early plants the earliest plants were similar to today’s mosses. they grew close to damp ground...
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Early Plants
• The earliest plants were similar to today’s mosses. They grew close to damp ground and depended on water to complete their life cycles (to carry the gametes).
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Kingdom Plantae (page 550)
• Characteristics:- eukaryotic- multicellular (most)- have cell walls made of a complex carbohydrate called cellulose - sessile (anchored by roots)
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- Autotrophic - Contain chlorophyll in chloroplasts within their cells. (The green pigment necessary for photosynthesis) Some plants though, are also parasitic or saprobes.
-Reproduce both sexually (production of sex gametes) and asexually (fragmentation, budding, spores)
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Life cycle (page 552)
- Undergo a life cycle called “alternation of generations”. This means the plant alternates between a gametophyte (produces gametes/haploid cells) and a sporophyte (produces spores/diploid cells).One generation is usually dominant.
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Land plants
• Land plants are divided into non-vascular and vascular plants.
• Vascular plants have a system of “vessels” that carry food and water around. Non-vascular plants do not.
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• Special cells, called tracheids which transport water were developed.
• Tracheids are hollow cells with thick cell walls that resist osmotic pressure. They join together and die, leaving a long hollow tube like a straw.
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• Tracheids allowed for the development of vessels and vascular plants.
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• Xylum is the transport system in plants that carries water.
• Phloem transports the solutions of nutrients and carbohydrates produced by photosynthesis.
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Xylem and Phloem
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Phylum Bryophyta (Bryophytes) (mosses and their relatives)
• Non-vascular plants• Depend on water for
reproduction (HOW?)• Draw up water by
osmosis only• Have to be short,
growing only a few centimeters above ground (WHY?)
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Phylum Bryophyta continued
• The sperm must swim to reach neighbouring eggs
• Must live in, near water or heavy dew for at least some of the year. (near streams, forest floor)
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Phylum Bryophyta continued
• Have no true roots
• Can tolerate low temperatures and fairly harsh climates
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• ”leaves” are only one cell thick
• has rhizoids rather than true roots
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• In the life cycles of plants, there are two “generations” (phases) ; gametophyte or sporophyte.
• Gametophyte is the dominant generation (Moss spends most of its life cycle in this generation).
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Life Cycle of a Bryophyte, including peat moss (page 558)
• Moss spore lands in a moist place
• Germinates and grows into protonema.
• As the protonema grows, it forms rhizoids that grow into the ground and shoots that grow into the air.
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Bryophyte Life Cycle
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• The shoots are the gametophyte stage of the moss’s life cycle and this is what we see and think of as “moss”
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• http://www.youtube.com/watch?v=jcWYAnmm-QE
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Know this!
• Antheridium (antheridia – plural)• Archegonium (archegonia - plural).• Homework:
Questions 1, 3, 4, and 5 on page 559.
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Vascular Plants (all plants except those in the Phylum Bryophyta)
• Ferns, herbs, trees, flowers, vegetables.• The vascular system allows these plants to
transport nutrients and water throughout the plant, even against gravity.
• Sporophyte generation is dominant (diploid)• Gametophyte generation is short (haploid)
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Seedless vascular plants (club mosses, horsetails and ferns)
• Have:Roots: underground organs that absorb water and minerals. Water-conducting tissues are in the center of the rootLeaves: photosynthetic organs that contain one or more bundles of vascular systems gathered into veins made of xylem and phloem.
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• Stems: supporting structures that connect roots and leaves, carrying water and nutrients between them
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Phylum Pterophyta (ferns)
• Most numerous phylum of seedless vascular plants (over 11 000 species).
• Ferns have:– Vascular tissue– Strong roots– Underground systems
called rhizomes– Large leaves called fronds
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Pterophyta
• Like wet habitats
• Like shady areas
• In tropical areas can grow as large as small trees
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Life cycle of the fern • Ferns and other
vascular plants have a life cycle in which the diploid sporophyte is the dominant stage.
• Fern sporophytes develop haploid spores on the underside of their fronds in tiny containers called sporangia.(also see page 562).
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• Sporangia are grouped together in tiny clusters called sori (singular, sorum).
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• When the spores germinate, they develop into haploid gametophytes.
• The gametophyte first grows a set of root-like rhizoids.
• It then flattens into a thin, heart-shaped green structure that is the mature gametophyte.
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• The gametophyte contains both egg (in the archaegonia) and sperm (in the antheridia).
• Once the egg is fertilized by the sperm, it grows into a sporophyte.
• See the diagram on page 562 in your text for the life cycle of the fern.
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Answer these questions from page 559• 1. How is water essential in the life cycle of a
bryophyte?• 3. What is the relationship between the
gametophye and the sporophyte in mosses?• 4. What is an archegonium? An antheridium?
How are these structures important in the life cycle of a moss?
• 5. What characteristic of bryophytes is responsible for their small size?