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What is Growth ? - PowerPoint PPT Presentation


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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

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What is growth l.jpg
What is Growth ?

  • a permanent increase in size, weight & complexity of an organism

  • involves Cell Division (Mitosis) & Cell Enlargement


What is mitosis l.jpg
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


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Stage of Mitosis

Chromosomes appear as chromatins at resting stage


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Stage of Mitosis

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


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Stage of Mitosis

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


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Stage of Mitosis

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


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Stage of Mitosis

The chromatids become chromosomes of the two daughter cells


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Growth in Plants

  • Primary growth

    • grow in length

      • by apical meristem (the plant tissue that retain the ability for cell division)

meristem


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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)


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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


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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


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Investigation 20.1

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


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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.


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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.


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Growth Patterns in Plants

dry

mass

annual plant

time


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Growth Patterns in Plants

dry

mass

biennial plant

time


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Growth Patterns in Plants

unlimited

growth

dry

mass

perennial plant

time


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Animal Growth

  • different parts have different growth rate

  • eg. the brain grows first in baby

  • eg. the reproductive system grows only at puberty


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Animal Growth

head & brain

relative

growth

general body

limited growth

reproductivesystem

age


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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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~END~


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