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. Systems help organismsmeet their needs • Groups of people working at the restaurant are each doing something different in order to produce and serve the meals. • In a complicated process like this one, it helps to have different people doing different tasks at the same time. If everyone made salads, for example, how do you think the process would fail?

3. Living things have common needs • All organisms require: • Energy • Water and other materials • Living space • Plants use energy in sunlight, live where they can receive enough sunlight…and survive • Animals live where they can find protection and materials • Organisms are found everywhere, and have structures that allow them to use energy and materials and to find living space • Single celled organisms have structures to grow, respond to environment, and reproduce • Multicellular organism have structures as well, but made of specialized cells

4. Multicellular organisms have organ systems • As plants and animals develop, their cells specialize (differentiate) • Same cell type = same job • Different cell type = different job

6. Levels of Organization • Cells • animals: skin cells, nerve cells, and muscle cells • Tissue • Group of many similar cells • Work together to perform a particular function • Skin tissue: provide protection • Nerve tissue: carries signals • Muscle tissue: provides movement

7. Levels of Organization • Organ • Two or more types of tissue that work together to carry out a function • Brain • Lungs • Heart: muscle tissue contracts at a signal from nerve tissue • Pumps blood to lungs and body • Organ system • Group of organs working together to perform a function • Circulatory system: heart pumps blood through blood vessels • Blood transports nutrients to rest of body, carries back wastes • Cells  tissues  organs  organ systems  _____________

8. How an Organ System Works • Circulatory system: heart pumps blood that vessels carry • Failure of one can cause failure of the whole • Digestive system: breaks down food to release nutrients • Food travels through mouth, esophagus, stomach, small intestine, and large intestine • Pancreas, liver, and gall bladder, release chemicals • Smooth operation: food chewed, mixed with saliva  strong stomach muscles mix some more, chemicals break down food  small intestine, nutrients are absorbed, passed to blood  large intestine, water and other nutrients are absorbed  waste material compacted and moved through… • Failures: • Acids in stomach may back up • Large intestine causing pain, fever, nausea, vomiting • malnutrition

9. How an Organ System Works

10. Organs and systems respond to changes in conditions • …to help organisms meet their needs • Examples: • Plant Responses to Stimuli • Animal Responses to Stimuli • Stimulus: something that causes a response from an organism

11. Plant Responses to Stimuli • Plants grow and move in response to: • Ex: light, gravity, moisture, temperature, and touch • Leaves are the organs that hold the chloroplasts in position to capture sunlight • Many plants move their leaves during the day in response to changes in light • Broad flat leaves presented to sun early and late in the day, vertical at mid-day to prevent over-heating damage • leaf movements are caused by changes in the cells of the joint where the leaf meets the stem Figure 1. Cross-section through a typical leaf illustrating types of cells and also the intracellular organelles called chloroplasts, where photosynthesis takes place. The cuticle is a waxy coating, layers of cells (epidermis, palisade and spongy mesophyll) and vascular bundles (xylem and phloem, which are specialized cells) that transport water and nutrient solution. The stoma (plural: stomata) is a pore that allows the entry of air and therefore CO2 into the leaf (image source: Oregon State, botany)

12. Plant Responses to Stimuli • Stems are the organ that supports a plant • Plants “bend to the light” • A hormone, or chemical messenger, called auxin is produced in the growing tip of the stem • Auxin flows down the dark side of the stem, collects in the cells causing them to grow faster than the light side

13. Phototropism 1 Phototropism 2

14. Plant Responses to Stimuli • Venus flytrap • grows in areas where the soil lacks materials that the plant needs • Get important nutrients from insects • relies on the stimulus of touch • leaves of the Venus flytrap fold in the middle, have long teethlike spines around the edges • Insect lands, two sides of the leaf fold together, form a trap

15. Animal Responses to Stimuli • New environment or a change of season • Some frogs, fish, and octopi are able to change the color and patterns of their skin to blend in with new surroundings • An adaptation to hide from predators and their prey! • Chameleons change color in response to mood, temperature, and light (not usually to a change in environment) • can communicate anger or willingness to mate • Due to several layers of specialized cells in the skin of these organisms Chamelon 1 more info

16. Animal Responses to Stimuli • Hibernation - a sleeplike state that lasts for an extended time period • Body systems slow down • the animal needs less energy to survive. • raccoons, skunks, woodchucks, chipmunks, hamsters, hedgehogs, bats, and bears • Bears: • Before hibernation, eat rich foods – put on weight – curl into ball • Heartbeat slows from 40-50 bpm to 8 • Metabolism (chemical reactions in their cells and organs) slows • Require less oxygen • Up to 100 days hibernation

18. Without a nucleus, a red blood cell cannot store DNA or direct cellular activities. Without mitochondria, a red blood cell cannot release the chemical energy stored in sugars. Explain why both of these consequences are acceptable for cells in a multicellularorganism such as humans, but would be fatal for a Paramecium. • Explain why specialized cells, such as red blood cells, are a necessary characteristic of multicellular organisms.

19. Without a nucleus, a red blood cell cannot store DNA or direct cellular activities. Without mitochondria, a red blood cell cannot release the chemical energy stored in sugars. Explain why both of these consequences are acceptable for cells in a multicellular organism such as humans, but would be fatal for a Paramecium. • Explain why specialized cells, such as red blood cells, are a necessary characteristic of multicellular organisms. • Multicellularorganisms continually make new red blood cells to replace old red blood cells as they die. A Paramecium, however, is a single-celled organism that would not be able to survive and reproduce without a nucleus or mitochondria. • Because multicellular organisms are large, many of their cells are far away from one another or from the outside of the organism where oxygen can be obtained and wastes such as carbon dioxide can be released. Therefore, multicellularorganisms must have specialized cells to efficiently perform the tasks necessary for survival and reproduction.