Plant Diversity I and II

Labs 6 and 7BIOL 171

A B C D F0

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Practical Exam I Results

Frequency

A B C D F0

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Current Grades 10/18/2010

Frequency

IntroductionFirst land plants were related to green algae – 500

million years ago

Plant Life Cycles

• All land plants have a common sexual reproductive life cycle called alteration of generations

• Gametophyte – haploid (n) generation• Sporophyte – diploid (2n) generation• One generation is always dominant (more

conspicuous)– In the Bryophytes (mosses and liverworts) the

gametophyte is dominant– In all other land plants the sporophyte is dominant

Alteration of Generations(also look at figure 2 in lab manual)

Alteration of Generations Vocab• Spores – (n) produced by the sporophyte generation

through meiosis – germinate to produce the gametophyte (n)

• Sporangium – a protective nonreproductive jacket that contains the spores

• Gametes – produced inside the gametangia located on the gametophyte

• Eggs (n) are produced inside the archegonia through mitosis• Sperm (n) are produced inside the antheridium through

mitosis• Zygote – (2n) formed by fusion of the gametes, this is the

first stage of the sporophyte generation

Bryophytes• 3 divisions (phyla): Bryophyta (mosses),

Hepatophyta (liverworts), and Anthocerophyta (hornworts).

• Small plants, lacking vascular tissue (specialized cells for transport of material)

• The gametophyte generation is dominant and conspicuous plant.

• Restricted to moist habitats– Both because they lack vascular tissue– And because this enables their mobile sperm to swim and

fertilize the egg• Have a cuticle, but lack stomata on the surface of

the thallus (plant body)

Bryophyta (mosses)

• Most common group• Occurs in moist environments, but also found

in dry habitats that are periodically moist

Peat moss (Sphagnum)

Alternation of generations (mosses) GAMETOPHYTE (n)

SPOROPHYTE (2n)

(gametangia)

Ovum

Sperm

Embryo (2n)

Spore (n)

Gametophyte

Gametophyte (n)

Sporophyte (2n)

Hepatophyta (liverworts)

• Flattened and lobed thallus (plant body)• Early herbalists believed that these plants

were could treat liver disorders.• Found along streams on moist rocks• Very small

Liverwort body form

• Rhizoids – rootlike extensions on the lower surface of the thallus

• There are pores on the leaflike thallus that function in gas exchange, but lack guard cells so are always open.

• Gemmae cups are located on the upper surface of the thallus, they are circular cups that contain flat disks of green tissue called gemmae.

• The gemmae are washed out of the cups when it rains, and they grow into new, genetically identical liverworts.