The Plant Kingdom Plant Characteristics Plant Characteristics Multicellular

The Plant Kingdom

Plant Characteristics Plant Characteristics: Multicellular organisms with tissues and organs. Contain chlorophyll and make food (photosynthesis). Can not move from place to place. Made of eukaryotic cells with cell walls.

Evolution of Plants Evolved from one-celled, plant-like protists in the ocean. Oldest plant fossils are 420 million years old. Many adaptations slowly appeared to allow plants to move from water to land.

Land Adaptations Plants had to overcome the following problems before they could colonize land: Prevent water loss: cell walls made of cellulose help prevent water loss. Most land plants have a waxy, protective cuticle on their stems and leaves that also aids in preventing water loss. Support their own weight: cell walls provide structure and support. Reproduce without water: seeds allow plants to reproduce without water.

Classification of Plants 9 Divisions (260, 000+ species) Nonvascular Division Vascular spore-producing plants: Bryophyta—mosses and liverworts spore-producing plants: Division Lycophyta—club mosses and spike mossses Division Sphenophyta—horsetails Division Pterophyta—ferns Vascular seed-producing plants: Division Ginkgophyta—ginkgos Division Cycadophyta—cycads Division Coniferophyta—conifers (evergreens) Division Gnetophyta—gnetum Division Anthophyta—flowering plants

Nonvascular Spore-producing Plants Division Small Bryophyta plants found in damp, shady environments. Nonvascular—no vessels for transporting water and food. 23, 000 species No true roots, stems or leaves. Produce spores instead of seeds. Examples: Mosses, Liverworts, and Hornworts

Mosses—simple, rootless plants with leaf-like growths in a spiral around a stalk. Root-like threads called rhizoids replace true roots and hold the moss in place. Most range in size from 2 -5 cm in height

Moss Reproduction Mosses and other bryophytes reproduce through a process known as Alternation of Generation which involves a gametophyte and a sporophyte stage. Stalk Leaf-like structures The sporophyte is made of a stalk and capsule. The gametophyte is the green, leafy part and the rhizoids.

Moss Life Cycle Two stages: Diploid stage (2 n)-- which has a full set of chromosomes. This is the sporophyte stage. It produces spores, by meiosis, that only have half the number of chromosomes. They grow into gametophytes. Haploid Stage (n)—which only has half the number of chromosomes. This is the gametophyte stage. Separate male and female plants produce sperm and egg cells that unite to produce the sporophyte.

Liverworts Liverworts—simple, rootless plants that have a flattened, leaf-like body. Their name means, “liver herb” and in the Middle Ages, people believed this plant looked like one’s liver.

Hornworts Hornworts—small plants with flat, round, leaf-like structures. It’s sporophyte looks like an animal’s horn. They live near lakes and rivers.

Vascular Spore-producing Plants The remaining spore-producing plants are vascular. Vascular means they have vessels for transporting water and food. Three divisions of seedless vascular plants: Lycophyta, Sphenophyta, and Pterophyta.

Division Lycophyta—produce spores in structures that look like tiny pinecones. Sometimes called ground pine. Examples: Club moss and spike moss

Division Sphenophyta— stems are jointed with a hollow center. They contain silica (a gritty substance found in sand). They were used by pioneers to scour their pots and pans. Examples: horsetails

Pterophyta— largest group of seedless vascular plants. Examples: Ferns Ancient species were huge (25 meters). Today, the largest species are 3 -5 meters. These ancient fern forests formed today’s coal deposits. Division

Fern Reproduction Ferns and other seedless vascular plants also reproduce through Alternation of Generations, using sporophytes and gametophytes. Fern sporophyte with spore cases called sori Fern gametophyte with young sporophyte beginning to grow

Fern Life Cycle The sporophyte is the fern leaf or “frond”. On the underside of the frond are spore cases called sori. These release thousands of spores. A spore grows into a heart-shaped gametophyte called a prothallium. It is held in place by root-like structures called rhizoids and has both sperm and egg cells on it. They unite and a new sporophyte begins to grow.

Seed Plants Both mosses and ferns rely on water for reproduction because the sperm cells must swim to egg cells. Therefore, these plants live only in fairly moist areas. It wasn’t until plants evolved seeds for reproduction that they truly became successful in all land habitats.

Seeds have: Seed coat—surrounds and protects the developing plant from drying out or freezing. Cotyledons—stored food source for the developing plant. Embryo—young, developing plant made of a small stem and root

Classification of Seed Plants Two main types of seed plants are divided into five divisions: Gymnosperms: Vascular plants that produce seeds inside cones. (About 700 species) Angiosperms: Vascular plants that produce seeds inside fruits. (More than 275, 000 species).

Gymnosperms Name means “naked seed”. Seeds are inside cones not fruit. Do not produce flowers. Leaves are needle-like or scale-like. Most are evergreens (Conifers) and keep their leave all year long. Four divisions: Ginkgophyta, Cycadophyta, Coniferophyta, Gnetophyta

Division Gingkophyta—ginkgos: deciduous gymnosperms with fan -shaped leaves. Example: Maidenhair Ginkgo Division Cycadophyta—cycads: palmlike gymnosperms. Example: Florida Cycad

Division Coniferophyta— Conifers: Most are evergreens with needlelike or scalelike leaves and pinecones. Examples: Pines, firs, spruces, cedars, junipers. Division Gnetophyta—gnetum: Most are shrubs or woody vines found in the deserts of Asia, Africa and S. America. Example: Welwitchia

Gymnosperm Reproduction Most gymnosperms produce both male and female cones. Female cones (seed cones) are large with many woody scales. Ovules form in each scale and produce egg cells. Male cones (pollen cones) are small. They produce pollen grains containing sperm cells.

Wind carries pollen grains from male to female cones. (Pollination) A pollen tube grows from the pollen grain to the ovule. Sperm cells swim down the tube and fertilize the egg. A seed forms. (Fertilization) Female cones mature and open, releasing their seeds during the fall or winter months. This entire process can take as long as two years. Seeds that fall may be carried away, eaten, or buried. (Dispersal) When conditions are right, some seeds will grow into new pine trees. (Germination)

Importance of Gymnosperms have many important commercial uses such as : Lumber Paper Soap, paint, varnish and some medicines all made from plant resin

Angiosperms Name means “Covered seed” Seeds are inside some sort of fruit. All produce flowers and fruits. All belong to the Division Anthophyta Two classes in this division: Monocots and Dicots.

Monocots—all monocots have: Petals in groups of three Narrow leaves with parallel veins Scattered vascular bundles in stems One cotyledon in the seeds Examples: grass, tulips, and corn

Dicots—all Petals dicots have: in groups of 4 or 5 Broad leaves with branched veins Vascular bundles of stem are in a ring Two cotyledons in seeds Examples: oak tree, roses, and beans

Monocot vs. Dicot Diagram

Angiosperm Reproduction Flowers are the reproductive organs of angiosperms. Parts of a flower: Petals—colored parts (usually): function to attract pollinators. Sepals—small and leaf-like (usually): function to protect the developing bud. Stamen—male part of the flower: produce pollen grains which contain sperm cells. Pistil—female part of the flower: top part is the stigma which catches pollen; bottom part is the ovary which produces ovules containing egg cells.

Flower Diagram Flowers missing one or more of these parts are known as imperfect. Flowers with all of these parts are known as perfect.

Pollination and Fertilization Pollen grains containing sperm cells are carried from stamens to stigma. (Pollination) A pollen tube grows from the pollen grain to the ovule. Sperm swim down the pollen tube and fertilize the egg cells. (Fertilization) Ovules develop into seeds and the ovary becomes the fruit.

Importance of Angiosperms are an important source of food for all life. All of our fruits and vegetables are angiosperms. Angiosperms stabilize the atmosphere by taking in huge amounts of carbon dioxide for photosynthesis and releasing oxygen. Other uses: clothing, medicines, rubber, oils, perfume, and pesticides.

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