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Dr. Julian I. Schroeder .
Biology 2 - Multicellular Life 6,?
6,) List and brieﬂy deﬁne four major levels of organization of multicellular life. 989%?
- tissues: consist of cells of same type 53st
- organs = tissues producing a joint function
— organ system = groups of organs with shared responsibility
- networks = communication and transport systems throughout the body (cg. circulatory system, nervous
ersystem) , , , 7 ,, 7 a... - -- — .
7.) Name 5- main types of plant cells and hﬁgﬂy describe the function of each.
Parenchyrna: carry out most of the metabolism (photosynthesis) in a plant; store starch.
Collenchvma; support young plant parts without restraining growth; can elongate with growth (ﬂexible
Sclerenghma: rigid support, cannot elongate; 2 types: ﬁbers and sclereids.
Water—conducting: xylem; 2 types: tracheids and vessel elements. ,
Sieve-tube members: make up phloem; carry sucrose and other organic compounds.
8.) Explain the process of secondary growth as seen in stems.
The layer of cells between the primary xylem and primary phloem becomes meristematic (reproductive).
At this point this vascular cambium tissue reproduces new cells to the interior and exterior of the vascular
cambium ring. The interior cells differentiate into secondary xylem. The exterior cells differentiate into
9.) Draw and label a picture that shows assimilation of nitrogen by plants.
10.) How and where arenutrients such as amino acids and sugars transported through a plant? Nutrients such as amino acids and sugars are synthesized in leaves and transported down the stem to the
root system through the phloem. Movement is thought to occur (according to the “pressure ﬂow” model)
by a low osmotic potential at the top of the phloem system (source) due to the high local concentration of
solutes (sugars and amino acids). This draws water into the phloem causing an increase in hydrostatic
pressure in the phloem, which forces ﬂuid down the phloem carrying nutrients with it. The nutrients are
taken up by cells at the sink (eg. storage roots) such that the pressure gradient from source to sink is
maintained and water continues to ﬂow through the phloem. ...
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- Spring '08