Bài giảng Biology 25: Human Biology - Chapter 1: Introduction: The Scientific Study of Life

I. Life is based on many structural levels Levels of biological organization: Atoms Molecules Subcellular organelles Cells Tissues* Organs* Organ systems* Organism: May consist of a single cell or a complex multicellular organism. * Level of organization not found in all organisms

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Chapter 1 Biology 25: Human BiologyProf. GonsalvesLos Angeles City CollegeLoosely Based on Mader’s Human Biology,7th editionChapter 1Introduction: The Scientific Study of LifeBiology: The study of life.Greek origin:Bio: LifeLogos: Study ofI. Life is based on many structural levelsLevels of biological organization:AtomsMolecules Subcellular organellesCellsTissues*Organs*Organ systems*Organism: May consist of a single cell or a complex multicellular organism.* Level of organization not found in all organismsLevels of organization beyond organism:Population: Group of organisms of the same species that interact with one another.Community: Several different populations living together in same area (e.g.: lake, forest, jungle).Ecosystem: Interactions of community with non-living environment (air, water, soil).Ecosphere: All ecosystems on planet earth. Includes: Biosphere: All biological communities on earth.Atmosphere (air)Hydrosphere (water)Lithosphere (crust) Common features of all organisms:1. Cells: Basic structural and functional unit of life. Genetic information contained in DNA.2. Growth and Development:Growth: Occurs by an increase in cell size, cell number, or both.Development: Changes that take place during an organism’s life.3. Energy use and metabolism: All organisms must take in and transform energy to do work, to live.Metabolism: All chemical reactions and energy transformations essential for growth, maintenance, and reproduction. 4. RegulationExternal environment may change, but internal environment remains fairly constant.Homeostasis: Organisms constantly strive to maintain a “steady state” (e.g.: constant body temperature or blood pH) despite changes in the internal and external environment.Metabolism is regulated by homeostatic mechanisms.5. Movement: Internal movement: Characteristic of all life.Locomotion: Self-propelled movement from point A to point B. Not observed in all life forms.6. Respond to environmental stimuli: Organisms respond to internal and external changes (visual stimuli, temperature, light, sound, pressure, etc.).7. Order: Organisms are highly organized, when compared to nonliving environment.8. Reproduction: Organisms come from other organisms. Reproduction may be sexual or asexual.9. Evolutionary adaptation: Populations, not individuals, “evolve” or change over many generations so they can survive in a changing world.Evolution is the core theme of biologyCharles Darwin: Wrote “On the Origin of Species by Means of Natural Selection” (1859) in which he proposed the theory of evolution.Evidence that led to the principle of evolution:Fossils: Most species that ever existed are extinct; appear to be gradual progressionArtificial selection of domestic/farm animalsAdaptations: Organisms appear uniquely suited to their environment (especially in Galapagos).Darwin’s finches are a classic exampleThe theory of evolution by natural selection:1. Genetic Variation: Due to genetic differences there is variation within a population (size, color, structure, etc.). These differences can be passed on to an individual’s offspring.2. Overproduction: Many more organisms are born, than those that survive and reproduce.3. Limits on population Growth: Limited resources (food, water, space, sunlight, etc.) creates competition4. Differential reproduction: Organisms with features that help them compete will be more likely to survive and reproduce.Natural Selection Changes PopulationsTheory of evolution by natural selection:Consequences of natural selectionOver time, the characteristics of a population will “evolve” and assume those features that are “naturally selected”.What is the heritable molecule with the blueprints for the traits of an organism?DNA: Deoxyribose nucleic acidAll life can be classified taxonomicallyTaxonomy: The branch of biology concerned with naming and classifying organismsMost Biologists Recognize Five Kingdoms: Monera, Protista, Plantae, Fungi, and Animalia1. Kingdom Monera (Procaryotae): Most widespread organisms. Procaryotes (“Before nucleus”):Lack nuclear membrane around DNA.Lack membrane bound organelles (mitochondria, chloroplast, golgi, endoplasmic reticulum).Unicellular: Single celled organisms.Have a cell wall.Include: Bacteria. Kingdom Prokaryotae: Bacteria lack nucleus and membrane bound organellesFive Kingdoms of Living World:2. Kingdom Protista: Eucaryotes (True nucleus):Have nuclear membrane around DNA.Have membrane bound organelles (mitochondria, chloroplast, golgi, endoplasmic reticulum).Unicellular or simple multicellular. Most are larger and more complex than bacteria. Some have cell walls, others don’t.Some make their own food (phothosynthetic), others must eat other organisms.Include: Protozoa, algae, slime molds.Kingdom Protista: Eucaryotic Unicellular or Simple Multicellular OrganismsFive Kingdoms (Continued): 3. Kingdom Fungi: Most are multicellular. Eucaryotes: Have nuclear membrane around DNA.Have membrane bound organelles (mitochondria, chloroplast, golgi, endoplasmic reticulum).Have cell walls.Heterotrophs: Obtain food from other organisms.Most are decomposers, which absorb food from dead organisms.Include: Mushrooms, yeasts, and molds.Five Kingdoms (Continued):4. Kingdom Plantae: Complex multicellular organisms. Cellulose cell walls.Eucaryotes: Have nuclear membrane around DNA and membrane bound organelles.Autotrophs: Convert sunlight, water, and carbon dioxide into food through photosynthesis.Other features:Waxy cuticle that prevents water loss.Multicellular sex organs.Openings in leaves and stems for gas exchange (stomata).Include: Trees, flowering plants, and mosses.Five Kingdoms (Continued):5. Kingdom Animalia: Complex multicellular organisms. Lack cell walls.Eucaryotes: Have nuclear membrane around DNA and membrane bound organelles.Heterotrophs: Obtain chemical energy from living sources. Eat other organisms for nourishment.Features of complex animals:High degree of tissue specialization and body organization.Locomotion.Well developed sense organs, nervous system, and muscles.Include: Sponges, worms, insects, and vertebrates.Interdependence of Biological Groups1. Producers or Autotrophs: Self-nourishing organisms (plants, algae, etc.). Produce food from simple raw materials.Most carry out photosynthesis:CO2 + H2O + Sunlight -----> Food + OxygenDepend on nonproducers for carbon dioxide2. ConsumersMainly animals.Heterotrophs that obtain food directly or indirectly from producers.Carry out cellular respiration:Food + Oxygen -----> CO2 + H2O + ENERGYGas exchange between producers and consumers helps maintain balance of life-sustaining gases in atmosphere.Interdependence of Biological Systems3. Decomposers:Some bacteria, fungi, and animals. Recycle nutrients by breaking down products and bodies of dead organisms.Process is vital because makes nutrients available for use by other organisms.All organisms interact with each other and the environment they live in.Interactions between producers, consumers, and decomposers are essential to maintain proper conditions for life on earth.Photosynthesis Helps Counteract the Greenhouse EffectThe earth’s atmosphere contains about 0.03% of carbon dioxide. Carbon dioxide traps solar energy in the atmosphere, making the earth about 10oC warmer than it would otherwise be.Since the mid 1800s, the atmospheric levels of carbon dioxide have risen steadily due to the burning of fuels and forests.The “Greenhouse Effect” refers to the global warming that is caused by increased atmospheric carbon dioxide levels.Global warming may cause polar ice caps to melt, which in turn could cause massive coastal flooding and other problems.Plants use up about half of carbon dioxide generated by humans and other organisms.Greenhouse Effect: Heat is Trapped by Carbon DioxideSCIENCE AS A METHOD OF INVESTIGATION Scientia (Latin): To knowScience is a systematic way of thinking, answering questions, and solving problems.Steps of scientific method:1. Observations2. Question3. Hypothesis4. Predictions5. Test predictions (Experiments)Results of experiments may:Support (but not prove) hypothesisDisprove hypothesis -----> Change hypothesis.Scientific method (Continued):Hypothesis:Proposed explanation for observationsAn “educated guess”, should be consistent with established factsCapable of being tested, should generate predictions.Falsifiable, may be proven false (but not proven true).Variables in an ExperimentDependent Variable: What a scientist measures.Independent variable: What a scientist controls or manipulates.Standardized variables: What remains the same throughout experiment. E.g.: Age, sex, race, nutrition, health, etc.Control Treatment:Independent variable is eliminated or set at a standard value.Levels of TreatmentValues set for the independent variable.Scientific method:ReplicationExperiments are repeated numerous times.Consistent results increases confidence in results.Sample size: Larger sample sizes are generally better.Theory:Hypothesis supported by a large body of observations and experiments.Good theories relate previously unrelated facts and grow as new information is obtained.Principle:A theory that over time has yielded true predictions.Almost universally accepted.Law:A principle of great basic importance.Law of gravity or biogenesis.
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