Chapter 21.4, Problem 4MI

Summary Introduction

To compare:

The characteristics of different divisions of seed plants by completing the given table

Introduction: Plant kingdom can be classified into vascular and nonvascular plants. Vascular plants can be further classified as seedless and seed plants. Seed plants include Cycadophyta, Gingkophyta, Gnetophyta, Conierophyta and Anthophyta.

Answer to Problem 4MI

	Reproduction	Environment	Examples
Cycadophyta	Males produce pollen grains from cones, pollen produce motile sperm	Tropics and sub tropics	There are about 100 species today
Gingkophyta	Males produce pollen grains from cones, pollen produce motile sperm	China, Male gingkoes planted in cities as they can tolerate smog and pollution	Gingko biloba
Gnetophyta	None given	Deserts and mountains of Asia, Africa, North America, Central or South America	Tropical climbing plants and shrub like plants
Conierophyta	Reproductive parts produced in cones	Temperate forests	Fir, spruce, pine, cedar, juniper, redwood, larch
Anthophyta	Seeds enclosed in a fruit	Variety of environments	Fruit trees

Explanation of Solution

Cycadophyta- Cones contain male or female reproductive structures of cycads. Plants with cones evolved before plants with flowers. A male cone produces thousands of pollen grains that produce male gametophytes. Female cones produce female gametophytes. Male and female cones grow on separate cycads. Their natural habitats are tropics or subtropics.

Gingkophyta- This division has only one living species Gingko biloba. The gingko disappeared from North America during Ice Age but they survived in China where it was grown for seeds. They have male and female cones on separate plants. Male tree produces pollen grains in strobilus like cones growing from the base of leaf clusters. Female tree produces female cones which when fertilized give foul smell. Since gingkoes can tolerate smog and pollution, mae trees are grown in cities.

Gnetophyta- Plants in this division can live for 1500 to 2000 years. Ephedra, Gnetum and Welwitscia are common species of this division. They are found in deserts of Southwest Africa, United States and in tropical forests.

Conierophyta- Pines, firs, cypresses and redwoods belong to this division. These are very important economically. Reproductive structures develop in cones. Male and female cones are found in different branches of same tree. Small male cones produce pollen and large female cones remain on trees till the seeds are matured. Conifers are well adapted to survive in snowy climates.

Anthophyta- These are flowering plants that are widely distributed in terrestrial and aquatic environments. Also called angiosperms, they make up more than 75 percent of plant kingdom. They are further classified into monocots and dicots. Plants produce seeds that are enclosed within fruits. Based on the life span they are annuals, biennials and perennials.