15.4: Mutation

15.4: Mutation The most powerful force in altering allele frequencies is an environmental change that makes certain individuals with certain phenotypes more likely to survive and reproduce than others in the population.

Natural Selection, the ‘differential survival rate” based upon variations in phenotype, can operate on both the human populations and the “bugs” that bother them. Tb & cholera

Tuberculosis TB (bacteria) first appeared on the reservation of the Plains Indians in Saskatchewan, Canada in the 1880’s, affecting organs and killing 10% of the population. TB in 1921 affected only the lungs, and killed only 7% TB Mortality dropped to 0.2 % by 1950

People with high immune resistance survived while the strongest bacteria killed the hosts so quickly that they were not transmitted to the next victim. The “new” TB is resistant to the 11 drugs that treat it historically. This is because the patient “complacency” The strongest bacteria survive for 18 months. The 1990s MORTALITY RATE pushed 5%

Viruses Because viruses lack repair enzymes, mutations are rapid. They are under selective pressure from both the immune system and the drugs we use to treat them. The Genetic Diversity of the HIV virus enables the survival of the population of viruses

This bacteria is able to survive on radioactive Elements Bacteria: Uranium waste bacteria (metallireducens bacteria) [the green in the image] Electron microscopy… This bacteria is able to survive in radioactive environments and turn the uranium waste from a soluble form (that can contaminate water supplies) to a solid form.

15.5: Basic Evolution Evolution is the theory that species change over millions of years because of the changing environment.

Theory of Evol. –Main Points Variations exist within every population Some of these variations are more beneficial to a species than others Over time, organisms who possess these beneficial traits tend to survive and reproduce more efficiently, and dominate the population

Jean Lamarck 1809 "the inheritance of acquired characteristics" EX: Salamanders that did not use legs lost them and began to slither. The next generations would also have no legs or small legs.

Charles Darwin NATURALIST who took a Voyage on the Beagle - (1831) in order to collect specimens and map South America and the South Pacific. Observed that over time the land changed - creating new HABITATS. Ex: Earthquakes, old marine fossils in mountains Animals would have to ADAPT to these changes.

Darwin Continued He collected 13 different finch species, with different types of beaks(bills). Darwin infered that they shared a common ancestor, but were SPECIALIZED for different foods. He also collected fossils of extinct mammals that were similar to modern mammals. This led him to believe that species changed over time. In 1838, Darwin read Malthus’s Principles of Populations, in which Thomas Malthus explained the "struggle for existence" brought on by competition for the Earth’s limited resources.

Darwin's THEORY OF EVOLUTION: VARIATION exists among individuals of a population. There exists a SCARCITY OF RESOURCES. Those better SUITED than the competition would survive and REPRODUCE, while others dies off due to NATURAL SELECTION. ADAPTATIONS which helped an individual to survive could be INHERITED by the offspring.

Alfred Russell Wallace came up with the same idea in 1858 which convinced Darwin to publish Darwin published The Origin of Species in 1859. His book is now the unifying theme for all of Biology.

Evidence of Change 1. Fossils – traces of once-living organisms (EX: HARD PARTS like shells, bones, teeth, and woody stems)

Fossils Found in SEDIMENTARY ROCKS. The bottom layers are usually older. Quick burial to avoid decay Otzi, the “Iceman,” from 3300 BC

Types of Fossils ORIGINAL REMAINS have been found: Mammoth, insects in amber, and frozen humans. Imprints form when the critter itself is decayed, but a CARBON FILM remains.

Types of Fossils A MOLD is a fossil impression of the shape of a critter A CAST forms when sediments fill in a MOLD Fossils can be DATED by testing for radioactive decay

Carbon Dating C-14 DECAYS into N-14 losing a proton at a constant rate. Use the HALF-LIFE to determine the age of a fossil. The half-life of C-14 is about 5700 years. Only Useful up to 50,000 years. Use U-238 to find age of the oldest rocks.

LIVING EVIDENCE: 1. Homologous structures Come from the same part of the EMBRYO, but have different functions in different animals. Ex: bones of alligator, human, penguin.

2. Vestigial Organs Organs or structures that are seemingly functionless. They are often similar to structures that are functional in other organisms. Ex: Human ear muscles, tailbone, and appendix, pelvic and limb bones in snakes, eyes in blind cave-dwelling salamanders.

3. Biochemistry The same chemicals serve the same function in vastly different organisms. Ex: - Metabolism (digestion) is based on the same biochemical compounds in vastly different species. DNA can tell how closely related two organisms are.

4. Embriological Development Embryos of different species develop almost identically, especially in early stages.

5. Analogous Structures Structures that serve similar functions but differ in structure. Ex: Fin on a dolphin and a fish. Wings on a butterfly and a bird.

EVOLUTIONARY PATTERNS The Galapagos finches most likely evolved from one ancestor by ADAPTIVE RADIATION: from common ancestor spreading into new HABITATS. DIVERGENT RADIATION is the process by which two related species become more and more dissimilar as the adapt to differing HABITATS. -The Kit Fox’s sandy color helps it to hide in the desert while the Red Fox’s color is good for blending in with trees. The colors are an adaptations.

Convergent Evolution CONVERGENT EVOLUTION occurs when two separate species must both adapt to similar environments. EX: Plant leaves from the Sahara are similar to those in Arizona. American African

Coevolution COEVOLUTION can be thought of as a sort of “jockeying for position” between two species. -Bees and the flowers they POLLINATE.

Balanced Polymorphism Notes

If natural selection ELIMINATES individuals with DETRIMENTAL (bad) phenotypes from the population, then how do harmful mutant alleles PERSIST in a gene pool? They were introduced through MUTATIONS. Persist in HETEROZYGOTES. Sometimes the heterozygotes enjoy some unrelated HEALTH ADVANTAGE. EX: resistance to disease.

A BALANCED POLYMORPHISM is when there is some ADVANTAGE to carrying a recessive, disease causing allele, as long as you only have ONE. “balanced variant” PROTECTIVE EFFECT of the bad allele counters the NEGATIVE EFFECT of the bad allele when the condition is present, maintaining its frequency.

EXAMPLES: Sickle Cell Disease and MALARIA Malaria is caused by Plasmodium. The parasite enters the blood when an infected MOSQUITO bites an individual. Malaria parasites enter the red blood cells, which transport them to the LIVER. The red blood cells burst, releasing parasites throughout the body.

People with Sickle cell – many RBCs burst prematurely – EXPELS PARASITES. Blood is also THICKER - may hamper parasite. Sickle Cell carrier’s blood is ABNORMAL enough to be inhospitable to the malaria parasite. They don’t have Sickle cell anemia and they don’t get malaria. Only 8 % of African Americans are sickle cell carriers, but in parts of Africa 45-50% of the population are carries.

PKU and Fungal Infection Phenylketonuria – PHENYALANINE builds up and devastates the nervous system unless individuals follow a restrictive DIET. Carriers have elevated phenylalanine that does not cause illness but PROTECTS from fungal infection during pregnancy – REDUCING MISCARRIAGE. Ireland and Scotland – fungus on grains eaten during famine.

Tay-Sachs Disease Infected children lack an enzyme the gets rid of lipids (fats) that build up and choke out (KILL) NEURONS. Carriers are somehow PROTECTED AGAINST TB.

Cystic Fibrosis Protects against diarrheal illnesses, such as CHOLERA and TYPHUS. Severe diarrhea rapidly dehydrates the body and leads to shock, kidney and heart failure, and DEATH in days. Cholera causes diarrhea by opening chloride channels. CF does just the OPPOSITE.

Diabetes Mellitus and Surviving Famine Carriers of CF DO NOT DIE from cholera. TYPOID FEVER – bacteria enters cells through CF channels. No bacteria gets in Diabetes Mellitus and Surviving Famine