IB Biology-Chapter 5-Evolution and Biodiversity

1. IB Biology-Chapter 5-Evolution and Biodiversity

2. Evidence for Evolution • Darwin and Wallace • @ age 22 Darwin sailed the HMS Beagle (1831)-for 5 years • Alfred Russel Wallace independently developed a similar theory • They presented ideas to Linnaean Society (1858)

3. Process of_________________________________ • Heritable implies it’s not necessarily fast • Cumulative implies that 1 change is not usually enough to have a major impact on species Process of cumulative change in the heritable characteristics of a population

4. Population-tells us it does not just affect 1 individual • Speciation can arise if enough changes occur in a population-because the members of the new population do not have enough from pre-existing population to interbreed-rarely observable during human lifetime • All life on earth unified by common origins • Neo-Darwinism (modern synthesis)-how DNA shows evidence for evolution by natural selection more than any evidence thus far

5. The fossil record and evolution • It is impossible to go back in time-thousands or millions of years ago and come up w/all the possible fossil evidence • Fossils-petrified remains/traces of animals and plants-been collected for ~ 2 centuries • Fossil record=accumulation of evidence from fossils

6. Convincing evidence compiled by paleontologists: • Life that existed > 500 mya greatly different than today • While earth has had oceans most of its existence, fish fossils have only been found in rocks 500 my old or younger (< 15% of the 3.5 billion y existence of life on earth • Although most top predators today are mammal-e.g. Bears, orcas, big cats, and wolves, none were here @ time of dinosaurs or before • Apart from organisms such as certain sharks, cockroaches, and ferns, most organisms present today have no similar form in fossil record • Life on earth appears to constantly be changing, but most changes are over 100’s, thousands, or millions of years

7. Aging fossils • By examining the differences in ratios of isotopes • E.g. A fossil of higher amt C-14 is younger than one w/less C-14 • C-14(14C)-slowly loses radioactivity to become N-14----Decay=process of radioactive parent isotope changing into stable daughter isotope • Half-life-speed by which this decay happens-_________________ • time it takes ½ parent isotope to decay into stable daughter isotope

8. 14C half-life=__________-so, when an animal dies, their bones will have lost ½ their14C after 5730 yrs./after 11,460 yrs. ½ of that (25% original) will be decayed • So-looking ratio of radioactive C-14 to stable N-14, you can determine age of fossil—If there is 12.5 of radioactive isotope and 87.5 of stable,3 half-lives have passed (17,190 yrs.) • After a certain # of half-lives, there are so few 14C atoms that it’s difficult to determine age accurately 5730 yrs

10. There are other isotopes w/longer half-lives, such as K-40. When minerals in rocks crystalize from magma, they contain a % K-40-Once they have hardened and crystallized, no more K-40 can be Added-However the # reduces as the isotope decays into more stable forms-used to determine age of rocks having formed from magma or lava between 100,000 yrs-4.6 billion years ago

12. Artificial selection and evolution • Fossil record far from complete, but we have a good record of changes in heritable characteristics from science of breeding domesticated animals • After practicing selective breeding for dozens and sometimes hundreds of generations, farmers and breeders realized that certain varieties of animals now had unique combinations of characteristics that did not exist before-evolution as a result of an accumulation of sm changes over time-_______________ • ∴ this is artificial selection = people choose the traits to be reproduced—not a driving force in evolution of natural ecosystems by human choice

14. Evolution of homologous structures by adaptive radiation • __________________________-similar in form but found in SEEMINGLY different species-as evidence of evolution • E.g.- pentadactyl limbs in humans, bats and whales-shape and # bones may vary, general format the same, even though they may have different functions • Darwin explained homologous structures were evidence of common ancestors • Whales should be able to swim fine whether or not they have 5 phalanges-indicating more the reasoning behind common ancestry Homologous anatomical structures

17. Species divergence • ________________-process of an evolving population changing significantly enough so that the production of offspring w/ original population becomes impossible—i.e. 2 pop’s of a species have diverged(separated) and new species evolves from old one-both species continuing on separate ways speciation

18. Adaptive radiation • Occurs when many similar but distinct species evolve relatively rapidly from a single or sm # species • Happens when variations w/in a population allow certain members to exploit a slightly different niche in a more successful way • By natural selection and the presence of some kind of barrier (such as water or a mt range), a new species can evolve

19. E.g.-primates of Madagascar and Comoro Islands-off SE coast of Africa.MYA, w/o competition from other primates, lemurs were prolific-large # offspring meant a greater chance for diversity • Among the range of variation in Lemur species-some are better adapted to trees and some to the ground-and some to the desert • Some are nocturnal while most are diurnal • There are so many species due to _______________ • Not a single species found anywhere else in world, yet fossils have been found on coast of Africa, Europe, and Asia • It is believed lemurs were not successful in competing w/apes and monkeys-since as soon as traces of the other primates started to become prevalent in the fossil record, the lemur –like organisms became rare adaptive radiation

20. This would explain why continents and islands tend to have either prosimians or anthropoids-but not both • Dozens of species have become extinct recently-esp. because of human anthropoids

21. Darwin’s finches of Galapagos Islands and Hawaiian Honeycreepers

22. Continuous variation and the concept of gradual divergence • In the diagram (phylogenetic tree) above-species A, B, C, D came from a common ancestor-If any 2 tried to mate-they would not produce fertile offspring • The above picture show how one species can have various splits over time-creating more diversity among species • Sometimes branches on phylogenetic tree are so far apart that the species no longer physically resemble each other (eg-Darwin’s finches)-yet many species can spread over a wide geographical area

23. Eg-NOS-p.225 saltmarsh grass—species that has a wide geographical distribution, there can be measureable differences in DNA-because the climate and soil are different in different locations-∴ the pop’s adapt to the conditions available to them-and some versions of genes will be selected for and others will be selected against, so that the pop’s are best adapted to their areas=___________(any phenomena which alters the behavior and fitness of living organisms within a given environment) • If this continues to produce genetic differences over a long enough time, it is not difficult to imagine a point @ which the differences are so separated that they become different species • There comes a tipping pt beyond which differences outweigh similarities and can no longer freely reproduce selective pressure

24. Transient morphism---w/in a pop-there is often more than 1 common form • Polymorphisms-different versions of a species - (different shapes-) can be result of mutation • E.g.-Bison betularia-peppered moth-can have a peppered(grey) form or a melanic(black) form-melanic is a rare mutation that usually affects <1% of a population • Grey form well camouflaged against light-colored surfaces, such as tree branches covered w/lichens • The melanin(bulk) form is easily preyed upon by birds against light lichens • From ~ 1860 a phenomenon was underway that cont’d for more than a century-Melanic form(carbonaria) was increasing in #’s • Lichens sensitive to air pollution-industrial revolution producing SO2, which kill lichens-also a lot of blk soot • Result was lichen –free, soot –darkened branches-more difficult for light –colored moths to survive predation • Near industrial areas, the carbonaria were 95-100% of all the peppered moths • @ present carbonariararely go above 30%-often 0%(improvement in air quality-UK Clean Air Act of 1956) • Transient polymorphisms—changes from light –to dark-and back to light

26. II. Natural selection • The mechanism for evolution • Natural selection-involves overproduction of offspring and the presence of natural variation in the population, struggle for existence between competing varieties-survival of only the “fittest” • Variation within populations • Bacteria do binary fission and have little chance to produce changes • More chance for change w/those sexually reproducing

27. Variation and success • Variation closely related to how successful an organism is-eg. The camouflaged peppered moth survives predators more • Traits that may appear to be beneficial, may not be-e.g.-a brightly colored baby bird may appear to be endangered by predators, while the bright coloration may make it attractive to a mate • How frequent an allele is can change over time-as w/ seen w/peppered moth-only possible if there is more than one form of an allele • Mutation of an allele presents this possibility • An adverse change in an asexual organism would cause all to die, while sexually reproducing would only have some perish from an adverse variation

28. Mutation,meisosis,and sexual reproduction • 3 main mechanisms giving species variation-mutations in DNA, meiosis, sexual reproduction

29. Mutation • May sometimes produce genes that lead to genetic diseases-endangering survival • May produce advantageous characteristic-e.g. Plant that is frost resistant • In each generation, only a few genes mutate, and most mutations produce no effect • Sexual reproduction via meiosis is a much more powerful tool for variation

30. Meiosis • Produces haploid cells to make gametes-4 cells genetically different • Only 50% of parent’ genome • Recall the great diversity possible via meiosis (look back to this section in chapter 3 of your text-or ch.1 of your notes) • In a woman’s lifetime it’s basically impossible to produce the same 2 identical egg cells-only way is by identical twins • Recall role of random orientation during metaphase I and of crossing-over in prophase I

31. Sexual reproduction • Rarer situations of mutations or gene transfer may produce variation in asexual organisms-otherwise, only in sexually reproducing organisms • For asexual organisms-either survive or die-recall example of the great potato famine (potato blight) • ∴ vital to natural selection-more possibilities lead to more possible outcomes • Conditions must be optimal w/in female’s body and sperm must be present at opportune time-only 1 sperm fertilizes 1 egg • w/many species-this is very much up to chance • however, there are elements not involving chance

32. To adapt or not to adapt? • The question to adapt-can be a conscious decision (humans) • In nature vast amount of adaptations are unconscious ones made by a population…e.g.-peppered moth • An organism that is well adapted for its environment is said to be fit • Natural selection tends to eliminate from a population individuals w/ low fitness • Individuals usually are incapable of changing themselves to adapt-it will just perish • Hence the alleles for an adverse characteristic will not be present in a population

33. Too many offspring • Darwin noticed that plants and animals produce far more offspring than could ever survive • May seem paradoxical because because production of seeds, spores, and eggs uses energy and nutrients that are also vital to parent’s survival-all to the end of maximizing the chances of some offspring surviving • Some defend their resources-animals and plants (plants via tannins and alkaloids)-making it difficult for a new arrival to find enough resources---i.e. Struggle for survival-competition for limited resources • Less offspring-less chance to have genes passed on

34. Adaptation and survival • Evolution not just based on chance-in a situation where too many organisms exist for the possible resources, obviously some will succeed in getting resources and some will fail—i.e. There is selection • Not based on just chance but also by surroundings and the compatibility of their characteristics w/that environment

35. Steps of evolution by natural selection- • 1-Overproduction of offspring and in those offspring, natural variation due to genetic differences (e.g. Body size, morphology, pigmentation, visual acuity, resistance to disease in the offspring) useful variation allow some to have a better chance to survive and b) harmful variations make it difficult to survive • 2-Individuals w/genetic characteristics that are poorly adapted for their environment tend to be less successful @ assessing resources and have less chance of surviving to maturity

36. 3-Individuals w/genetic characteristics that ARE well adapted to environment tend to be more successful @ assessing resources-better fitness-since they are more equipped to survive • 4-Since they survive to adulthood, the successful ones have a better chance of reproducing and passing on successful genetic traits to next generation • 5-Over many generations, the accumulation of changes in the heritable characteristics of a population results in evolution-the gene pool have changed

37. More complex than “survival of the fittest”—he did not say “only the strongest survive” • Many subtleties of evolutionary theory (by natural selection) may explain some misconceptions-e.g.-an organism well adapted is not guaranteed success-e.g.-dinosaurs-also-see plover eggs p. 234

38. Passing on successful characteristics • Individual that never reaches maturity obviously will not pass on genes and one w/more fitness has better chase to reach maturity and pass on genes • However, no guarantee that fitness will allow survival or reproduction—survival must come first

39. Pesticide resistance in rats • Pesticides-chemicals that kill any animal regarded as pests-consider this scenario • 1-Once applied in the field-all rats killed---the farmer thinks1 • 2-But, from natural variation, a few rats from the population are slightly different and not affected by poison • 3-They are adapted to survive pesticide and have no other rats for competition for food---∴ they survive and reproduce—making new pop in which some or all the members possess the genes giving pesticide resistance • 4-Farmer puts out more pesticide (original chemical), but fewer rats die • 5-To kill rats new chemical used

40. The term ‘immunity” not always interchangeable w/ “resistance” …but not the case here • The evolution happened in a pop-not a single rat-an individual rat cannot adapt and evolve into a resistant rat • Those changes that evolve must be heritable (e.g.-if you continually cut off the tails of sheep-they will not be born w/ short tails

41. Antibiotic resistance in bacteria • Antibiotics are meds-e.g. penicillin-that kill or inhibit bacterial growth/given to those w/bacterial infections-but also others who are ill-and w/ a weak immune system-because they are @ greater risk of bact infection-can produce resistant strains

42. Resistance develops in several steps-scenario- • 1-Patient gets bact infection, such as TB • 2-Dr gives her antibiotic • 3-Pt gets better because most bact destroyed • 4-By modification of its genetic makeup,1 bacterium is resistant to antibiotic • 5-Bact multiplies and makes pt sick • 6-Dr gives same antibiotic • 7-W/no result • 8-Dr gives different antibiotic—if the pop's cont to acquire mutation-they could become resistant to all antibiotic

43. Since bact repro asexually, they don't genetically change often-but 2 sources of genetic change- • Mutations(see 3.1) • Plasmid transfer: One bacterium donates genetic info to another in a ring of nucleotides---plasmid/Both donating and receiving cells open their cell walls so that the genetic material can pass from donor to recipient

46. Development of antibiotic resistant bacteria has happened in many cases-e.g.-new strains of syphilis w/multiple resistance. Some strains of TB are resistant to as many 9 antibiotics • New antibiotics are just a temporary solution-thus minimizing antibiotic use preferred • This is an example of how theory of natural selection allows us to understand natural phenomena

48. Classification of biodiversity • The binomial system of names for species • System of naming organisms using 2 names=binomial nomenclature • Genus always capitalized and italicized if type or underlined when handwritten • Most are Latin or Greek • Mostly developed by Carolus (Carl) Linneaeus-1735(book System Naturae) • Every 4 yrs. International Congress of Zoology meets about animal behavior, classification, and genetics-began Paris 1889-make decisions about newly discovered organisms and ones that may need to be reclassified

50. 3 main objectives to binomial nomenclature and associated rules: • To be sure each organism has a unique name that cannot be confused w/another • So, names can be universally understood, no matter the nationality or culture • So that there is some stability in the system by not allowing people to change the name w/o valid reasons