Structure and Function in Living Systems

1. Structure and Function in Living Systems Chapter 8: Systems in Organisms 8.1: Systems help organisms meet their needs 8.2: Plants have several levels of organization 8.3 Animals have several levels of organization 8.4 Human health depends on a balance among systems

2. Plants have severallevels of organization • 1. Living organisms need only water and air to survive. • Living organisms need energy, materials, water, and air to survive. • 2. Plants and animals are multicellular organisms. • true • 3. If the muscles in the heart stop working, blood will continue moving through the blood vessels and circulatory system. • If the heart muscles stop working, the whole circulatory system will fail to function correctly.

3. Plants are a diverse group of organisms • Earth = amazing variety of plant life • Each is suited to its own environment • **All have in common… • multicellular organisms, their cells have cell walls, and they capture energy from sunlight in the process of photosynthesis • Examples: • cold and harsh tundra: • birch trees - shrubs that can be only a few centimeters tall • warm and rich central California: • giant sequoias grow 90 meters (about 300 ft) tall • dry climates: plants tend to have thick leaves and stems that conserve moisture • dense tropical rain forests: tall trees prevent sunlight from reaching the forest floor - orchids grow on the trunks of trees

4. Plants have three main types of tissue • Some plants, like mosses, are nonvascular • *We are most familiar with vascular plants • Specialized plant cells form three basic tissues in vascular plants • dermal tissue for protection and exchange • vascular tissue for support and transport • ground tissue for photosynthesis, storage, and support

5. Dermal Tissue • Covers a plant - like skin • Protects the underlying tissue from injury or drying out • Can be: • thin and flexible - a blade of grass, or • rigid and tough - the bark of trees • At the root ends, dermal tissue is only one cell thick • allows the roots to absorb water and nutrients from thesoil. • Dermal tissue is thicker in the stems and leaves

6. Dermal Tissue • Photosynthesis: • Through stomata – allow enough CO2 without drying plant out…to prevent this: • outermost layer of dermal cells on the leaves and stems may secrete a waxy coating • protects against water loss and repels bacteria and fungi • Stomata closing in dry weather • water vapor, oxygen,carbon dioxide • Salty environment: may have salt glands to get rid of excess salt

8. Vascular Tissue • Provide support and transport • specialized cells move water, nutrients, and the products of photosynthesis throughout the plant • Usually two types of long, tubelikecells: • xylem: transports water and dissolved nutrients from the roots up a stem to the leaves • like straws bundled together • Phloem: carries the energy-rich sugars and carbohydrates down a stem and to the roots

10. Ground Tissue • makes up the bulk of a plant • Found between vascular bundles and dermal tissue in all parts of the plant • three main functions: • contain most of the chloroplastsmost of the photosynthesis • Some cells are specialized for storing sugars and starches • found in stems, roots, fruits, and seeds • provides support for the plant

11. Plant tissues work together in systems • Most plants have three main organs—roots, stems, and leaves • make up two organ systems, the • root system and shoot system • Both are subsystems of the vascular system • Also have reproductive organs and a reproductive system

12. The Root System • Anchors plant • Exchange of materials with soil • Stores excess sugar (as starch) • Examples: • Beets, turnips, and carrots

13. The Shoot System • Stems and leaves • Structures for photosynthesis, support, storage, and the exchange of materials with the atmosphere • Stems: • provide support for plants above ground • Pathways of the vascular system • Some plants modify this for food storage • Potatoes, taro, yams, garlic, and onions • Leaves: the organs of photosynthesis • Most chloroplasts are found here (produce sugar)

14. System Failure • Trees: damage by • Natural: strong winds, lightning, ice storms, and heavy snow can break limbs…deer can strip bark • Construction • injure a tree’s trunk or roots • Healthy trees can repair small wounds • Weakened trees cannot • wound becomes an entry place for viruses, fungi, and insects • Houseplants: • Roots can outgrow their space • grow around and around into a tangled ball • can no longer absorb enough water for the plant, and the plant weakens

15. Plants have adapted to their environments – modified stems • Adaptations by species to their environments • Modified Stems • Ex: Desert plants, cactus: • Thick, leathery dermal tissue covering their stems – protective • resist the drying effects of sunlight and wind • stems are swollen with water • Roots vs stems: • stem has joints along its length, called nodes • shoots and buds can grow from these • root does not have these nodes

16. Plants have adapted to their environments – modified stems • Some stems are soft, and some are hard • Some plants (ex: trees and shrubs), have tough, thick stems that do not die each year • stems keep growing taller and thicker • develop a type of tough xylem tissue that is not found in soft stems • This tough tissue is called wood • Underground Stems: • Potatoes • have nodes, called eyes, from which new plants can grow • Iris: • underground stem called rhizomes • horizontal stems just below the surface of the ground • Onion bulbs - underground stem • the short, central part of the bulb is the stem • the layers of flesh around the stem are modified leaves

17. Plants have adapted to their environments – modified leaves • Some plants develop long, thin organs – tendrils • Usually modified leaves • Ex: peas, morning glories, tropical vines, grape vines, • grows out from the plant – when it touches a source of support, the tendril winds itself around it • helps the plant grow upward = more sunlight • The leaves of the cactus have become modified into spines, and the chloroplasts are in the stem • Spines do not dry out • protection

18. Plants have adapted to their environments – modified roots • Shallow, broad root system allows the plant to capture as much water as possible from a quick rain • Ex: Cactus • Some plants have roots that never reach the ground • adapted to being exposed to air - aerial roots • Ex: orchids grow on the trunks of the very tall trees in rain forests • High enough for photosynthesis • Tree trunk is support • Do not harm tree (commensalism) • Ex: mistletoe • roots that grow into the vascular tissue of tree branches to obtain water and nutrients • take nutrition from the trees - can harm their hosts (parasitic)

20. PLANTS HAVE SEVERAL LEVELS OF ORGANIZATION • Comparing StructuresDuring photosynthesis, plants capture energy from sunlight and convert it to chemical energy in the form of sugars. Plants often store extra sugars as starches. When the plant needs energy, the starches are broken down into sugars and energy is released. Many plant stems or roots, such as the examples shown below, are adaptations for storing sugar or starch.

21. Sugar cane is a commercially valuable crop plant that stores large amounts of sugar in its stems. Where does the sugar come from? • A sugar beet is a biennial plant. A biennial plant is a plant that takes two growing seasons to produce seeds. The flowers and seeds of biennial plants do not form until the second growing season. Explain an advantage that the storage root offers to sugar beets. • A potato forms sprouts that can become new plants. What is the energy source for the sprouts? • Plants living in extreme environments sometimes have unusual adaptations. For example, the desert cactus has a fleshy, green stem covered with spines instead of leaves. Suggest two purposes of the unusual cactus stem.

22. Sugar cane is a commercially valuable crop plant that stores large amounts of sugar in its stems. Where does the sugar come from? • A sugar beet is a biennial plant. A biennial plant is a plant that takes two growing seasons to produce seeds. The flowers and seeds of biennial plants do not form until the second growing season. Explain an advantage that the storage root offers to sugar beets. • A potato forms sprouts that can become new plants. What is the energy source for the sprouts? • Plants living in extreme environments sometimes have unusual adaptations. For example, the desert cactus has a fleshy, green stem covered with spines instead of leaves. Suggest two purposes of the unusual cactus stem. • The sugar is produced during photosynthesis. • The plant will use the stored sugars in the root as an energy source for producing flowers and seeds during the second growing season. • The starch stored in the potato will provide energy for the growing sprouts. • The cactus stem captures sunlight and performs photosynthesis. The cactus stem also stores a large amount of water.