Plant Kingdom

Plants are members of the Domain Eukarya.

For a large part of the earth's past the land was barren and no life existed. It wasn't until about 500 million years ago that land plants evolved.

Some of the earliest plants evolved from ancient protists like the "Chara" shown below.

Plants fall under four smaller categories Bryophytes, Pteridophytes, Gymnosperm, and Angiosperm.


Bryophytes- Are land plants that don't have a vascualr system like moss. This means that they have to live very close to water and they can't grow very tall, as water and nutrients could not be transported to the upper parts of the plant.

Pteridophytes- Are Vascular plants that lack seeds. Although these plants can grow taller they still must remain fairly close to water as their sperm are transported through water(swimming sperm) just like Bryophytes.

Gymnosperm- Are the conifers, these plants have pollen and "naked" seeds meaning they do not have a fruit covering the seed. Pollen allows conifers to colonize almost any enviornment because their seeds can now travel through the air and do not rely on water for transport.

Angiosperm- Are the flowering trees that are most prevelant in our area. Angiosperms have flowers and fruit to cover their seeds. Flowers are used to attract birds and insects to help spread their pollen.

Life Cycles- Unlike humans and all other mammals plants spend much more of their life cycle as haploid organisms. This means at any given moment a plant could have only one pair of chromosomes while in humans there are two.

This video explains the life cycle of a fern very nicely. I apologize for not being able to embed the video.

http://video.google.com/videoplay?docid=2342399186796367569
Due to the lack of time i cannot cover all life cycles of each group of plants but the concept between them is very similar.