Chapter 1 The Science of Biology

1-1 What is Science? Goal of science Observations vs. inferences What is a hypothesis?

Goal of science To investigate and understand nature To explain events in nature Use those explanations to make useful predictions Science- organized way of using evidence to learn about the natural world It’s a process! Term can also refer to the body of knowledge scientists have built up after years using this process

Observations vs. Inferences Observation- gather information using one or more of the senses Information gathered is called evidence or data Two types of observations Qualitative- involves characteristics that cannot be easily measured or counted Quantitative- involves numbers like when measuring or counting objects

Observations vs. Inferences Inference-logical interpretation based on prior knowledge and experience

Observations vs. Inferences Statement Observation Inference Object A is round and orange. X Object A is a basketball. Object C is round and black and white. Object C is larger than Object B. Object B is smooth. Object B is a table-tennis ball. Each object is used in a different sport.

Explaining the Evidence A hypothesis is a possible explanation for a set of observations or an answer to a scientific question Must be testable!

Formulating a Hypothesis Mystery Worms A teacher collected some beetles from a rotting log and placed them in a container of dry oatmeal in her classroom. She kept the box covered with a light cloth so that the beetles could not escape. She also asked one of her students to add potato and apple pieces once a week to provide food and moisture for the beetles. After several weeks, the student reported that there were some strange-looking, wormlike organisms in the container. 1. Formulate a hypothesis that might explain the presence of the “worms” in the container. 2. How could you test your hypothesis?

1-2 How Scientists Work Designing an Experiment Publishing and Repeating Investigations When Experiments are Not Possible How a Theory Develops

Designing an Experiment State the Problem Analyze Results Form a Hypothesis Draw a Conclusion Set Up a Controlled Experiment Publish Results Record Results

Controlled Experiment Only one variable must be changed at a time All other variables should be kept unchanged or controlled Manipulated (independent) variable- variable that is deliberately changed Responding (dependent) variable- variable that is observed and changes in response to the manipulated variable

Redi’s Experiment, designed to refute Spontaneous Generation- the idea that life could arise from nonliving matter OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: whether maggots appear Maggots appear No maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

Recording and Analyzing Results Lab reports Scientific drawings Online storage

Drawing a Conclusion After testing your hypothesis… Option 1: Data supports it “data supports the hypothesis” Never proves it Option 2: Data proves it wrong “hypothesis is refuted” Rewrite and test again

Repeating Redi Key assumption in science- experimental results can be reproduced because nature acts in a consistent manner Redi’s work followed by Needham-used an experiment with “animalcules” to attack Redi’s work Spallanzani- improved upon Needham’s experiment Pasteur-allowed broth to come into contact with the air

Spallanzani’s Experiment Gravy is boiled. Flask is open. Flask is sealed. Gravy is free of microorganisms. Gravy is boiled.

Pasteur’s Experiment Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms. Showed that all living things come from other living things

When Experiments are Not Possible Examples: Observing animals Prohibited by ethical considerations Attempting to maintain a controlled experiment Study large groups of subjects ID as many relevant variables as possible

Developing a Theory Theory- well-tested explanation that unifies a wide range of observations Happens when a hypothesis is so well supported by the scientific community No theory is considered absolute truth May be revised or replaced by a more useful explanation

1-3 Studying Life Characteristics of living things Branches of biology Biology in everyday life

Characteristics of Living Things 1. Made Up of Cells 2. Reproduce 3. Based on a Genetic Code 4. Grow and Develop 5. Need Materials and Energy 6. Respond to the Environment 7. Maintain Internal Balance 8. Evolve

Characteristic Examples Living things are made up of units called cells. Many microorganisms consist of only a single cell. Animals and trees are multicellular. Living things reproduce. Maple trees reproduce sexually. A hydra can reproduce asexually by budding. Living things are based on a universal genetic code. Flies produce flies. Dogs produce dogs. Seeds from maple trees produce maple trees. Living things grow and develop. Flies begin life as eggs, then become maggots, and then become adult flies. Living things obtain and use materials and energy. Plants obtain their energy from sunlight. Animals obtain their energy from the food they eat. Living things respond to their environment. Leaves and stems of plants grow toward light. Living things maintain a stable internal environment. Despite changes in the temperature of the environment, a robin maintains a constant body temperature. Taken as a group, living things change over time. Plants that live in the desert survive because they have become adapted to the conditions of the desert.