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INTRODUCTION TO BIOLOGY How does life begin? • There were 2 theories: – Spontaneous generation – Biogenesis Spontaneous Generation • Process by which life begins when ethers enter nonliving things • Francesco Redi conducted an experiment to disprove this theory Redi’s Experiment • During Redi’s time maggots were • • • thought to come from rotting meat Redi placed meat in an open jar and maggots appeared on the meat Redi placed meat in a closed jar and no maggots appeared Critics of Redi suggested that the ethers could not enter the container which is why the maggots did not appear Redi’s Revised Experiment • Redi placed meat in a jar covered • with a mesh cloth to allow ethers to enter but nothing else Maggots did not appear on the meat Biogenesis • Principle that life comes only from life • After Francesco Redi disproved the theory of spontaneous generation, Louis Pasteur conducted an experiment to prove biogenesis Pasteur’s Experiment • Broth is placed in a flask with a • • • curved neck to prevent dust from entering the broth The broth is heated and after one year, the broth was still free of bacteria The curved neck is broken off so that dust can now enter the flask After one day, the broth was cloudy and filled with bacteria Characteristics of Life • Organization: living things are organized; the basic unit of organization is the cell • Energy: living things use sound, light and chemical energy; all living things take in energy from the environment and use it for their life processes • Growth and Development: – Growth is an increase in size – Development is a change in shape or form Characteristics of Life (cont.) • Reproduction: process by which new living things are formed • Response and Adaptation: – Response includes migration, movement, color changes, etc. – Adaptation is a way for an entire population of organisms to respond to long-term changes in their surroundings; these are passed on from generation to generation Levels of Organization Atom Molecule Cell Tissue Organ Organ System Organism Population Community Ecosystem Biosphere Population, Community, Ecosystem & Biosphere • Population: group of organisms of the same species that live together in a particular location • Community: include all organism populations in a particular location • Ecosystem: all the communities and the non-living parts in a particular location • Biosphere: thin layer of air, land and water on the surface of the earth