Saturday, December 8, 2007

Concept 30.3

Q1: It has been said that an oak tree is an acorn’s way of making more acorns. Write an explanation that includes these terms:

A1: In the oak's life cycel, the tree (the sporophyte) produces flowers, which contain gametophytes in pollen grains and ovules; the eggs in ovules are fertilized; the mature ovaries develop into dry fruits called acorns; and the acorn seeds germinate, resulting in embryos giving rise to seedlings and finally to mature trees, which produce flowers then acorns.

Q2: Compare and contrast a pine cone and a flower in terms of structure and function.

A2: Pine cones and flowers both have sporophylls , modified leaves that produce spores. Pine trees have separate pollen cones (with pollen grains) and ovulate cones (with ovules inside cone scales). In flowers, pollen grains are produced by the anthers of stamens, and ovules are within the ovaries of carpels. Unlike pine cones, many flowers produce both the pollen and the ovules.

Q3: Explain the use of the terms monocot, dicot and eudicot.

A3: Recent molecular evidence pointed out that while monocots are a clade, dicots are not. Based on phylogenetic relationships, most dicots form a clade, now known as eudicots.

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