20.2, classification of plants

• Mosses


  • Mosses and their relatives grow close to the ground because they do not have vascular systems
  • They also need water so sperm can swim to the eggs
• Phyla of mosses


  • Liverworts
  • Hornworts
  • Mosses
• Liverworts


  • Most liverworts live in damp environments
  • They get moisture from the soil
• Hornworts


  • They are found in tropical forests and along streams all over the world
• Mosses


  • They do not have true leaves
  • Instead, they have a leaf like structure only one cell thick
  • Some species have cuticles, and most have stomata
  • Mosses use structures called rhizoids to anchor themselves to soil, rocks, or tree trunks
• Club mosses


  • The oldest living group of vascular plants
  • But they are not true mosses
  • Ancient species looked like trees and were even bigger
  • Only the smaller species survived when the climate cooled
• Whisk ferns


  • They grow mostly in the tropics and subtropics
  • They do not have true roots and leaves
• Horsetails


  • They grow in wetland areas and along rivers and streams
  • Their leaves grow in a circle around the stem
  • Horsetails' cell walls contain a rough compound called silica, the main ingredient in glass, and colonial settlers used the plant to scrub pots
• Ferns


  • They are the most successful members of this phylum
  • Their large leaves are called fronds
  • Some small ferns can be houseplants
  • The larger tree ferns live in the tropics and can grow over three stories tall
• Seed plants


  • They can reproduce without free-standing water
  • Seeds nourish and protect plant embryos
  • Seeds allow plants to disperse to new places
• Types of seed plants

  • Gymnosperms
  • Angiosperms
• Gymnosperms


  • Their seeds are not inside a fruit
  • Most gymnosperms have cones and are evergreen, such as pine trees
  • A woody cone is the reproductive structure of most gymnosperms
  • Male cones produce pollen and female cones produce eggs
  • The three living phyla of gymnosperms are the cycads; Ginkgo biloba; and the conifers
• Cycads


  • They provided food for the dinosaurs
  • They look like palm trees with large cones
  • Today they grow in tropical areas in the Americas, Asia, Africa, and Australia
  • Many species are endangered because of their slow growth and habitat loss
• Ginkgo


  • Today, only one species survives, Ginkgo biloba
  • It is native to China
  • The ginkgo may be the oldest living species of seed plant
• Conifers


  • The most diverse and common gymnosperms alive today
  • All conifers have needlelike leaves and most are green all year round
  • Conifers grow quickly and supply most of the timber used for paper, cardboard, housing lumber, and plywood
  • They also live a long time and can grow very tall and massive
• Angiosperms


  • Their seeds are enclosed in some type of fruit
  • A flower is the reproductive structure of these plants
  • It protects the plants gametes and fertilized eggs
  • A fruit is the mature ovary of a flower
  • It can be juicy and good to eat, like a peach, or it can be the fluff around a dandelion seed