on your skin to a blue whale breaching in the Southern Ocean, It’s the ocean itself and everything in it. It’s vast and tiny, planet-wide and microscopic.

Organismal ecology is all about looking at how individual organisms are shaped—both physically and behaviorally—to thrive in their environments.

For example:

  • Morphological adaptations: A cactus has thick, fleshy stems to store water and spines instead of leaves to reduce water loss.
  • Physiological adaptations: Arctic foxes can change their fur color seasonally—white in winter for camouflage in snow, brown in summer to blend with tundra.
  • Behavioral adaptations: Birds migrating to warmer regions during winter to access food and better living conditions.

Population Ecology

Population ecology is the study of how the number of individuals of a particular species in a given area changes over time, and the factors that influence these changes.

It focuses on population size, density, distribution, and the processes such as birth, death, immigration, and emigration that regulate population dynamics.

Community ecology It’s the study of how different species interact within the same area and how those interactions shape the structure and dynamics of the community.

Types of interactions:

Competition (species competing for the same resources) Predation (one species feeding on another) Mutualism (both species benefit, like bees and flowers) Commensalism (one benefits, the other is unaffected) Parasitism (one benefits at the expense of the other) Consequences of interactions: Influence on species diversity and abundance Shaping of food webs and trophic structures Driving adaptations and co evolution Affecting ecosystem stability and resilience.

Ecosystem Ecology the study of communities to include both the living components (biotic) and the non-living physical and chemical factors (abiotic) in a given area. It examines how organisms interact with each other and with their environment, creating a dynamic system.

The environment simply refers to the surroundings without necessarily emphasizing those interactions.

  • Interaction vs. Surroundings: The environment is about the general surroundings, while the ecosystem highlights the interactions between organisms and their surroundings.
  • Functional Unit vs. Habitat: An ecosystem is a functional unit of nature, whereas the environment is the broad habitat itself.
  • Interdependence: An ecosystem emphasizes the interdependence of its components to maintain stability, a concept not necessarily implied in the broader environment.

  • Abiotic Factors

    Physical Factors: Temperature: The level of heat or cold in an environment.

    Water: The availability of water, including precipitation, and its properties like salinity and dissolved oxygen.

    Light: The amount of sunlight available for processes like photosynthesis.

    Soil: The type, composition, and nutrient content of the soil.

    Atmosphere: Gases in the air, humidity, and wind patterns.

    Elevation/Altitude: The height above sea level.

    Chemical Factors:

    pH: The acidity or alkalinity of the soil or water.

    Salinity: The amount of salt in the water, especially relevant in marine ecosystems.

    Nutrients: The mineral and organic compounds available in the soil or water.

Temperature

Temperature of the air and water affect animals, plants and humans in ecosystems. A rise in temperature has the potential to change the way a living thing develops, because it changes the metabolic rate of the organism. All living organisms have a tolerance level for temperature range. For example, a human being would die if he stood out in minus 50 degree temperatures for any length of time. Light exposure often affects the temperature. Areas with direct sunlight are warmer.

  • Organisms which can tolerate wide fluctuations in temperature are termed – Eurythermal. Eg: Lizards, Birds and Mammal
  • Organisms which can tolerate only small variation in temperature are termed Stenothermal organisms Eg: Coral animals, Fishes
  • The number of hours of daylight triggers seasonal events, such as: -plants flowering -birds migrating.

Homeothermic animals The term ‘homeo’ derives from Greek and means ‘same’ or ‘similar’. This is because the definition of a homeotherm is:

An animal or organism that maintains a relatively constant body temperature.The ability to maintain a relatively steady body temperature is due to internal physiological processes.

Since these process are internal, it means they are endothermic (i.e. their heat comes from within). Such processes allow the organism to maintain their bodily functions, even when the external environment changes drastically.

Traditionally, homeothermic animals have been known as ‘warm-blooded animals’.

Only birds and mammals are currently considered true homeothermic animals. There is an exception in the reptile group of animals, specifically the Argentine black and white tegu (Salvator merianae). This homeothermic lizard has some endothermic behavior, but also relies on environmental temperature for survival.

Poikilotherm animals The term ‘poikilo’ is also of Greek origin and means ‘varied’. In this case, the definition of a poikilotherm is: An animal or organism that has a considerably variable temperature.

The reason why poikilotherms have a highly variable temperature is because they cannot self-regulate it. Accordingly, their body temperature varies according to the environmental temperature. This means that poikilotherms are exothermic since their heat comes from external sources. It is for this reason they are known as ‘cold-blooded animals’, despite this being and imprecise description of their type of thermoregulation. Poikilothermic animals are exposed to various temperatures in their environment. Unlike homeotherms, poikilothermic animals can survive without eating for much longer periods. This is because they do not depend on metabolizing what they ear to maintain body temperature.

Light

Light is a complex environmental factor that produces diverse ecological effects. Light energy (sunlight) is the primary source of energy in nearly all ecosystems. It is the energy that is used by green plants (which contain chlorophyll) during the process of photosynthesis; a process during which plants manufacture organic substances by combining inorganic substances.

Photoperiodism can be defined as the relative lengths of daylight and darkness that effect the physiology and behaviour of an organism.

Phototropism is the directional growth of plants in response to light where the direction of the stimulus determines the direction of movement; stems demonstrate positive phototropism i.e. they came towards the light when they grow.

  • Light requirements of plants differ and as a result distinct layers, or stratification, can be observed in an ecosystem.

Plants which grow well in bright sunlight are called heliophytes (Greek helios, sun) and plants which grow well in shady conditions are known as sciophytes (Greek skia, shade ) can be defined as the relative lengths of daylight and darkness that effect the physiology and behaviour of an organism. 

Salinity

Salinity is an important abiotic factor because the normal functioning of animals depends on the regulation of the water and ions in their internal environment, which is influenced by the water and ions in their external environment . The relative concentration of salts inside organisms compared to their external environment affects biophysical processes such as diffusion and osmosis, which impacts chemical reactions including metabolism.

  • In a hyposmotic environment, such as a lake, the solute concentration in the environment is typically lower than in the cells. Cells will swell up due to the osmotic influx of water.
  • In a hyperosmotic environment, such as ocean, the solute concentration in the environment is often higher than in the cells. This causes water to move out of the cells.
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