Presentation on theme: "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."— Presentation transcript:
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).
Kingdom Plantae (page 550) Characteristics: - eukaryotic - multicellular (most) - have cell walls made of a complex carbohydrate called cellulose - sessile (anchored by roots)
- 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)
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.
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.
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.
Tracheids allowed for the development of vessels and vascular plants.
Xylum is the transport system in plants that carries water. Phloem transports the solutions of nutrients and carbohydrates produced by photosynthesis.
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?)
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)
Phylum Bryophyta continued Have no true roots Can tolerate low temperatures and fairly harsh climates
”leaves” are only one cell thick has rhizoids rather than true roots
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).
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.
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)
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 root Leaves: photosynthetic organs that contain one or more bundles of vascular systems gathered into veins made of xylem and phloem.
Stems: supporting structures that connect roots and leaves, carrying water and nutrients between them
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
Pterophyta Like wet habitats Like shady areas In tropical areas can grow as large as small trees
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).
Sporangia are grouped together in tiny clusters called sori (singular, sorum).
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.
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.
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?