Sunday, February 8, 2009

Gymnosperms


Characteristics:
Gymnosperms are vascular, seeded plants, that can be found everywhere.

Life Cycle and Development:



  • The gymnosperm life cycle and reproduction cycle start off with a mature sporophyte releasing the ovulate cone and one releasing the pollen cone.
  • The sporophyll of the pollen cone releases microsporocytes which eventually reach the megasporangium.
  • A pollen tube forms.
  • The female gametophyte develops within the megaspore and holds two to three archegonia, each of those containing an egg.
  • When the eggs are mature, the two sperm cells have developed in the pollen tube and fertilize the eggs.
  • Fertilizations occurs a year after pollination and the seed develops into a seedling and grows into a mature sporophyte.

Examples:

An image of Pinus Longaeva.

The pinus longaeva, or bristlecone pine is found in the White Mountains of California.

It’s adaptation is that it grows where most other plants can’t, reducing competition and risk of fires.