Seedless Plants: Evolution and Characteristics

Algal Ancestry

Plants evolved from charophytes in Archaeplastida.

Green Algae

Includes chlorophytes and charophytes, ancestors of plants.

Multicellularity

Characteristic shared by green algae and plants.

Cellulose Cell Walls

Plants and green algae have cellulose-based structures.

Chloroplasts

Contain chlorophyll a & b for photosynthesis.

Starch Storage

Plants and algae store energy as starch.

Desiccation

Risk of drying out for land organisms.

Alternation of Generations

Life cycle alternates between haploid and diploid stages.

Haplontic Life Cycle

Dominant haploid stage, typical in some algae.

Diplontic Life Cycle

Dominant diploid stage, typical in humans.

Gametophyte

Haploid generation producing gametes in plants.

Sporophyte

Diploid generation producing spores in plants.

Walled Haploid Spores

Spores with protective walls against desiccation.

Multicellular Gametangia

Structures producing gametes in land plants.

Sporophyte Embryos

Develop within female gametophyte for protection.

Apical Meristem

Tissue at tips of roots and shoots.

Waxy Cuticle

Layer preventing water loss in plants.

Secondary Compounds

Chemicals providing protection against herbivores.

Mycorrhizae

Fungal associations aiding plant nutrient uptake.

Adaptations to Land

Structural support and reproduction strategies for survival.

Advantages of Land

Higher CO2, light, minerals; less competition.

Disadvantages of Land

Desiccation risk and lack of buoyancy.

Walled haploid spores

Spores protected by sporopollenin for air dispersal.

Sporangium

Multicellular structure producing haploid spores.

Sporophyte

Diploid phase producing spores via meiosis.

Gametophyte

Haploid phase producing gametes for reproduction.

Multicellular gametangia

Structures protecting gametes in land plants.

Antheridium

Male gametangium producing sperm cells.

Archegonium

Female gametangium housing the egg.

Zygote

Fertilized egg developing into a sporophyte.

Apical Meristems

Regions of continuous cell division for growth.

Waxy cuticle

Protective layer preventing water loss in plants.

Stomata

Pores regulating gas exchange in leaves.

Secondary metabolites

Chemicals deterring herbivores and competitors.

Mycorrhizae

Fungal symbiosis aiding in nutrient absorption.

Bryophytes

Non-vascular plants with dominant gametophyte stage.

Rhizoids

Structures anchoring gametophytes, not true roots.

Anthocerotophyta

Phylum of hornworts with horn-like sporophytes.

Marchantiophyta

Phylum of liverworts, often thalloid or leafy.

Bryophyta

Phylum of mosses, most numerous non-vascular plants.

Sporophyte structure

Includes foot, seta, and capsule for spore release.

Capsule

Sporangium at the tip of sporophyte.

Plagiochila deltoidea

Example of a leafy liverwort species.

Polytrichum commune

Example of a hairy-cap moss species.

Mosses

Bryophyta, nonvascular plants thriving in moist environments.

Pioneer species

First organisms to colonize nutrient-poor soils.

Sphagnum

Type of peat moss, forms important wetlands.

Peatlands

Wetlands that preserve organic material over time.

Tollund Man

Preserved ancient corpse found in peat bog.

Protonema

Initial stage of moss life cycle from germinating spores.

Bud

Develops from protonema, leading to mature moss.

Seedless vascular plants

Plants with vascular tissue but no seeds.

Vascular tissue

Specialized tissue for transporting water and nutrients.

Xylem

Vascular tissue transporting water and minerals.

Phloem

Vascular tissue transporting sugars and organic compounds.

Microphylls

Small leaves with single vascular strand, found in Lycophytes.

Megaphylls

Large leaves with branched vascular system in most vascular plants.

Sporophylls

Leaves modified to bear sporangia for spore production.

Homosporous

Producing one type of spore, typical in most SVPs.

Heterosporous

Producing two types of spores, seen in seed plants.

Strobilus

Cone-like structure of sporophylls in some plants.

Monilophytes

Phylum including ferns, horsetails, and whisk ferns.

Whisk ferns

Plants with dichotomous branching and no true leaves.

Horsetails

Jointed stems with tiny leaves, homosporous.

Ferns

Diverse plants with large megaphylls and sori.

Sori

Clusters of sporangia on the underside of fern leaves.

Ecological importance

Seedless plants enhance soil formation and weathering.