Ch 1 – The Science of Life

The World of Biology Biology: The study of life Characteristics of life Organization and Cells Response to Stimuli Homeostasis Metabolism Growth and Development Reproduction Change Through Time

Organization and Cells All living things are composed of one or more cells Cells are the smallest units that can perform all life’s processes In multicellular organisms, many are specialized to perform specific functions Cells are always very small The size of multi-celled organisms depends on the number of cells NOT their size 3

Organization and Cells, cont. Organized at both the molecular and cellular levels Take in substances from the environment and organize them in complex ways Specific cell structures (organelles) carry out particular functions 4

In multicellular organisms, cells and groups of cells are organized by their function (hierarchy of life) Atom  Biological Molecule  Organelle  Cell  Tissue  Organ  Organ System  Organism 5

Response to Stimuli Organisms can respond to a stimulus, or a physical or chemical change in the internal or external environment 6

Homeostasis The maintenance of a stable level of internal conditions even though environmental conditions are constantly changing, (like: body temperature, water content, glucose levels)

Metabolism PHOTOSYNTHESIS The sum of all the chemical reactions that take in and transform energy and materials from the environment PHOTOSYNTHESIS

Growth and Development All living things grow and increase in size from the division and enlargement of cells Development is the process by which an organism becomes a mature adult; involves cell division and cell differentiation, or specialization

Reproduction Production of new organisms is essential for the continuation of a species Hereditary information is transferred to offspring during two kinds of reproduction Sexual reproduction – hereditary information recombines from two organisms of the same species Asexual reproduction – hereditary information from different organisms is not combined ~ original and new organisms are genetically the same

Evolution or Change Through Time Populations of living organisms evolve or change through time to better adapt to changing conditions Charles Darwin’s SURVIVAL OF THE FITTEST through the process of natural selection

THEMES IN BIOLOGY Diversity and Unity Unity in the Diversity of Life Three Domains of Life Interdependence of Organisms Evolution of Life Natural Selection

Unity in the Diversity of Life Genetic code: rules that govern how cells use the hereditary information in DNA (deoxyribonucleic acid – makes up our genes or instructions for life) Presence of organelles: carry out all cellular activities “Tree of Life” – suggests all living things have descended with modification from a single common ancestor; thus, all of life is connected

Three Domains of Life Bacteria Kingdom Bacteria (Eubacteria) Archaea Kingdom Archaea (Archaebacteria) Eukarya Kingdom Animalia Kingdom Plantae Kingdom Fungi Kingdom Protists

Interdependence of Organisms Ecology: branch of biology that studies organisms interacting with each other and with the environment Ecosystems: communities of living species and their physical environments; e.g., minerals, nutrients, water, gases, heat, etc.

Evolution of Life Descent with modification: process in which the inherited characteristics within populations change over generations, such that genetically distinct populations and new species can develop Natural Selection: organisms that have certain favorable traits are better able to survive and reproduce successfully than organisms that lack these traits Adaptations: traits that improve an individual’s ability to survive and reproduce

Scientific Method

Scientific Processes and Methods 1. Observations/Questioning 2. Measuring, Organizing Data, and Classifying 3. Hypothesizing -- a testable explanation based on experience, reading, and/or previous experiments. (NOT A GUESS) Inductive Reasoning 4. Predicting -- stating in advance the result that will be obtained from testing Deductive Reasoning (If…then…statement)

Scientific Method, cont. 5. Experimenting -- A controlled procedure for testing a hypothesis Control Group -- all conditions remain constant Experimental Group -- same as control, except for ONE factor Variable Independent Variable - condition that changes Dependent Variable - response to changed condition Data Qualitative ~ descriptive (think quality) Quantitative ~ numbers (think quantity)

Scientific Method, cont.

Scientific Method, cont. 6. Organizing and Analyzing Data

Scientific Method, cont. 7. Inferring Conclusions (concluding from evidence collected during experimentation using facts and previous knowledge rather than direct observations) 8. Modeling and Communicating 9. Test and Re-test ~ law or theory formed

Scientific Method, cont. LAW -- general statement that describes a wide variety of phenomena If a hypothesis describes HOW things happen and continues to be supported by evidence, it becomes a law. THEORY -- most probable explanation for a set of data based on best available evidence If a hypothesis describes WHY things happen and continues to be supported by evidence, it becomes a theory.

Scientific Method -- Example Observations: Fish populations in Twin Lakes are declining. The pH (acidity) of the water in the lakes is dropping to 4.2. One hundred miles west of Twin Lakes is a power plant that is burning tons of coal every year, releasing sulfur dioxide into the air.

Problem Twin Lakes -- Acid Rain Problem East Branch West Branch 100 miles East Branch West Branch Power Plant

Questioning/Hypothesizing (Inductive Reasoning) Question: Is there a link between the power plant, the pH of the lake, and the fish decline? Hypothesis: If acid rain falling on Twin Lakes is related to fish reproduction, then increasing acid rain amounts will cause the fish to have poor reproduction.

Experiment Experiment Twin Lakes is a lake in the mountains that can be divided by a barrier. A complete inventory will gather baseline data. One arm of the lake, on the east side of the barrier, will be treated with sulfuric acid to reduce the pH to 4.0. The west arm of the lake will be left alone, other than monitoring.

Experiment Twin Lakes -- Acid Rain Problem East Branch West Branch 100 miles East Branch West Branch Barrier Power Plant Acid Rain Added No Acid Added

Results East Branch: Fish stop reproducing. West Branch: No change in fish reproduction.

Conclusion The power plant emits sulfur dioxide into the air which combines with rain to produce acid rain. The addition of this acidic rain to the lakes lowers the pH and causes the fish to stop reproducing. This results in declining fish populations and jeopardizes the survival of the fish.