Chapter 29: Plant Diversity

How plants colonized landChapter 29.1

Admit Slip3. List 3 words you think of when you look at the picture/diagram

2. Write 2 ideas you have based on the picture and your words. If possible, use your words as you write your ideas.

1. Write 1 question you have.

Plants supply oxygen and are the ultimate provider of most of the food eaten or absorbed

by other organisms.

Terminology

• -phyte=Plant• Bryo=moss• Ptero=fern• Gymno=naked• Mitosis: division of cells-forms identical copy with full set of

chromosomes (2n), body cells• Meiosis: division of cells-forms a cell with a half set of

chromosomes (n), sex cells• Haploid: half the total chromosomes for an organism

(egg/sperm)• Diploid: full number of chromosomes for an organims (somatic)

What problems do terrestrial habitats offer for plants????

Land plants evolved from green algae

• Evolved from Charophytes (green algae) more than 500 million years ago.

• Evidence for evolution from Charophytes1. Both produce cellulose for cell walls the same way2. Their peroxisomes have enzymes that reduce effects of

photorespiration (unique to both)3. Both produce cell plates the same way during cell division4. Structure of sperm is closely related5. Nuclear and chloroplast genetic evidence suggests close

relation

2007-2008

Charophytes

Spirogyra

Coleochaete

Chara

Problems of life on land

Problems of life on land

Movement of plants from sea to land

• Advantages:– Increased sunlight (unfiltered by water)– More carbon dioxide in atmosphere than

water– Soils rich in nutrients– Fewer predators

• Challenges– Lack of water– Desiccation– Lack of structural support against gravity

Adaptations of Land Plants1. Adaptations in growth– apical meristem: localized region of cell

division at tips of roots and shoots2. Adaptations in reproduction– alternation of generations– walled spores: protect spores in harsh

environments– multicellular gametangia: structures for

gamete production– multicellular dependent embryos:

transfer of nutrients from tissue to embryo

3. Adaptations against water loss– Cuticle

Alteration of Generations

• All land plants have two multicellular stages– Gametophyte• plant cells are haploid• Gametes are produced

– Sporophyte• plant cells are diploid• Divides mitotically• Sporophyte produces spores through meiosis

Alteration of Generations

• During fertilization: gametes (egg and sperm-both haploid) fuse to form a diploid zygote (sporophyte)

• Zygote develops in tissues of female parent getting nutrients from it, sometimes called an embryophyte

Gametangia

• Plants produce gametes in multicellular structures called gametangia– Female: archegonia-produces a single egg– Male: antheridia-produces many sperm

Chapter 29: Plant Diversity

How plants colonized landChapter 29.2

Bryophytes

• Moss• Nonvasular (small size)• Seedless• Life cycle dominated

by gametophyte stage• Water required for

sperm to swim to the egg during fertilization

Bryophyte life cycle

Chapter 29: Plant Diversity

How plants colonized landChapter 29.3

Pteridophytes/Ferns

• First plants with vascular tissue– Allowed plants to grow tall and gain access to

sunlight• Seedless• Require film of water for sperm to reach egg

• Life cycle dominated by the sporophyte stage– Meiosis occurs in sporangia producing haploid

spores which may grow into gametophytes with anteridia (release sperm) and achegonium (produce egg, house zygote after fertilization)

Pteridophytes/Ferns life cycle

Evolution of land plants