Animal Hormones, functions and growth curves

Animal Hormones

In animal, hormones are produced inductless glands called endocrine system and release straight to the blood stream which transport them to the target organ. Animal hormones include the following

1.          Pituitary glandbase of headPituitrin
2.          Pituitary glandNeckThyroxine
3.         ParathyroidNeckParathormone
4.         PancreasLoop of duodenumInsulin
5.         Adrenal glandTop of each kidneyAdrenaline
6.         TestesTestesTestosterone
7.         OvariesOvariesProgesterone


  1. It controls body metabolism
  2. It promotes growth of the animal

iii.        It induces or stimulates reproduction


Growth is quantative and measurable, so that the amount of growth achieved by plant can be expressed. The measures for growth in plant include

  1. increase in the height or length of the stem, root and any other organ of the plant
  2. Increase in the girth or width or circumference of the stem

iii.        Increase in the area of leaves

  1. Increase in weight
  2. Increase in the number of branches
  3. In animal measurement in growth in length of animal

The rate of growth of a plant is usually studied by measuring the rate of increase in length or height of the shoot or root of the plant. Rate of growth varies with age of the plant. A young seedling is a good choice. The amount of growth achieved by a seedling of 24hrs interval over a known period of time represent the rate of growth.

The increase in height (mm) can be plotted on a graph over a time intervals. The rate of enlongation or height growth is seen to vary from individual to individual and from species to species. The graghs are the same.

sigmoid curve

In all cases, the rate of growth is at first slow, then rises up to a part and continuous at this rapid rate until maturity and later declines. The graphs shows a typical s-shaped curve called sigmoid growth curve. The sigmoid growth curve is characteristic of all living organisms. It is the typical growth curve for the whole plant as well as for its individual organs.

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