Chapter 1

1. Chapter 1 Biology 25: Human Biology Prof. Gonsalves Los Angeles City College Loosely Based on Mader’s Human Biology,7th edition

2. Chapter 1 Introduction: The Scientific Study of Life Biology: The study of life. Greek origin: Bio: Life Logos: Study of

3. 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

4. Levels 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)

6. 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.

7. 4. Regulation • External 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.).

8. 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.

10. Evolution is the core theme of biology • Charles 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 progression • Artificial selection of domestic/farm animals • Adaptations: Organisms appear uniquely suited to their environment (especially in Galapagos). • Darwin’s finches are a classic example

11. The 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 competition 4. Differential reproduction: Organisms with features that help them compete will be more likely to survive and reproduce.

12. Natural Selection Changes Populations

13. Theory of evolution by natural selection: Consequences of natural selection Over 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 acid

14. All life can be classified taxonomically • Taxonomy: The branch of biology concerned with naming and classifying organisms • Most Biologists Recognize Five Kingdoms:Monera, Protista, Plantae, Fungi, and Animalia 1. 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.

15. Kingdom Prokaryotae: Bacteria lack nucleus and membrane bound organelles

16. Five 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.

17. Kingdom Protista: Eucaryotic Unicellular or Simple Multicellular Organisms

18. Five 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.

19. 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.

20. 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.

23. Interdependence of Biological Groups 1. Producers or Autotrophs: • Self-nourishing organisms (plants, algae, etc.). • Produce food from simple raw materials. • Most carry out photosynthesis: CO2 + H2O + Sunlight -----> Food + Oxygen • Depend on nonproducers for carbon dioxide 2. Consumers • Mainly animals. • Heterotrophs that obtain food directly or indirectly from producers. • Carry out cellular respiration: Food + Oxygen -----> CO2 + H2O + ENERGY Gas exchange between producers and consumers helps maintain balance of life-sustaining gases in atmosphere.

24. Interdependence of Biological Systems 3. 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.

29. Photosynthesis Helps Counteract the Greenhouse Effect • The 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.

30. Greenhouse Effect: Heat is Trapped by Carbon Dioxide

31. SCIENCE AS A METHOD OF INVESTIGATION Scientia (Latin): To know Science is a systematic way of thinking, answering questions, and solving problems. Steps of scientific method: 1. Observations 2. Question 3. Hypothesis 4. Predictions 5. Test predictions (Experiments) Results of experiments may: • Support (but not prove) hypothesis • Disprove hypothesis -----> Change hypothesis.

32. Scientific method (Continued): Hypothesis: • Proposed explanation for observations • An “educated guess”, should be consistent with established facts • Capable of being tested, should generate predictions. • Falsifiable, may be proven false (but not proven true). Variables in an Experiment • Dependent 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 Treatment • Values set for the independent variable.

33. Scientific method: Replication • Experiments 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.