Notes: Plants Angiosperms

Flowers and Fruits.

Angiosperms are either monocot or dicot.  "Cot" stands for cotyledon, the tiny leaves that are first to form in the plant embryo.  If there is one cotyledon, the angiosperm is a monocot; if there are two, it is a dicot.  Another major feature separates the two distinctions:  Monocots always have parallel veins in their leaves, and dicots have a network of veins.

For most angiosperms, the mode of pollination is animal:  Pollen attaches to a bee for example and the bee transports the male germ cells to the female germ cells of another plant.

Vascular Tissue Evolution.

tracheids vessel elements + fiber cells
elongated, tapered
early xylem cells
supports and conducts		 shorter, wider
arranged end to end
specialized for water transport		 lignified cells
support only
evolved in conifers without vessel elements

The Flower.

The flower is the major angiosperm reproductive structure.  The anther is where pollen is produced.  The sticky stigma is where pollen is received.  The ovule is where the fertilized ovum will develop into a seed.  The petal and sepal are sterile structres.  If the petals are uncolorful most likely the plant uses wind pollination.  If the petals are pretty to you then probably they use animals to spread the pollen.

a labeled diagram of the flower

Four Evolutionary Trends Involving the Flower.

  1. Increasingly fewer parts.
  2. e.g., "pistil" can refer to 1 carpal or several fused ones.
  3. Symmetry changed from radial to bilateral.
  4. The ovary is better protected when dropped below the petals and sepals.

Fruit.

Fruits are simply mature ovaries.  After fertilization the ovary wall thickens to protect the dormant seeds and aid in dissemination (e.g., edible fruits, burrs, wind-blown fruit).

Angiosperm Life-Cycle.
Flower

anther

ovary
meiosis

microspores

1 surviving megaspore
mitosis

pollen grains

embryo sacs (8 haploid nuclei in 7 cells)

Double Fertilization
2 sperm enter the ovary 1 forms the zygote and 1 forms a triploid endosperm with the dikaryotic cell.

Endosperm is to be used as food and envelopes the zygote.

Coevolution.

Dependencies of one organism on another lead to coevolution, or the simultaneous evolving due to the evolving of the other.

Next:  "Plant Structure and Growth."