The variable-length chains may exhibit large inter-species variation even when the remainder of the sequence is highly conserved; and as is in the case of insulin, sometimes the variable length chain is cleaved out by secretory endoproteases, leaving a two-chain protein held together by disulfide bonds.
12.
In the 19th century, deists, who championed the watchmaker analogy, held that Darwin's theory fit with " the principle of uniformitarianism the idea that all processes in the world occur now as they have in the past " and that deistic evolution " provided an explanatory framework for understanding species variation in a mechanical universe ."
13.
Related to this is the idea of a life history strategy, which can be conceptualized as a chain of resource-allocation decisions ( e . g ., allocating resources towards growth or towards reproduction ) that an organism makes . and, more recently, some anthropologists and psychologists have applied this continuum to understand within-species variation in trade-offs between reproductive and somatic effort.
