What is Growth ? a permanent increase in size, weight & complexity of an organism involves Cell Division (Mitosis) & Cell Enlargement

What is Mitosis ? Mitosis occurs when… –cell divides during growth –an organism reproduces asexually –repairing a damage part of body 2 daughter cells have exactly the same number & kinds of chromosomes as the parent cell significance: keep the number of chromosomes constant after cell division

Chromosomes appear as chromatins at resting stage Stage of Mitosis

Chromatin threads condense to form distinct chromosomes. The chromosomes become shorter & thicker - each seems to consist of two identical chromatids Stage of Mitosis

Chromosomes line up in the middle part (equatorial region) of the cell Stage of Mitosis

Two chromatids of each chromosome separate & move to opposite poles of the cell Stage of Mitosis

The chromatids become chromosomes of the two daughter cells Stage of Mitosis

Growth in Plants Primary growth –grow in length by apical meristem (the plant tissue that retain the ability for cell division) meristem

Growth in Plants Secondary growth –grow in diameter (only in dicotyledonous plants) –by cambium to produce secondary xylem and secondary phloem which forms annual ring –cork cambium : to form cork layer to replace the broken epidermis (6-yrs)

Root Tip (L.S.) root cap –to protect the growing point region of cell division (growing point) –to increase the number of cells for growth region of cell elongation –actual cell elongation region (growth) –about 2 to 4 mm from the tip Root Tip

Root Tip (L.S.) region of differentiation –similar cells differentiate to different tissues region of root hair (maturation) –various tissues fully developed –main water absorption area Root Tip

Measurement of Growth in length of the Main Root using marking ink

Do all parts of the radicle grow during the experiment ? Ans: No. Growth occurs only in the region behind the tip. pin cork cotton wool cork beaker strip of filter paper water radicle marked at 1mm intervals

Where is the region of maximum growth in the root ? Ans: The region of elongation which is located immediately behind the tip. pin cork cotton wool cork beaker strip of filter paper water radicle marked at 1mm intervals

Growth Patterns in Plants dry mass time annual plant

biennial plant Growth Patterns in Plants time dry mass

unlimited growth perennial plant dry mass time Growth Patterns in Plants

Animal Growth different parts have different growth rate eg. the brain grows first in baby eg. the reproductive system grows only at puberty

age relative growth head & brain general body reproductive system limited growth Animal Growth

How to Measure Growth ? by height / length –defect : do not take into account the growth in other dimensions by fresh weight –defect : the amount of water always varies by dry weight –defect : too destructive (the organisms die) –defect : too time consuming

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