IB Development of Life Study Guide

This study guide key is meant to be an aid of studying.  Attempting to answer these questions/standards yourself using the blank study guide then consulting the key will be most beneficial; unless you have a photographic memory (most people do not) simply reading this will probably not result in you memorizing, trust me I tried this in college.  

Origin of Life on Earth

Read this article concerning development of first organic molecules on Earth.  It is extremely relevant and very interesting

• How might organic compounds appeared on Earth?

• Comets

• What may have cells have been preceded by?

• Protobionts; examples coacervates & microspheres

• Outline the experiments of Miller and Urey into the origin of organic compounds

• 1950s experiment to simulate the ability to abiotically produce organic molecules based on hypothesized early earth conditions
• Used water, methane, ammonia, hydrogen sealed inside sterile glass tubes/flasks; water heated to induce evaporation, sparks provided to simulate lightning, atmosphere was cooled; within two weeks 10-15% of carbon within system was in form of organic compounds with 2% forming amino acids

• Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere

• Lack of free oxygen in early atmosphere
• After 1.5-2 billion years of life, evolution of chlorophyll and prokaryotes able to photosynthesize
• Early oxygen accumulated in seas and lakes, eventually “gas out” of water into atmosphere
• Caused rusting of iron in rocks
• Oxygen levels increased rapidly from 1% to 10% of present level
• Eliminated most anaerobic life but provided opportunity for aerobic life

• Describe four processes needed for the spontaneous origin of life on Earth

• Non-living (abiotic) synthesis of simple organic molecules
• Assembly of organic molecules into polymers
• Origin of self-replicating molecules that allow for inheritance
• Packaging of these molecules into membranes with an internal chemistry different from their surroundings

• Outline two properties of RNA that would have allowed it to play a role in the origin of life.

• RNA can store transmit (genotype)  and replicate genetic information while expressing that information (phenotype)
• Thought that only enzymes could catalyze necessary reactions for cell survival, enzymes produced by dna; in 1980s Sidney Altman & Thomas Cech found that RNAs can also catalyze chemical reactions, called ribozymes; they won 1989 nobel prize in chemistry
• Suggests and supports hypothesis that rna was used to store genetic information before evolution of DNA (dna most likely evolved because of rna’s instability and poor catalytic properties)
• Hypothesis further supported by the fact that rna makes up ribosomes which makes enzymes and rna catalyzes assembly of peptide chain

• Discuss possible locations where conditions have allowed the synthesis of organic compounds

• Deep Sea Vents: presence or necessary molecules (ammonia & methane), extremely high temperatures and pressures; temperature may suggest not possible due to unstable organic molecules at high temperatures
• Volcanoes: involve release of methane, ammonia, hydrogen gas & water vapor; combined with lightning creates a real version of Miller-Urey experiment
• Extraterrestrial: September 28, 1969 meteor in Australia crashed, organic molecules found within interior of meteor

• Discuss the endosymbiotic theory for the origin of eukaryotes

• Suggests mitochondria, chloroplasts and other organelles were formerly small prokaryotes that began living within larger cells
• Gained entry by undigested prey or internal parasites
• Mutually beneficial relationship
• Supporting Evidence: Grow and divide like cells, Mitochondria have own DNA, synthesis of own proteins, double membranes

Human Evolution

• Define half-life

• Half Life: radioactive parent isotope decays to a daughter isotope at a fixed rate; rate of decay is half-life, time required for 50% of parent isotope to decay

• State that, at various stages in hominid evolution, several species may have coexisted

• Describe the major anatomical features that define humans as primates

• Grasping pentadactyl limbs
• Binocular Vision
• Reduced snout leading to reduced olfaction (sense of smell
• Generalized Dentition
• Twistable Forelimbs
• Clavicle allows for wide range of arm movement
• Slower reproduction (long gestation, usually one offspring at a time)
• Large skull relative to body size
• Larger brain, more complex and more folds
• Better visual acuity
• Social dependency

• Outline the trends illustrated by the fossils of Ardipithecus ramidus, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis  and H. sapiens

• Increased brain size, bipedalism, migration out of Africa, decreased relative size of snout and increase of flattened face
• Know general characteristics for species listed above as examined on NOVA Who’s who in human evolution

• H. neanderthalensis: 200,000-30,000 years ago; rugged physique adapted to ice age, hunted and buried dead; found in Europe and Asia
• H. erectus: 1.8 million - 50,000 years ago; large brain (relative to previously existing species), large browlines and oblong brain case, mostly vertical face, small teeth; China, Africa, Georgia
• A. africanus: 3-2 million years ago; bipedal but also probably well adapted to climbing; found in Africa, primarily southern

• Distinguish between genetic and cultural evolution

• Genetic: Evolution of DNA sequences, genetic changes; for example bipedalism
• Cultural: Evolution of ideas held and actions taken; for example social behavior

• Deduced the approximate age of materials based on a simple decay curve for a radioisotope

• Outline the method for dating rocks and fossils using radioisotopes, with reference to 14C and 40K (you must know the half life, dating range, and parent/daughter isotopes for these two).

• Discuss the incompleteness of the fossil record and the resulting uncertainties about human evolution

• Fossil record gives us clues, but it doesn’t paint a complete picture
• Fossils are rare and very few organisms become fossils

• Soft body parts rarely fossilized
• Scavengers usually destroy remains
• Conditions have to be just correct in order for fossil to form
• Difficult to actually discover fossils

• Human Fossil Record is not complete

• Discuss the correlation between the change in diet and increase in brain size during hominid evolution

• Look at the posters on the wall

• Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans

• Cultural evolutions: Hominid Learning: language, tools, hunting, agriculture, religion, inventions, art, others behaviors passed from one generation to the next

• Has continued to occur since existence of Homo sapiens

• Genetic evolution:innate behaviors, physical traits, is vertical and chronological meaning that can track changes in species over time

• In terms of physical appearance, for the most part, little additional evolution since the existences of Homo sapiens

• Genetic evolution led to hominid cultural evolution, particularly evolution of larger brains

Phylogeny & Systematics

• Outline the value of classifying organisms

• Identification of Organisms
• Examine evolutionary links
• Prediction of similar characteristics shared by members of a group

• Define clade & cladistics

• Clade: group of species that includes an ancestral species and all of its descendants
• Cladistics: Approach to systematics by placing organisms into groups, clades, based primarily on common descent

• Distinguish, with examples, between analogous and homologous characteristics

• Homologous: similar in structure, position and development, similar due to common ancestor; may not be similar in function

• Example: Pentadactyl arm bones

• Analogous: similar in function, differ in fundamental structure, not common ancestor

• Example: Wings of birds and bats

• Outline the methods used to construct cladograms and the conclusions that can be drawn from them

• See video and or labs

• Explain the biochemical evidence provided by the universality of DNA and protein structures for the common ancestry of living organisms

• DNA: genetic code is universal; experiments have shown where sequences inserted in different organisms express same proteins
• Isomers: All living organisms use left orientated isomers; panspermia hypothesis suggest more left handed amino acids found in meteorites
• Cytochrome c: 100-104 amino acid protein used in electron transport chain; found in plants, animals, and unicellular organisms, too complex to have evolved independently so must have come from a common ancestor

• Explain how variations in specific molecules can indicate phylogeny

• Variations in DNA sequence for proteins exist between species
• Species with less variation would be expected to be more closely related
• Example: Humans, Chimpanzees & Rhesus Monkeys
• Variations can be caused by mutations

• Discuss how biochemical variations can be used as an evolutionary clock

• Can deduce the amount of time between evolution of two different species or ancestor and species based on comparison of DNA & protein sequences
• If changes occur at regular rate, can estimate time of divergence or relatedness
• Examination of cytochrome c protein (helps to break down food particles and release energy); comparison of cytochrome c protein between humans, chimps, and rhesus monkeys indicates greater number of amino acid differences between humans and rhesus than humans and chips which suggests humans and chimps are more closely related

• Construct a simple cladogram

• Watch the cladogram video found here

• Analyze cladograms in terms of phylogenetic relationships

• Completed on each cladogram lab conducted in class

• Discuss the relationship between cladograms and the classification of living organisms

• Completed on each cladogram lab conducted in class