Lecture 1 Introduction to Biology

1. Lecture 1Introduction to Biology

2. Animalia Bacteria Protista Fungi Archaea Plantae The Diversity of Life • Biology is the study of living things • Living things can be divided into six kingdoms

3. What is Life? • Biology is the study of life - but what does it mean to be alive? • Ludwig von Bertalanffy – life is a system where the whole is greater than the sum of the parts • Living organisms and many non-living things share three properties • Complexity • Movement • Response to stimulation

4. Properties of Life • All livingorganisms share five basic properties • Cellular Organization • All living organisms are composed of at least one cell • Metabolism • All living organisms use energy • Homeostasis • All living organisms maintain stable internal conditions • Growth and reproduction • All living organisms grow and reproduce • Heredity • All living organisms possess a genetic system that is based on DNA (Deoxyribonucleic acid)

5. The Organization of Life • Living organisms function and interact with each other at many levels • These levels are organized in a hierarchy of increasing complexity: • Cellular Level • Organismal Level • Population Level 1. 3. 2.

6. Life is an Emergent Property • Each higher level of organization contains novel properties not present at the simpler level of organization • Birth rate & death rate – populations NOT individuals • Evolution – populations evolve biologically NOT individuals • These properties are termed emergent properties • They are a consequence of the structural organization that is the hallmark of life • They characterize many aspects of the living world

7. Five Themes That Unify Biology • Evolution • The gene frequencies change in a species over time • Causes include: • Genetic drift • Natural & artificial selection • Founder effects • The Flow of Energy • All living organisms require energy • The sun is the source of energy for most ecosystems • Plants capture energy via photosynthesis • They then act as an energy source for other organisms • Interaction • Interaction between organisms is critical for evolution • Social behavioroccurs when organisms of the same species live in direct contact • Community dynamics occur when organisms of different species live in direct contact (Competition, Predation, Symbiosis) • Structure Determines Function • Biological structures are well suited to their function • This is true at every level of organization • Homeostasis • All living organisms act to maintain a relatively stable internal environment • Maintaining homeostasis requires energy and a lot of signaling back-and-forth between cells

8. How We Learn & Think • Our brains consist of billions of interconnected neurons • Our senses stimulate specific neuron pathways • Pathway residual sensitivity • Short term memory • Pathway physical changes • Long term memory • Caused by: • repeated stimulation • intense emotion • Sensory input & memory storage share the same circuits • This causes associations

9. How We Know Things • Our brains are great at two things • Recognizing patterns • Filling in sensory gaps (story telling) • Both of these can get us into trouble • Pattern Matching • Recognizing patterns that are not real • Not recognizing patterns that are real • Story Telling • Not checking to see that our stories are true • 80% of personal disagreements between people begin as wrong stories each has told himself about the other’s motivations

10. Science: Testing Our Patterns & Stories • The Classic Scientific Method • Observation • Hypothesis • Test • Analysis (observation) • Modify hypothesis if necessary • The Null-Hypothesis • No hypothesis is valid if it cannot be tested • No test is valid if its results cannot disprove the hypothesis • The null-hypothesis is the formal statement of the hypothesis not being true and the test results that will support the null-hypothesis • Minimizing Results Based on Chance • Control groups: checking to make sure the same results would not occur without the test intervention • Statistical analysis: checking to see if the same result could be caused by chance (e.g. how likely is it to get 4 heads in a row when flipping coins randomly versus always starting with the coin on tails?)

11. How Scientists Think • Inductive Reasoning • Recognizing patterns • Is used by scientists to develop hypotheses about how the world works • Deductive Reasoning • Telling stories based on patterns • Uses accepted general principles as a “guide” to explain specific observations

12. Inference vs. Observation • An observation is limited to a description of actions or events without interpretation • An inference is a conclusion we draw based on what we observe • Inference or observation? • Example 1 (The cat is happy) • Example 2 (The cat is chewing on the plant leaves) • Example 3 (The cat is sleeping) • Example 4 (The cat is a female)

13. Theory and Certainty in Science • A theory is a set of hypotheses that have been tested many times and not rejected • It indicates a high degree of certainty • However, there is no absolute truth in science • Everything is open to more testing and reinterpretation • Acceptance of a theory is always provisional • Note: • To the general public, the word theory is often used to mean what a scientist would call a hypothesis, a lack of knowledge or a guess • To scientists, a theory represents that of which they are most certain, explanations supported by a wealth of evidence and experimental data

14. The Limitations of Science • Science is limited to organisms and processes that can be observed and measured • Many spiritual and religious explanations are beyond the scope of science • Most religious explanations do not allow formation of a realistic null hypothesis • However, the physiological and evolutionary basis of spiritual and religious experience is a current hot research topic in both neurophysiology & evolutionary biology • There are also practical limits • Science can provide options and understanding • Science cannot be relied upon to solve all problems • For example, what constitutes “acceptable risk” cannot be answered by science!

15. Four Theories Unify Biology & This Class • The Gene Theory • The information that determines what an organism is like is encoded in its genes • Genes are located along DNA molecules • The entire set of DNA instructions that specifies a cell is termed its genome • The Cell Theory • All living organisms are composed of cells • Cells are the basic units of life • All cells come from other cells • The Theory of Heredity • Genes represent traits of an organism and are inherited as discrete units • Chromosomal theory of inheritance: Genes are physically located on chromosomes • The Theory of Evolution • All living organisms are related to one another in a common tree of life • Diversity of the living world is the result of natural selection

16. The Brain & Study Implications • 3 hours of study at one time is not effective for long term memory formation • Studying the same thing 20 minutes, 3 times a day for three days is more effective for long term memory formation • Using your brain to rephrase or rework the material is more effective for long term memory formation than repetitive reading or listening