INTRODUCTION: MAIN THEMES IN THE STUDY OF LIFE Chapter 1 Campbell and Reece. Biology 6th edition.

Exploring life on its many levels A basic characteristic of life is a high degree of order. A Hierarchy of Organization  Biological organization is based on a hierarchy of structural levels, each level building on the level’s below (see next slide)  Starting at the lowest level, chemicals come together to form complex biological molecules.  Many small molecules come together to form small structures called organelles, which in turn are the components of cells.  Cells are the subunits of life. Many organisms are made of a single cell, and others are multiple cells coming together to work toward a common goal.

Exploring life on its many levels  Multicellular organisms exhibit three major structural levels above the cell: Tissues, organs, and organ systems. Organism Organ Tissue Cell Organelle Molecule

Exploring life on its many levels  In the hierarchy of biological organization, there are tiers beyond the individual organism.  Classification of organisms  Populations making a biological community  Communities interacting to form an ecosystem.

Exploring life on its many levels Emergent Properties  With each step upward in the hierarchy of biological order, new properties emerge that were not present at the simpler levels of organization  For example, the human nervous system allows us to think, feel, move, etc. Break the system down to its parts, the brain, spinal cord, nerves. The nerve by itself is a cell that can carry out cellular respiration, removal of waste products, and production of proteins, but does not allow us to feel.

Cells are an organism’s basic units of structure and function The cell is the lowest level of structure capable of performing all the activities of life. All organisms are composed of cells, the basic units of structure and function.

Cells are an organism’s basic units of structure and function The Cell Theory  Robert Hooke, Anton van Leeuwenhoek, Matthias Schleiden, and Theodor Schwann discovered and researched cells in the 17 th century.  Schleiden and Schwann summarized their findings, creating the basis of the Cell Theory  The ability of cells to divide to form new cells is the basis for all reproduction and for the growth and repair of multicellular organisms, including humans.

Cells are an organism’s basic units of structure and function The Two Main Cell Types  All cells are enclosed by a membrane that regulates the passage of materials between the cell and its surroundings.  Every cell, at some stage of its life, contains DNA, the heritable material that directs the cell’s many activities.  The two major types of cells, prokaryotic and eukaryotic cells, can be distinguished by their structural organization.  Prokaryotic are a simpler cell- example: bacteria  Eukaryotic are a more complex cell- examples: protists, fungus, plants, animals

The continuity of life is based on heritable information in the form of DNA Order implies information; instructions are required to arrange parts or processes in an organized way. Biological instructions are encoded in a molecule called DNA, Deoxyribonucleic acid  Each DNA molecule is made up of two long strands composed of chemical building blocks called nucleic acids. These strands come together forming what looks like a ladder

Organisms are open systems that interact continuously with their environments Life does not exist in a vacuum.  An organism is an example of what scientists call an open system, an entity that exchanges materials and energy with its surroundings.  Each organism interacts continuously with its environment, which includes other organisms, as well as nonliving factors (water, air, rocks, soil, etc)  The exchange of energy between an organism and its surroundings involves the transformation of one form of energy to another.  Example, when a leaf produces sugar, it converts solar energy to chemical energy.

Regulatory mechanisms ensure a dynamic balance in a living system Organisms are able to obtain useful energy from molecules such as sugar because cells break the molecules down in a series of closely regulated chemical reactions  Regulation of chemical reactions within cells centers on protein molecules called enzymes.  Produced by the cells in which they function, enzymes are catalysts, substances that speed up chemical reactions.

Regulatory mechanisms ensure a dynamic balance in a living system Many biological processes are self-regulating, operating by a mechanism called feedback, in which an output or product of a process regulates that process.  Negative and Positive feedback systems

Regulatory mechanisms ensure a dynamic balance in a living system Negative Feedback: slows or stops processes

Regulatory mechanisms ensure a dynamic balance in a living system Positive Feedback: Speeds a process up

The Process of Science The Scientific Method  Make an observation  “My flashlight doesn’t work”  Form a question  “What’s wrong with my flashlight?”

The Process of Science The Scientific Method  Form a hypothesis  “The flashlight’s batteries are dead.”  Prediction  “If the flashlight’s batteries are dead, and I replace the batteries with new ones, then my flashlight will work.”

The Process of Science The Scientific Method  Test  Replace the batteries with new ones  If the test supports the hypothesis, i.e. the flashlight works, congratulations.  If the test does not support the hypothesis, form a new hypothesis, and retest.

Using themes to connect the concepts of biology Modern biology requires the knowledge of chemistry, physics, and mathematics. Much of what you will learn will be delving into more detail about things you have already learned. A good understanding of general biology will help you greatly in this course.