The phenomenon of interaction between organisms living in the same habitat
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The phenomenon of interaction between organisms living in the same habitat.Including species interaction between individuals of the same species: on the one hand, heterosexual individuals can formspouseThey can feed their children together, and multiple families can form a larger community to feed and defend against the enemy;On the other hand, individuals of the same species can compete with each other for the same resource, or even kill each other.These two seemingly contradictory phenomena, ifspeciesFrom the perspective of, it can be unified.Because competition can eliminate the unfit, keep the population in the scale appropriate to the environment, and avoid resource depletion and greater disasters.
Chinese name
Biological interaction
Interpretation
The phenomenon of interaction between organisms living in the same habitat
The phenomenon of interaction between organisms living in the same habitat.This impact may promote the survival or reproduction of the other party (favorable impact), or may reduce the survival or reproduction ability of the other party (harmful impact).Different from general biological research, this kind of research on the interests of organisms has a utilitarian perspective, but it is not only of great practical value, but also an important part of evolutionary theory.for exampleMedical ScienceOne of the most important topics in the research is the interaction between pathogenic microorganisms and parasites and human beings.Today's colorful biological world is the result of biological interaction, mutual adaptation and coevolution for hundreds of millions of years.
Specifically, biological interaction is manifested between individuals.For example, there can be multiple interactions between individuals of the same kind: on the one hand, individuals of the opposite sex can form a spouse, can jointly nurture their children, and multiple families can form a larger community, feed together, and fight against enemies together;On the other hand, individuals of the same species can compete with each other or even kill each other in order to obtain the same resources.These two seemingly contradictory phenomena can be unified from the perspective of the whole species.Because not only reproductive behavior and social behavior contribute to the survival and reproduction of ethnic groups, but also when the environmental resources are insufficient for the needs of the growing population, competition can eliminate the unfit, keep the population in the scale appropriate to the environment without declining the quality of life of organisms, and avoid resource depletion leading to greater disasters.
Key points of modern research
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Because of this, modern research focuses on interspecificInteractionOn.Although the specific interaction still occurs between individuals (allogeneic), modern biology emphasizes to focus on the whole population and take the population as the basic unit of interaction.It is generally believed that in the interaction, one of the parties can benefit, or be injured, or not be affected, so the following six categories of interactions are obtained: "+" is benefit;"-" means victim;'0' is not affected.But in fact, it is difficult to find the situation that is not affected at all;In cases that are generally regarded as unaffected, some direct or indirect impacts will be found after in-depth research.At present, the most studied cases are those in which both sides of the first three categories have been significantly affected (or benefited or harmed), because this is the most important, whether based on practice or evolutionary theory.In addition, there is the word "symbiosis", which has a broad original meaning, but is now often used only to refer to mutual benefit;This word is not used here to avoid confusion.
Stake analysis
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complexity
The analysis of stakeholders is sometimes complicated.Take the human intestinal bacteria as an example. On the one hand, the human body provides them with suitable living space and nutrition, on the other hand, the intestinal defense mechanism inhibits or even eliminates its members, and regular defecation also makes a large number of bacteria be cleared to the outside world and eventually die.But by the wholeIntestinal floraFrom the perspective of reproduction, bacteria are the beneficiaries.As for their impact on the human body, although they generally do not cause obvious diseases, it is uncertain whether they will affect the digestion and absorption of nutrients and whether there are other insignificant harmful effects.They can synthesize some essential vitamins for the human body, but how much can the human body absorb from them?They seem to be able to inhibit the reproduction of some pathogenic bacteria, but how much benefit does this bring to human health?These need further study.
Different from time to place
In fact, the specific contents and interests of biological interaction vary from time to place.For example, some root fungi, on the one hand, obtain nutrition from the plant roots, on the other hand, can help the roots absorb minerals in the soil.In the soil lacking phosphorus, the two promote each other's growth, which should be considered as mutually beneficial relationship.However, on the soil rich in phosphorus, only the parasitic relationship of root fungi is left.Moreover, in the process of evolution, many relationships that originally competed with each other or even killed the other can gradually transform into long-term coexistence and mutual benefit relationships: some individuals are still hurt, but both populations are thriving.For example, the grass's meristem grows from the base while the shrub's meristem grows from the top,HerbivoresEating the aboveground part of the pasture will not affect its sustainable growth, but eating the top part of the shrub can eliminate the shrub invading the pastureForage seedIt can also be expanded to a larger range through defecation through the transfer of herbivores, so herbivores are beneficial to forage.This is especially true of the relationship between human beings and crops. Human beings consume a large number of grains, vegetables and edible livestock and poultry every year, but human farming and animal husbandry activities have made these species unprecedented prosperous.
performance
Biological interaction can be expressed at different levels.Obvious behavioral reactions can be observed in animals, such asReproductive behavior、Community behavior、Domain occupying behavior、Feeding behaviorEtc.In plants and microorganisms, physiological and biochemical studies are often needed.For example, the interactions between roots, between roots and soil microorganisms, and between soil microorganisms are often realized through chemical substances secreted by one or both parties.Organisms secrete some chemical substances to inhibit the growth and reproduction of other individuals. This phenomenon is often referred to as heterologous anti growth among plants and anti growth among microorganisms (seeInterspecific chemical interaction）。The interactions between parasites and hosts in vivo are also mainly conducted at the molecular and cellular levels.However, the following does not go deep into the relevant mechanism of action, but only gives a brief introduction of biological interaction from the perspective of ecology.
compete
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It can happen between the same kind of individuals: the strong can plunder the food of the weak, and the strong can monopolize a piece of resource land (seeDomain occupying behavior）, while the weak are forced to move out (seemigrate）, or even the same kind of cannibalism may occur.But competition is more common among heterogeneous individuals.Heterogeneous organisms may also kill each other for food or release toxic substances to poison each other, which is often called interference competition, and is mainly found in higher organisms.However, the competition for the same scarce resources is more common and has been studied most.
The objects of competition among heterogeneous organisms include space, food, light, etc.withfoodFor example, the result of the competition may be that the two sides are evenly matched and maintain a certain balance for the time being, or one side wins the other and the other side perishes, or the loser is forced to flee or change other food.Therefore, creatures with similar morphology and habits rarely live in the same area, that is, they use different resources or they go out at different times (for example, one day and one night).In other words, they are specificNicheDifferent.The phenomenon that two species with the same ecological needs cannot coexist for a long time due to competition is called Gauss'sPrinciple of competition exclusion。
Predation and parasitism
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Predation mainly includes animals eating plants (plant feeding) and animals eating animals (narrow sense predation);Plants such as plastergrass and pitcher grass can also catch small animals such as insects, digest and absorb nitrogen containing substances, but this is a rare exception.Vegetation is the food chain (seeecosystem）The first link of.Rats and locusts may eat most or all of a plant, while other creatures may destroy vital parts of the plant and cause it to die. For example, the bark beetle bites off a ring of phloem layer along the trunk of a pine tree, which affects the nutrient transport in the plant.However, most herbivores only eat some branches, leaves or roots, which does not cause the death of the plant being eaten.Many plants have evolved protective structures, such as crusts and spines.More plants have evolved a variety of defensive chemicals that make them unpalatable or toxic.But many animals also evolved sharp and hard mouthparts and decomposed various kinds ofPhytotoxinThe ability of.The result is the emergence of a large number of oligophagous animals that can only feed on a few plants.Grasses are the more evolved category of flowering plants, and they adopt completely different ecological strategies.Their aboveground parts lack protective structures and defensive chemicals, which can be eaten by large herbivorous mammals without affecting the continuous growth of their underground parts.
Similar coevolutionary phenomena also exist in predation (narrow sense).This interaction is more intense because animals always kill their victims when they eat animals.The prey may be covered with hard and thick crustaceans, or have a huge body, or live deep at the bottom of the cave, or prowl in the dark to avoid predators.The predator has sharp claws and teeth, and may be supplemented by poison glands.The ability to run quickly is very important for both. The difference between life and death is often determined by the running speed of the pursuer and the fugitive.
The main difference between parasitism and predation is that parasites usually do not kill their hosts.In addition, parasites are often smaller than the host and often attach to or even reside inside the host.Parasites often have specialized structures to adapt to parasitic life (for example, intestinal parasites may lack senses and digestive tract, but their genitals are extremely developed).
Favorable and mutually beneficial
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It is difficult to prove that one creature has no influence on the other creature close to it, so it is impossible to give examples of pure favoritism.More favorable examples may be insects living in bird nests and animal caves, and other small aquatic animals living in underwater benthos' cavesinvertebrate。Because they feed on the remains of the owner of the nest and get some protection, in turn, they do no harm to the owner.
Mutual benefit is common in nature.The two sides are mutually beneficial but not yet interdependent. This phenomenon is called primary cooperation or facultative symbiosis.For example, the individuals of the Genus Eriocheir or the Genus Eriocheir live in the shell of a snail, and a sea anemone is carried on the shell.The prickly touch of sea anemones?The hermit crabs are protected, and the food residue stirred by the hermit crabs is used by sea anemones.But both can live alone.
There are many examples of mutual benefit, also known as specialized symbiosis.Lichens associated with bacteria and algae can resist extremely harsh environments, while coral and algae symbiosis makes coral reefs one of the most productive biological communities.The fungi and bacteria parasitic on the roots can help to absorb the mineral and nitrogen fixation in the soil.Microbes in ruminant stomach help to decompose cellulose in grass and provide sugar source for host.Termites feed on wood and rely on flagellates in their intestines to help them break down cellulose.These flagellates are even affected by the ecdysone in termites, and they are transformed into cysts when termites molt,termiteSlough off the intestinal lining and expel it from the bodyFlagellatesThe cysts are eaten by termites.
