Lecture 4: Chapter 24

Alberts, B

ray, H

opkins, Johnson

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Professor: Dr. BarjisRoom: P313Phone: (718)2605285Email: [email protected]

General BiologySylvia S M

ader

Lecture 4: Chapter 24

Evolution and Diversity of Plants

Outline

• Evolutionary History • Alternation of Generations• Nonvascular Plants• Vascular Plants

– Seedless– Seed– Angiosperms

Monocots and EudicotsFlowers

Evolutionary History of Plants

• Plants are thought to have evolved from freshwater algae

• Among the adaptations of plants to life on land are:

– Protection of the embryo from drying out.– Waxy cuticle on leaves to prevent drying out.– Internal skeleton (in flowering plants) to

oppose gravity.– Vascular system (in most plants) to move

water internally.

Other Terrestrial Adaptations

• Vascular tissue transports water and nutrients to the body of the plant.

• Cuticle provides an effective barrier to water loss.

• Stomata bordered by guard cells that regulate opening, and thus water loss.

Four Major Plant Groups

Alternation of Generations

• Plant life cycle(s) include alternation of generations cycle only.

– Sporophyte produces spores by the process of meiosis and represents diploid generation.

– Gametophyte produce gametes and represents haploid generation.

Alternation of Generations

Alternation of Generations

Nonvascular Plants

• Nonvascular plants (bryophytes) lack specialized means of transporting water and organic nutrients.

• Do not have true roots, stems, and leaves.• Produces eggs in archegonia • Produces flagellated sperm in antheridia

Nonvascular Plants

• Liverworts have either flattened thallus (body) or leafy appearance with no true root, no stem.

• Asexualy reproduce by gemmae (group of cells that detach from the thallus and can start a new plant)

Nonvascular Plants

• Mosses usually have a leafy shoot.– Can reproduce asexually by

fragmentation.– Mosses prefer dump, moist and shaded

location, but could survive in deserts too

Vascular Plants

• They contain vascular tissue (Xylem and Phloem).

• Xylem transports water and dissolved minerals up from roots.

• Phloem transports sucrose and other organic compounds throughout the plant.

• Vascular plants are divided into plants with seed and seedless plants

Seedless Vascular Plants

• Vascular seedless plants are homosporous.

• Ferns are example of seedless vascular plant.

– Most abundant in warm, moist, tropical regions,

– An egg is produced in an archegonium.– A sperm is produced in an antheridium.

Seed Plants

• Vascular plants with seed are heterosporous ( have two kind of spores)

– Microspores develop into pollen grain – Megaspore develop into egg

• Vascular plants with seed are classified into Gymnosperms and Angiosperms

Gymnosperms

• Gymnosperms have ovules and seeds exposed on the surface of sporophylls.

• Examples of Gymnosperms are Conifers and Ginkgoes

• Conifers - bear cones• Ginkgoes - some trees produce seeds and

some produce pollen.

Pine Life Cycle

Pine Life Cycle

In the pine life cycle, female cones remain on the tree over two years.

Angiosperms (flowering plants)

• Angiosperms are an exceptionally large and successful group of plants.

• live in all sorts of habitats, from fresh water to desert, and from rigid north to the torrid tropics.

Monocots and Eudicots

• Two classes of flowering plants.– Monocotyledones (Monocots)

Flower parts in three or multiple of three.

Usually parallel venation in leaves – Eudicotyledones (Dicots)

Flower parts in four or fives or multiples of fours or five .

Usually net venation

The Flower

– Flower consists of petals, sepals, stamen (male reproductive organs) and carpel (female reproductive organs).

– Each stamen consists of an anther (produce pollen) and a filament (stalk).

– Carpel has three major regions.Ovary Style Stigma

Flowering Plant Life Cycle

Flowering Plant Life Cycle