Post on 28-Jan-2016
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
FERNS
CONE BEARING PLANT
FLOWERING PLANT
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:
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 VASCULAR TISSUE 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
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