Plants (Kingdom Plantae)

• Multicellular eukaryotes

• Photoautotrophs

• Terrestrial?– Not all plants are terrestrial

• Return to water from land

• Move to land was a major step

Move to Land Required Significant Adaptations

• Water uptake and loss

• Gas exchange

• Reproduction

• Support

Move to Land

• Plants probably evolved from a group of green algae called the charophytes

• Are a fringe species exhibiting multicellular traits

• Why a fringe species?

Features Common to Green Algae and Plants

• Chlorophyll a and other accessory pigments (Chl b, -carotene)

• thylakoid membranes stacked into grana

Features Common to Green Algae and Plants

• Chlorophyll a and other accessory pigments (Chl b, -carotene)

• similar photosynthesizing organelles

• cell walls of cellulose

• store carbohydrates as starch

• alternation of generation

Highlights of Plant Evolution

• Four major periods

• Move onto land (~425 - 475 mya)

– prevent desiccation of whole plant

– protect reproductive structures

– Features seen in mosses (bryophytes)

Highlights of Plant Evolution

• Evolution of vascular tissue and diversification (~400 mya)– simple diffusion not an option–Mosses - water-conducting tubes– transport and support– larger body sizeThese are features first seen in ferns, horsetail,

whisk ferns****Similar protection of gametes

Horsetail

Whisk Fern

Highlights of Plant Evolution

• Evolution of seed (~360 mya)

– additional protection from desiccation and predation

– dispersal

Highlights of Plant Evolution

• Emergence of flowering plants (~130 mya)– Seeds in protective ovary– Expanded potential for diversity–Complex structure with great potential

for adaptation–Greater sexual reproductive success–Coevolution between insects and

angiosperms

Nontracheophytes

• Mosses, liverworts and hornworts

• Probably closest to ancestral form

• protected gametangia

• lack vascular tissue

• Encrusting

• Water needed for fertilization

Gametophyte

Sporophyte

Sporophyte relies on gametophyte for nutrients

Nonseed Tracheophytes Plants

• Ferns, horsetail, club mosses

• Retain some traits of mosses

• Evolved some traits also seen in seed-producing vascular plants

Traits Shared with Nontracheophytes

• Antheridia and archegonia retain similar structure

• Require water/moisture for sexual reproduction

• Production of spores

Traits Shared with Seed-Producing Plants

• Vascular tissue - greater body size

• Sporophyte is dominant stage of life cycle

Gametophyte

Sporophyte

Seedless tracheophytes were the dominant vascular plants for ~ 50 million years

• Continents in tropical/subtropical zone

• As continents drifted away from equator, conditions changed

• Seed-producing plants were present during height of seedless vascular plant success

Rise of Seed-Producing Tracheophytes

• Well suited for environmental changes

• Gametophyte smaller and retained in moist tissues of sporophyte

• Pollination rather than swimming sperm

• Evolution of seed

• gymnosperms and angiosperms

Gymnosperm

• “naked seed”

• still have a seed coat

• four divisions

• Coniferophyta best known

• evergreens

• needle-shaped leaves, thick cuticle

Gametophyte

Sporophyte

Gametophyte passes within sporophyte

• “protected seed”

• most diverse group– 235,000 known species vs. 721 species of

gymnosperms

• One division - Anthophyta

• Two classes– Monocotyledones– Dicotyledones

Angiosperms

Angiosperms

• successful and effective design

• different themes of the same design

Gametophyte

Sporophyte

Gametophyte passes within sporophyte

Develops into fruit

Develop intoseeds