Chapter 1 - An Introduction to Life on Earth

Transcription

1 Chapter 1 - An Introduction to Life on Earth Characteristics of Living Things What are the characteristics of living things? Living things: ORGANISMS 1. Living Things are Organized subatomic particles --> atoms --> molecules -->cells --> tissues --> organs --> organ systems --> organism --> population --> community --> ecosystem --> biosphere Emergent Properties: properites that occur due to interactions of the parts, governed by the laws of physics 2. Living Things Must Acquire and Use Energy Organisms extract these nutrients from their environment and incorporate them into the molecules of their own bodies. Animals eat, plants use photosynthesis Energy: the capacity to do work Metabolism: all the chemical reactions that occur in a celln. Homeostasis: state of biological balance. Organization tends to disintegrate into chaos unless energy is used to sustain it. reptiles bask in sun to raise body temperature humans sweat to lower body temperature metabolizing fat when food is scarce 3. Living Things Respond To Stimuli Sensory systems give animals and even single celled organisms the ability to respond to their environment. Information about light, temperature, sound, pain then result in changes in the organisms

2 behavior. 4. Living Things Reproduce and Develop Continuity of Life: Reproduction: giving rise to offspring of the same type Diversity of Life: sexual reproduction combines genetic informatin from both parents to create like offspring, but offspring that is slightly different from both parents. The mechanism by which traits are passed from one generation to the next is called Heredity, DNA (deoxyribonucleic acid) is the molecule of heredity. Sometimes DNA can change spontaneously and accidentally - mutations- which can also account for variety and is the basis for evolutionary change 5. Living Things Have Adaptations Adaptations: modifications that make an organism suited to its way of life Adaptations occur through natural selection (Darwin's Theory of Evolution) Species: Group of similar organisms that can interbreed HOW THE BIOSPHERE IS ORGANIZED 1. The biosphere is the zone of air, land, and water where organisms exist. 2. A population consists of all members of one species in a particular area. 3. A community consists of all of the local interacting populations. 4. An ecosystem includes all aspects of a living community and the physical environment (soil, atmosphere, etc.). 5. Interactions between various food chains make up a food web. 6. Ecosystems are characterized by chemical cycling and energy flow.

3 7. Ecosystems stay in existence because of a constant input of solar energy and the ability of photosynthetic organisms to absorb it. Biodiversity 1. Biodiversity is the total number of species, their variable genes, and their ecosystems. 2. Extinction is the death of a species or larger group 3. The continued existence of the human species is dependant on the preservation of ecosystems and the biosphere. HOW LIVING THINGS ARE CLASSIFIED Taxonomy is the discipline of identifying and classifying organisms according to certain rules. Categories of Classification From smaller (least inclusive) categories to larger (more inclusive), the sequence of classification categories is: species, genus, family, order, class, phylum, kingdom, domain. Domains: Biochemical evidence suggests that there are three domains: Bacteria, Archaea, and Eukarya. Archaea can live in water devoid of oxygen, and are able to survive harsh environmental conditions (temperatures, salinity, ph). Bacteria are variously adapted to living almost anywhere (water, soil, atmosphere, in/on the human body, etc.).

4 1. Protists (kingdom Protista) range from unicellular forms to multicellular ones. 2. Fungi (kingdom Fungi) are the molds and mushrooms. 3. Plants (kingdom Plantae) are multicellular photosynthetic organisms. 4. Animals (kingdom Animalia) are multicellular organisms that ingest and process their food. Scientific Name (Binomial Nomenclature) 1. A binomial name is a twopart scientific name: the genus (first word, capitalized) and the specific epithet of a species (second word, not capitalized). 2. Binomial names are based on Latin and are used universally by biologists. 3. Either the genus name or the specific epithet name may be abbreviated Examples: Panthera leo & Panthera tigris & Panthera pardus Subspecies: added onto the end of the genus + species Canis lupus familiaris Chapter 1 - Biology: The Science of Life Scientific Principles Natural Causality is the principle that all events can be traced to natural causes o all events can be traced to natural causes that are within our ability to comprehend o supernatural forces are excluded o if we cannot trust the evidence provided by nature, then studying and trying to understand nature is futile o The natural laws that govern events apply everywhere and for all

5 time o natural laws do not change with time o behavior of light, gravity, and genes is the same now as it was billions of years ago Scientific inquiry is based on the assumption that people perceive natural events in similar ways science does not address value systems or morality science only addresses that which can be perceived science is objective, not subjective The Scientific Method 1. Observations (Gathering Knowledge,Questions) 2. Hypothesis (prediction, testable, falsifiable) 3. Experimentation (further observation) 4. Data (objective only) 5. Conclusions Inductive Reasoning - combine isolated facts into a cohesive whole, as in to develop a hypothesis Deductive Reasoning - Using "if - then" logic to make a prediction, as in to test the hypothesis A Controlled Study Variable - a single factor that causes and observation Independent (Experimental) Variable -what you manipulate Dependent (Responding) Variable - what you measure Control - a group in the experiment that remains constant, so the variable can be compared.

6 Conclusions: Data gathered from the experiment can support or reject a hypothesis. A hypothesis is never PROVEN. *A Hypothesis becomes credible when repeated attempts to disprove it fail. *Publishing is an important aspect of scientific research *A Model is a representation of an actual object, used sometimes to conduct an experiment EXAMLPLE: Observation: Babies are born with severe birth defects, mothers of these babies report taking the drug thalidomide during pregnancy for morning sickness. Question: Does thalidomide cause birth defects? Hypothesis: Thalidomide causes birth defects. Experiment: Control group: Mice not given thalidomide during pregnancy Variable: Mice given thalidomide during pregnancy In this experiment, mice born from both the control and variable group will not have birth defects. This experiment was performed long before thalidomide was marketed and prescribed to pregnant women. Does these mean that the hypothesis is not supported? What is a Theory? A Theory is an explanation for natural events that is based on a large number of observations. Can also be referred to as a PRINCIPLE or a LAW. Scientific Theories join together well supported and related

7 hypotheses Its important to realize that theories EXPLAIN what we observe. For instance, the Germ Theory explains why we get sick and why we get infections, in short it uses observation of viruses and bacteria as well as data from those who get ill to create a theory on what causes the illness. Theories must explain a wide range of observations Theories must be falsifiable Theories can be changed if new evidence presents itself Examples of Scientific Theories: Germ Theory, Cell Theory, Atomic Theory, Theory of Evolution, Heliocentric Theory What is Occam's Razor? Ockham's Razor (Occam is the latinized and more common spelling) is a principle proposed by William Ockahm in the 15th century. The original principle stated "Pluralitas non est ponenda sine neccesitate" which translates as "entities should not be multiplied unnecessarily" Modern times - it basically means that the simplest explanation is usually the right one. Example: A paper clip is placed on a scale, the scale reads 600 pounds. The following hypotheses can be proposed 1. The paperclip weighs 600 pounds 2. The scale is broken 3. There is a miniature black hole producing a gravitational pull on the paperclip at that moment, creating such a force to make the paperclip weigh 600 pounds

8 Though all three hypothesis may be correct, in fact we could probably make up a dozen other explanations, Ockham's razor would suggest that the simplest explanation is probably the correct one (the scale is broken)