University:
University of Phoenix
Course:
BIO 280 | Conservation Biology
Academic year:

2023
Views:

458

Pages:

42
Author:

kvoterefgk

Gymnosperms Definition: Gymnosperms (Gk Gymnos: naked, sperm: seed) produce seeds that are not enclosed in an ovary. Ancient group of seed plants that originated in the Mesozoic era. Characteristics: Most gymnosperms have cone-bearing structures. Lack flowers and fruits. Possess needle-like or scale-like leaves. Includes conifers, cycads, Ginkgo, and Gnetales. Morphology: Plant Body: Sporophyte is dominant (diploid), differentiated into root, stem, and leaves. Present-day gymnosperms are woody trees or shrubs. Leaves: Needle-like or scale-like. Xerophytic characteristics. Root: Taproot system with symbiotic fungi (mycorrhiza). Stem: Usually branched, showing secondary growth. Reproductive Organs: Separate male and female cones or strobili. Reproduction: Male Cones: Produce microspores, which develop into pollen grains. Female Cones: Produce megaspores that develop into female gametophytes. Pollination and Fertilization: Wind pollination is common. Fertilization occurs through pollen tubes, without water. Classification: Divided into several classes and orders, such as Coniferopsida, Cycadopsida, and Gnetopsida. Further subdivided based on morphological and reproductive traits. Economic Importance: Provide timber, resin, and other products. Important in horticulture and landscaping. Gymnosperm Divisions: Cycadophyta: Palm-like plants. Ginkgophyta: Only one living species, Ginkgo biloba. Coniferophyta: Includes pines, firs, and spruces. Gnetophyta: Diverse group with unique characteristics. Evolution and Adaptation: Evolved during the Carboniferous period. Adapted to diverse habitats from tropics to temperate regions.