Transcript Plants
Kingdom Plantae • Arose from Green Algae approximately 1 billion years ago • Red and brown algae are not included • A single species of freshwater green algae gave rise to the entire Kingdom • Green algae subsequently split into two groups – the Chlorophytes which never made it to land, and the Charophytes, the sister group of all land plants Kingdom Plantae is monophyletic Kingdom Plantae • Eukaryotic • Multi-cellular • Cell walls are made of cellulose • Autotrophic Kingdom Plantae • Adaptations for living on land – Waxy cuticle – secreted onto surface; impermeable – Stomata – tiny mouth-shaped openings, which can be opened and closed – Gametangia – structures that produce (and house) gametes Plant Life Cycles • Reproduction is accomplished by an alteration of generations • A multi-cellular diploid phase alternates with a multi-cellular haploid phase • The gametophyte (“gamete plant”) is haploid; produces gametes by mitosis • The sporophyte (“spore plant”) is diploid; formed by two gametes; produces spores by meiosis, which germinate and develop into gametophytes! Plant Life Cycles • The diploid sporophyte is the dominant portion of the life cycle in most land plants (vascular plants: ferns, gymnosperms and angiosperms) • However, the haploid gametophyte is the dominant portion of the life cycle in Bryophytes (liverworts, hornworts and mosses) Plant Life Cycles • Bryophyte gametophyte • Vascular plant sporophyte (sori on the back of a fern) Plant Life Cycles • In seed plants, the haploid gametophytes are male and female; the males occur as pollen and the females occur as seeds • The seed growing on the diploid sporophyte ‘parent’ contains a haploid female gametophyte bearing an egg cell, and is fertilized by a pollen grain which contains a miniature male gametophyte • diploid zygote diploid sporophyte Plant Life Cycles • Pine cones contain seeds and pollen • The familiar pine cone is the female • The male (containing pollen) is not really a cone at all, but rather a cluster Chlorophytes • Green Algae • Aquatic • Unicellular and multi-cellular Bryophytes • The closest living descendents of the first land plants • Simple, but highly adapted • Lack roots • Mycorrhizal associations are found in many groups • Typically small (the conspicuous form are gametophytes!); <7cm in height • Non-vascular but have conducting cells for water and nutrients Bryophytes • Liverworts and Hornworts Bryophytes • Mosses – Multi-cellular rhizoids – Rhizoids function as roots; anchor to substrate and absorb water – Green parent plant is the gametophyte; sporophyte nutritionally dependent on gametophyte Tracheophytes • The first vascular plants • Evolved lignified tissues for conducting water, nutrients and photosynthetic products through the plant • Xylem – draws water and nutrients up from roots to the upper sections of the plant • Phloem – conducts photosynthetic products and hormones throughout plant • “Xylem up, Phloem down!” You are Here Tracheophytes Tracheophytes (cont.) Lycophytes and Pterophytes • The Club Mosses (Lycophytes; not true mosses) and Ferns (Pterophytes) Seed Plants • Seeded plants • Embryo protected by an extra layer of sporophytic tissue; during development, this tissue hardens to produce the seed coat • Seed protects embryo from drought, allows for easier dispersal, and introduces a dormant stage, that allows the embryo to survive until environmental conditions are favorable for growth Seed dispersal nationalzoo.si.edu/Anima lsBackyardBiology/Urban NatureWatch/Watches/Pl antAdap...ersal.cfm http://www.uni-heidelberg.de/institute/fak14/ipmb/phazb/birdsberries.htm http://www.ise514.org.uk/members/Photos/Plants/seed%20dispersal/fruit%20bat%20on%20%20fig.JPG www.flickr.com/photos/elancel/3608295338/ Gymnosperms • Plants with “naked seeds” Gymnosperms • Gametophyte stage is further reduced • Male gametophyte is inside pollen • Female gametophyte inside seed… Reminder – conifers are gymnosperms • Pine cones contain seeds and pollen • The familiar pine cone is the female • The male (containing pollen) is not really a cone at all, but rather a cluster Angiosperms • Flowering Plants • Include Monocots (one cotyledon) and Dicots (two cotyledon) Angiosperms • Flowers – reproductive organs; considered to be modified stems with modified leaves • Consist of: – Stamen - produces pollen, bears pollen on anther – Carpel – includes the ovary (the swollen base), stigma (sticky, pollen grains adhere to), style (connects the stigma to the ovary) • Ovary later develops into a fruit Angiosperms Angiosperms • The flower is designed (evolved) to attract pollinators (or to aid in wind dispersal) • The flower uses color, scent, morphology and reward to attract pollinators – Color – advertises to pollinators – Scent – attracts pollinators – Morphology – can be specific, attracts pollinators (hummingbird bills, bee orchids) – Reward – nectar; sweet and nutritious • Flowers that self-fertilize tend to small, inconspicuous and unscented! http://www.flickr.com/photos/41019338@N00/2808113879/ Coevolution