Biology: Concepts and Applications 10th Edition
Links to Earlier Concepts
Whether or not you have studied biology, you already have an intuitive understanding of life on Earth because you are part of it. Every one of your experiences with the natural world —from the warmth of the sun on your skin to the love of your pet—contributes to that understanding.
Interactions among the components of a biological system give rise to complex properties.
We can understand life by studying it at increasingly inclusive levels, starting with atoms that compose matter, and extending to the biosphere. Each level is a biological system composed of interacting parts. Interactions among the components of a system give rise to complex properties not found in any of the components. Interactions among organisms and their environment result in the movement of matter and energy.
Evolution underlies the unity and diversity of life.
Shared core processes and features that are widely distributed among organisms provide evidence that all living things are linked by lines of descent from common ancestors. All biological systems are sustained by the exchange of matter and energy; all store, retrieve, transmit, and respond to information essential for life.
The field of biology relies upon experimentation and the collection and analysis of scientific evidence.
Science addresses only testable ideas about observable events and processes. Observation, experimentation, quantitative analysis, and critical thinking are key aspects of research in biology. Carefully designed experiments that yield objective data help researchers unravel cause-and-effect relationships in complex biological systems.
Biologists study life. What, exactly, is “life”? We may never actually come up with a concise definition, because living things are too diverse, and they consist of the same basic com-ponents as nonliving things. When we try to define life, we end up with a long list of properties that differentiate living from nonliving things. These properties often emerge from the interactions of basic components. To understand how that works, take a look at the groups of squares in Figure 1.1. The property of “roundness” emerges when the component squares are organized one way, but not other ways. Another example is a complex behavior called swarming. When hon-eybees swarm, they fly en masse to establish a hive in a new location. Each bee is autonomous, but the new hive’s location is decided collectively based on an integration of signals from hivemates. The swarm’s collective intelligence is the emergent property in this example.
A characteristic of a system (a colony of bees swarming, for example) that does not appear in any of the system’s com-ponents (individual bees) is called an emergent property. The idea that structures or systems with emergent properties can be assembled from the same components is a recurring theme in our world—and also in biology.
Biologists view life as having nested levels of organization; interactions among the components of each level give rise to emergent properties (Figure 1.2). This organization begins with atoms. Atoms are the smallest units of a substance; they and the fundamental particles that compose them are the building blocks of all matter 1. Atoms bond together to form molecules 2. There are no atoms unique to living things, but there are unique molecules. A cell 3, which is the smallest unit of life, consists of many of these “molecules of life.”
Some cells live and reproduce independently. Others do so as part of a multicelled organism. An organism is an individual that consists of one or more cells 7. In most multicelled organisms, cells are organized as tissues 4. A tissue consists of specific types of cells in an arrangement that allows the cells to collectively perform some function—protection from injury (dermal tissue) or movement (muscle tissue), for example. An organ is a structure composed of tissues that collectively carry out a particular task or set of tasks 5. For example, a flower is an organ of reproduction in plants; a heart, an organ that pumps blood in animals. An organ system is a set of interacting organs and tissues that fulfill one or more body functions 6. Examples of organ systems include the aboveground parts of a plant (the shoot system), and the heart and blood vessels of an animal (the circulatory system).
Unique types of organisms—California poppies, for example —are called species. A population is a group of interbreeding individuals of the same species living in a given area. For example, all California poppies growing in Califor-nia’s Antelope Valley Poppy Reserve form a population 8. A community consists of all populations of all species in a given area. The Antelope Valley Reserve community includes California poppies and all other plants, as well as animals, microorganisms, and so on 9. Communities may be large or small, depending on the area defined. The next level of orga-nization is the ecosystem, which is a community interacting with its physical and chemical environment 0. Earth’s largest ecosystem is the biosphere, and it encompasses all regions of the planet’s crust, waters, and atmosphere in which organisms live a.
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