How do animals obtain usable nitrogen?
The composition of Nitrogen Gas is 78.09% in the atmosphere which is more than any other gas. But, that nitrogen can’t be taken by the biological system directly so, it has to be converted into ammonia (NH3), nitrate(NO3−), etc. to enter the plants and then to the animals.
Now, when the animals eat the plants, the nitrogen content from the plants enters the animal body.
We all know that herbivores like cows, goat, zebra, etc. will feed on plants. And that carnivores, omnivores, and scavengers will feed on the herbivores.
So, as a result, the nitrogen that was previously present in the plants will first enter the herbivores animals and will next move towards the carnivores, omnivores, and scavengers in the form of a nitrogen flow cycle.
In general, we know that the nitrogen-fixing bacteria will fix the atmospheric nitrogen into the soil and the plants will take this nitrogen.
So, both nitrate ions (NO3−) and ammonium ions (NH3) can be taken up by plants. although some plants may prefer one to the other.
The main goal of these ions is to provide nitrogen to the plant to make its own amino acids for protein synthesis and also for the various other metabolic needs.
So, in very simple words, the plants will get the nitrogen from the soil, and the next, the animals will get the nitrogen they need by eating plants or other animals that contain nitrogen. That’s how animals obtain usable nitrogen.
And, it is also to be noted that, when the nitrogen enters the animal body from plants then they may be incorporated into the animal’s body in forming various biomolecules like amino acids, DNA, RNA, etc. or broken down and excreted as waste such as the urea found in urine or in the form of feces.
What is the main source of nitrogen for animals?
The main source of nitrogen for animals are the plants. The availability of nitrogen in the plants is the most.
For herbivore animals, they directly get the nitrogen content by eating green plants and shrubs. While for the carnivores, omnivores, and scavengers they get it by eating the herbivores.
So, it can be stated that the flow of nitrogen from plants to herbivores is direct and in a one-way flow. While the flow of nitrogen from plants to herbivores to the other meat eaters is indirect and in a two-way flow system.
Plants like grass clippings, hay, peas, beans, alfalfa, or clover are the richest source of nitrogen for plant-eaters.
For meat-eaters, dried blood and blood meal, feathers and fur are good sources of nitrogen.
Feathers contain about 15% nitrogen, dried blood contains about 12% nitrogen, and blood meal contains about 14% nitrogen, muscles are the main sources that contain about 13% to 20% nitrogen content.
For meat-eaters, it is also to be noted that when they eat proteins, their body breaks the protein down into amino acids to repair and grow new muscle fibers. When they consume an adequate amount of protein by eating a healthy animal, their body will experience something called a positive balance of nitrogen. It’s all because proteins contain nitrogen.
It is also to be noted that about 5% to 10% of nitrogen is lost when passing from one trophic level to the other.
Why actually do animals need nitrogen? Can life survive without nitrogen?
Nitrogen is very much necessary for making the various biomolecules we need in our body. Just like the amino acids of proteins, the nucleic acids DNA & RNA, etc. are all made up of nitrogen.
We know that proteins are the building blocks of life. Proteins are present in hormones, cell signaling pathways, hair, muscles, skin, and almost everywhere we can imagine in the animal body.
The structure of proteins wouldn’t have been possible without amino acids and the structure of amino acids wouldn’t have been possible without nitrogen in it.
DNA & RNA contains nitrogen. The genes are the heredity carriers that are made up of DNA & RNA.
So, the structure of genes wouldn’t have been possible without DNA & RNA. And also, the structure of DNA & RNA wouldn’t have been possible without nitrogen as the nitrogenous bases are made up of nitrogen.
Similarly in a broad view, if we see, then all of the body cells contain proteins and genes and we can’t imagine the animals’ life surviving in the absence of nitrogen.
And also, all animal tissue – muscles, skin, hair, nails, and blood – contains protein as already said above. So, the normal growth, cell signaling, body working, cell replacement, and tissue repair, etc, all require nitrogen.
And also, the body’s metabolic processes need proteins made up of nitrogen in the form of enzymes to carry out the proper functioning leading to proper homeostasis in the body.
So, Can life survive without nitrogen? The answer is a big “NO!” No life on earth can survive without nitrogen. It’s because nitrogen is as important as other molecules like carbon, hydrogen, etc. in its own unique form, structure, and functionality in the body.
What actually is the nitrogen cycle? What does the nitrogen cycle do for animals?
Nitrogen cycle is the repeating cycle of the flow of nitrogen from the biotic components to the abiotic components and back to the biotic components constantly in the ecosystem.
The biotic components include air (atmosphere), water (hydrosphere), and soil (lithosphere). While the abiotic components include plants and animals.
The atmospheric nitrogen is fixed by the nitrogen-fixing bacteria into the soil. This will be then taken by the plants in the form of ammonia (NH3), nitrate(NO3−), etc.
The nitrogen can also enter from soil to the water bodies due to the surface runoff of the excess chemicals into the water bodies which can also harm the water quality.
So, the nitrogen in the water bodies will be taken by the aquatic plants due to the various nitrogen-fixing bacteria present inside water.
Now, the plants will be consumed by the animals and so the nitrogen will next pass into the animal body.
Now when the animals die the nitrogen will go back to the soil and then the various denitrifying bacteria will release it back to the atmosphere or hydrosphere.
That’s how the nitrogen will flow between the various biotic and abiotic components of the ecosystem. And, this repeating flow of nitrogen is better known as the nitrogen cycle.
So, What does the nitrogen cycle do for animals? As the nitrogen enters the animal body it will find its way from food towards the various cells where it will be utilized in the formation of proteins, and nucleic acids, and other necessary biomolecules. These nitrogen-containing biomolecules will form hair, body tissues, fur, skin, cell organelles, muscles, bones, etc.etc.
How do animals return nitrogen to the environment?
Living animals return nitrogen to the environment when they urinate or excrete their feces in the soil.
Animals can also return nitrogen in their body to the environment when they die and then the decomposers in the soil starts to decompose the dead body.
The decomposers start to decompose the nitrogen in the waste or in the dead body into Ammonia (NH3).
Decomposers are the various aerobic and anaerobic bacteria, fungi, invertebrates like earthworms, snails, beetles, millipede, etc. They all contribute to the decomposition of organic waste particles.
Next, the nitrifying bacteria will help convert the Ammonia (NH3) in the soil to Nitrites (NO2–), and then to Nitrates (NO3–) respectively.
The famous examples of nitrifying bacteria are some of the species of Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrosospira, Nitrospina, etc.
Next, at the final step if the plants want to take Ammonia (NH3) and Nitrates (NO3–) present in the soil then it can easily take. And, the remaining Nitrates (NO3–) will be returned to the atmosphere by the working of denitrifying bacteria.
Actually, when there is no available oxygen, denitrifying bacteria use the oxygen present in the nitrate to oxidize the carbon. This leads to the creation of Nitrogen gas (N2) from Nitrate (NO3–) which will be then released to the air.
Some well-known examples of denitrifying bacteria are Thiobacillus denitrificans, Micrococcus denitrificans, and some species of Serratia, Pseudomonas, and Achromobacter.