I. Exploring Life A. Biologists explore life from the microscopic to global scale 1. A Hierarchy of Biological Organization i. The Biosphere consists of all the environments on Earth that are inhabited by life ii. Ecosystems consists of all living things in a particular area, along with all the nonliving components of the environment with which life interacts, such as soil, water, atmospheric gases, and light. All earth’s ecosystems make up the biosphere iii. Communities are the entire array of organisms inhabiting a particular ecosystem iv. Populations consist of all the individuals of a species living within the bounds of a specified area v. Organisms are individual living things vi. Organs are body parts that consists of one or more tissues Organ systems are a “team” of organs that cooperate to perform a specific function vii. Tissues are groups of similar cells viii. Cells are life’s fundamental unit of structure and function ix. Organelles are the various functional components that make up cells x. Molecules are chemical structures that consist of two or more small chemical units called atoms 2. A Closer Look at Ecosystems i. Each organism interacts continuously with its environment, which includes other organisms, as well as nonliving factors ii. Ecosystem Dynamics include two major processes, one is the cycling of nutrients, and the other is the flow of energy from sunlight to producers to consumers iii. Producers are plants and other photosynthetic organisms that convert light energy to chemical energy iv. Consumers are organisms, such as animals, that feed on producers and other consumers v. Energy Conversion is the transformation of one form of energy to another 3. A Closer Look at Cells i. In life’s structural hierarchy, the cell has a special place as the lowest level of organization that can perform all activities required for life ii. Within cells there are structures called chromosomes, which are partly made up of a substance called deoxyribonucleic acid (DNA) iii. DNA is the substance of genes, the units of inheritance that transmit information from parents to offspring. iv. Each chromosome has one very long DNA molecule, with hundreds or thousands of genes arranged along its length v. The DNA of chromosomes replicates as a cell prepares to divide; thus, each of the two cellular offspring inherits a complete set of genes vi. In each cell, the genes along the length of DNA molecules encode the info for building the cell’s other molecules vii. In this way, the DNA directs the development and maintenance of the entire organism viii. Each DNA molecule is made up of two long chains arranged into what is called a double helix ix. Each link of a chain is one of four kinds of chemical building blocks called nucleotides x. The entire “library” of genetic instructions that an organism inherits is called a genome xi. Every cell is enclosed by a membrane that regulates the passage of materials between the cell and its surroundings, and every cell uses DNA as its genetic info xii. The cells of two groups of microorganisms called bacteria and archaea are prokaryotic, all other forms of life, including plants and animals, are composed of eukaryotic cells xiii. A eukaryotic cell is subdivided by internal membranes into various membrane-enclosed organelles, including chloroplasts xiv. In most eukaryotic cells, the largest organelle is the nucleus, which contains the cell’s DNA xv. The other organelles are located in the cytoplasm, the entire region between the nucleus and outer membrane of the cell xvi. Prokaryotic cells are much simpler and generally smaller than eukaryotic cells xvii. In a prokaryotic cell, the DNA is not separated from the rest of the cell, they also lack the other kinds of membrane-enclosed organelles that characterize eukaryotic cells B. Biological systems are much more
