Human Evolution Exam 1 Study Guide Questions & Answers

Natural Selection: - ANSWERS1. All species are capable of producing offspring at a faster rate than food supplies increase 2. Because in each generation more individuals are produced than can survive, there is a competition for limited resources 1. There is biological variation in all species 2. Some individuals in the population will possess traits that allow them to survive and reproduce more successfully than others in the same environment 3. Environmental conditions determine whether a trait is beneficial 4. Traits are inherited and passed on to the next generation. Individuals who possess favorable traits contribute more offspring to the next generation than do others, so these traits become more common. Those individuals that produce more offspring have greater reproductive success. 5. Over long periods of time, favorable traits accumulate in a population so that later generations are distinct from ancestral ones. In time, a new species appears 6. Geographic isolation may also lead to the formation of a new species • Natural selection causes evolutionary change • Evolution is the change in the genetic structure of a population over time - Changes in allele frequencies due to differential reproductive success - Systematic (not random) - Increases variation between populations - Decreases variation within populations Three types of natural selection: - ANSWERS- Directional selection - Stabilizing selection - Disruptive selection Unit of natural selection: - ANSWERS- Is the individual - Counter Lamarck Unit of evolution: - ANSWERS- the population Gene Flow: - ANSWERS- use of codons to make certain proteins - some proteins can be created by several different nucleotide makeups, codons - redundancy helps protect against a mutation / mistake - we only need 20 amino acids, so we don't need a more complex system than three base codons / triplet codons • The exchange of alleles between populations • Migration • Systematic • Increases variation within populations • Decreases variation between populations Genetic Drift: - ANSWERS- Change in allele frequencies produced by random factors - Increases variation between populations - It is unlikely every population will be fixed on the same allele (the other allele could go into fixation in other populations by random chance) - Decreases variation within populations (one allele will eventually disappear because eventually an entire population is fixed on a certain type of allele) Mutation: - ANSWERS- Change in DNA sequence - Point mutation: change in single base of DNA sequence - Most simple mutation - Ex: CTC CAC (glutamic acid valine) • The only source of new genetic variation • If in gametes creates evolutionary effect • Only source for new alleles • Shows evolution is an imperfect system - Random alternation in DNA sequence - Sources of mutation: radiation, chemicals - If in gametes evolutionary effect - Creates NEW alleles - Random - Mutation rates are low - Increases variation both within and between populations - Most mutations are fatal because they're random, though every now and then a mutation may be beneficial and increase over time Characteristics of DNA: - ANSWERS1. code is universal 2. code is triplet 3. code is redundant Mendel's three "laws" of inheritance: - ANSWERS- Dominance, Segregation, Independent Assortment Dominance: - ANSWERS- The effects of some alleles will be inhibited by other (dominant) alleles - Dominant: alleles that are expressed (A) - Recessive: alleles that are masked when combined with a dominant allele (a) Segregation: - ANSWERS- Allele pairs separate (segregate) during gamete formation and randomly unite at fertilization - Different expressions of a trait are controlled by discrete units of heredity - These units occur in pairs: one from each parent - Members of each pair segregate into gametes during meiosis (haploid) - Pair is formed again during fertilization - Alleles separate, you only have one or the other Independent Assortment: - ANSWERS- No relationship between traits for plant height and seed color - The expression of one trait is not influenced by the expression of another trait - Traits assort independently of each other during gamete formation - Linked genes, pleiotropic, and polygenetic traits (not distinct variations) are the exception to this principle Mitosis: - ANSWERS- ordinary cell division - mass majority of our cells go through this process - occurs with body cells - results in 2 identical diploid (n=46) daughter cells Process of mitosis: • interphase: resting phase and later growth to prepare for division • prophase: chromosome spiralize & chromosomes replicate • metaphase: spindle fibers appear and chromosomes align with their centromeres on the equator and attach to the spindle • anaphase: chromatids of each chromosome separate into daughter chromosomes and move to opposite poles • telophase: two nuclei reform at poles • daughter cells: after cytokinesis, two daughter cells form Meiosis: - ANSWERS- Forms gametes - Results in 4 non-identical haploid cells - ½ genes form each parent - how genetic information is passed from parents to offspring - involved in reproduction - gametes are haploid (N=23) - chromosomal elements are varied (produces four unique and haploid daughter cells) Mitosis vs Meiosis: - ANSWERS- Somatic v. sex cell - One v. two divisions - 2 v. 4 daughter cells - meiosis has two cell divisions because the genetic makeup needs reduced by 50% so that the individual will only be diploid - diploid v. haploid - identical v. unique daughter cells (because of crossing over) DNA replication: - ANSWERS1. Enzymes unwind and break apart double helix 2. New nucleotides attach to expose bases 3. New bases join via rules of complimentary 4. Results in 2 double-stranded DNA molecules exactly like the original (Identical to each other) a. Each strand has one new strand and one original strand Protein synthesis: - ANSWERS- transcription and translation - DNA (never leaves nucleus itself) transcription RNA (very short strand that is a copy of one gene) translation protein - RNA goes to ribosome to be read and will translate the RNA sequence into a protein Transcription: - ANSWERS- Occurs in nucleus - Copying double-stranded DNA molecule into single-stranded RNA template - mRNA is transcribed from this process - Process 1. section of DNA unzips 2. RNA nucleotides attach to complementary bases on DNA molecule (U replaces T) 3. RNA breaks away forming single stranded molecule called mRNA Translation: - ANSWERS- RNA -- proteins - RNA leaves nucleus and travels to ribosomes - This is where recipe gets turned into protein Crossing Over (Recombination): - ANSWERS- Does not change allele frequencies - Feeds natural selection, but is not an evolutionary force - Creates new combinations of traits that natural selection can act upon - Sections of DNA from one chromosome exchange with that of another - Resulting chromosomes differ from that originally inherited from parents Hardy-Weinberg Equilibrium: - ANSWERS- A set of conditions in a population under which no evolution occurs 1. Infinitely large 2. No mutation 3. No gene flow 4. Natural selection is not occurring 5. Mating is random - If all these conditions are met, there will be no change in allele frequencies between generations - No population meets these conditions because evolution is always occurring The connection between the distribution of malaria and that of the sickle-cell allele: - ANSWERS- sickle cell maintained in central Africa, parts of the middle east, and south asia - Sickle cell and malaria are connected - this is an example of heterozygote advantage • NN: Normal, die of malaria • SS: Die of sickle cell anemia • NS: natural immunity to sickle cell anemia and malaria, normal life space - the sickle cell allele hasn't been killed off by natural selection because NS is helpful for the population DNA vs RNA structure: - ANSWERS- DNA 1. double-stranded 2. long strands 3. deoxyribose 4. thymine, not uracil - RNA 1. single-stranded 2. shorter than DNA 3. Different sugar (ribose) 4. Uracil rather than Thymine • mRNA is transcribed from this process • rRNA is at the ribosome cite, ribosome itself is made of rRNA tRNA sends amino acids to the ribosomes Blending inheritance: - ANSWERS- the idea that characteristics in the offspring are the result of blending the parents' characteristics together - prediction: tall-stemmed plant X short-stemmed plant = medium-stemmed plant Adaptations to heat stress: - ANSWERS- adaptions to heat: UV radiation from sun shielded by melanin pigment, a protecting folate that helps synthesize vitamin D in skin - Climate adaption: heat stress • Vasodilation • Sweating • Body shape: Bergmann's and Allen's rules Adaptions to cold stress: - ANSWERS- Shivering: generates body heat - Vasoconstriction: restricts heat loss - Inuit: alternating period of vasoconstriction and vasodilation (eriodic warmth to skin and prevents frostbite - Behavioral: clothing, fire Adaptions to high altitude: - ANSWERS- Over 10,000 feet above sea level - Barometric pressure is reduced: oxygen is less concentrated - Hypoxia: less oxygen available for human body o Increased infant mortality o Lower birth weights - Acclimatization (physiological response) occurs upon exposure to high altitudes in people born at low elevations - Short-term modifications: o Increase in: respiration rate, heart rate, and production of red blood cells (because they carry oxygen = more oxygen available) Bergmann's Rule: - ANSWERS- Large body size adaptive for cold climates - Reduces heat loss because there is less area relative to mass Allen's Rule: - ANSWERS- Short limbs adaptive to cold climates (less heat loss) - Long limbs adaptive to warm climates Wolff's Rule: - ANSWERS- Skeletal adaptation: osteoblasts and osteoclasts • Wolff's Law - states that bone in a healthy person or animal will adapt to the loads under which it is placed. Lactase Persistence: - ANSWERS- Enzyme lactase breaks down lactose - All infants produce lactase; most adults do not - Certain pastoral groups relied on goats, sheep, and cows' milk as food source - Developed mutation that allowed them to continue producing lactase into adulthood - example of a nutritional adaption "Geologic Time": - ANSWERS- is a system of chronological dating that relates geological strata (stratigraphy) to time, and is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history. "Fixity of species": - ANSWERS- The idea that species were universally thought to be fixed prior to Darwin is simply wrong — many creationist thinkers of the classical period through to the 19th century thought that species could change Uniformitarianism: - ANSWERS- the doctrine suggesting that Earth's geologic processes acted in the same manner and with essentially the same intensity in the past as they do in the present and that such uniformity is sufficient to account for all geologic change Catastrophism: - ANSWERS- Regional disasters destroyed local plant and animal life - Repopulated by new forms that migrated from neighboring regions - These new forms were the results of recent creation events - Explained complexities Gene vs. Allele vs. Locus: - ANSWERS- gene: a segment of DNA (that serves as the blueprint for a physical trait) - allele: an alternative form of a gene or trait - combination of 2 alleles (genotype) determine the expression of trait (phenotype) - loci is the location of a gene Genotype vs Phenotype: - ANSWERS- Genotype: the alleles in an individual - Phenotype: the observable trait Homozygous vs heterozygous: - ANSWERS- Homozygous: having two same alleles for a trait (AA or aa) - Heterozygous: having two different alleles for a trait (Aa) Biocultural evolution: - ANSWERS- The evolution of humans is characterized by an interaction between our biology and our culture - What is a human?