The Nature of Life
Outline Attributes of Living Organisms Chemical and Physical Bases of Life Molecules Bonds and Ions Acids and Bases Elements in Cells Carbohydrates, Lipids, Proteins Enzymes Nucleic Acids
Composition and Structure All living things are made of cells. Cells - Structural units of organisms. Cytoplasm Interior souplike fluid, bound by thin cell membrane, outside of the nucleus. Nucleus - Contains genetic material (DNA). Cell Wall Outside of the cell membrane, provides support and rigidity.
Single-cell organisms have everything they need to be self-sufficient. In multicellular organisms, specialization increases until some cells do only certain things.
Growth Increase in mass accompanied by an increase in volume. Most growth results from production in new cells and includes variation in form. An organism gets larger as the number of its cells increases. Cell enlargement - the increase in size of a cell. Cells grow to a certain size and then divide.
Reproduction Reproduction is not essential for the survival of individual organisms, but must occur for a species to survive. All living things reproduce in one of the following ways: Asexual reproduction - Producing offspring without the use of gametes. Offspring genetically identical to parent. Sexual reproduction - Producing offspring by the joining of sex cells. Offspring genetically different from both parents.
Response to Stimuli Living things will make changes in response to a stimulus in their environment. Plants respond to stimuli such as light, temperature, and gravity. Callose and callus are two substances that may accumulate at wound sites in plant cells. Plants grow toward the sunlight. A behavior is a complex set of responses.
Metabolism Collective product of all biochemical reactions in an organism. Respiration - Energy release. Photosynthesis - Energy harnessing. Digestion - Large insoluble food molecules converted to smaller soluble molecules. Assimilation - Conversion of raw materials into cell substances. Living things take in energy and use it for maintenance and growth.
Movement Occurs at all levels of organization. Cytoplasmic streaming. Organization Complexity Molecules are organized into compartments, membranes, and other structures within cells and tissues. Environmental Adaptation Natural selection adapts organisms to their environment.
Movement Plants generally don t move from one place to another. This does not mean that plants don t move. Movement occurs at all levels of organization. Cytoplasmic streaming- movement of chloroplasts in cytoplasm. Leaves of mimosa plant closing when disturbed. Venus fly trap closing to trap insect.
Living things have different levels of organization. Both molecular and cellular organization. Living things must be able to organize simple substances into complex ones. Living things organize cells at several levels: Tissue - a group of cells that perform a common function. Organ - a group of tissues that perform a common function. Organ system - a group of organs that perform a common function. Organism - any complete living thing.
Attributes of Living Things Environmental Adaptation Natural selection adapts organisms to their environment. Adaptations are traits giving an organism an advantage in a certain environment Variation of individuals is important for a healthy species