. Principles of modern biology. Biology. 476 - Heredity and Evolution CONTINUITY OF THE GERM CELLS In multicellular species, some but not all of the cells retain the potentiality of trans- mitting their chromosomes to the cells of the next generation. These germ cells stand in contrast to the somatic cells, which cannot perpetuate their chromosomes beyond the lifetime of the individual organism. The somatic cells of an organism are destined to die with the individual, but the germ cells are potentially immortal (Fig. 26-1). Only the germ cells establish continuity from in- dividual to individu
. Principles of modern biology. Biology. 476 - Heredity and Evolution CONTINUITY OF THE GERM CELLS In multicellular species, some but not all of the cells retain the potentiality of trans- mitting their chromosomes to the cells of the next generation. These germ cells stand in contrast to the somatic cells, which cannot perpetuate their chromosomes beyond the lifetime of the individual organism. The somatic cells of an organism are destined to die with the individual, but the germ cells are potentially immortal (Fig. 26-1). Only the germ cells establish continuity from in- dividual to individual in each successive generation, and only changes in the germ cells are effective in changing the hereditary destiny of the species. Accordingly, it is neces- sary to follow the germ cells and to deter- mine how these cells transmit their chromo- somes to the gametes and to the offspring. Among sexual organisms, any cell that stands in line of descent of the eggs or sperm is a germ cell. The germ cells include not only the sperm and eggs but also the zygote and some of the cells of the developing em- bryo, even before the gonads become differ- entiated (Fig. 26-2). These early primordial germ cells eventually come to lie in the gonads—but now they are called by a differ- ent name. In the gonads, while they are mul- tiplying by repealed mitotic divisions, the germ cells of an animal are called gonia; more specifically, in the testis of the male animal the germ cells are called sperma- togonia, in contrast to the oogonia, which lie in the ovaries of the female. Gametogenesis: Maturation of the Gam- etes. In the gonads of the adult, the eggs and sperm begin to undergo maturation; and during maturation the chromosomes of the ripening eggs and sperm go through similar stages of development. However, there are SUCCESSIVE GENERATIONS. GERM PLASM (PROTOPLASM OF THE GERM CELLS) SOMA (CELLS OF THE BODY) L3 RELATION BETWEEN GERM PLASM AND SOMA IN ASEXUAL REPRODUCTION. Please note that
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