SBI3U Grade 11 Biology Evolution Test Biology – Evolution Study Notes Evolution: Organisms changed because they had to adapt to the changing earth Charles Darwin: had credit for being first to say why evolution occurred with evidence, but not the first with the idea. 2 Main ideas: 1) Organisms are products of a history of descents with modifications from common ancestors 2) The principle mechanisms is the natural selection of hereditary variations. 1 Organisms change from one common ancestor with changes over time -Started with one, then changes differ between each species. 2. Nature will favor changes that survives -Accumulation of traits that allows the to survive -Whatever that doesn’t work well will die -Earth changes + Mutation + trait changes. Controversy : People thought that the earth was unchanged -Believed that god made everything just as it is today -Said that things didn’t change, as that’s how god says it should be Other than Darwin: Baron Georges Cuvier (1769 – 1832) -Investigated fossils, found that there were layers that contained different species -Species were unique to that layer. Shell found in one layer couldn’t be found in another. -Suggested that catastrophes (changes in earth), caused extinctions -Then another form migrated later on – Theory of Catastrophism : how species are extinct due to a catastrophe, then species from the surrounding environment will repopulate the area.
James Hutton (1726 – 1797) -Said that the earth is very old -Small changes here and there adds up to big changes (ie Mountains) Sir Charles Lyell (1797 – 1875) -Supported Hutton’s theory with the Theory of uniformitarianism – said that the earth’s surface is always changing and continues to change. -supported with fossil samples Impact of Lyell and Hutton: Earth is very old, and changes are slow and become dramatic over time. George Buffon (1707 – 1788) -Said species change over time into new species -Introduced idea about common ancestry and similarities between species Carolus Linnaeus (1707 – 1778) -Father of Taxonomy -Classified species based on their origin with names. Alfred Russell Wallace (1823 – 1913) -Proposed the idea of natural selection to Darwin -Influenced Darwin to publish his papers about the idea of Natural Selection Jean-Baptiste Lamarck (1744 – 1829) -Said species adapt to changing environment, and has some role in evolution – Theory of Inheritance of Acquired Traits: said that a muscle man would give birth to a muscle baby; from which he was wrong -Traits from a mother with some influence could pass onto the child -But that doesn’t mean a full evolution and mutation -Giraffe elongated neck a bit, and with further exercise after each generation, it might make it grow longer; Theory of I A T was proven wrong
Thomas Robert Malthus (1766 – 1834) -Said that too many organisms born and survive -But with limited supply of resources, only the brighter and better will survive; supporting the idea of natural selection Evolution Myths -Often misunderstood -Many people alter Darwin’s theories to misinterpret it for economics, social, or scientific reasons -More serious of which is for Social Darwinism or Eugenics -Adolf Hitler’s Aryan Race idea was an example of using Eugenics – Eugenics: to purify a race Myth #1: Individuals evolve -Populations evolve Myth #2: Natural selection has a purpose, to increase the complexity of living things -Natural selection has no purpose, direction, or goal. Not even the survival of the species. There is no indication of progress implicit in the idea of natural selection. Myth #3: Evolution by natural selection produces higher and more advanced humans -Evolution does not produce a higher or more advanced human species Myth #4: Evolution proves that there is no god -Evolution does not seek to negate the existence of a god Myth #5: Humans beings are descendants of apes -Human beings are not from apes. We share a common ancestor with apes. Humans share a common ancestry with all other living things Evidence of Evolution: Common Ancestry Analysis Evolution: Species change over time to adapt to changing environment -All living things have descended with modifications from a common ancestor. Mammalian Sea Creatures: -Breaths air into lungs, warm blooded, and mammary glands for feeding
-But these animals (whales) are in the water. -How could this be? Answer: evolution from land to water. Fossil Record -Physically preserved organism from ancient rocks or amber -Used to see them change over time from old fossils Limitations: -Dead organisms decay -Rocks inaccessible -Destroyed by erosion -Analyze bones, teeth, skin, and feather – Used for comparing anatomy. Whale Evolution: -Descendants from aquatic wolf from land animals -Had a wolf like skull, ear, pelvis bone, and structures to facilitate 4 legs Vestigial Structures -Physical structures with no function -Suggests an evolutionary past Human vestigial features -Ear-wiggling muscles -Tail bone in human and embryos -Appendix structure -Wisdom molar teeth – When people used to eat vegetables, they needed to chew harder, so there were molar teeth that helped that -When people used to eat vegetables, it took more digestion. Now, there’s less digestion required, so the intestines shrunk, and the Appendix is the remaining piece that dangles down
Homologous Structures -Structures with similar organization and function – Suggest common ancestry -Structures are similar; conclude that they are common, but diverged from a common ancestor. : Diverging Evolution. Cladogram – Show relationships of creatures based on their anatomical features Converging Evolution -looks similar, but different internal structures -suggests that they’ve come form a different branch, but evolved to have similar looks -Bat vs Butterfly; different things – Similar features, but not the same ancestor Analogous Structures: -Evolved to have similar colors, but not from same ancestor -Just adapting to their own individual environment. Embryology: -Studying the embryos of animals -All very similar suggesting ancestry Molecular Evidence: -Amino Acids make proteins -Similarities in DNA and amino sequences are molecular evidence of similarity and common ancestry. DNA sequence similarity -Humans and chimps have 97.5% identical genes -Humans and lemur have 58% identical gene -Means that we were in a divergence between sooner than with a lemur.
Homologous Sequences -Have similar sequence of genes -Genes in cytochrome C (used for cellular respiration) -nearly identical in app species: suggests that they’re all related Vestigial Sequences – DNA sequences that’s part of a non-functional gene -Called a Pseudogene -once functional, but not anymore; evidence of evolutionary past Human Pseudogene -L-gulonolactone Oxidase is an enzyme that creates vitamin C in most mammals. -mutation caused this to be deactivated in all primates -So once it works, but now it doesn’t because we’ve evolved Protein Sequence -Analyzed to determine homology -Cytochrome C highly similar across species Phylogeny Phylogenetic Trees: are created. Uses sequence Data from DNA or proteins to make trees to show relationships Theories on Natural Selection “Individuals having any advantage, however slight over others, would have the best chance of surviving and procreating their kind?” “Any variation that was even slightly harmful would be rigidly eliminated. Natural selection is the preservation of advantageous variations and the rejection of harmful variations.” Charles Darwin 1) More individuals are born than survive 2) There is variation in traits 3) Some traits are more advantageous than others
4) Advantageous traits -> better chance of surviving and reproducing 5) Traits that are not suitable for a certain environment will be destroyed Natural Selection: Selection of the favorable characteristics and rejection of unfavorable characteristics. 1) More individuals are born than can survive -Leads to competition among individuals within a population -any creature with traits who can help them win food can survive to carry on their traits to the new generation. 2) There is variation in heritable traits -Heritable: A trait that is passed down from generation to generation Traits passed down through alleles and all the genetics in it Example: -white coloured mouse in a black environment can’t hide and will be eliminated. While a dark mouse in a white situation would do the same -Over time, dark areas would have darker creatures, and lighter coloured creatures will live in lighter coloured areas. Mutation: rare mistake in DNA copying Only in reproductive cells that affect the gametes and passed onto the offsprings -Most are harmless, but ones that change phenotypes are deleterious (bad) 3) Some traits may be advantageous -They increase their chances of survival -Their traits allow them to get food or not to be eaten, then to survive Examples: -Herds of animals (scare and confuse their predators) -Camouflage (bug shaped plants) -Horns/Thongs (For defense and battle) -Batesian Mimicry (to mimic some other thing’s looks to defend itself)
-Monarch butterflies have poison, so birds avoid it -Viceroys have no poison, but have evolved to look just like monarchs so that they can be avoided from being eaten Survival -Depends on the environment, selection will occur to see who lives -Survival is one thing, whether or not they can survive long enough to reproduce is another –Fittest: most number of reproduction offspring’s -Creatures must survive long enough to reproduce -They must attract mates to fertilize (females pick males) Sexual Selection -Adaptations have evolved to increase reproductive success -Females choose, Males must adapt to “attract the ladies” w/o these adaptations, the males may not attract the females, and therefore not reproduce and not creating off springs to carry on that trait. Lions: Darker = higher testosterone = higher sperm count = stronger = healthier = longer life = sexier lion = better reproduction success Exceptions: -Death-causing sickle cell trait, in heterozygous form, will have defense from malaria. Thus, it’ll keepthat trait there as an advantageous trait. Summary of Natural Selection -Not enough resources -Competition -Whoever wins will get resources -With resources, they can survive and reproduce; victorious traits will be passed onto offspring and possibly the entire species. Hardy-Weinberg Equilibrium Agents for Evolutionary Change Evolution: shift in allele frequencies in a population
Genetic difference occurs with genetic variation through mutations -For evolution to occur, there must be genetic variation Gene Pool: collection of alleles in a population Population: group of interbreeding individuals Allele Frequency: how common that allele is in the population (how many A vs a) (1) Mutation : UV Radiation causing things like nondisjunction -Changes the DNA in organisms -New alleles, allele frequencies change through genetic drift in mutation (2) Genetic Flow : Gains or reduction in alleles due to immigration or migrations -large amounts of the one type of alleles leave, the traits for those phenotypes are wiped out -Or, new type of person is introduced, the entire population would evolve around that. (African in Norway example) (3) Non-Random Mating : Sexual Selection -one of the traits are favored by girls, then that trait will be passed on (4) Genetic Drift : Some parts of population are lost, that allele will be lost Bottlenecks -after disaster, they’re killed off, leaving only a few traits -High genetic diversity > disaster > only a few left, then the entire population will be based off of those genes Founder Effect – Physical boundaries that separate a small population of the gene pool. Whatever dominates the gene pool will soon make up the entire generation. (small number of them colonize in a new area) (5) Natural Selection: Some traits are favored over others – simple. Hypothetical Situation – If none of the agents for evolution occurs, there will be no change in allele frequency. Hardy Weinberg used Hypothetical situations to compare changes in allele frequency. If there is change, then evolution has occurred.
Formulas: p + q = 1 p^2 + 2pq + q^2 = 1 Derives: p^2 = number of AA alleles q^2 = number of aa alleles 2pq = number of Aa alleles In context: p^2 = number of AA genotype 2pq = number of Aa genotype q^2 = number of aa genotype p = 1-q = number of A alleles q = 1-p = number of a alleles Speciation and Reproductive isolation mechanisms Species: group of individuals who are able to mate amongst themselves to make healthy offsprings Exceptions: Horses and donkeys mate to make mules -Hooded crow and carrion crows can make hybrids, but are geographically separated Reproductive Isolation Mechanisms: factors that does not allow for successful reproduction Pre zygotic Barriers: prior to when a zygote is formed – Prevention of Mating: doesn’t allow for having sex -Behavioral Isolation: each species may use different signals or behaviors to attract mates. Sometimes they don’t work or are incompatible. -Birds and frogs sing a song -Temporal Isolation: mating at the wrong time cannot allow them to mate even though they could be in the same habitat.
– Flower mating seasons -Ecological/Habitat Isolation: species occupy different habitats within the same area where they're separated and cannot mate -Northwest Garter snakes prefer meadows while common garter snakes are in water all the time Prevention of fertilizing: doesn’t allow for fertilization -Mechanical Isolation: Different species don’t mate because their genitals aren’t compatible for mating – Genitals of damsel flies are different from other flies and can only mate with their own species -Gametic Isolation: If gametes from different species do not meet, barriers preventing sperm and eggs from forming a zygote. – Sperm might not survive in female, or molecular markers on eggs signal sperms that this isn’t the right egg, and will ignore it Post Zygotic Barriers: doesn’t allow for successful growth of the hybrid (refers to offspring from mating 2 species) -Reduction of Hybrid viability: Fetus forms after fertilization, but followed by spontaneous abortion due to genetic incompatibility. – lethal alleles terminates the process – chromosome number mismatches, first stage of mitosis terminates -Reduced zygotic barriers: Offspring from hybrids might develop sterility. Chromosome number during mating is problematic because parental chromosomes vary between species or parental species. – Donkey and horse’s hybrid is sterile -Hybrid Breakdown: F1 hybrids may work, but F2 hybrids are often always sterile. Speciation Events: how new species are created. -Branching Events: that make 2 species that were only one Darwin’s Finches: Darwin went to Galapagos islands and saw many birds -He thought that they were many different types of birds -Their sizes and feature were different. Adaptive Radiation: when evolution of many different types of species who’ve come from one common ancestor, which adapted to different local conditions.
– Finches from island one went to island 2, over time, they’ve adapted to island 2’s environment, then they moved to island 3, and adapted to that and so on. Modes of speciation -Allopatric Speciation: no connection and isolation, resulting in genetic change -geographic blockage > adapt to the different place > becomes 2 diff species -Sympatric Speciation: slight differences in that population isolates itself and becomes it’s own species Long Example: – Male maggot flies live on one Apple on trees, females like to pick males that live on the same type of tree – With the introduction of domestic Apples, some males and females went over to that Apple – Females born and lived on that Apple will recognize to mate people who are of live on the same type of Apple – New domestic Apple though, so not enough yet to mate, mates people from own Apple again – Then more females are born to mate own type of Apple, and as more of that type of Apples grow, they only mated with them – Eventually, they’ll be “isolated” to only mate with them, any other males from other Apples won’t be mated by females born on this type of Apple – Thus, their genes from that Apple are isolated within those who live on them. Rates of Evolution Gradualism: occurs in a gradual process -rate at which species morph over time and rate of speciation aren’t set. -species will change over time and can create new species at any time Punctuated Equilibrium: happens in rapid bursts of new species -species don’t change over time -daughters could live alongside parents for many year without change until they go extinct -Parents will undergo a big series of changes resulting in an offspring, then no change for that offspring. Just new species. -Both proven by fossils.