Quiz 15: Mutualism

Geology/Geography/Oceanography/Atmospheric Sciences

Mutualism refers to a symbiotic association between two species, in which both the partners derive benefit from each other. Mutualism exists throughout the biosphere and it is an integral part of nature. Absence of mutualism in the biosphere would make it biologically impoverished. There are several examples of the mutualisms that are essential to maintain life on earth. The elimination of even a few of them could bring life to a still. Some examples of the mutualisms that contribute to ecological integrity are described below. 1. Mutualism between plants and birds/animals: In a plant bird mutualism, the bird receives nectar that is food for its survival. In turn, the bird performs the job of pollination for the plant. Birds, while feeding on the nectar of flowers, pick up the pollens and transfer them on to different flowers to bring about pollination. Pollination is essential for plants, as is feeding for the birds. In the absence of such a mutualism, pollination would become very difficult and eventually only the wind-pollinated plants would survive. The birds, butterflies, and bees would disappear. 2. Mycorrhizae: It is an association between the plants and fungi. The fungal partner receives organic compounds required for growth and reproduction from the plant. The fungus greatly improves the accessibility of the plants to inorganic nutrients like phosphorous, nitrogen, copper, zinc, and most importantly water. This mutualism is also extremely important for the survival of plants. In the absence of mycorrhiza, plants would be restricted only to the most fertile soils on earth. 3. Mutualism between corals and algae: Corals provide the shelter and inorganic nutrients like nitrogen, phosphorous and others to the algal partner, which in turn provide organic nutrients to the corals. This mutualism is responsible for the biological structures called coral reefs. In the absence of this association, we would not have seen Great Barrier Reef, the largest biological structure on earth. Absence of the coral reefs and other mutualisms between ocean species would lead to great loss of biodiversity in the oceans. 4. Mutualism between herbivorous animals and plants: The plant material contains cellulose which cannot be digested alone by the animal's enzymes. The large number of protozoa and bacteria living in the gut of the animal produce enzymes that degrade cellulose for the animal. In turn, the microbes receive a steady food supply and a protective environment for survival and multiplication.

A confidence interval is a range of values within which the true population mean occurs with a particular probability. The level of confidence is calculated using the formula: img Using this level of confidence produces what is called a 95% confidence interval which is calculated as follows: img …… (1) Given, img Substituting the given values in equation (1) img img Hence, the 95% confidence interval for the Gila River sample of loach minnows is img

The term mycorrhiza refers to a mutualistic association between a fungus and a green plant. Mycorrhizae have played an important role in the evolution of terrestrial plants. The fugal partner in the association colonizes the roots of the host plant. The two most common types of mycorrhizae are arbuscular mycorrhizal fungi and ectomycorrhizae. The fungal hyphae profusely extend into the soil and thus, increase the plants accessibility to inorganic nutrients like phosphorus, copper, zinc, nitrogen, and water. The plant in return provides the fungus with organic nutrients and shelter, a well-protected environment for growth and reproduction. Kay Hardie performed experiments with the plant red clover to test the hypothesis that mycorrhiza improve the ability of the plant to absorb soil water. In the first experiment, plants with and without mycorrhizae were grown in conditions, in which their growth was not limited by nutrient availability. These conditions produced plants with similar leaf surface area and root: shoot ratios. However, the plants with mycorrhizae showed higher rates of transpiration than the plants without mycorrhizae. This experiment indicated a role of mycorrhizae in plant water relations. To confirm that mycorrhizae plays a role in plant water balance, Hardie performed another experiment in which, mycorrhizal fungi from half of the mycorrhizal plants were removed. Removal of fungal hyphae significantly reduced the rate of transpiration in these plants. Thus, the experiments of Hardie confirmed that mycorrhiza improves water balance in plants of red clover. Mycorrhizal fungi improve the ability of plants to extract soil water; however, they are not directly involved in water absorption. They play an indirect role by increasing the plant's ability to extract water from soil. Mycorrhizae greatly improve the plant's access to phosphorus. Plants with greater access to phosphorus develop roots that are more efficient in extracting water from the soil.

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