Gymnosperms
KEY CHARACTERISTICS
Gymnosperms are seed-bearing vascular plants whose seeds are exposed to the environment, rather than being enclosed in a fruit. The seeds are usually located on the scales of cones.
Organization True roots, stems, and leaves
Movement Adults stationary; within pollen grains, male gametophytes drift in air or are carried by animals to female structures, where they release sperm that move to eggs.
Water Transport Through vascular tissue
Reproduction Sexual; alternation of generations; the sporophyte stage is dominant. Female gametophytes live within the parent sporophyte. Pollen grains carry sperm to eggs, so open water is not needed for fertilization.
Some bristlecone pines are thousands of years old, like this one growing in Nevada.
• Did You Know?
Rising From the Ashes
Fire's Role in Seed Germination
We generally think of forest fires as being natural disasters, and that's typically true. Some gymnosperm species, however, are so well adapted to the arid conditions of the American West that they actually depend upon such fires to spread their seeds.
The best-known example is the Jack Pine, Pinus banksiana. Its seed cones are thick and heat resistant. When engulfed in a fire, its seeds escape damage. The fire's high heat helps to open the outer coat of the cone, enabling the seeds to pop out afterward. As a result, Jack Pines are among the very first plants to repopulate a forest that has been damaged by fire.
The high heat of a forest fire opens the cones of the Jack Pines, releasing their seeds. The inset shows a Jack Pine seedling growing in the charred remains of the fire.
Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis