1. Plants
Chapter 23 and 24

2. 23.1 The Green Algal Ancestor of Plants
Biology, 9th ed, Sylvia Mader
Chapter 24
23.1 The Green Algal Ancestor of Plants
Plants are multicellular, photosynthetic eukaryotes
Plant evolution is marked by adaptations to a land existence.
A land environment offers certain advantages
Plentiful light for photosynthesis
Carbon dioxide is present in higher concentrations and diffuses more readily in air than in water
Evolution and Diversity of Plants

3. The Green Algal Ancestor of Plants
Biology, 9th ed, Sylvia Mader
Chapter 24
The Green Algal Ancestor of Plants
Adaptations are required for a land environment
Constant threat of desiccation (drying out)
Protect all phases of reproduction (sperm, egg, embryo) from drying out
Seed plants disperse their embryos within the seed, which provides the embryo with food within a protective seed coat
The water environment provides
plentiful water
support for the body of the plant
Evolution and Diversity of Plants

4. The Green Algal Ancestor of Plants
Biology, 9th ed, Sylvia Mader
Chapter 24
The Green Algal Ancestor of Plants
To conserve water, the land plant body is covered by a waxy cuticle.
Impervious to water while still allowing carbon dioxide to enter so that photosynthesis can continue
Vascular system transports water in the body of the land plant.
Plants are thought to have evolved from freshwater green algae about 450 mya
Evolution and Diversity of Plants

5. Evolutionary History of Plants
Biology, 9th ed, Sylvia Mader
Chapter 24
Evolutionary History of Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
flowers, double fertilization, endosperm, fruit
common ancestor
seeds
Flowering plants
Seed
megaphylls
Gymnosperms
vascular
tissue
Vascular
Ferns and allies
apical
growth
microphylls
Seedless
Lycophytes
embryo
protection
Mosses
Hornworts
Bryophytes
Nonvascular
common
green
algal
ancestor
Liverworts
Charophytes
550
500
450
400
350
300
250
PRESENT
Million Years Ago (MYA)
Evolution and Diversity of Plants

6. The Green Algal Ancestor of Plants
Biology, 9th ed, Sylvia Mader
Chapter 24
The Green Algal Ancestor of Plants
Additional terrestrial adaptations:
Waxy cuticle to prevent water loss
Stomata to allow gas exchange
Apical tissue, which has the ability to produce complex tissues and organs 6
Evolution and Diversity of Plants

7. Biology, 9th ed, Sylvia Mader
Leaf Adaptation
Chapter 24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cuticle
a. Stained photomicrograph
of a leaf cross section
Plant leaves have a
Cuticle and stomata
Stomata
Stomata
400 x
b. Falsely coloured scanning
Electron micrograph of leaf surface
(Left): © Kingsley Stern; (Right): © Andrew Syred/SPL /Photo Researchers, Inc.
Evolution and Diversity of Plants

8. Evolution of Seed Plants: Full Adaptation to Land
Biology, 9th ed, Sylvia Mader
Chapter 24
Evolution of Seed Plants: Full Adaptation to Land
Flowers and Diversification:
Wind-pollinated flowers are usually not showy
Bird-pollinated and insect-pollinated flowers are often colorful
Night-blooming flowers attract nocturnal mammals or insects
Usually white or cream-colored and aromatic
Fruits of flowers protect and aid in seed dispersal
Utilize wind, gravity, water, and animals for dispersal
Evolution and Diversity of Plants

9. Chapter 24

10. 24.1 Organs of Flowering Plants
Biology, 9th ed, Sylvia Mader
Chapter 25
24.1 Organs of Flowering Plants
Flowering plants, or angiosperms, are extremely diverse but share many common structural features.
Most flowering plants possess a root system and a shoot system
The root system simply consists of the roots,
The shoot system consists of the stem and leaves.
A typical plant features three vegetative organs
roots, stems, and leaves
Vegetative organs are concerned with growth and nutrition.
Flowers, seeds, and fruits are structures involved in reproduction.
Structure and Organization of Plants

11. Organization of Plant Body
Biology, 9th ed, Sylvia Mader
Organization of Plant Body
Chapter 25
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
terminal bud
blade
leaf
vein
petiole
axillary bud
stem
node
internode
node
vascular tissues
shoot system
root system
branch
root
root hairs
primary
root
Structure and Organization of Plants

12. Organs of Flowering Plants
Biology, 9th ed, Sylvia Mader
Chapter 25
Organs of Flowering Plants
Roots
Generally, the root system is at least equivalent in size and extent to the shoot system
Anchors plant in soil
Absorbs water and minerals from the soil
Produces hormones
Root hairs:
Projections from epidermal root-hair cells
Greatly increase absorptive capacity of root
Structure and Organization of Plants