Introduction to Biology

Introduction to Biology Biology – The Study of Life • • • • • • • Life arose more than 3.5 billion years ago First organisms (living things) were single celled Only life on Earth for millions of years Organisms changed over time (evolved) New organisms arose from older kinds Today there are millions of species They inhabit almost every region of Earth today Themes of Biology • • • • • • Cell structure and function Stability and homeostasis Reproduction and inheritance Evolution Interdependence of organisms Matter, energy, and organization Cell Structure and Function • • • Cell basic unit of life All organisms are made of and develop from cells Some composed of only a single cell (unicellular) which is usually identical to parent Cells • • • • • • • • Most organisms are composed of many cells (multicellular) Cells are different (undergo differentiation) Cells are small Cells are highly organized Cells contain specialized structures (organelles) that carry out the cell’s life processes Many different kinds of cells exist All cells surrounded by a plasma membrane Contain a set of instructions called DNA (genetic information) Stability and Homeostasis • • Organisms must Maintain very stable internal conditions - HOMEOSTASIS Temperature, water content, chemical content, etc. must be maintained Reproduction and Inheritance • • All organisms produce new organisms like themselves REPRODUCE Organisms transmit hereditary information to their offspring INHERITANCE DNA • • • • Genetic Information in all cells Deoxyribonucleic Acid DNA contains instructions for traits GENES Make the structures and complex chemicals necessary for life PROTEINS • DNA in every body cell (SOMATIC CELLS) is exactly alike Sexual Reproduction • • • Hereditary information from two different organisms of the same species are combined Egg and sperm → zygote (fertilized egg) Zygote contains hereditary information from both parents Asexual Reproduction • • • Hereditary information from one, usually unicellular, organism that divides Resulting cells contain identical hereditary information Genetic information from single parent Evolution • • • • • Populations of organisms change (evolve) over generations (time) Explains how many different kinds of organisms came into existence SPECIES Explains how modern organisms are related to past organisms Explains why organisms look and behave the way they do Provides a basis for exploring the relationships among different groups of organisms Natural Selection • • • • Natural selection is the driving force in evolution Organisms that have certain favorable traits are better able to successfully reproduce than organisms that lack these traits Survival of organisms with favorable traits cause a gradual change in populations over many generations Also Called “Survival of the Fittest” Interdependence of Organisms • • • • Interaction of organisms with one another and with their environment ECOLOGY Insects depend and flowers DEPEND on each other for food & pollination COEVOLUTION All organisms need substances such as nutrients, water, and gases from the environment The stability of the environment depends on the healthy functioning of organisms in that environment Matter, Energy and Organization • • Living things are highly organized Require a constant supply of energy to maintain their orderly state Energy • • ALL energy comes from the SUN (directly or indirectly) Photosynthesis is the process by which some organisms capture the energy from the sun (solar) and transform it into energy (chemical) that can be used by living things Autotrophs • • • • Organisms that make their own food are called autotrophs Phototrophs – use solar energy (photosynthesis) to get energy Convert H2O and CO2 into sugar and O2 Chemotrophs – use different chemical processes to get energy Heterotrophs • • • Organisms that must take in food to meet their energy needs are called heterotrophs Consume autotrophs (herbivores), other heterotrophs (carnivores) or both (omnivores) for their energy needs Complex chemicals are broken down and reassembled into chemicals and structures needed by organisms Characteristics of Life Cells • • • • All living things are composed of cells 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 Organization • • • • 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 In multicellular organisms, cells and groups of cells (tissues) are organized by their function Cells → tissues Tissues → organs Organs → systems Systems → ORGANISM Energy Use • • • Use energy in a process called metabolism Sum of all chemical processes Require energy to maintain their molecular and cellular organization, grow and reproduce Homeostasis • • Maintain stable internal conditions Temperature, pH, etc. Growth • • • • Grow occurs as the result of cell division and cell enlargement Cell division is the formation of two cells from a preexisting cell New cells enlarge as they mature When a cell grows to a size where its surface area isn’t big enough for its volume, the cell divides Development • • The process by which an adult organism arise is called development Repeated cell divisions and cell differentiation Reproduction • All species have the ability to reproduce • Not essential to survival of individual but is essential for continuation of a species Responsiveness • • • Respond to stimuli in the external environment Detect and respond to changes in light, heat, sound and chemical and mechanical contact Coordinates it’s responses Evolve • • • • Ability to adapt to their environment through the process of evolution Favorable characteristics are selected for and passed on to offspring Called adaptations Driven by natural selection or “survival of the fittest” Scientific Method Observation – STEP 1 • Employing your five senses to perceive objects or events Asking a Question • Based on observations; one or more questions are generated Forming a Hypothesis – STEP 2 • • • A statement is testable if evidence can be collected that either does or doesn’t support it It can never be proven beyond doubt Often must be refined and revised or discarded The Hypothesis • • Is a statement made in advance that states the results that will be obtained from testing the hypothesis Often written in the form of an “if-then” statement Experimenting – STEP 3 • • Testing a hypothesis or prediction by gathering data under controlled conditions – conducting a controlled experiment Based on a comparison of a control group with an experimental group Both groups are identical except for one factor (independent variable). Observations and measurements are taken for a particular factor (dependent variable) in both groups • • • • • Driven by or results from independent variable Measuring Involves quantitative data that can be measured in numbers &/or qualitative data information that isn’t numbers Sampling Technique of using a sample – a small part – to represent the entire population Organizing Data – STEP 4 • • Involves placing observations and measurement (data) in order Graphs, charts, tables, or maps • • Collected and organized data must be analyzed Process of determining whether data are reliable or whether they support or do not support a hypothesis or prediction Conclusion – STEP 5 • • • • Conclusions are made on the basis of facts, not observations Often drawn from data gathered from a study or experiment Should support the hypothesis Should be re-testable Communication – STEP 6 • • • • • • • • • Scientists must share the results of their studies with other scientists (peers) Publish findings in journals Present their findings at scientific meetings Scientists must be unbiased Should not tamper with their data Only publish & report tested & proven ideas Sharing of information is essential to scientific process Subject to examination and verification by other scientists Allows scientists to build on the work of others Theories • • • • A theory may be formed after many related hypotheses have been tested and supported with experimental evidence A broad and comprehensive statement of what is thought to be true Supported by considerable evidence Ties together related hypotheses Laws • • • • • A Statement of fact that concisely explains an action or group of actions e.g. Law of Gravity Accepted to be true Universal May be expressed as a math equation e.g. E=mc2 MICROSCOPES Microscopy and Measurement • • • • • Microscopes – produce an enlarged image of an object Used to study organisms, cells, and cell parts Increase in apparent size is called magnification The ability to show details clearly is called resolution Microscopes vary in both magnification and resolution Compound Light Microscopes • • • Specimen mounted on a glass slide Must be thinly sliced or very small Pair of lenses • • • • • • Ocular lens (eye piece) Objective lens (nose piece) Can be used to study LIVE specimens Magnification determined by multiplying power of both lenses Eyepiece 10X times Objective power (20X, 40X…) Highest Maximum magnification is around 1000X Electron Microscope • • • • • • • • • • • • Transmission EM (TEM) Uses a beam of electrons to produce an enlarged image of very thinly sliced specimen on screen or photographic plate Image focused by magnetic lenses 200,000X magnification Cannot be used to view living specimens Scanning EM (SEM) 3D image Specimens not sliced for viewing Surface sprayed with fine metal coating Also uses electron beam and fluorescent screen or photographic plates 100,000X magnification Cannot be used to view living specimens