As mentioned in the tutorial, when measuring growth it is more desirable to use dry mass as a reliable indication. However, since you cant just 'suck' an organism dry, we tend to measure growth as an increase in height or 'fresh' weight.
The following indicates various growth curves for the corresponding organisms.
Sigmoid Growth Curve
The sigmoid curve is a 'growth average' representing all organisms, where young organisms experience rapid accelerating growth to cope with their environment, followed by a continuous steady growth. Towards maturity, an organisms growth rate slows down until no growth occurs.
Annual Plant Growth
Annual plants only live for one year. At first, the embryo of the seed harnesses the seed food supply, and is illustrated by a decrease in growth to begin with as the food supplies shrink. Once this energy kicks in, and photosynthesis can occur in the plant, growth begins to accelerate. Throughout the year the plant will continue to grow, and when it has reached the Winter months, and seeds have been dispersed, it withers and dies, illustrated by the decrease in mass.
Perennials such as trees continue to grow year after year, and in the instance of trees, can grow for an immense space of time. As explained on the next page of the control and regulation tutorial, most growth occurs in Spring, illustrated in the graph by the accelerated increases in height.
Humans have two phases of growth 'spurts', one in infancy and one in adolescance. In between infancy and adolescance there is a period of steady growth while adulthood is when growth halts.
Insects possess exoskeletons (an exterior skeleton) which means continuous growth cannot occur without this skeleton allowing so. In light of this, the insects must shed their outer layer for growth to continue. This moulting of the skin allows body mass to increase.