Flowering plants Section 22.4

Flowering plants (angiosperm) overview Most abundant plant species on Earth First appeared 135 million years ago Flower – reproductive organ Contain ovaries – surround and protect seeds Gives rise to name angiosperm – ‘enclosed seed’. Reproduce via sexual reproduction After fertilization, fruit development provides protection for the seed

Why do they have flowers? Attract animals such as bees, moths and hummingbirds Attracted by scent, color or shape Take pollen away when they leave Pollinate as they move – more efficient than wind

Why do they have fruits? All fruits contain one or more mature ovaries Wall helps to disperse seeds inside – carrying away from parent plant Can be spread by animals….

How do you classify angiosperms? Originally classified on the basis of number of seed leaves (Cotyledons) One seed leaf – monocots Two seed leaves – dicots Actually, life is more complicated Ancient chinese fruiting plant fossil (Archaefructus – oldest known plant with reproductive organs found resembling modern flowers) Can not be classified as either monocot or dicot Amborella – from pacific island of New Caledonia also can’t be classified as either Now monocots are placed in a single group, but dicots are divided into a variety of distinct and different categories Dicot not used for classification, but still used today

What If you aren’t a scientist? Alternative widely used classifications exist Angiosperms can be grouped according to: Number or seed leaves Strength and composition of stem Number of growing seasons

Monocots vs Dicots

Woody and Herbaceous plants Flowering plants can be divided on the basis of stem characteristics Woody plants – plants made with cells that have a thick cell wall which supports plant body Include trees, shrubs and bines Herbaceous plants – do not produce wood as they grow Smooth and nonwoody

Annuals, Biennials and Perennials Some flowers plants will grow, flower and die in a single year Other grow from year to year Lifespan determined by genetic and environmental factors Harsh environmental conditions can shorten life cycles

Summary questions What are the key features of angiosperm reproduction? What aspects are unique to angiosperms? What is the importance of a fruit? How can angiosperms be categorized? How are scientific and everyday classification methods different?

Writing assignment Compare and contrast seeded and seedless plants? What are the main differences in terms of their structure and life cycle? It may help to produce a summary graphic organizer before you begin