Back to Biology 1402 pagePlant Diversity I -
the Colonization of Land
Chapter 29
Requirements for Terrestrial Life
Physical support for plant body
Transport of water and nutrients within plant
Protection of plant tissues from desiccation (excessive loss of water)
Reproduction - dispersal mechanisms and water-retention mechanisms for gametes and zygotes
Adaptations to a Terrestrial Life -
(1) the Embrophyte Condition
Adaptation to prevent desiccation (drying) of developing gametes and embryos - first appeared in the nonvascular plants (bryophytes)
Gametes produced within specialized structures - antheridium (sperm) and archegonium (eggs) - collectively known as gametangia
Zygote retained within archegonium - nourished and protected by parent - fundamentally different from algae - plants known as
Adaptations to a Terrestrial Life -
(2) Alternation of Generations
Life cycles of all plants include a gametophyte (haploid generation) and sporophyte (diploid generation) - the two generations alternate - each produces the other -
In nonvascular plants (the bryophytes), gametophyte is the dominant (most conspicuous) stage - in all other plant groups, sporophyte generation is dominant
Not the same as diploid and haploid stages in meiosis
Adaptations to a Terrestrial Life -
(3) other factors
Vascular tissue - transport of water (in xylem tissue) and nutrients (in phloem tissue) - secondary products (lignin) for structural support)
Root systems - support - acquisition of nutrients and water
Leaves with cuticle, protective waxes and stomata - photosynthesis and related processes on land without desiccation (excessive loss of water)
Sporopollenin - resistant polymer in spores
Four Major Events of Plant Evolution
Origin of plants - evolved from charophytes (green algae)
Appearance of vascular tissue - first evident in seedless vascular plants
Origin of the seed - protection of plant embryos from desiccation and other factors - diversification of gynmosperms (conifers and relatives)
Appearance of flowers - dispersal of seed by factors other than wind - diversification of angiosperms
Classification of Plants
Classification based on phylogenetic relationships
Division is used instead of Phylum - the two are equivalent
11 Divisons in Kingdom Plantae
the Bryophytes - Nonvascular Plants
Characterized by embryophyte condition, lack of vascular tissue and gametophyte-dominant life cycle in alternation of generations)
Includes 3 Divisions:
Bryophyta - mosses
Hepatophyta - liverworts
Anthocerophyta - hornworts
Seedless Vascular Plants
Characterized by presence of vascular tissue and sporophyte-dominant life cycles (sporophyte dominant stage in alternation of generations) Includes 3 Divisions:
Lycophyta - lycophytes - also known as club mosses and ground pines
Sphenophyta - horsetails
Pterophyta - ferns