INTRODUCTION TO BIOLOGY How does life begin There

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 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 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 water on the surface of the earth