Chapter 1

1. Chapter 1 An Introduction to Life on Earth

2. 1.1 Why Study Biology? • Biology helps you understand your _____________. • Biology helps you become an _____________ ____________. • Biology can open ____________ opportunities. • Biology can enrich your appreciation of the ___________.

3. 1.2 How Do Biologists Study Life? • THE SCIENTIFIC METHOD • 1) • 2) • 3) • 4) • 5) • 6)

4. 1.2 How Do Biologists Study Life? Observation Question Hypothesis Prediction Experiment or Observation Hypothesis supported: make more predictions Hypothesis not supported: pose new hypothesis Conclusion Fig. 1-2

5. 1.2 How Do Biologists Study Life? • The scientific method in everyday life Observation Question Hypothesis Prediction Experiment or Observation Conclusion Fig. 1-3

6. Observation: Flies swarm around meat left in the open; maggots appear on the meat. Question: Why do maggots appear on the meat? Hypothesis: Flies produce the maggots. Prediction: If flies are kept away from the meat, then no maggots will appear. Experiment Obtain identical pieces of meat and two identical jars Place meat in each jar Experimental variable: gauze prevents entry of flies Cover jar with gauze Leave jar uncovered Leave covered for several days Leave exposed for several days Controlled variables: time, temperature, place Flies swarm around and maggots appear Flies kept from meat; no maggots appear Results Experimental situation Control situation Conclusion: Spontaneous generation of maggots from meat does not occur; flies are probably the source of maggots. Fig. E1-1

7. 1.2 How Do Biologists Study Life? • *A well-designed experiment tests a single variable and controls all other variables.* • Question: Have all other variables been eliminated? • Example: loose battery cables • Example: broken electrical wires • Solution: Control for other variables • Make sure cables are tight. • Make sure electrical wires are in good condition. • A _________ ________ is a general explanation of natural phenomena supported by extensive, reproducible tests and observations.

8. 1.2 How Do Biologists Study Life? • LIFE CAN BE STUDIED AT DIFFERENT LEVELS OF ORGANIZATION cell nerve cell tissue nervous tissue organ brain organism pronghorn antelope population herd of pronghorn antelope community snakes, antelope, hawks, bushes, grass Fig. 1-5

9. 1.2 How Do Biologists Study Life? • SCIENCE IS A HUMAN ENDEAVOR • Scientists are real people and sometimes make mistakes. • One of the greatest medical advances in history was made by mistake, by Alexander Fleming. • The mold _______________, which kills bacteria, was discovered by chance by Fleming. • This led to the discovery of penicillin, an important antibiotic that has saved millionsof lives.

10. 1.2 How Do Biologists Study Life? • Penicillin kills bacteria. A petri dish contains solid growth medium Bacteria grow in a pattern created by streaking A substance from the mold diffuses outward and inhibits the growth of nearby bacteria A colony of the mold Penicillium Fig. 1-7

11. 1.3 What Is Life? • LIVING THINGS ARE BOTH ____________ AND ________________ Fig. 1-8

12. 1.3 What Is Life? • LIVING THINGS CAN __________ AND ______________ • LIVING THINGS RESPOND TO ___________ • Light, Sound, Chemicals, Hunger, Pain, Touch, Heat, Cold, Motion, Gravity Fig. 1-9

13. 1.3 What Is Life? • LIVING THINGS ACQUIRE AND USE _______________ AND ______________ Fig. 1-10

14. 1.3 What Is Life? • LIVING THINGS USE _______ TO STORE INFORMATION • Each segment of DNA that contains a set of instructions is called a ______. • ___________: offspring inheriting their parents’ characteristics/genes. Fig. 1-11

15. 1.4 Why Is Life So Diverse? • DNA: THE UNIVERSAL MOLECULE OF LIFE • DNA is found in the bodies of all organisms • Its universal presence suggests that all organisms have descended from a common ancestor having the same molecule. • DNA is passed from generation to generation during periods of reproduction. • Organism diversity results from small changes in DNA over billions of years of evolution.

16. 1.4 Why Is Life So Diverse? • LIFE’S UNITY AND DIVERSITY ARE A RESULT OF EVOLUTION • An organism changes over long periods of time. • Groups of organisms change from generation to generation. • The changes that accumulate in populations of organisms over time is called evolution. • Life’s unity arises from the fact that diverse descendants arise from single ancestors. • The unifying principle of biology is that all of life’s features in today’s organisms arose through evolution.

17. 1.4 Why Is Life So Diverse? • NATURAL SELECTION IS THE BASIS OF EVOLUTIONARY CHANGE • Characteristics of individuals in a group vary. • Some characteristics help individuals survive and reproduce. • Those that reproduce pass on these traits to future generations. • The favored traits are accumulated in populations over time, changing the individuals within the group. • Example: Big teeth in beavers favor survival and are passed on to future generations.

18. 1.4 Why Is Life So Diverse? • BIODIVERSITY IS THREATENED BY HUMAN ACTIVITY • Biodiversity is the wealth of species in the world and the interrelationships that sustain them. • Human expansion in the world has severely reduced habitats for these interrelationships to flourish. • Extinction of many organisms have followed from the growth of human populations on all the world’s continents. • Pollution and chemical wastes kill organisms.