PLANT EVOLUTIONEvolutionary TrendsBryophytesThe rise of the vascular plantsThe rise of the seed plants

KINGDOM PLANTAE General features:

Eukaryotic, multicellular, photosynthetic autotrophic organisms

P.S.= H2O + CO2+ sunlight oxygen + sugar C.R. = sugar + O2 CO2 and H2O + NRG

Origins = blue-green bacteria ancestral green algae algae bryophytes tracheophytes

THE PHYLA Phyla grouped into:

- Nonvascular plants (lack true (lignified) vascular tissue)

- Seedless vascular plants (true vascular tissue (phloem and xylem), but reproduce only by spores (no seeds made)

- Seed bearing vascular plants

SETTING THE STAGE Earth’s atmosphere was originally

oxygen free Ultraviolet radiation bombarded

the surface Photosynthetic cells produced oxygen and

allowed formation of protectiveozone layer

PIONEERS IN A NEW WORLD

Cyanobacteria were probably first to produce oxygen

Later, green algae evolved and gave rise to plants

ADVANTAGES AND DISADVANTAGES OF LIFE ON LAND

Sunlight unfiltered by water and plankton

Atmosphere had more CO2 than water

Soil was rich in mineral nutrients

Originally relatively few herbivores and pathogens

Relative scarcity of water

Lack of structural support against gravity

Advantages: Disadvantages:

EARLY PLANTS

EVOLUTIONARY TRENDS IN PLANTS STRUCTURE:

Plants came from the sea which support, keep temp constant, bath whole plant with nutrients

Adaptations to terrestrial Life = Roots to anchor and absorb Conducting vessels xylem & phloem to carry

nutrients up and glucose around Stiffening ligin to support the plant Waxy cuticle on leaves and stem to prevent

evaporation Stomata pores in leaves to allow gas exchange,

but close to prevent water loss

ADAPTATIONS TO LAND

Root systems – underground absorptive structures evolved as plants colonized the land

Shoot systems – evolved where stems and leaves intercepted sunlight energy and took in CO2 from the air.

ADAPTATIONS TO LAND

Vascular tissues - evolution of roots and shoots forming components – xylem and phloem for transporting water and sugars to all tissues.

Waxy cuticle – evolved to assist plant to conserve water on dry, hot days.

Stomata – evolved to allow control of water loss and transport of gases.

EVOLUTIONARY TRENDS IN REPRODUCTION:

Algae reproduce in water so gametes are carries by water, form zygotes in water and disperse in water. Ie No protection from dehydration required

Land plants needed: Transport gametes (pollen, flowers) Protection from drying out (seeds) Dispersal (seed coats & fruits)

EVOLUTIONARY TRENDS IN PLANT LIFE CYCLES: Alternation of Generations = haploid

gametophytes produces sex cells by mitosis. Gametes unite to from a diploid zygote, which develops into diploid sporophyte that develops haploid spores by meiosis

HAPLOID TO DIPLOID

Gametophyte Haploid gamete producing body

Sporophyte Diploid product of fused gametes

Spore Resting structure

The most recently evolved groups produce seeds and pollen grains which were the key innovations that allowed the seed plants to spread widely into diverse habitats.

EVOLUTIONARY TRENDzygote

SPOROPHYTE (2n)GAMETOPHYTE (n)

GREEN ALGAE BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM

Relative size

Life span

GENERAL TREND = DECREASED SIZE, DURATION, AND PROMINENCE OF GAMETOPHYTE GENERATION RELATIVE TO SPOROPHYTE

Algae = some have no sporophyte or only the zygote

Mosses = gametophyte is green leafy and sporophyte is small and short lived

Ferns = sporophyte is the fronds of the ferns, gametophyte is smaller yet independent

Seeded plants = male and female gametophytes are microscopic and produce gametes to form sporophyte embryo

Recall: evolution occurs because of advantageous traits being selected therefore what is the advantage of diploid sporophyte

dominance?

SPOROPHYTE

The generation in the life cycle of a plant that produces spores.

Is diploid but its spores are haploid. Either completely or partially dependent

on the gametophyte generation in mosses and liverworts, but is the dominant plant in the life cycle of clubmosses, horsetails, ferns and seed plants.

LE 29-9D

Polytrichumcommune,hairy capmoss

Sporophyte

Gametophyte