Introduction: Themes in the Study of Life Chapter 1 - AP Biology

Biology The Study of Life Unifying Themes Order Emergent Properties The Cell Heritable Information Structure relates to Function Interaction with the Environment Regulation Unity and Diversity Evolution Scientific Inquiry Science, Technology and Society

LIFE’S HIERARCHICAL ORDER One of life’s most distinctive features is it’s ORDER. Because life is ORDERED, it can be studied in terms of a structural hierarchy. Hierarchy of structural levels Each structural level builds on the levels below it. Emergent properties – special qualities that result from the structure at each level.

Hierarchy of Structural Levels Atoms Molecules Organelles Cells Tissues Organs Organ systems Organisms Population Community Ecosystem

Atoms The chemical building blocks of all matter The lowest, most basic level of the structural hierarchy

Molecules Composed of two or more atoms Atoms become organized into the many complex biological molecules (like proteins, carbohydrates, etc.) that make up living things

Organelles The components of cells Made up of many complex biological molecules

Cells The subunits of all organisms Fundamental units of life An organism’s basic units of structure and function The lowest level of structure that is capable of performing ALL the activities of life. ALL organisms are composed of cells.

Tissues Groups of cells similar in structure that are doing a common function

Organs Groups of different tissues working toward a common function

Organ Systems Groups of different organs working toward a common function

Organisms The units of life May be single celled (Amoeba) OR multicelluar with a division of labor among different cells Multicellular organisms exhibit 3 major structural levels above the cell. Tissues Organs Organ Systems So, just keep in mind that an organism may be UNICELLULAR and may NOT necessarily have tissues, organs, organ systems.

Population Localized group of organisms belonging to the same species

Community Populations of different species living in the same area

Ecosystem Community interactions that include nonliving (Abiotic) features of the environment (like soil and water)

Emergent Properties Properties that result (emerge) from the interactions between components within a level of the structural hierarchy. KEY: The Whole is greater than the sum of its parts. The ARRANGEMENT and INTERACTIONS of molecules (or organelles, or cells, or tissues, etc.) are integral in causing the unique properties of life at each level of the hierarchy.

Emergent Properties Examples A molecule like a protein has properties that are not exhibited by any of its component atoms. The human brain, if disrupted by a head injury, may cease to function, even if all its “parts” are still present.

Scientists and the History of the Cell Since cells are the fundamental units of life, this section will focus on their discovery and some of the scientists who First observed them, AND Realized their significance

Robert Hooke English Scientist First to describe and name cells – 1665 Observed cork (oak bark) magnified 30x Hooke never realized the significance of his discovery For more on Robert Hooke, click HERE.

Anton van Leeuwenhoek Dutch; working at the same time as Hooke. Discovered organisms we now know to be single-celled. He observed: Microbial world in a drop of pond water Blood cells Sperm Developed magnifying glasses that magnified up to 300x

Anton van Leeuwenhoek Views to the right show Top: A microscope like van Leeuwenhoek’s Bottom: What he would have seen through such a microscope – these are bacteria For more on van Leeuwenhoek, click HERE.

Schleiden and Schwann 1839 German biologists Acknowledged cells as the fundamental units of life Summarized their own microscopic studies and those of others by concluding that all living things consist of cells Formed the basis of the CELL THEORY Schwann is on the left, Schleiden on the right.

Cell Theory Cell Theory began with the summative ideas of Schleiden and Schwann; 1: All living things are made of cells 2: All cells come from other cells

2 Major Cell Types Prokaryotic cells No nucleus No membrane bound organelles Tough cell walls ALL bacteria

Eukaryotic Cells Eukaryotic cells Have a Nucleus DNA in chromosomes Membrane bound organelles May or may not have cell walls Everything EXCEPT bacteria

Inheritable Information All life is connected by a common genetic code DNA, RNA

STRUCTURE RELATES TO FUNCTION! Anatomy/shape of structures nearly always relates to how they work.

Examples of Form Fitting Function: Aerodynamically efficient shape of a bird’s wing

Examples of Form Fitting Function: Skeleton of the bird is strong but light to aid in flight.

Examples of Form Fitting Function: Flight muscles (indeed all muscles) are controlled by neurons Neurons transmit impulses Neuron structure is especially well suited for communication like this

Examples of Form Fitting Function: Muscle cells need enormous amounts of energy, which they obtain from organelles called mitochondria Mitochondria consist of highly folded membranes which allow lots of energy to be made in a small space.

Organisms Continuously Interact with their Environments Organisms interact with each other AND nonliving components of their environment Photosynthesis Cell Respiration Nutrient Cycling Energy Flow through the environment Transformation of energy from one form to another Solar energy to chemical energy Chemical energy to mechanical energy

Living Things Must Maintain Balance – Regulatory Systems Homeostasis Maintenance of homeostasis is achieved by using regulatory systems Chemical reactions are regulated by the use of enzymes Feedback mechanisms Allow for the self-regulation of biological processes Product of a process regulates the process Positive feedback Speeds up a process Negative feedback Slows or stops a process

Example of Positive Feedback Loop

Example of Negative Feedback Loop

Unity and Diversity Diversity 1.5 million species identified Estimates of total diversity range from 5 million to over 100 million species

Unity and Diversity Unity Universal genetic code Similarities in cell structure, etc. The diagram at right shows the fundamental similarity between ALL eukaryotic flagella, whether on a paramecium or in the human windpipe.

Organizing the Diversity of Life Taxonomy – science that names and classifies species We have a 6 kingdom system

3 Domains of Life

6 Kingdoms of Life

Evolution is the Core Theme of Biology All of Life is Connected Remember diversity AND UNITY Evolution is the process that has transformed life from its earliest beginnings to the vast diversity of today.

Charles Darwin 1859, published Origin of Species For lots more information about Charles Darwin, Click HERE. The photo is of Darwin with his son, William in 1842.

Origin of Species Darwin’s book presented two themes: “descent with modification.” Darwin’s theory of HOW life evolves – the mechanism called, Natural Selection. Darwin developed his ideas by putting together pieces of the puzzle that were already known at the time – he, however, was the only one to put them all together.

Darwin’s Observations Individuals are varied Individuals produce more offspring than the environment can support, thus leading to competition

“Survival of the Fittest” Some organisms will be better suited for this competition than others Those best suited to compete in their environment will have greater reproductive success than those not as well suited They will be better represented in the next generation and so on. This is Natural Selection

Natural Selection and Evolution Darwin proposed that natural selection could produce new species from ancestral species Cumulative effects of many small adaptations adding up from one generation to the next Over the span of many years. Descent with Modification (evolution) accounts for both the unity and diversity of life.

Science as Process Science is simply a way of knowing. Remember, it is not the only way of knowing. It seeks to answer questions about the natural world Science operates under the premise that questions about the natural world are answerable by making observations of the natural world and that the events observable in nature can be explained in terms of natural laws.

Pseudoscience The supernatural is BEYOND the realm of scientific discussion because the supernatural is not bound by the laws of the natural world. Science has no means of studying something that is not bound by the laws of nature.

Scientific Method Outlines a series of steps for answering questions about the natural world Scientists do not adhere strictly to this method in a step-wise fashion, but it is used by all scientists in some form. Indeed, all of us use some form of this method each day to solve problems.

The Importance of a Testable Hypothesis Hypothesis – a tentative answer to some question Having a TESTABLE hypothesis is critical to carrying out the scientific method. Having a hypothesis that is actually testable by the scientific method LIMITS the kinds of questions the scientific method can answer.

Other Important Points Regarding Hypotheses Hypotheses are possible explanations for some phenomenon. Never just a statement or observation. Must seek to explain WHY something is happening. Hypotheses reflect past experience In other words, hypotheses should seem reasonable…at least this is where hypotheses should start. Multiple hypotheses should be proposed whenever possible This helps a scientist avoid “favoring” a particular outcome in an experiment. Again, Hypotheses should be TESTABLE. Hypotheses can be eliminated but NOT confirmed or “proven” with absolute certainty. Even the most thoroughly tested hypotheses are accepted only conditionally , pending further investigation.

Controlled Experiments Subjects are divided into two groups Experimental (group with variable changed) Control (group without variable) The two groups should be treated exactly alike EXCEPT for the ONE variable the experiment is designed to test This provides a basis for comparison

A Critical Problem in Today’s Science Be aware that science, like any other type of information can be politicized by different groups seeking certain political/commercial outcomes. It is VERY difficult for even an educated person to tell the difference between “bad” science and “good” science. Bad science – experiments designed to support a desired result Good science – experiments designed to determine the answer to some question.

Questions? Please feel free to ask any questions now. At the end of each page of notes- please add 3-4 sentences (summary) of that page. Please add in your left column questions, notes and clarification.