盲蝽科昆虫的食性

盲蝽科是半翅目最大的科 ,该科昆虫既有植食性和肉食性类群 ,又有杂食性类群 ,有很大的经济价值。作者综述了盲蝽科昆虫各食性类群中重要种类的寄主范围 ,指出在杂食性盲蝽中作为害虫的天敌作用远远大于对植物的危害 ,同时探讨了盲蝽科昆虫与植物的关系类型及食性的进化。     

Feeding habits of deer

The importance and application of an understanding of the feeding habits of deer in their management is stressed. Methods of diet determination are briefly outlined. Factors affecting the feeding habits are complex and include social ones, weather and available shelter, interactions with other species of animals, feeding patterns and the quality, quantity and availability of the food.     

Inheritance of Variegation

Ohne Zusammenfassung     

Patterns of Inheritance

SYNOPSIS. Every individual living organism on earth developsaccording to the specificationsof its individualized and uniqueDNA that is encoded as its genotype. The genotype consists ofmany genes and is established at the time of the individual'sbirth or separation from itsparent. Although offspring resembleparents, they are rarely if ever genetically identical to them.This result is a function of both the pattern of inheritanceand the organization imposed by the genetic system embodiedin the chromosomes. Genes are not just loose in the nucleus:they are organized into linear arrays on chromosomes. In thediploid, cross-fertilizing genetic system, the parents contributeabout equally to the offspring's genotype through the haploidnucleiof their gametes. In most diploids, vast amounts of geneticvariability are produced by the process of genetic recombination.This alone assures the genetic uniqueness of every individualof the new generation. The ultimate source of the variabilityis the process of gene mutation but the great storage capacityof the diploid system enhances recombinational variability.The powerful sources of recombination are: synapsis and crossing-over,processes that serve to scramble the genes. Independent assortmentat meiosis provides unique gametes; this latter effect is enhancedby high chromosome numbers. Since two parents are involved inthe formation of the individual, still another level of recombinationis achieved at fertilization. Patterns of genetic systems varygreatly from species to species: man, mouse, maize and melanogasterare considered. In a significant number of cases, chromosomenumber reductions, balanced chromosomal aberrations and polyploidyare present and serve to restrict recombination potential. Evengreater restrictions are imposed by the evolution, in naturalpopulations, of patterns of inheritance that partially or evencompletely by-pass recombination. Thus, total dependence onvegetative reproduction, loss of meiosis, self-fertilizationor parthenogenesis are examples. In organisms that have discardedthe attributes that assure recombination, the formation of bothnew species and new adaptations is impaired. This emphasizesthe key importance of the mode of inheritance for activatingprocesses that adjust the genes of living things to their environments.Future studies of patterns of inheritance in relation to theevolution of life on earth are needed.