共栖是指两种生物生活在一起,对一方有利,对另一方也无害,或者对双方都有利,两者分开以后都能够独立生活。自然界除了互惠互利,各自都能从对方身上获取生存利益的共生共栖关系外,还存在着另一种变相的共栖关系,那就是单惠共栖。
互利共生
要 点
互利共生和
共生现象
互利共生是不同种两个体间一种正的互惠关系,可增加双方的适合度.互利共生可以是共生性的,生物体以一种紧密的物理关系生活在一起.
专性互利共生
有些互利共生者,如地衣,是永久性成对组合,其中一方或双方不能独立生活.大多数共生者是专性共生,还有一些非共生性的互利共生也是专性的,如蘑菇-耕作蚁之间的互利共生.
共生:地衣
Mutualism is a positive reciprocal relationship between two individuals of different species which results in increased fitness for both parties. Mutualism may be symbiotic,in which the organisms live together in close physical association.
Key Notes
Mutualism and symbiosis
L1 MUTUALISM
Some mutualisms, such as lichens, are permanent pairings in which one or both partners cannot lead an independent life. Most symbioses are obligate, as are some nonsymbiotic mutualisms, such as those formed by fungus-farming ants.
Obligate mutualism
兼性互利共生
互利共生的多数是非专性和机会性的.这些互利共生可能是散开的,包含有不同的物种混合,如许多传粉者与其传粉植物之间的互利共生.
传 粉
异型杂交植物需要将其花粉转移到同种植物的柱头上,并接受同种植物的花粉.一些植物种类靠风来传播花粉,如果植物生长在广大的植物种类单一的地方如草地和松林,这种传播方式会很有效.但是大多数开花的双子叶植物,依靠昆虫,鸟,蝙蝠或小型哺乳动物来传播花粉,作为交换,这些动物或以花蜜或以花粉本身为食.
传粉
The majority of mutualisms are nonobligatory and opportunistic. They may be diffuse, involving a varying mixture of species, as occurs between many pollinators and their plants.
Facultative mutualism
An out crossing plant needs to transfer its pollen to the stigma of a conspecific plant, and receive pollen from a conspecific. Some plant species rely on the wind to achieve this, which can work acceptably well if plants grow in large homogeneous stands of few species, as occurs in grasslands and pine forests, However, in most species of flowering dicotyledonous plants, insects, birds bats or small mammals are employed to transfer pollen from plant to plant, usually in exchange for either nectar or pollen itself as a foodsource.
Pollination
种子扩散
大型种子无法有效的被风传布,除非靠水传布(如椰树的种子),或依靠动物来散布.啮齿动物,蝙蝠,鸟和蚂蚁都是重要的种子扩散者.
防御性互利
共生
一些互利共生为其中一方提供对捕食者或者竞争者的防御.这种防御性互利共生的例子见于一些草和产生植物碱的真菌之间,以及许多种植物和蚂蚁之间.
浦公英
Large seeds cannot be effectively wind-dispersed, and unless dispersal by water (as occurs in the coconut palm) occurs, such plants are dependent on animals for dispersal. Rodents, bats, birds and ants are all important seed dispersers.
Seed dispersal
A number of animal species rely to some extent on mutualisms with mutualists which reside within their bodies. Ruminants (deer and cattle) possess a multi-chambered stomach in which bacterial and protozoan fermentation take place. In some termites, which feed on wood, the necessary breakdown enzymes are provided by bacterial mutualists. Intracellular bacterial symbionts which transform amino acids occur in a number of insect groups, including aphids and cockroaches.
Symbiotic mutualists within animal tissues and cells
动物组织或细胞内的共生性互利共生
一些动物种类在某种程度上依赖于同生活在其体内的共生体间的互利共生.反刍动物(鹿和牛)拥有多室胃,在其中发生细菌和原生动物的发酵作用.在一些以木为食的白蚁中,必需的分解酶由细菌共生体提供.在一些昆虫种类,包括蚜虫和蟑螂,存在转换氨基酸的细胞内细菌共生体.
白蚁
Some mutualisms provide one partner with a defense against predators or competitors. Examples of such defensive mutualisms are found between some grasses and alkaloid-producing fungi, and between many plant species and ants.
Defensive mutualisms
互利共生和
进化
互利共生可能起源于寄生物-寄主和捕食者-猎物之间的关系,或起源于没有协作或相互利益的紧密共栖物种之间.然后双方的进化变化(协同进化)导致双方从这种关系中获益,虽然也可能共生"恶化",成为使一方受益,另一方受非平衡的剥削的寄生关系.互利共生的相互作用在多细胞动物进化过程的一些关键阶段中起着中心作用.高等生物的许多细胞器官,包括线粒体和叶绿体,被认为来自共生性细胞.
相关主题
竞争的性质(I1) 寄生的性质(J1)
线粒体
Related topics
The nature of competition (I1) The mature of parasitism (K1)
Mutualism and evolution
Mutualism may have arisen form parasite-host and relationships, or between closely coexisting species with no cooperation or mutual benefit, Evolutionary changes in both partners (coevolution) have then resulted in both partners benefiting from the relationship, although it is possible for mutualisms to 'deteriorate' into unbalanced exploitation of one partner to the benefit of the other – parasitism. Mutualistic interactions have been central to number of important steps in the evolution of multicellular organisms. Many of the cell organelles of higher organisms, including mitochondria and chloroplasts are believed to be derived from symbiotic bacteria.
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