Seeds and Flowers

Objectives

• Outline the classification and evolution of seed plants
• Summarize the adaptations and evolution of flowering plants

Seed plants are called spermatophytes.

Parts of a seed

• Embryo develops into fertilized egg
• Seed coat protects the embryo
• Endosperm is the stored food

While still inside the seed, the embryo forms its first leaf (cotelydon) and starts to develop a stem (hypocotyl) and root (radicle).

Seed Dispersal Methods

Classification of Seed Plants

• Gymnosperm (~1,000 living species)
• Angiosperm (hundreds of thousands living species)

The majority of gymnosperms are conifers.

Evolution of Seed Plants

The earliest seed plants evolved about 300 million years ago. they were similar to modern ginkoes.

Earth became drier, so seed plants adapted to live with less water, and some adapted to live in colder environments.

Flowering Plants

Angiosperms form seeds in ovaries. As seed develop, ovaries may develop into fruit.

Flower Parts

• Stamen (male) with anther at the end
• Pistil (female) composed of stigma, style, and ovary
• Petals
• Sepals

Flowers and Pollination

• Bright colors, strong scent, sweet nectar
• Insects, birds, mammals, reptiles

The fruits are brightly colored to encourage animal consumption and thus dispersal of seeds.

Vascular tissue is more efficient than that of gymnosperms.

Evolved ~200 million years ago. About 10,000 years ago humans began domesticating grasses like wheat.

Classification

• Monocots (form one cotyledon)
• Eudicots (two cotyledons)
• Magnolids (two cotyledons)
• Vascular tissue arrangement is different

Structures like leaves, flowers, and cones grow at nodes.