Download An Overview of Plants Section 2 Seedless Plants

An Overview of Plants
A. Plant cells
1. Unlike animal cells, plant cells have cell walls, which provide
structure and protection.
2. Most plant cells contain the green pigment chlorophyll.
a. Photosynthesis—process where plants use chlorophyll to make food
b. Chlorophyll is found in a cell structure called a chloroplast.
3. Most of the space inside many plant cells is taken up by a large, membrane-bound structure
called a central vacuole, which regulates water content.
B. Scientists think plants probably evolved from green algae in the sea because:
1. Plants and green algae have the same types of chlorophyll and carotenoids.
2. Fossils of early plants are similar to the ancient green algae.
C. When plants moved to land, they had to adapt to new conditions.
1. More sunlight and carbon dioxide were available.
2. Plants developed a cuticle—a waxy, protective layer secreted onto the surface of the plant
which holds water in and allows plants to live in drier conditions.
3. Cell walls developed cellulose, a chemical compound that provides structure and support,
which allows plants to stand upright on land.
4. Water-resistant spores and seeds enabled plants to reproduce on land.
D. Plant classification
1. Vascular plants use tubelike structures that carry water and nutrients throughout the plant.
2. Nonvascular plants lack tubelike structures and use other ways to move water and
nutrients.
DISCUSSION QUESTION: How are plant cells different from animal cells? They contain cell walls, chlorophyll, and
chloroplasts. They perform photosynthesis.
Section 2 Seedless Plants
A. Nonvascular plants—very small plants that have rhizoids rather than roots
1. Water is absorbed and distributed directly through cell membranes and cell walls.
2. Grow in damp environments
3. Reproduce by spores rather than seeds
4. Examples of nonvascular plants:
a. Mosses—green, leaflike growths arranged around a central stalk
b. Liverworts—flattened, leaflike bodies
c. Hornworts—have only one chloroplast in each of their cells
5. Frequently pioneer species – organisms that are the first to grow in new or disturbed areas
and which change environmental conditions
B. Seedless vascular plants—reproduce by spores, but have vascular tissue that carries water and
nutrients throughout the plant
1. Can grow bigger and thicker than nonvascular plants
2. Ferns—largest group of seedless vascular plants
a. Have stems, leaves, and roots
b. Leaves are called fronds
c. Reproduce by spores found on the back of their fronds
3. Club mosses—needlelike leaves
4. Horsetails—jointed stem with a hollow center
C. Importance of seedless plants
1. Fuel—decaying seedless plants are compressed into peat and eventually coal
2. Soil conditioners
3. Ferns can be used for weaving material and basketry.
DISCUSSION QUESTION: If you wanted to find a nonvascular plant, where would you look? You would look in a damp
area, very close to the ground (because they are very small). They might be growing on a rock or tree, because they don’t
have roots.
Section 3 Seed Plants
A. Characteristics of seed plants
1. Have leaves, stems, roots, and vascular tissue
2. Reproduce by seeds, which contain an embryo and stored food
B. Leaves trap light and make food through photosynthesis.
1. Epidermis—a thin layer of cells on the upper and lower surfaces of a leaf
a. May have a waxy cuticle coating the epidermis
b. Stomata—small openings in the epidermis that allow carbon dioxide, water, and
oxygen to enter and exit a leaf
c. Each stoma is surrounded by two guard cells that open and close it.
2. Palisade layer—contains chloroplasts, where most food is made
3. Spongy layer—loosely arranged cells and air
C. Stems allow the movement of materials between leaves and roots.
1. Usually above ground
2. Support the branches, leaves, and flowers
3. May store food
4. Two kinds:
a. Herbaceous stems—soft and green
b. Woody stems—hard, rigid, and woody
D. Roots collect water and nutrients from the ground.
1. Roots anchor plants so they don’t blow away.
2. May store food or water.
E. Vascular tissue
1. Xylem tissue—transports water from the roots throughout the plant
2. Phloem tissue—moves food from where it is made to other parts of the plant
3. Cambium tissue—produces new xylem and phloem cells
F. Gymnosperms—vascular plants that produce seeds that are not protected by fruit
1. Oldest trees
2. Gymnosperms have no flowers.
3. Leaves are often needlelike or scalelike, evergreens
4. Four divisions: conifers, cycads, ginkgoes, and gnetophytes
5. Conifers reproduce by male and female cones.
G. Angiosperms—vascular plants that flower and have fruit that contains seeds
1. Fruit develops from flowers.
2. Most fruit contains seeds.
3. Two groups:
a. Monocots—have one cotyledon used for food storage inside their seeds
b. Dicots—have two cotyledons inside their seeds
4. Different angiosperms have different life cycles:
a. Annual—the plant’s life cycle is completed within one year
b. Biennial—the plant’s life cycle is completed in two years
c. Perennial—takes more than two years to grow to maturity
H. Human life depends on seed plants.
1. Wood for construction and paper products comes from conifers.
2. Angiosperms form the basis of diets for most animals, including humans.
DISCUSSION QUESTION: If you are a gardener, why is it important to know whether your plants are annuals, biennials,
or perennials? If your plants are annuals, they will die every year and will need to be replaced. If they are biennials, they
will die every two years and will need to be replaced. If they are perennials, they will flower again and don’t need to be
replaced.