Chapter 12.3

Seed Plants

Characteristics of Seed Plants Life Cycle

Alternates between two stages Differs from life cycle of seedless plants:

Seed plants produce seed. Seeds nourish and protect young sporophytes.

Gametophytes of seed plants do not live as separate plants from the sporophytes

The sperm of seedless plants need water to swim to the eggs of female gametophytes. The sperm of seed plants do not need water to reach an egg. Sperm form inside tiny structures called pollen. Pollen can be transported by wind or animals.

These characteristics allow seed plants to live almost anywhere on earth!

The Structure of Seeds A seed forms after fertilization, once the

sperm and egg have joined Seed is made up of three parts.

A young plant or sporophyte A seed coat Stored food found in the cotyledons

What advantages do seed plants have over seedless plants?

Gymnosperms Seed plants that do not have flowers or

fruit are called gymnosperms. Their seeds are usually protected by a

cone Conifers are the most important

gymnosperms. Their wood is used for paper and building materials Produce resin which is used to make soap,

paint, ink, anticancer drugs and allergy medication.

Gymnosperm Life Cycle Conifers (meaning cone-bearing) have

both male and female cones. The spores from each cone become tiny gametophytes. The male gametophytes produce pollen

which the wind carries to the female gametophyte cones which produce the eggs. This is called pollination.

A young sporophyte develops in the female cone surrounded by a seed.

Angiosperms Vascular plants that produce flowers and

fruit are angiosperms. These are the most abundant plants today.

Angiosperm reproduction Flowers help angiosperm reproduce,

relying on the wind or animals to transfer the pollen

Fruits surround and protect angiosperms seeds which are then transported by animals or the environment to new places.

Angiosperms are divided into two classes Monocots – only have one cotyledon (or

seed leaf) Dicots – have two cotyledons