Angiosperms: The Successful Flowering Plants, Slides of Biology

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Angiosperms-the flowering plants

have arrived

Introduction

 Angiosperms are flowering plants that cover their seeds in a true fruit.

 Their reproductive organs; an androecium (male) and/or gynoecium (female) lies within the flower structure.

 Primitive angiosperms are dioecious whereas modern angiosperms are monoecious.

 Angiosperms are highly successful and dominate the vegetation of the earth’s surface.

Morphology and anatomy

 Angiosperms are also anatomically complex

organisms.

 Dicots have vascular tissues within their stems,

roots and leaves that is made up of xylem and phloem bundles in a fixed arrangement this arrangement distinguishes dicots from monocots as monocots’ bundles are scattered.

 Dicots’ vascular bundles consist of secondary

xylem and phloem produced by the cambium within.

Origin

 The Cretaceous era (145-65 million years ago) saw the rise of flowering plants and their associated insect pollinators through the process of co- evolution.

 This process between plants and insects was most probably the most influential driving force behind the origin and diversification of angiosperms, although it has been disputed that flexibility in seed production, dispersal and seeding establishment was the most important factors in angiosperm origin.

Impact on other eco-systems

 Angiosperms had major impacts on

the evolution of other types of plants and animals.

 The increase in angiosperms was

paralleled by the decline of ferns.

 Another major driving force behind the

rise of angiosperms and angiosperm fruit is the co-evolution feedback between plants and vertebrates that dispersed the fruit.

Angiosperm adaptations to pollination

 Pollination is a process where pollen is transported from the anther to the

stigma.

 Flowers have adapted in order to attract pollinators. Adaptations include

visual cues whereby colour patterns that resemble a “bull’s eye” are utilized.

 Pollinators therefore see the flower as the target and can be differentiated

from the background green foliage.

Angiosperm adaptations to pollination

 The shape of the flower plays a major role for example corollas of some Erica’s are strongly curved to match the beak shape of the main pollinator, the Orange-breasted Sunbird found in South Africa.

 In fly-pollinated Erica’s, the mouth of corolla is much smaller and lobes are large, star-shaped and spreading thereby providing a landing pad for flies as they insert their long proboscis into the flower to drink nectar.