Being Alive
Biology is the study of life, so let's take a simpleminded look at what we mean by being alive before we get into the complexities. It is generally accepted that a rabbit and a plant are alive while a rock isn't, so a comparison may be useful.
Movement: Color the rabbit (A), the plant (B), and the rock (C) in the center of the diagram. Color the heading Movement gray, and color the related structures in that section. Use green for the plant and any colors that seem appropriate for the rabbit and the rock. (Yellow should be reserved for the sun.)
We need only to see a rabbit run across a field to be convinced that it is alive. If we saw a rock run across a field, we would be amazed. We might even exclaim, "Good grief, its alive!" So one obvious feature of being alive is movement. We wouldn't expect a plant to run across a field, but careful observation does disclose slow movement, as when flowers open or close or leaves turn to follow the movement of the sun.
Organization: Color the heading, titles D, E, and F, and their related structures. It is a tradition among biologists to use red for arteries and blue for veins. The heart can be a reddish brown.
Another feature of being alive is a very high level of organization. If we look closely at a rock, we can see a certain amount of organization; any particular kind of rock will be composed of the same minerals in the same proportions as other rocks of that kind. But the way they are arranged is very different from one rock to the next. Any rabbit, however, has a structure virtually identical to that of any other rabbit. Each one has its heart, veins, arteries, and other organs in almost exactly the same places. Plants, too, have their organs: leaves, stems, roots, and flowers, although there is more variation in their arrangement. Closer examination shows that each of these organs is made up of several different tissue. These tissues are made of tiny units called cells, and the cells, although they are microscopic in size, have their own highly organized internal structure.
Homeostasis: Color the heading and section.
Another feature of living things is the tendency to maintain constant conditions inside the body. This tendency is called homeostasis, which means “remaining the same.” In very hot weather the rabbit keeps its ears erect and spread out to radiate away the maximum amount of heat, while in cool weather the ears are kept closer to the body to conserve heat. Plants do not regulate their temperature much, but in very hot, dry weather the guard cells close the numerous holes (stomata) in the leaves to reduce the evaporation of water, some plants can change the angle of the leaves to change the amount of direct sunlight the receive.
Energy Utilization: Color the heading, title G, and the related structures in the section. Color the sun yellow.
The sun shines on a rock, the rock will absorb a little bit of heat energy, but it doesn't do anything with it. A plant will absorb some heat energy too, but it will also absorb much of the light energy falling on it and will convert it into the chemical energy of carbohydrates, proteins, and fats, which can be used to keep the plant alive and make more leaves, stems, and roots. The rabbit will eat parts of the plant and use that energy to keep itself alive and to run, grow new fur, and do other jobs.
Reproduction: Color the heading and the related section, including titles A1, B1, and B2. Color the seed (B1) and the seedlings (B2) green. Color the juvenile rabbits (A1) the rabbit color.
Reproduction is so characteristic of living things that it hardly needs comment. We are not surprised when two rabbits produce baby rabbits or when plants produce seeds that grow into more plants. If two of our favorite rocks produced baby rocks, however, we would be very surprised.
Growth and development. Color the heading and section, including titles and structures A2, A3, and B3.
Although some living things consist of only a single cell that reproduces by dividing in half, there is always a period of growth sooner or later. In animals and plants, which consist of numbers of cells, growth from a fertilized egg cell (called an ovum in animals and an ovule in plants), is accompanied by a process of development. During this process, cells not only increase in number but also change themselves into different kinds of cells and form the various tissues and organs that make up the new individual.
1. What color do biologists traditionally use when coloring arteries?
2. What color do biologists traditionally use when coloring veins?
3. What are tissues made out of?
4. Define homeostasis.
5. What living things can change sunlight into chemical energy?