What is Growth ?

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

3. 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

4. Stage of Mitosis Chromosomes appear as chromatins at resting stage

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

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

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

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

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

10. 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)

11. Root Tip (L.S.) Root Tip • 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

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

13. Investigation 20.1 Measurement of Growth in length of the Main Root using marking ink

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

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

16. Growth Patterns in Plants dry mass annual plant time

17. Growth Patterns in Plants dry mass biennial plant time

18. Growth Patterns in Plants unlimited growth dry mass perennial plant time

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

20. Animal Growth head & brain relative growth general body limited growth reproductivesystem age

21. 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

22. ~END~