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/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• 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