Structure and Function in

Living Systems

Chapter 8: Systems in Organisms

8.1: Systems help organisms meet their needs8.2: Plants have several levels of organization

8.3 Animals have several levels of organization8.4 Human health depends on a balance among systems

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?

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

Multicellular organisms have organ systems

As plants and animals develop, their cells specialize (differentiate) Same cell type = same job Different cell type = different job

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

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 _____________

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

How an Organ System Works

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

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)

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

Phototropism 1Phototropism 2

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

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 organismsChamelon 1

more info

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

1. 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.

2. Explain why specialized cells, such as red blood cells, are a necessary characteristic of multicellular organisms.

1. Multicellular organisms 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.

2. 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, multicellular organisms must have specialized cells to efficiently perform the tasks necessary for survival and reproduction.

1. 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.

2. Explain why specialized cells, such as red blood cells, are a necessary characteristic of multicellular organisms.