Living organisms interact with one another

Biology Is Studied at Many Levels of Organization Life’s properties emerge when DNA and other molecules are organized in cells. Energy flows through all the biological levels shown here

1.6 Biology Is Studied at Many Levels of OrganizationLife’s properties emerge when DNA and other molecules are
organized in cells. Energy flows through all the biological levels shown here

The internal hierarchy of the individual organism is matched by the external hierarchy of the biological world (Figure 1.6). Organisms do not live in isolation. A group of individuals of the same species that interact with one another is a population, and populations of all the species that live and interact in the same area are called a community. Communities together with their abiotic environment constitute an ecosystem. Individuals in a population interact in many different ways. Animals eat plants and other animals (usually members of another species) and compete with other species for food and other resources. Some animals will prevent other individuals of their own species from exploiting a resource, whether it be food, nesting sites, or mates. Animals may also cooperate with members of their species, forming social units such as a termite colony or a flock of birds. Such interactions have resulted in the evolution of social behaviors such as communication. Plants also interact with their external environment, which includes other plants, animals, and microorganisms. All terrestrial plants depend on complex partnerships with fungi, bacteria, and animals. Some of these partnerships are necessary to obtain nutrients, some to produce fertile seeds, and still others to disperse seeds. Plants compete with each other for light and water, and they have ongoing evolutionary interactions with the animals that eat them, evolving anti-predation adaptations or ways to attract the animals that assist in their reproduction. The interactions of populations of different plant and animal species in a community are major evolutionary forces that produce specialized adaptations. Communities interacting over a broad geographic area with distinguishing physical features form ecosystems; examples might include an Arctic tundra, a coral reef, or a tropical rainforest.

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Cells use nutrients to supply energy and to build new structures

1.5 Energy Can Be Used Immediately or Stored (A) Animal cells break down and release the energy contained in the chemical bonds of food molecules to do mechanical work—in this kangaroo’s case, to jump. (B) The cells of this Arctic ground squirrel have broken down the complex carbohydrates in plants and converted their molecules into fats, which are stored in the animal’s body to provide an energy supply for the cold months. Cells use nutrients to supply energy and to build new structures Living organisms acquire nutrients from the environment. Nutrients supply the organism with energy and raw materials for carrying out biochemical reactions. Life depends on thousands of biochemical reactions that occur inside cells. Some of these reactions break down nutrient molecules into smaller chemical units, and in the process some of the energy contained in the chemical bonds of the nutrients is captured by high-energy molecules that can be used to do different kinds of cel...

Why are frogs croaking?

A mphibians—frogs, toads, and salamanders—have been around for a long time. They watched the dinosaurs come and go. But today amphibian populations around the world are in dramatic decline, with more than a third of the world’s amphibian species threatened with extinction. Why? Biologists work to answer this question by making observations and doing experiments. A number of factors may be involved, and one possible cause may be the effects of agricultural pesticides and herbicides. Several studies have shown that many of these chemicals tested at realistic concentrations do not kill amphibians. But Tyrone Hayes, a biologist at the University of California at Berkeley, probed deeper. Hayes fo cused on atrazine, the most widely used herbicide in the world and a common contaminant in fresh water. More than 70 million pounds of atrazine are applied to farmland in the United States every year, and it is used in at least 20 countries. Atrazine is usually applied in the spring, w...

What is Biology?

blue dragonfly Biology is the scientific study of living things. Biologists define “living things” as all the diverse organisms descended from a single-celled ancestor that evolved almost 4 billion years ago.Because of their common ancestry, living organisms share many characteristics that are not found in the nonliving world. Living organisms: • consist of one or more cells • contain genetic information • use genetic information to reproduce themselves • are genetically related and have evolved • can convert molecules obtained from their environment into new biological molecules • can extract energy from the environment and use it to do biological work • can regulate their internal environment This simple list, however, belies the incredible complexity and diversity of life. Some forms of life may not display all of these characteristics all of the time. For example, the seed of a desert plant may go for many years without extracti...

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