GYMNOSPERMS

CHAPTER 8 SECTION 4

GYMNOSPERMS

• A seed plant that produces naked seeds

• Not enclosed by a protective fruit

• Many gymnosperms have needle-like or scale-like leaves, and deep-growing root systems

• Oldest type of seed plant

CYCADS

•Grow mainly in tropical and subtropical areas

•Look like palm trees with cones•Cone can grow as large as a football

CONIFERS

•Cone-bearing

• Largest and most diverse group of gymnosperms

•Most keep their needles year round

GINKGOES

•Only one species exists today, Ginkgo biloba

•Chinese and Japanese cared for it in their gardens

•Planted along city streets because they can tolerate air pollution

GNETOPHYTES

•Live in hot deserts and in tropical rain forests

•Trees, shrubs, and vines

REPRODUCTION OF GYMNOSPERMS

• Cones: reproductive structures in most gymnosperms• Males cones• Produce tiny grains of pollen (the male gametophyte)• Later become sperm cells

• Female Cones• Ovule: female gametophyte• Contains egg cell• Develops into seed

Pollen falls from male cone

onto female cone

Sperm cell and egg cell join together in an ovule

on the female cone

After fertilization,

the seed develops on the scale of the female

cone

Gymnosperm Reproduction

POLLINATION

• Transfer of pollen from male reproductive structure to female reproductive structure

•Wind often carries the pollen

FERTILIZATION

•Once pollination occurs, the ovule closes and seals in the pollen

•Sperm cell and egg cell are inside each ovule

• The egg is fertilized and develops into the embryo

SEED DEVELOPMENT

• Female cones remain on tree while seeds mature

•Can take up to 2 years

•Male cones usually fall off tree after they shed their pollen

SEED DISPERSAL

•When seeds mature, scales open

•Wind shakes seed out of cone and carries them away

•Only a few seeds will land in suitable place

Page 275