BIOLOGY IS THE SCIENCE OF LIFE ORGANIZATION OF
BIOLOGY IS THE SCIENCE OF LIFE ORGANIZATION OF LIVING THINGS CH 1
n Living organisms share common aspects of structure, function and energy flow n Living things on earth are all of the diverse organisms descended from a single-celled ancestor. n BIOLOGY is the study of these living things and their relationships
n Life is difficult to define, so we look at characteristics/properties of life – Cellular organization – Order(cellular structures) – Sensitivity-response to stimuli (Regulation) – Growth, development, reproduction(heredity) – Energy utilization (Cellular Respiration) – Evolutionary adaptation & interaction – Homeostasis – Excretion
HEIRARCHICAL ORGANIZATION Each level builds on the one below it: § Cellular level: atoms molecules organelles cells § Organismal level: cells tissues organs systems organism § Population level: organisms of same species population community ecosystem biosphere
HEIRARCHY OF LIFE
LIFE’S CALENDAR n If we look at the evolution of life as if it were a 30 -day calendar…. . – Each day represents 150 million years – Life appeared some time around day 5 (3. 8 bya)
– Day 8 ---oldest fossils (unicellular heterotrophs only) – Day 13 ---photosynthesis evolves – Day 20 ---eukaryotic cells evolve – Day 24 ---multicellular organisms appear – Day 28 ---first land plants, first land animals – Day 29 ---dinosaurs dominant – Day 30 ---first birds, rise of mammals, first flowering plants – Homo sapiens (modern humans) arose in the last 5 minutes of day 30(500, 000 yrs ago) – Recorded history covers the last few seconds of day 30
Early Life on Earth
n According to evolutionary theory…. life arose from non-life by chemical evolution. – Early earth’s atmosphere…no Oxygen – First biological molecules arose from random associations of chemicals.
– Critical step was appearance of nucleic acids which could reproduce themselves and serve as templates for synthesis of larger molecules that were more stable PROTEINS – Proteins became enclosed by membranes. . . evolution of first cellular organisms
n For more than 2 billion years, all organisms were single cell heterotrophic prokaryotes (no membrane bound organelles)
n Photosynthesis (about 2. 7 billion years ago)—allowed organisms to capture energy from the sun. n No oxygen so existing prokaryotes were anaerobic. As oxygen was produced from photosynthesis, it was in atmosphere and organisms began to adapt to it and use it. We now have aerobic organisms
n Organisms were originally protected by the water…. as oxygen increased in the atmosphere, ozone layer was created and this protected the life on earth from the harmful radiation…. more organisms could now adapt to land life
n Eukaryotic cells evolved from prokaryotes. – Contained membrane bound organelles
n Some organelles may have originated by endosymbiosis (living inside another) – Mitochondria and chloroplasts – ENDOSYMBIOTIC THEORY § (endo=inside; symbiosis=cohabitating) § Certain organelles originated as free-living bacteria that were taken inside other cells…. . § Mitochondria and chloroplasts have double membranes and have their own DNA (which is different from cell DNA) and it is also circular rather than linear. § Possibly peroxisomes may have fit this theory but they do not contain DNA…………
n If all organisms on earth are descendants of a single kind of cell that lived 4 billion years ago, how have they become so different? ? – MUTATIONS n Millions of species exist so we need a system to classify them— – Carrolus Linnaeus –system of binomial nomenclature – Phylogenetic trees document evolutionary relationships
NATURE OF SCIENCE Biology is one of the most successful of the natural sciences § Scientists use the basic tool of thought, reasoning § § Deductive reasoning—applies to principles that predict specific results § Logic flows from general specific Ex. Inferring the species of a specimen from its characteristics
n The Origin of Life
§ Inductive Reasoning—uses specific observations to construct general scientific principles § Logic flows from specific general § Leads to generalizations that can then be tested
HOW SCIENCE IS DONE (Scientific Method) n Observations n Hypothesis n Experimentation (variables, control) n Rejection or additional hypotheses n Predictions n Theory proposal n Continue testing
DESIGN AN EXPERIMENT AND DISCUSS EXPECTED RESULTS (AP EXAM) Include the following: nhypothesis n. Ind/dep variables (only 1 variable) n. Describe experimental treatment n. Describe control treatment n. Random sample of subjects n. Describe procedure n. Describe expected results---graphs? ? n. Give explanation of results in relation to biological principles
MEET CHARLES DARWIN!!
Darwin and his monkey ancestor!!!
ABOUT CHARLES DARWIN Darwin’s theory exemplifies how a scientist develops a hypothesis and how a scientific theory grows and gains acceptance n 1809 -1882 n The Origin of Species (his book) n Natural Selection n Operation of natural laws change over time (EVOLUTION) put him at odds with most people--Bible n HMS Beagle-5 yr. trip around S. America n
Human evolution? ? ? ?
Darwin/his voyage HANDSOME YOUNG CHAP HUH? ? ? . . . . . .
n Darwin thought that species were immutable. n He observed several phenomena on his trip that made him believe otherwise n Galapagos Islands---14 finch species with different beaks n Darwin’s great achievement lies in his formulation of the hypothesis that evolution occurs because of natural selection
DARWIN AND MALTHUS § Thomas Malthus was of key importance to Darwin’s work § Populations of organisms tend to increase geometrically while humans are able only to increase their food supply arithmetically § Overproduction, competition, survival of the fittest, natural selection § Alfred Wallace also was important in Darwin’s final theory (agreed with him)
Geometric/arithmetic progression
Malthus Theory
EVIDENCES OF EVOLUTION n Fossil record – Earth is 4. 5 billion yrs old – Microscopic fossils-2. 5 billion yrs
Fossils in rock layers
n Comparative anatomy – Homologous structures-(similar structures/different functions – Analagous structures-(similar functions/different structures) § Not involved in common ancestry
Carbon-dating……… Carbon-14 dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50, 000 years old. It is used in dating things such as bone, cloth, wood and plant fibers that were created in the relatively recent past by human activities
n Comparative genes/DNA biochemistry-sequence of – Ex. Hemoglobin Cytochrome c-nucleotide sequence has more differences in organisms that diverged further apart in time (this gene plays a key role in oxidative metabolism of all terrestrial vertebrates and appears to have accumulated changes at a constant rate)
n Comparative embryology
n Comparative cytology n Phylogenetic trees- represents evolutionary history of a gene. . family tree – Molecular phylogeny agrees well with those derived from fossil record THE PATTERN OF ACCUMULATING DNA CHANGES REPRESENTS THE FOOTPRINTS OF EVOLUTIONARY HISTORY!!
Unifying Themes of Biology n Organization of life (cell theory) n Continuity of life (molecular basis of inheritance) n Diversity of life (evolutionary change) n Unity of life (evolutionary conservation)
The Nature of Molecules ch 2 n About 14 billion years ago, an enormous explosion marked the beginning of the universe. When put into perspective, life within our solar system is a recent development. Events that took place much earlier are responsible for the evolution of molecules…. . Thus our study of life one earth begins with physics and chemistry.
Chemistry terms… n Matter-any substance that has mass and occupies space… n Atom-extremely small particles composing mass – Consist of protons, electrons, neutrons – #protons= #electrons…if not it is an ion – Difference in # neutrons creates isotopes
n Ion – Atoms in which the number of electrons does NOT equal the number or protons
Isotope – Atoms of a single element that possess different numbers of neutrons
– In some rx, electrons are passed from one atom to another--§ Loss of e- is oxidation § Gain of e- is reduction LEOGON RA GERLON OA
BONDS arrangement of electrons and how they interact with other atoms determines how they bond n Ionic bonds-form crystals, electrons transferred – Ex: Na. Cl Na+, Cl- n Covalent bonds-form stable molecules, electrons are shared – Strong bonds, strength increases with # of shared electrons (single, double, triple) – Can be polar(atoms are different, creates poles) or non-polar
n Think of bond types as a continuum… nonpolar _____polar ____ionic covalent equally shared e- unequally shared e- completely transferred e- varying degrees of electron sharing
n Crash Course Carbon
WATER Of all molecules on earth, WATER is the only one that exists as a liquid at the relatively low temperatures on the earth’s surface n When life originated, water provided a medium in which other molecules could interact. (life evolved n because of these interactions) 2/3 of an organism’s body is water n No org can grow or reproduce in an environment without water (desert vs. rainforest) n
n Chemistry of life= Water chemistry n The most outstanding chemical property of water is its ability to form weak chemical associations with little strength (only 5 -10% of strength of covalent bonds) Hydrogen bonds which are very weak are involved in these associations n Water molecules have distinct “ends” like poles of a magnet(polar) n Due to polarity of water, it is attracted to other polar molecules (adhesion, cohesion, capillary action) n
Water transport
Properties of water n 1. Cohesion---surface tension (insects walking on water) n 2. High specific heat (amount of heat absorbed or lost by 1 n 3. Powerful solvent gram of substance to change temp by 1 degree C. ) The more polar a substance, the higher the specific heat. Water heats up slowly, holds temp longer. This aids in organisms ability to maintain a constant internal temp. – Ionic substances are soluble in water b/c poles of the polar water interact with charged substances and separate them into ions – Polar covalent substances dissolve in water because they share the same hydrogen bonding with water as it shares with itself
--polar covalent substances are called hydrophilic (water loving) -- Non polar covalent substances are called hydrophobic (water fearing). . do not dissolve in water (cell memb. ) § 4. High heat of vaporization § Many bonds must be broken for water to evaporate (cooling of body surfaces)
Insect walking on water
n 5. Ionization – Covalent bonds within water may break spontaneously and form ions. – p. H expresses H+ ion concentration in a solution – For every H+ ion formed when water dissociates, An OH- ion is also formed § H+ and OH- are produced in equal amounts, therefore a p. H value of 7 indicates neutrality § A stronger acid produces more H+ ions so lower p. H
Remember… --At 25 degrees Celsius, a liter of water contains 10 -7 mole H+ ions --Difference of 1 on p. H scale has a difference of 10 on logarithmic scale (p. H is negative logarithm of the hydrogen ion concentration in solution) --p. H 3 -4 has 10 times difference in acidity-
n Hydrochloric water acid dissociates completely in – 10 -1 mole/liter HCl 10 -1 mole/liter H+ ions so p. H of solution = 1 – Champagne, stomach acid, lemon juice 2 – Vinegar, cola, beer 3 – Urine, saliva 6 – Pure water, blood 7 – Baking soda 9 – Household ammonia 11 – Sodium hydroxide, oven cleaner 14
p. H/examples
n. A substance that combined with H+ ions when dissolved in water is a base. A base lowers the H+ concentration in solution – Basic=alkaline p. H=7
n Crash Course Water
BUFFERS n Buffers keep p. H relatively constant – p. H in living cells is close to 7 – Most enzymes (catalysts) are sensitive to p. H – A buffer acts as a reservoir of H+ ions— donating them to the solution when their concentration falls and taking them from solution when their concentration rises.
Most buffers consist of pairs of substances (1 acid and 1 base) n The human blood buffer is the acid-base pair of carbonic acid and bicarbonate (base) n – CO 2 + H 2 O H 2 CO 3 (carbonic acid) – H 2 CO 3 dissociates HCO 3 -(bicarbonate ion)+ H+ § carbonic anhydrase is an important enzyme in this rx.
n If + some other substance adds H ions to blood, the HCO 3 ions act as base to + remove excess H by forming H 2 CO 3 + n If a substance removes H ions from blood, H 2 CO 3 dissociates, releasing more + H ions. n This stabilizes the blood p. H and maintains it by the reversible reactions
n ACIDOSIS---when the blood p. H becomes more acidic; many causes; can harm the kidneys…needs to be neutralized
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