Biology: Semester I

Sections:

Introduction | Section 1 | Section 2

Section One:

Part 1 | Part 2 | Part 3 | Part 4 | Part 5

Biology: The Nature of Science and Biology: Part Four Characteristics of Life Life is characterized by the presence of all seven of the following properties at some stage in an organism’s life. Cellular structure and function Reproduction Metabolism Homeostasis Heredity Adaptation and Evolution Interdependence Cellular Structure and Function All living things are made up of one or more cells. Some organisms are single-celled (described by the term unicellular), while others are multicellular (composed of many cells). Cells are the smallest units capable of all life functions. Reproduction Because nothing lives forever, reproduction is an essential part of living. All living things are able to reproduce either by making copies of itself or by having offspring. We can look at reproduction as the making of new cells or as the making of completely new organisms. New cells are created from existing cells. New multicellular organisms come from a parent or parents. Asexual reproduction produces offspring identical to a parent. Sexual reproduction produces offspring from two parents that have traits of both, but are not identical to either. Most multicellular organisms reproduce sexually. Metabolism All living things need energy to survive. Organisms use energy gained from their environment to grow, repair damage, and reproduce. Most self-feeders, known as autotrophs, get their energy from the sun through photosynthesis. Other-feeders, known as heterotrophs, eat other organisms to get the energy they need. All organisms carry out a series of building-up and breaking-down processes that store and release energy. Are humans autotrophic or heterotrophic? Heterotrophic Homeostasis Organisms take in the materials they need from the environment around them. Metabolism creates waste and the waste must be removed from the cells. This happens through a process of homeostasis. Heredity Living things have a way to pass traits along to their offspring. Most living things use the chemical DNA (deoxyribonucleic acid) to carry this genetic information. In a way, DNA is the instruction book for how an organism lives. Adaptation and Evolution Changes in the environment require adaptations by the organism. The change of inherited characteristics within a species over time is referred to as evolution. Favorable variations have spread through populations, with the best adapted individuals typically reproducing and passing their favored traits onto the next generation. Interdependence Living things interact with each other in a process known as symbiosis. They also interact with their environment. Discussion: Unifying Themes, 20 points Previously, you were asked to take a moment to write down on a sheet of paper your own list of the characteristics of life, and to keep it available to compare our list to your own list. Were there any characteristics that you did not originally have on your list? Were there any you had that we did not? Compare what you wrote with that of the other students in your class. Please post your response to the Unifying Themes discussion link, and respond thoughtfully to the posts of other students. For information on how this assignment will be graded, please visit the orientation. Return to the Section menu by using the Breadcrumb Trail at the top of the page (above the blue line) and clicking the link titled N-Discussion: Unifying Themes. In the menu, move to the Discussion Board. (Note: You can also get to the Discussion Board by using the link in the course sidebar menu on the left.) Vocabulary Practice  Click on the button labeled “New Word.”  Type out your definition in the box labed "Your Definition".  Check your answer by clicking ”Show Definition.” Vocab Word Your Definition Definition Now go on to the next part.

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