Chapter 1, Introduction

Chapter 1, Introduction - Case Study: LIFE ON EARTH - AND...

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Case Study: LIFE ON EARTH --- AND ELSEWHERE? Extremophiles (“Survivalist microbes”): single-celled organisms that inhabit the most inhospitable environments on Earth – hydrothermal vents on the ocean floor, 1200 feet below an Antarctic lake frozen for thousands of years, the highly acid environments of mining wastes and hot springs, and rock layers 4 miles below the Earth’s surface. They represent the potential for life on other planets. Section 1.1, pp. 2-3 HOW DO SCIENTISTS STUDY LIFE? Levels of Organization Atom (element), molecule, cell, tissues, organ, organ system, (Multicelled) organism, species, population, community, ecosystem, biosphere Organic molecules contain carbon and hydrogen, to which other atoms may be attached. All life has an organic chemical basis. The quality of “life” emerges at the cellular level . The majority of life on Earth is single- celled. Multicelled organisms are individual living things composed of many cells. Organisms of the same type that are capable of interbreeding are the same species . A population is made of members of one species inhabiting the same area. A community is comprised of two or more different species living and interacting in the same area. An ecosystem includes all the organisms and their nonliving environment in a given area. The biosphere includes all the areas on Earth in which living things are found. Section 1.2, pp. 9-10 EVOLUTION: THE UNIFYING THEORY IN BIOLOGY Three Natural Processes Underlie Evolution Evolution : modern organisms descended (with modification) from pre-existing life forms. 1) Genetic variation in members of a population results from differences in DNA. 2) Inheritance of different forms of DNA produces variations in offspring. 3) Natural selection acts on inherited variations that help some organisms reproduce more successfully than those without the inherited trait. The hereditary information in all known forms of life is contained in DNA. Genes are segments of DNA which direct formation of crucial molecular components of an organism. Genes are contained on chromosomes of each living cell. DNA is passed to offspring during reproduction.
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This note was uploaded on 10/14/2011 for the course BIO 1421 taught by Professor Farr during the Spring '08 term at Texas State.

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Chapter 1, Introduction - Case Study: LIFE ON EARTH - AND...

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