PLANTS plants Chapters 23, 24, 25 and 26
the purpose of this chapter is to recognize the importance and diversity of the plant kingdom. In the many plant species alive on Earth today, you can find evidence of the adaptations that allowed plants to first colonize land, then diversify and flourish.
You will learn the common characteristics of all plants, as well as the unique characteristics of different groups of plants. Some of these characteristics make plants extremely important to humans.
Plant structure and function video • http://www.youtube.com/watch?v=-MCd4okcHXs&feature=youtube_gdata_player
Key Terms • cuticle • guard cell • nonvascular plant • stoma • vascular plant • seed • embryo • flower • phloem • xylem • root • meristem • transpiration (560) • translocation (564) • germination (572) • perennial (573) • annual (573) • biennial (573)Section 2 • auxin (580) • tropism (582)
Establishment of Plants on Land • Plants are the dominant group of organisms on land, based on weight. The kingdom Plantae is a very diverse group. Individuals range from less than 2 mm across to more than 100 m tall. Most plants are photosynthetic; they produce organic materials from inorganic materials by photosynthesis.
Plants probably evolved from multicellular aquatic green algae that could not survive on land.
Before plants could thrive on land, they had to be able to do three things: • absorb nutrients from their surroundings, • prevent their bodies from drying out, and • reproduce without water to transmit sperm
Absorbing Nutrients • Aquatic algae and plants take nutrients from the water around them. On land, most plants take nutrients from the soil with their roots. Although the first plants had no roots, fossils show that fungi lived on or within the underground parts of many early plants. Symbiotic relationships between fungi and the roots of plants are called mycorrhizae.
Preventing Water Loss • A watertight covering called the cuticle, which reduces water loss, made it possible for plants to live in drier habitats. • Pores called stomata permit plants to exchange oxygen and carbon dioxide.
Reproducing on Land • Aquatic algae reproduce sexually when sperm swim through the water and fertilize eggs. The structures that contain sperm make up pollen. Pollen permits the sperm of most plants to be carried by wind or animals rather than by water
Advantages of Conducting Tissue • The first plants were small allowing materials to be transported by osmosis and diffusion. Today, most plants have strands of specialized cells that transport materials. Some strands carry water and mineral nutrients from the roots to the leaves. These are called xylem. Other strands called phloem carry organic nutrients from the leaves to wherever they are needed.
Specialized cells that transport water and other materials within a plant are found in vascular tissues. The existence of vascular tissue allowed for larger and more-complex plants. The larger, more complex plants have a vascular system,a system of well-developed vascular tissues that distribute materials more efficiently. Three groups of plants alive today lack a vascular system. These relatively small plants that have no vascular system are called nonvascular plants. Plants that have a vascular system are called vascular plants.
All nonvascular plants lack true roots, stems, and leaves, although most have structures that resemble them.
Moss • Draw a sample of moss on 40X
Nonvascular plants Some key adaptations that have enabled them to survive on land are: 1. Water and other nutrients are transported within their bodies mostly by osmosis and diffusion, which move materials short distances. This greatly limits the size of a nonvascular plant’s body. 2. The gametophytes of nonvascular plants are larger and more noticeable than the sporophytes. 3. Nonvascular plants must be covered by a film of water in order for fertilization to occur.
The nonvascular plants include the mosses and the two simplest groups of plants—liverworts and hornworts
Seedless vascular plantsPteridophytes Seedless vascular plants are much larger and more complex than the nonvascular plants. Other key features enabled them to spread and adapt to drier habitats on land. The seedless vascular plants include ferns and three other groups of plants known as fern allies—whisk ferns, club mosses, and horsetails.
Draw a fern frond • Front and back of the frond under 40X
Life cycle of a typical fern: • A sporophyte (diploid) phase produces haploidspores by meiosis. • A spore grows by mitosis into a gametophyte, which typically consists of a photosynthetic prothallus. • The gametophyte produces gametes (often both sperm and eggs on the same prothallus) by mitosis. • A mobile, flagellate sperm fertilizes an egg that remains attached to the prothallus. • The fertilized egg is now a diploid zygote and grows by mitosis into a sporophyte (the typical "fern" plant).
Gymnosperms Gymnosperms are seed plants whose seeds do not develop within a sealed container (a fruit). The word gymnosperm comes from the Greek words gymnos, meaning “naked,” and sperma, meaning “seed.”
Gymnosperms are among the most successful groups of plants. All gymnosperms produce seeds. In all but one species of gymnosperm, male and female gametophytes develop in male and female cones. Wind pollination makes sexual reproduction possible even when conditions are very dry.
Four groups of living seed plants are referred to as gymnosperms—conifers, cycads, ginkgo, and gnetophytes
Angiosperms • Flowering plants that produce seeds and develop enclosed within aspecialized structure called a fruit. The word angiosperm comes from the Greek words angeion, meaning “case,”and sperma, meaning “seed.” • Adaptations include: flowers, which promote pollination and fertilization more efficiently than do cones.
Advantages of Seeds • A seed is a structure that contains the embryo of a plant. Most plants living today are seed plants—vascularplants thatproduce seeds. The first seed plants appeared about 380 million years ago. Seeds offer a plant’s offspring several survival advantages
1. Protection.Seeds are surrounded by a protective cover called the seed coat. The seed coat protects the embryo from drying out and from mechanical injury and disease. • 2. Nourishment.Most kinds of seeds have a supply of nutrients stored in them. These nutrients are a ready source of nourishment for a plant embryo as it starts to grow. • 3. Plant dispersal.Seeds disperse (spread) the offspring of seed plants. Many seeds have structures that help wind, water, or animals carry them away from their parent plant. Dispersal prevents competition for water, nutrients, light, and living space between parents and offspring. • 4. Delayed growth.The embryo in a seed is in a state of suspended animation. Most seeds will not sprout until conditions are favorable, such as when moisture is present and the weather is warm. Thus, seeds make it possible for plant embryos to survive through unfavorable periods such as droughts or cold winters.
Seed structure • A seed forms from an ovule after the egg within it has been fertilized. • The seeds of angiosperms develop a nutritious tissue called endosperm. • Leaflike structures called Cotyledons, or seed leaves, are a part of a plant embryo.
Bean seed Germination 1. Observe a bean that is dry. Draw it true size. Measure its mass, length and width. 2. Soak several beans in water over night. Observe a bean and draw it true size. Compare it to the dry bean. Measure its mass, length and width after soaking. • Peal off the seed coat and open the bean. Look at it under the dissecting scope. Draw a diagram of it on 20X power. What happened to the bean after soaking it in water?
3. Roll the beans in paper toweling that is moist. Place this in a cup and cover it with a plastic bag. Let the beans germinate for several days. Draw a true size diagram of a bean on day 5 of the germination process. Label the parts using the diagram in the book on page 572.
4. Select one part to observe under the dissecting scope. Look at it and draw a diagram. Make sure to label the power and label what part of the bean you selected to draw. Put the beans back in paper toweling and let then continue to grow for another 2 days
5. Remove a bean and draw it true size. This will be around day 7. Replace the remaining beans in the paper toweling to continue to grow. • 6. Write a description of the process that the beans have been going through from day one. Use the book to help you use the proper terminology for the germination of a bean seed.
7. Plant the remaining sprouts in the cup with soil. Place them in an area where they will receive light. • 8. How could you do an experiment to show phototropism? • 9. Using a clear cup, you can see the roots growth. What can be observed about the direction of the root’s growth? What type of tropism is this called?
Day 1: true size.2 pts Day 1: measurements: mass 1pt, length and width 2pts Day 2: true size 2 pts Day 2: what happened to the bean? 1pt Day 2: measurements: mass 1pt, length and width 2pts Day 2: Draw a diagram of it on 20X power. 2 pts Day 5: Draw a true size diagram2 pts Day 5: draw a diagram of one partunder the dissecting scope2 pts Day 7: draw it true size 2 pts Write a description of the process 4pts How could you do an experiment to show phototropism? 2 pts What can be observed about the direction of the root’s growth? 1pt What type of tropism is this called? 1pt
Advantages of Flowers • The flower isa reproductive structure that produces pollen and seeds. Most plants living today are flowering plants—seed plants that produce flowers. The first flowering plants appeared more than 130 million years ago.
Flower parts In angiosperms, gametophytes develop within flowers. Flower parts are arranged in four concentric whorls. The outermost whorl consists of one or more sepals, which protect a flower from damage while it is a bud.