kingdom plantae arose from green algae approximately 1 billion years ago red and brown algae are not...
Post on 20-Dec-2015
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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• 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
• 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
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
• 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!”
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/AnimalsBackyardBiology/UrbanNatureWatch/Watches/PlantAdap...ersal.cfm
www.flickr.com/photos/elancel/3608295338/
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
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• 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• 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!