Chapter 1 The Nature of Life

1.1 What is Science? Key Concept What is the goal of science?

1.1 What is Science What is the goal of science? The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make predictions.

1.1 What is Science? 3 features of Science: Science deals ONLY with the natural world. Scientists collects and organize information in a careful, orderly way, looking for patterns and connections between events. Scientists propose explanations that can be tested by examining evidence. Ex:// Grandpa John checks

1.1 What is Science? Therefore, science is an organized way of using evidence to learn about the natural world

1.1 Thinking Like a Scientist Scientific thinking: Begins with a general observation, the process of gathering information about events or processes in a careful, orderly way. Observation generally involves using the senses, particularly sight and hearing. The information gathered from observations is called data.

1.1 Thinking Like a Scientist Data:2 main categories Quantitative data are expressed as numbers, obtained by counting or measuring. Qualitative data are descriptive and involve characteristics that cant usually be counted.

1.1 Thinking Like a Scientist Scientists use data to make an inference: An inference is a logical interpretation based on prior knowledge or experience.

1.1 Explaining and Interpreting the Evidence Scientists try to explain events in the natural world by interpreting evidence in a logical and analytic way. After observations, scientists will propose one more hypotheses. Hypothesis is a proposed scientific explanation or prediction for a set of observations. Scientific hypotheses must be proposed in a way that enables them to be tested. Some tested by using controlled experiments Some tested by gathering more data In the case of a mystery illness scientists will collect data by studying and collecting things at the location

1.1 Thinking Like a Scientist Worked in the meat packing district in the early 1900’s Very poor and dirty working conditions

1.2 How Scientists Work Key Concepts How do scientists test hypotheses? How does the scientific theory develop?

1.2 How Scientists Work Have you ever noticed what happens to food that is left is an open trash can for a few days in the summer? Creatures that look like worms appear on the discarded food. These creatures are called maggots. For thousands of years, people thought they came from thin air.

1.2 Designing an Experiment: Forming a Hypothesis For centuries, people accepted the explanation for the sudden appearance of some organisms, that somehow, life arose from nonliving matter. Spontaneous generation- life could arise from non-living matter

1.2 Spontaneous Generation Francesco Redi Observed that these organisms appeared on meat a few days after flies were present. He considered that flies laid eggs that were too small to see He was the first to propose a new hypothesis- that flies produce maggots

1.2 Setting Up a Controlled Experiment The factors in an experiment that change are called variables. Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged or controlled. This is a controlled experiment. The variable that is changed is the manipulated variable. The variable that changes in response to the manipulated variable is called the responding variable.

1.2 Recording and Analyzing Results Scientists usually keep written records or their data Previously was done by hand, now done by computers and displayed via charts or graphs

1.2 Drawing a Conclusion Scientists use the data from an experiment to evaluate the hypothesis and draw a valid conclusion. they use evidence to support or reject their hypothesis They assume that the patterns in the natural world are consistent.

1.2 Repeating Investigations A key assumption in science is that experiments can be reproduced because nature behaves in a consistent manner. Block activity Scientists expect to test one another’s investigations

1.2 When Experiments Are Not Possible Unethical reasons How animals in the wild interact Sometimes things can’t be reproduced

1.2 How a Theory Develops As evidence from numerous investigations (experiments) build up, a particular hypothesis may become so well supported that scientists consider it a theory. A theory applies to a very well tested explanation that unifies a broad range of observations. No theory is considered to be the absolute truth! As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation.

1.3 Studying Life Key Concepts What are some of characteristics of living things? How can life be studied at different levels? Biology is the science that seeks to understand the living world.

1.3 Characteristics of Living Things Living things share the following characteristics: Living things are made up units called cells Living things reproduce Living things are based on a universal genetic code Living things grow and develop Living things obtain and use materials and energy Living things respond to their environment Living things maintain a stable environment Taken as a group, living things change over time

1.3 Made Up of Cells Living things are made up of units called cells Cell- is a collection of living matter enclosed by a barrier that separates the cell from its surroundings. These are the smallest units of an organism Contains organelles Some organisms are unicellular and many are multicellular

1.3 Reproduction 2 basic kinds Sexual Reproduction- cells from two different parents unite to produce the first cell of the new organism Asexual Reproduction- the new organism has a single parent In some cases, a single celled organism cleaves to form two new organisms

1.3 Based on a Genetic Code Genetic Code Directions for inheritance of traits carried by a molecule called deoxyribonucleic acid (DNA) Percentage of shared genetic code = 98.6% (bonoboos)

1.3 Growth and Development Single celled organisms- growth is mostly a simple increase in size For most organisms, development include periods of rapid and dramatic change

1.3 Need for Materials and Energy Organism needs constant supply of energy to grow and perform daily functions Metabolism- the combination of chemical reactions though which an organism build up or breaks down materials for energy, as it carries out its life processes. Plants and algae use photosynthesis

1.3 Response to the Environment Organisms are constantly responding to their environment Stimulus- is a signal to which organisms respond to External stimuli- environmental factors such as heat and light

1.3 Maintaining and Internal Balance Organisms must always keep a stable internal environment, this is called homeostasis. In response to their external stimuli, internal feedback mechanisms respond to these Example- body temperature

1.3 Evolution Although individual organisms experience many changes during their lifetime, their basic traits (genes) that they inherit from their parents does not. As a group, tiny changes in their genes accumulate and differences can be noticed over thousand/ millions of years Evolution-change in an organism over time Example- ability of certain plants to survive without water for periods of time

1.3 Branches of Biology No single biologists could study all of the diversity that biology encompasses, so biology is divided into different fields Some are based on the levels of organization Zoologists- study animals Botanists- study plants Paleontologists- study ancient life Molecular Biologists- study the smallest living systems Ecologists- study the interaction of organisms in an ecosystem Microbiologists- study microorganisms Geneticists study genetics

1.3 Levels of Organization Some of the levels at which can be studied include molecules, cells, organisms, populations of a single kind of organism, communities of different organisms in an area, and the biosphere. At all these levels, smaller living systems are found within a larger system

1.3 Levels of Organization Smallest to Largest (Use your book to define) Molecules Cells Tissues- collection of the same cells Organs- collection of tissues Organ Systems- collection of organs working together for a particular system Organisms Populations Communities Ecosystems Biosphere

1.4 Tools and Procedures Key Concepts What measurement system do most scientists use? How are light microscopes and electron microscopes similar? How are they different? Known the different parts of the light microscope

1.4 A Common Measurement System Most scientists use the metric system when collecting data and performing experiments The metric system is a decimal system of measurement whose units are based on certain physical standards and are scaled on multiples of 10. SI units

1.4 A Common Measurement System

What would be the purpose of having a common measurement system among scientists

1.4 Analyzing Biological Data When scientists collect data, they are trying to find out whether certain factors changed or remained the same. Simplest way to do this is to record data in a data table and create a graph Sample Graph

1.4 Microscopes Microscopes- are devices that produce magnified images of structures that are two small to see with the unaided eye 2 types Compound Light Microscope Electron Microscope Transmission Scanning

1.4 Compound Light Microscope Most commonly used Light microscopes can produce clear images of objects at a magnification of about 1000 times. Compound Light microscopes allow light to pass through the specimen and use two lenses to form an image

1.4 Electron Microscopes Electron Microscopes- use beams of electrons, rather than light to produce images TEM- shine a beam of electrons through a thin specimen Provides details within a cell SEM- scan a narrow beam of electrons back and forth across the surface Provides dramatic 3-D images

1.4 Laboratory Techniques Scientists use a variety of techniques to study cells, two common techniques are: Cell Culture- a single cell is placed into a petri dish containing nutrient agar, this cell is able to reproduce in this environment to create more cells Cell Fractionation- separate the different parts of the cell Done by adding fluid and centrifuging