The BryophytesMosses, Liverworts, & Hornworts

Chapter 22

Evolution of Land Plants• Land plants evolved from

green algae– Evidences:

• Share chemical & metabolic traits

• Same photosynthetic pigments

• Store excess carbohydrates as starch

• Cellulose is a major component of both cell walls

• The most direct ancestors of plants are the Charophytes “stoneworts”

Adaptations for Life on Land• Cuticle– Waxy covering over the

epidermis of aerial plant parts– Prevents desiccation “water

loss”• Stomata– Small pore in the plant

epidermis– Allows gas exchange for

photosynthesis

The Plant Life Cycle

Alternation of Generations• Haploid (gametophyte)

stage alternates with a diploid (sporophyte) stage in the life cycle

Plant Reproduction

• Gametangia – Plant sex organs– Consists of 2 parts:

• A protective outer layer of sterile (non-reproductive) cells

• Gametes – sperm or egg cells.

• Male Gametangia = Antheridium– Bears numerous sperm cells

• Female Gametangia = Archegonium– Bears a single egg cell

Moss Gametangia

Antheridium – Male Archegonium – Female

4 Main Groups of Plants1. Bryophytes – Nonvascular; spores

– Mosses– Stoneworts– Liverworts

2. Seedless vascular plants; spores– Club Mosses– Ferns, whisk ferns, and horsetails

3. Gymnosperms; seeds– Conifers– Cycads– Ginkgoes– Gnetophytes

4. Angiosperms “Flowering plants”; seeds– Monocots– Eudicots

Quiz!

• What is vascular tissue?

• What are the two types of tissue that make up the vascular tissue system?

• What does each tissue do?

Bryophytes• “moss plant”• Nonvascular plants

– Cannot extensively transport water, sugar, and minerals

– Rely on diffusion and osmosis to obtain water and dissolved nutrients

– Typically small• Some have a cuticle• Some absorb water directly

through leaf surfaces• Most require moist

environments to reproduce

Bryphytes

• 3 Phyla of Bryophytes1. Phylum Bryophyta: Mosses2. Phylum Hepatophyta: Liverworts3. Phylum Anthocerophyta: Hornworts

• All are Gametophyte dominant– Spend most of their life cycle in the gametophyte

stage

Mosses

• Location: soil, rocks, tree bark• Help form soil• Colonize rocky sites that were previously colonized by lichens• Prevent soil erosion

– Grow packed together in dense colonies• The Moss Body

– Thallus – Body structure– Rhizoids – hair-like absorptive structures

• Do not have true roots, stems, or leaves

• Many mosses have separate sexes: male plants and female plants

• The gametophyte generation is dominant

Lifecycle of Mosses: Read p. 435

A filament of haploid cells that

grows from a spore

Bryophytes

Gametophyte Generation Sporophyte Generation

Liverworts

• Thallus– A body that lacks roots, stems, or

leaves– Liverworts get their name from

their liver shaped thallus• Gemmae– Asexual reproductive structure

of liverworts– Small balls of tissue– Borne in a saucer-shaped

structure – gemmae cup

Hornworts– Location: fields &

roadsides– Thalloids - 1-2 cm– Sporophyte generations

form hornlike projections out of the gametophyte thallus

Hornworts