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1.1: Characteristics of Life

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Characteristics of Life

1.1: Characteristics of Life


Biology is the natural science that focuses on the study of life and living organisms, including their structure, function, development, interactions, evolution, distribution, and taxonomy. The scope of the field is extensive and is divided into several specialized disciplines, such as anatomy, physiology, ethology, genetics, and many more.

All living things share a few key traits: cellular organization, heritable genetic material and the ability to adapt/evolve, metabolism to regulate energy needs, the ability to interact with the environment, maintain homeostasis, reproduce, and the ability to grow and change.

The Complexity of Life

Despite its complexity, life is organized and structured. The cell theory in biology states that all living organisms are composed of one or more cells. The cell is the basic unit of life, and all cells arise from previously existing cells. Even single-celled organisms, such as bacteria, have structures that allow them to carry out essential functions, such as interacting with the environment and carry out chemical reactions that maintain life, or metabolism. In multicellular organisms, cells work together to form tissues, organs, organ systems, and finally, entire organisms. This hierarchical organization can extend further into populations, communities, ecosystems, and the biosphere.

Genetics and Adaptation

An organism’s genetic material, the biological “blueprints” encoded in their DNA, is passed down to their offspring. Over the course of several generations, the genetic material is shaped by the biotic (living) and abiotic (non-living) environment. This process is called adaptation. Offspring of well-adapted parents have a high likelihood to survive in conditions that are similar to those that their parents lived in.

The process in which inherited traits increase survival and reproduction is called natural selection. Natural selection is the central mechanism of evolution. For example, some kangaroo rats live in hot and dry areas with little rainfall. To avoid the blistering heat and conserve water, they burrow into the soil where it is cooler and lower their metabolic rate to slow down evaporation. In this way, the kangaroo rat’s genetics—encoding this behavior and passed down through generations—enables the animal to survive in such extreme environmental conditions.

Environmental Interactions

Organisms must also be able to successfully interact with their environment. This includes being able to navigate the world around them in search of resources or potential mates but also includes regulating their internal environments. Homeostasis is the ability of an organism to keep steady internal conditions. For example, humans maintain constant body temperature. If they get cold, they shiver; if they are too hot, they start to sweat. Living things also maintain metabolism—the chemical processes that regulate energy needs. For instance, plants convert sunlight into sugar and store chemical energy in adenosine triphosphate.

Building Upwards from Basic Tenets

While “What is biology?” and “What is life” may seem like basic questions, they are important to understand and are prerequisites to asking more complicated questions. For example, without understanding the basic tenets of life—such as how cells divide and replicate—it would be difficult to investigate what causes cancer. This knowledge also allows scientist to develop the required tools and methods to study biological processes.

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