Chapter 1 -Learning About Human Biology.pptx

PowerLecture: Chapter 1 Learning About Human Biology  Learning Objectives  Learn the characteristics of life.  Learn the characteristics of humans.  Understand life’s organization and diversity.  Listthe steps of the scientific method of inquiry  Section 1 The...

PowerLecture: Chapter 1 Learning About Human Biology  Learning Objectives  Learn the characteristics of life.  Learn the characteristics of humans.  Understand life’s organization and diversity.  Listthe steps of the scientific method of inquiry  Section 1 The Characteristics of Life  The Characteristics of Life  Living and nonliving things share common characteristics, such as being composed of atoms, the smallest units of nature’s fundamental substances.  The Characteristics of Life  Living things, though, have many distinctive features: 1. Living things take in and use energy and materials. 2. Living things sense and respond to specific changes in their environment. 3. Living things reproduce and grow. 4. Living things consist of one or more cells. 5. Living things maintain homeostasis (dynamic balance). 6. Populations of living things are capable of evolving.  The Characteristics of Life 1. Living things require energy and raw materials. Plants, some bacteria and some protists (Autotrophs): Energy: from sunlight Materials: water, carbon dioxide, nitrogen, phosphorus etc. They create their own food through photosynthesis. Animals, fungi, some bacteria, some protists (Heterotrophs) Energy: chemical bonds from eating (decomposing) other animals / plants. Ultimately from the sun. Materials: from other organisms.  The Characteristics of Life 2. Living things sense and respond to the environment. Living things perceive and respond to external stimuli. Examples:  Humans withdraw their hands from hot objects.  Plants grow towards the light and move their leaves to catch the maximum amount of sun.  Bacteria swim away from noxious chemicals.  The Characteristics of Life 3. Living things: grow and reproduce DNA is the genetic material, which only living things have. Based on instructions in DNA, organisms can make more of their own kind.  The Characteristics of Life 4. Living things consist of one or more cells. Cell theory of biology: A cell is the smallest unit of life, so all living things have at least one cell. All cells come from pre-existing cells. Unicellular vs. multicellular. A unicellular amoeba A rabbit neuron  The Characteristics of Life 5. Living things: maintain homeostasis  Internal environment maintained within a narrow chemical and physical range for cells to survive  Maintenance of this environment is called: homeostasis.  Examples: Human body temperature around 37o C. (Warmer after exercise, cooler when sleeping) Maintained by: sweating, shivering, changing blood circulation to skin: less blood if it is cold out, more blood if it is warm out  The Characteristics of Life 6. Populations of living things are capable of evolving Evolution: a change in frequency of genetic traits in a population of organisms. Sometimes the population may change, over time, leading to new life forms emerging. Natural selection: (“survival of the fittest”) animals with “good genes” are more likely to survive and reproduce, thus passing these good genes on to their offspring. Nature “selects” animals with the best traits for survival and reproduction because unfit animals may die without reproducing and do not pass on their less fit genes.  Section 2 Our Place in the Natural World  Our Place in the Natural World  Humans have evolved over time.  Human beings are a part of biological evolution—the change in organisms through the generations.  Humans are mammals belonging to the animal kingdom, one of the four kingdoms of life in the domain Eukarya. Figure 1.3  Our Place in the Natural World  Humans are related to all other organisms— and humans also have some distinctive features.  Humans share characteristics with our closest primate relatives.  Humans also have distinctive features: increased dexterity, large brain, analytical skills, sophisticated communication, and social behaviours. Figure 1.4  Section 3 Life’s Organization  Life’s Organization  Life is organized on many levels.  Atoms and molecules are nonliving materials from which all of nature is built.  Cells are organized into increasingly complex levels: tissues >>> organs >>> organ systems >>> organisms.  Organisms, in turn, form populations >>> communities >>> ecosystems >>> biosphere. Levels of Organization in Nature Figure 1.5  Life’s Organization  Organisms are connected through the flow of energy and cycling of materials.  Energy flows from the sun. Plants (“producers”) trap this energy by photosynthesis. Animals (“consumers”) feed on the stored energy in plants. Bacteria and fungi (“decomposers”) break down the biological molecules of other organisms in order to recycle raw materials.  All organisms are part of webs that depend on one another for energy and raw materials. Flow of Energy and Cycling of Materials in the Biosphere Figure 1.6  Section 4 Science Is a Way of Learning about the Natural World  Science Is a Way of Learning about the Natural World  Science is an approach to gathering knowledge.  Biology, like all science, pursues a methodical search for information that reveals the secrets of the natural world. Science Is a Way of Learning about the Natural World  Explanations are sought using an approach known as the scientific method: 1. Observe some aspect of the natural world and ask a question. 2. Develop hypotheses (educated guesses) using all known information. 3. Predict what the outcome would be if the hypothesis is valid. 4. Test the hypothesis by experiments, models, and observations. 5. Repeat the tests for consistency. 6. Analyze and report objectively on the tests and conclusions. Fig. 1.8  Science Is a Way of Learning about the Natural World  Experiments are major scientific tools.  Experiments involve tests in which conditions are carefully controlled. Control groups are used to identify side effects during a test that involves an experimental group. The experimental group experiences all of the same conditions as the control except for the variable being studied.  The sample size must be large enough to be representative of the whole. Sampling Error  Section 5 Critical Thinking in Science and Life Critical Thinking in Science and Life  Critical thinking is an objective evaluation of information (evidence based).  Consider the source.  Let credible scientific evidence, not opinions or hearsay, do the convincing.  Question credentials and motives.  Evaluate the content.  Be able to distinguish between cause and correlation.  Separate facts from opinions. Figure 1.10  Section 6 Science in Perspective  Science in Perspective  A scientific theory explains a large number of observations.  A theory is a related set of hypotheses that form a broad-ranging explanation of many phenomena.  Theories are accepted or rejected on the basis of tests and are subject to revision.  Scientists must be content with relative certainty, which becomes stronger as more repetitions are made.  Scientists must be prepared to change their minds in light of new evidence.  Science in Perspective  Science has limits.  Science is limited to questions that can be tested; subjective questions do not readily lend themselves to scientific analysis or experiments.  Science has the potential to be used for controversial endeavors, which means that all of society must commit to responsible use of scientific knowledge.  1 General Observation “Many people that are smokers are having serious health problems, including lung cancer (and also high blood pressure, heart attacks, strokes, emphysema)”  2 General hypothesis People who smoke are more likely to get lung cancer than people who do not smoke. 3 Observational study and testable hypotheses Plan: Randomly sample from the UAE: 100,000 smokers and 100,000 non-smokers and count the number of people that get lung cancer in each group after many years. Why is random sampling important? What is the control group, and why is it important? What is the experimental group? Testable hypotheses: 1 There is no difference in the incidence of lung cancer between the two groups (null hypothesis) 2 There is a difference in the incidence of lung cancer between the two groups (alternate hypothesis)  Observational Study Results Smokers: 60 cases of lung cancer Non-smokers: 2 cases of lung cancer What does this mean?  Reject null hypothesis Testable hypotheses: 1 There is no difference in the incidence of lung cancer between the two groups (null hypothesis) 2 There is a difference in the incidence of lung cancer between the two groups (alternate hypothesis) Evidence supports the idea that cigarettes may cause lung cancer, but does not prove this! 4 Experimental study to test hypothesis Plan: Take 200,000 mice and randomly divide them into 2 groups of 100,000. Expose one group to cigarette smoke throughout their life, and do not expose the other group. Which is the control group? What is the experimental group? Testable hypotheses: 1 There is no difference in the incidence of lung cancer between the two groups 2 There is a difference in the incidence of lung cancer between the two groups Which is the null hypothesis, which is the alternate hypothesis?  Experimental study results Compare incidence of lung cancer in mice Results: Smoking Non-smoking 210 4 Once again, after doing statistics we reject the null hypothesis, and support the alternate hypothesis.  Cigarette company (skeptical) response: “These two studies do not prove that cigarettes cause lung cancer, the first was merely bad luck, and besides it only looked at one country. The second involved MICE not people”. We did not prove cigarettes caused cancer, but we did accumulate evidence. Only through the accumulation of overwhelming scientific evidence from a variety of studies the world over did cigarette companies admit that smoking causes lung cancer.