Botanist ______Date ______
22-2 Seedless Plants – PowerPoint
The First Plants
Green algae are mostly ______. They are found in fresh and salt water, and in some moist areas on land.
Green algae absorb moisture and nutrients ______from their surroundings and do not contain the specialized tissues found in other plants.
Life Cycle – Green Algae
Many green algae ______back and forth between haploid and diploid phases.
In the life cycle of Chlamydomonas, as long as living conditions are suitable, the haploid cell reproduces asexually by ______.
If conditions become unfavorable, Chlamydomonas can switch to a stage that reproduces ______.
Its cells release gametes that fuse into a diploid zygote (a sporophyte). The zygote has a thick protective wall, permitting survival in ______conditions.
The zygote begins to grow once conditions become favorable.
It divides by ______to produce four haploid cells that swim away, mature, and reproduce asexually.
Multicellularity
Green algae can form ______.
Spirogyra forms long threadlike colonies called filaments.
______colonies consist of as few as 500 to as many as 50,000 cells arranged to form hollow spheres.
Volvox shows some cell specialization and straddles the fence between ______and multicellular life.
Mosses and Other Bryophytes
Mosses have a ______, protective coating that makes it possible for them to resist drying, and thin filaments known as rhizoids that anchor them to the soil. Rhizoids also absorb water and minerals from the soil.
Mosses, hornworts, and liverworts all belong to a group of plants known as ______.
Bryophytes have specialized reproductive organs enclosed by other, non-reproductive cells.
Bryophytes show a higher degree of cell ______than do the green algae and were among the first plants to become established on land.
Why Bryophytes Are Small
Bryophytes do not make ______, a substance that hardens cell walls, and do not contain true vascular tissue. Because of this, bryophytes cannot support a tall plant body against the pull of gravity.
Life Cycle - Moss
Bryophytes display alternation of ______.
The ______is the dominant, recognizable stage of the life cycle and the stage that carries out most of the photosynthesis.
The ______is dependent on the gametophyte for its supply of water and nutrients.
Bryophytes produce sperm cells that swim using ______.
For fertilization to occur, the ______must swim to an egg. Because of this, bryophytes must live in habitats where open water is available at least part of the year.
Gametophyte
When a moss spore lands in a moist place, it sprouts and grows into a young gametophyte.
The gametophyte forms rhizoids that grow into the ground and shoots that grow into the air.
Gametes are formed in reproductive structures at the tips of the ______.
Eggs are produced in ______.
Sperm are produced in ______.
Sperm and egg cells fuse to produce a diploid ______.
Sporophyte
The ______marks the beginning of the sporophyte stage of the life cycle.
A sporophyte grows within the body of the gametophyte, depending on it for water and nutrients.
Eventually the sporophyte grows out of the gametophyte and develops a long stalk ending in a capsule called the ______.
Haploid ______are produced inside the capsule by meiosis and are released when the capsule ripens and opens.
Vascular Plants
About ____ million years ago, plants for the first time were able to grow high above the ground.
Fossil evidence shows these plants were the first to have a transport system with true vascular tissue. Vascular tissue carries ______and nutrients much more efficiently than does any tissue found in bryophytes.
Evolution of a Transport System
Vascular plants are known as tracheophytes, after a specialized type of water-conducting cell they contain. These cells, called ______, are hollow tubelike cells with thick cell walls strengthened by lignin.
Tracheids are found in ______, a tissue that carries water upward from the roots to every part of a plant. They also have a second transport tissue called ______that transports solutions of nutrients and carbohydrates produced by photosynthesis.
Seedless Vascular Plants
Among the seedless vascular plants alive today are three phyla commonly known as club mosses, horsetails, and ferns. The most numerous of these are the ______.
Life Cycle – Fern
In the life cycle of a fern, spores produced by the sporophyte grow into thin, heart-shaped haploid gametophytes. The gametophytes ______independently of the sporophyte.
Sperm and eggs are produced on the gametophytes in antheridia and archegonia.
Fertilization requires at least a thin film of water, so that the ______can swim to the eggs.
The diploid zygote produced by fertilization develops into a new sporophyte plant. This is the ______stage of the fern life cycle.
Haploid spores develop on the undersides of the fronds in sporangia, and the cycle begins again.