Predation excretion

Competition Predation Commensalism Mutualism Synergism Antibiosis A race for nutrients and space One feeds on another One lives off another with negligible help or barm Each benefits the other Combination has cooperative metabolism One excretes a factor harmful to the other... 

Aquatic organisms, such as fish and invertebrates, can excrete compounds via passive diffusion across membranes into the surrounding medium and so have a much reduced need for specialised pathways for steroid excretion. It may be that this lack of selective pressure, together with prey-predator co-evolution, has resulted in restricted biotransformation ability within these animals and their associated predators. The resultant limitations in metabolic and excretory competence makes it more likely that they will bioacciimiilate EDs, and hence they may be at greater risk of adverse effects following exposure to such chemicals. 

Predator secretions and excretions inhibit feeding in a variety of herbi-... 

Persson, A. 1997. The effects of predation and excretion on aquatic food webs. Oikos 79 137-146. 

Aplysia with chemical defenses in their tissues but without ink were consumed at a similar rate to those without toxins (20% vs. 12%), whereas those without toxins in their tissues, but with ink exhibited much greater survival (71%), suggesting that the excretion of ink may be the primary defense of these sea hares when being consumed by slow-moving predators like sea anemones.45 Pennings42 also found that ink from some (but not all) sea hares could deter predators, however he found no evidence that the metabolites responsible for defense were diet derived. Sea hares also secrete opaline when attacked by predators, although the function of this secretion has yet to be unambiguously determined.44... 

Aphids extract sap from plant stems, specifically the phloem tissue. They excrete honeydew which still contains plant sugars. Ants collect this honeydew, often by milking the aphids, and use it as food. In return, they protect the aphids against predators. Ants prey on predators of aphids such as ladybird beetles (coccinellids), thus defending the aphids. Ants also shelter aphids by taking them or their eggs into their nests during inclement seasons. In a sense, ants herd aphids like cows. Furthermore, without removal of honeydew, aphid colonies become fouled. 

Hofmann and Ambler, 1988). The Hofmann and Ambler (1988) model had 10 compartments which included NO3 and NH4, large and small phytoplankton size classes and a copepod submodel (Fig. 33.3). The latter included parameterizations for N assimilation, excretion, egg production, molting and predation. Steele and Frost (1977) incorporated comparable levels of detail more than 10 years earlier. Although not, strictly speaking, an N-based model, it specified N as the limiting inorganic nutrient and assumed a fixed C/N ratio for biota defined in carbon units, so the distinction is to some degree semantic. 

There are thousands of kinds of natural pesticides. Plants have been engaged for millions of years in chemical warfare with predators, most of which are insects. They have evolved a wide variety of complex protective mechanisms, many of which are toxic chemicals. Humans have probably known for a very long time that natural products such as uicotiue from tobacco, turpentine from pines, pyrethrum from chrysanthemum species, and quinine from cinchona bark can provide protection from pests and parasites. Our diet contains a large number of such chemicals but ordinarily we have mechanisms to detoxify or excrete them so that they are not a problem. 

Leaves turn yellow and fall tree declines. Cause Scales. Various types of scales infest citrus trees, causing decline. Trees may suffer from twig dieback and reduced vigor, and leaves may be covered with honeydew excreted by the scales as well as sooty mold, which feeds on the honeydew. Cottony cushion scale looks like white, cottony masses clustered on leaves, stems, and branches. Red. brown, or black scale may look like crusty, waxy, or smooth bumps on leaves, trunk, stems, or fruit. Many natural enemies keep scale insects in check. If scale infestation is heavy, introduce outside predators for additional control. You must choose the species of predator that feeds on your species of scale. For example, Vidalia... 

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