Question

1. What roles does succession and phytoremediation play in ecology, evolution and the ecosystems?

2. Biogeochemical cycles, succession and phytoremediation. Explain how all three work together for a positive outcome.

3. Explain how each of the cycles benefit from each other.

4. What role does nitrogen, carbon and water cycle play in ecology, evolution and ecosystems?

5. Explain the nitrogen and phosphorus cycles.

Answer 1

1. What roles does succession and phytoremediation play in ecology, evolution and the ecosystems?

Succession plays a major role to change in environmental conditions that causes a pronounced change in an ecosystem. Disturbances often act quickly and with great effect, to alter the physical structure or arrangement of biotic and abiotic elements. Disturbance can also occur over a long period of time and can impact the diversity within an ecosystem. Major ecological disturbances may

include fires, flooding, windstorms, insect outbreaks and trampling. Earthquakes, various types of volcanic eruptions, tsunami, firestorms, impact events, climate change, and the devastating effects of human impact on the environment (anthropogenic disturbances) such as clear cutting, forest clearing and the introduction of invasive species  can be considered major disturbances.

This can be attributed to physical changes in the biotic and abiotic conditions of an ecosystem. Because of this, a disturbance force can change an ecosystem for significantly longer than the period over which the immediate effects persist. With the passage of time following a disturbance, shifts in dominance, shifts in dominance may occur with ephemeral herbaceous life-forms progressively becoming over topped by taller perennials herbs, shrubs and trees. However, in the absence of further disturbance forces, many ecosystems will trend back toward pre-disturbance conditions. Long lived species and those which can regenerate in the presence of their own adults will finally become dominant. Such alteration, accompanied by changes in the abundance of different species over time, is called ecological succession. Succession often leads to conditions that will once again predispose an ecosystem to disturbance.

Phytoremediation play a major role to clean up contaminated environments including metals, pesticides, explosives, and oil. Also help prevent wind, rain, and groundwater flow from carrying contaminants away from the site to surrounding areas or deeper underground. Certain plants are able to remove or break down harmful chemicals from the ground when their roots take in water and nutrients from the contaminated soil, sediment, or groundwater. Plants can help clean up contaminants as deep as their roots can reach using natural processes to:

• Store the contaminants in the roots, stems, or leaves.

• Convert them to less harmful chemicals within the plant or, more commonly, the root zone. • Convert them to vapors, which are released into the air.

• Sorb (stick) contaminants onto their roots where very small organisms called “microbes” (such as bacteria) that live in the soil break down the sorbed contaminants to less harmful chemicals.

2. Biogeochemical cycles, succession and phytoremediation. Explain how all three work together for a positive outcome.

Biological diversity is dependent on natural disturbance. The success of a wide range of species from all taxonomic groups is closely tied to natural disturbance events such as fire, flooding, and windstorm. As an example, many shade-intolerant plant species rely on disturbances for successful establishment and to limit competition. Without this perpetual thinning, diversity of forest flora can decline, affecting animals dependent on those plants as well.

When the environment is disturbed by many activities, it wil be replaced by phytoremediation and the necessary requirements for the survival of the organism will be meet out by the biological cycles.

3. Explain how each of the cycles benefit from each other.

These cycles are important because they regulate the elements necessary for life on Earth by cycling them through the biological and physical aspects of the world. Biogeochemical cycles are a form of natural recycling that allows the continuous survival of ecosystems. The cycles move substances through the biosphere, lithosphere, atmosphere and hydrosphere. Cycles are gaseous and sedimentary. Gaseous cycles include nitrogen, carbon and water. These elements cycle through evaporation, absorption by plants and dispersion by wind.

Plants absorb carbon dioxide and release oxygen, making the air breathable. Plants also acquire nutrients from sediment. Animals acquire nutrients from plants and other animals, and the death of plants and animals returns these nutrients to the sediment as they decay. The cycle then repeats and allows other living things to benefit.

4. What role does nitrogen, carbon and water cycle play in ecology, evolution and ecosystems?

Nitrogen cycle

The nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. Nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and DNA, the building blocks of all life. Plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. Animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter. Nitrogen is commonly converted back into inorganic material when it joins the biogeochemical cycle through decomposition. The nitrogen is then typically changed into ammonium ion by bacteria and fungi through a process called mineralization.

When ammonium enters the soil, it is bound to certain clay particles. The ammonium is then released from these particles by cation exchange. When the ammonium is released, its chemical properties are altered by special bacteria and allowed to be dispersed from the soil. The new form of nitrogen can then be transferred to oceans by the hydrologic system, where it is released back into the atmosphere after being converted into gas through the denitrification process.

Carbon cycle

Carbon in the form of CO2 is present in the atmosphere in a very small amount, about 0.04 percent, but it has a big impact on sustainable life on the planet. The CO2 traps radiation in the atmosphere and acts like a warm blanket around the planet, trapping heat in and keeping the surface from freezing.

The way that humans live, using fossil fuels and other practices that release CO2 into the air, contributes to the amount of CO2 in the atmosphere. As this CO2 builds, the atmospheric blanket continues to grow, adding to the amount of heat trapped in the atmosphere, which raises the temperature on the surface of the planet. This is a major contributor to what is being called global warming or global climate change. If humans leave the excess CO2 in the atmosphere, it takes several thousands of years to work its way out of the air through natural mechanisms.

Water cycle

The water cycle is an important process that recycles water and nutrients. It brings freshwater to people, animals and plants all around the world. The water cycle begins with the ocean, lakes, ponds and other bodies of water on earth. Water evaporates from these bodies of water, and as the evaporated water lifts into the sky, it is cooled rapidly and condenses to form clouds. These clouds act as storage compartments for water. As they become filled with water, precipitation occurs. Clouds travel all around the world by wind currents and can bring precipitation to every part of the world. Once the water reaches the ground in the form of rain, snow, sleet or ice, some of the water may evaporate back into the air to form clouds, while other parts of the water may penetrate the soil and become groundwater. The groundwater can either return to the atmosphere and form clouds via transpiration, or it can flow into oceans, rivers, streams and other bodies of water. The cycle then begins again, with water evaporating from earth’s bodies of water.

5. Explain Nitrogen and phosphorus cycle

Nitrogen Cycle:

The chemical structure of nitrogen gas makes it chemically unreactive in nature and large amounts of energy are required to break the triple bond. When a lightning strike in the biosphere, enormous energy is released and breaks the nitrogen molecules. The nitrogen atoms can then combine with oxygen in the atmosphere to produce various oxides of nitrogen, which are carried by the rain into the soil where they can be used by existing plants in the ecosystem. This process is known as Atmospheric nitrogen fixation. About 5–8% of the total nitrogen is only fixed this way. Apart from this, most nitrogen fixation is done by free-living or symbiotic bacteria. Such Nitrogen-fixing microorganisms can fix about 60% of nitrogen gas in the atmosphere. This process is known as Biological nitrogen fixation. Nitrogen fixation is a process where N₂ is converted to ammonium, since it is the only way for organisms to attain nitrogen directly from the atmosphere. Only a relatively few bacteria are able to carry out this reaction and they are termed as the nitrogen-fixing bacteria. Nitrogen fixing plants are termed as legumes. The bacteria of the genus Rhizobium have the ability to fix nitrogen through their metabolic processes. They often form symbiotic relationships with the host legume plants such as beans, peas and clover. Ammonia produced by the nitrogen fixing bacteria is converted to organic nitrogen, which is then incorporated as protein and other organic nitrogen compounds mainly by some soil microorganisms.

Herbivores such as rabbits, cow etc secures their nitrogen compounds from plants and it circulates in their body to make their proteins and new cells. When these animals die, the nitrogen still exists in their body until decomposers take their action. Decomposers such as bacteria and fungi consume the organic matter and lead to the process of decomposition, where the nitrogen contained in the dead organism is converted into ammonium compounds, the process is known as Ammonification. Once ammonium is formed the further transformation into nitrates are carried out through the nitrification process.

Nitrification, a step process, refers to the biological conversion of ammonium in the soil to nitrate. In the first step, the compounds such as the ammonia and Ammonium are converted to nitrites (NO₂^-) with the help of the bacteria such as Nitrosomonas. These nitrites (NO₂^-) are highly toxic to plants and animals in their higher concentration. Thus the nitrites (NO₂^-) are then converted to nitrates (NO₃^-) by the bacteria such as Nitrobacter. The nitrates can then be taken in by plants. This oxidation reactions release large amount of energy is released which can be utilized by the nitrifying bacteria to produce organic compounds from inorganic ions. Examples of nitrifying bacteria include Nitrosomonas, Nitrosococcus, Nitrobacter and Nitrosospira. The conversion of nitrates (NO₃^-) to primarily nitrogen gas, by the denitrifying bacteria, is termed as Denitrification process. This also derives lower proportions nitrous oxide gas. The denitrifying bacteria are mainly heterotrophic bacteria such as Pseudomonas, uses NO₃^- instead of oxygen in their metabolic processes. The nitrogen gas is then returned to the atmosphere. Typical examples of denitrifying bacteria include Micrococcus denitrificans, Thiobacillus denitrificans, Paracoccus denitrificans and Pseudomonas. Once the nitrogenous compounds are converted into dinitrogen, converted back to biologically available forms since the gas is rapidly lost to the atmosphere. This process balances the nitrogen fixation process in the ecosystem.

Phosphorus Cycle

The phosphorus cycle differs from the other major biogeochemical cycles in that it does not include a gas phase; although small amounts of phosphoric acid (H3PO4) may make their way into the atmosphere, contributing—in some cases—to acid rain. The water, carbon, nitrogen and sulfur cycles all include at least one phase in which the element is in its gaseous state. Very little phosphorus circulates in the atmosphere because at Earth’s normal temperatures and pressures, phosphorus and its various compounds are not gases. The largest reservoir of phosphorus is in sedimentary rock.

It is in these rocks where the phosphorus cycle begins. When it rains, phosphates are removed from the rocks (via weathering) and are distributed throughout both soils and water. Plants take up the phosphate ions from the soil. The phosphates then moves from plants to animals when herbivoreseat plants and carnivores eat plants or herbivores. The phosphates absorbed by animal tissue through consumption eventually returns to the soil through the excretion of urine and feces, as well as from the final decomposition of plants and animals after death.

The same process occurs within the aquatic ecosystem. Phosphorus is not highly soluble, binding tightly to molecules in soil, therefore it mostly reaches waters by traveling with runoff soil particles. Phosphates also enter waterways through fertilizer runoff, sewage seepage, natural mineral deposits, and wastes from other industrial processes. These phosphates tend to settle on ocean floors and lake bottoms. As sediments are stirred up, phosphates may reenter the phosphorus cycle, but they are more commonly made available to aquatic organisms by being exposed through erosion. Water plants take up the waterborne phosphate which then travels up through successive stages of the aquatic food chain.