Chapter 22-4, p. 564 SEED PLANTS

Reproduction Free From Water ALL SEED PLANTS ARE VASCULAR. Seed plants alternate between a gametophyte stage and a sporophyte stage. Seed plants do not require water for fertilization of gametes. Seed plants can live just about anywhere. Adaptations that allow seed plants to reproduce without water include flowers or cones, the transfer of sperm by pollination, and the protection of embryos in seeds.

Four Major Parts of a Seed A young plant embryo (which developed from the zygote). One or two embryonic leaves (cotyledons) A “food” supply – nutrients (endosperm), and A tough, protective coating (seed coat)

Seed Plants: 2 Types Seed Plants are classified into 2 groups depending on whether or not they have (or are enclosed in) a fruit. Gymnosperms – “naked” seeds with no fruit. Angiosperms – have fruit and flowers.

Cones and Flowers The gametophytes of seed plants grow and mature within sporophyte structures called Cones in Gymnosperms. Gametophytes of seed plants grow and mature within sporophyte structures called Flowers in angiosperms.

Pollen A Pollen Grain contains the entire male gametophyte. Pollen is carried to the female gametophyte by wind, insects, birds, etc… Pollination is the transfer of pollen from the male gametophyte to the female gametophyte.

Seeds A seed is an embryo of a plant that is encased in a protective covering and surrounded by a food supply. The Seed Coat surround and protects the embryo and keeps the seed from drying out.

Gymnosperms: Cone Bearers The most ancient surviving seed plants. Include gnetophytes, cycads, ginkgoes and conifers. All Reproduce with seeds that are exposed. Gymnosperms means “naked seeds”.

Gnetae (Gnetophytes) Phylum Gnetophyta About 70 current species. Reproductive scales are clustered into cones. Ex: Welwitschia (south Africa) and Ephedra (America)

Cycads Phylum Cycadophyta Palmlike plants that reproduce with large cones. First appeared in Triassic period. Are found in tropical and subtropical regions. Have dioecious (unisexual) individuals – meaning have separate Male and Female trees. Ex: Sago Palms

Ginkgos Phylum Ginkgophyta Common when dinosaurs were alive. Only one species currently exists. Ex: Ginkgo biloba Thought of as a living fossil. Popular shade trees and dietary supplement

Conifers Phylum Coniferophyta Conifers Most common. Ex: pines, spruce firs, cedars, sequoias, redwoods and yews. Large trees that produce seeds in cones. Typically known as “evergreens” due to modified needle-like leaves that remain green year round.

Adaptations of Conifers Wood: thick-walled vascular tissue that aids in supporting upright growth. Needle-shaped leaves: reduce surface area for evaporation (prevents water loss). Bark: a protective covering to reduce evaporation and protect the plant from being eaten.

Ecology of Conifers Thrive in a variety of habitats. Have specific adaptations to dry conditions. Adapted long, thin leaves. Evolved a thick-waxy layer that covers the leaves. Retain leaves throughout the year. Constantly reproduce new leaves.

Angiosperms: Flowering Plants Phylum Anthophyta. First appeared during the Cretaceous period. Originated on land and quickly came to dominate Earth’s plant life.

Flowers and Fruits Angiosperms have unique reproductive organs known as Flowers. They attract animals that transport pollen from flower to flower. Pollination is much more efficient. Flowers contain ovaries, which surround and protect the seed. Angiosperm means “enclosed seed”. Fruit is a thick wall of tissue surrounding the seed. Fruit allows for transport and protection of seeds until they find a place to germinate and grow.

Angiosperms Angiosperms are divided into 2 groups depending upon the number of cotyledons in their seeds.

Monocots and Dicots Comparisons Single cotyledon Parallel Veins Floral parts in multiples of 3 Vascular bundles scattered throughout stem. Fibrous Roots DICOTS Two cotyledons Branched Veins Floral parts often in multiples of 4 or 5 Vascular bundles arranged in a ring. Taproots

Monocot vs. Dicots

Woody and Herbaceous Plants Woody plants are made primarily of cells with thick cell walls that support the plant body. Ex: Trees, shrubs, vines. WOOD Herbaceous plants have plant stems that are smooth and nonwoody. Ex: dandelions, zinnias, petunias and sunflowers. GREEN

Woody vs. Herbaceous

Annuals, Biennials, Perennials Angiosperms that complete their lifecycle in two years. In the first year they germinate and grow roots, very short stems and sometimes leaves. In the second year they produce flowers and seeds, then die. Ex: evening primrose, parsley, celery and foxglove. Flowering plants that live for more than two years. Usually live through many years. Ex: peionies, asparagus, and many grasses, palm trees, sagebrush, maple trees and honeysuckle. Plants that grow from seed to maturity, flower, produce seeds, and die all in the course of one year are ANNUALS. Ex: marigolds, petunias, pansies, and zinnias.

Annuals, Biennials and Perennials

Review Questions 1. What reproductive structures are unique to angiosperms? 2. Briefly describe the function of each structure. 3. What are monocots/dicots? 4. How do annuals, biennials, and perennials differ? 5. Compare the growth forms of plants with woody stems to those with herbaceous stems. 6. Which are more likely to be dispersed by animals – the seeds of an angiosperm or the spores of a fern? 7. Explain your reasoning for number 6.