BIO II PDF

18.1 Intro to Evolution Evolution is the central theory of biology: It ultimately answers medical questions such as: Why do bacteria develop resistance to antibiotics? Why do fatal genetic disorders still exists among humans? Why are some people more likely to get cancer? “Nothing make...

18.1 Intro to Evolution Evolution is the central theory of biology: It ultimately answers medical questions such as: Why do bacteria develop resistance to antibiotics? Why do fatal genetic disorders still exists among humans? Why are some people more likely to get cancer? “Nothing makes sense in biology except in the light of evolution” -Theodosius Dobzhonsky Understanding the process of evolution helps us make scientific discoveries: Example: sickle cell anemia causes pain ? shorten : very common lives , Genetic blood disorder that afflicts 1/365 births among people of African descent (also found among other ethnic groups Scientists wondered: since evolution should promote the incidence of HELPFUL genes, why would a such harmful genetic trait be so common among people of African descent? Heterozygous have an advantage against the disease SCA ,. What is evolution? Evolution: change Biological evolution: change in the characteristics of a population of organisms that occurs of the course of generations - Evolutionary changes are inherited via genes Theory of evolution: all species present on earth today are descendants of a single common ancestor, and all species represent the product of billions of years of accumulated evolutionary chnag How does evolution occur? Mutations: UV light viruses changes , , in the Dra Random mutations create genetic DNA differences in a population affects phenotype If a genetic difference results in an organisms having different traits, it may affect positively or negatively their ability to reproduce and pass on those traits 18.2 Public perception of evolution Evolution: The Bible, Torah, Qu’ran Life on earth arose once God created all All things living today are living things in the descendants of that same form which original cell and they currently exist difference between them are the result of evolution The trial of Galileo Galilee in 1633 Galileo was ordered to stand trial for heresy, and threatened with torture for his belief in heliocentrism which is the idea that the sun is the center of the galaxy and that earth and other planets orbit around it This conflicts with several statements in the Bible, stating that the sun orbits around the Earth “Currently, I see…a somewhat fierce debate raging between so-called "creationism" and evolutionism, presented as though they were mutually exclusive alternatives: those who believe in the Creator would not be able to conceive of evolution, and those who instead support evolution would have to exclude God. This antithesis is absurd because, on the one hand, there are so many scientific proofs in favour of evolution which appears to be a reality we can see and which enriches our knowledge of life and being as such. But on the other, the doctrine of evolution does not answer every query, especially the great philosophical question: where does everything come from? And how did everything start which ultimately led to man? I believe this isof the utmost importance…” 98% of scientists and 76% of the US public believe in human evolution An incomplete list of resources for further reading on religion and evolution: Exploring Faith and Reason by Bruce Glass The Language of God by Francis S. Collins Finding Darwin’s God by Kenneth R. Miller Islamic Theory of Evolution: The Missing Link between Darwin and the Origin of Species by T.O. Shanavas Islam and Biological Evolution by David Solomon Jalajel The Challenge of Creation: Judaism’s Encounter with Science, Cosmology, and Evolution by Natan Slifkin  18.3 Darwin the father of evolution The voyage of the Beagle: Darwin was a medical school graduate, but was unsure what he wanted to do He accepted a position as a naturalist on a voyage around the world in 1831, including the Galápagos Islands in South America The Galapagos finches Darwin observed that the birds’ bodies looked similar but they had different diets and different shaped beaks Darwins observation about evolution: 1. Offspring tend to inherit traits from their parents 2. All species can produce more offspring than their environment can support and many of these offspring fail to survive and reproduce 3. Individuals whose inherited traits give them a higher probability of surviving and reproducing in an environment tend to leave more offspring than other individuals Evolution via natural selection Natural selection: is a mechanism of evolution in which individuals with adaptations that are favorable in their environment survive and reproduce at a rate If the environment changes, or individuals move to a new environment, adaptation to the new conditions may occur Natural selection requires genetic diversity Natural selection requires that individuals differ in their inherited traits Genetic diversity comes from 2 sources Mutations Sexual reproduction Adaptation: a heritable trait that helps the organism’s survival and reproduction in its current environment May or may not be helpful in a different environment 18.4 Evidence for evolution Fossil evidence Evidence for common descent found in Darwin’s time. Horse fossils provide a good sequence of evolutionary change within a lineage Shared developmental pathways Similarity among vertebrate embryos Anatomical similarities Mammalian forelimbs have the same set of bones. the underlying structure is similar despite the very different function Vestigially: Humans and other animals have structures and behaviors that are evolutionary relics Examples include: Muscles attached to stationary ears Goosebumps Tailbone Infant grasping reflex DNA similarities DNA similarities: species in the same genus have DNA that is similar to one another while distantly- classified species have DNA that is less similar 18.5 Misconceptions about evolution “Evolution is just a theory” Scientific theories: ideas that have been repeatedly tested and verified using a variety of methods Other scientific theories include Theory of heliocentrism Germ theory Cell theory “Evolution explains origin of life” The theory of evolution addresses how populations change over time It does not include an explanation of how life first came to be “Individuals evolve” Can you change your own DNA as needed? Neither can other species Population evolve; not individuals “Organisms Evolve on purpose” You cannot change your individual DNA to adapt to changing environmental conditions However, a changing environment might selectively promote the survival and reproduction of certain individuals 18.6 Speciation What is a species? The biological species concept: a species is a group of populations whose members have the potential to Interbreed in nature and produce viable, fertile, offspring with members of other such groups Does not apply to organisms that reproduce asexually Speciation Speciation: the formation of 2 species from one original species Recall that the theory of evolution states that all life evolved from one original cell So how did we get from one cell to billions of species? How do new species arrive? Allopatric speciation: a species splits as a result of physical separation, followed by phenotype divergence Sympatric speciation: a species splits but remains living in the same habitat Sympatric speciation Can result when meiotic errors change the policy of gametes Most successful in hermaphroditic species (like plants) that can mate with themselves s Allopatric speciation: adaptive radiation Adaptive radiation: is one type of Allopatric speciation where 1 species spreads out over an area with many types of habitats and splits into multiple species Island chains (like Galápagos Islands) are a great place for this to happen Mechanism by which reproductive isolation occurs Temporal isolation Difference in timing of reproduction Example: organisms might have different mating of flowering times Mechanisms of reproductive isolation Habitat isolation Mechanisms of reproductive isolation Behavioral isolation Differences in mating behavior may interfere with reproduction Example: many birds have mating songs or dances  Gametic barrier reproduction isolation Eggs and sperm of different species unable to fuse Common among organisms that release gametes into the environment Post-fertilization barriers to reproduction: Hybrid inviability: offsring do not survive Example: sheep crossed with goat produces an embryo, but it dies early in development Hybrid infertility horses have 32 pairs of chromosomes and donkeys have 31 Since offspring has an uneven # of chromosomes homologous chromosomes can not line up properly to undergo meiosis in Review questions Evolution (18.1) o The theory of evolution (18.1) o Natural selection (18.3) o Genetic diversity (18.3) o Adaptation (18.3) o The Biological Species Concept (18.6) o Speciation (18.6) o Allopatric speciation (18.6) o Sympatric speciation (18.6) o Adaptive radiation (18.6) Why is evolution considered to be the central theory of biology? How does it shape scientist’s work in forming and testing hypotheses? (18.1) What is the role of genes in evolution? (18.1) How did an understanding of evolution help scientists discover why sickle cell disease became widespread among certain human populations? (18.1) What are the steps in the process of evolution? (18.1) Why was Galileo put on trial in 1633? (18.2) Is belief in evolution incompatible with most people’s religious beliefs? (18.2) Approximately what percentage of scientists believe in evolution? (18.2) What are some steps someone could take to explore the question of how their personal religious beliefs can be compatible with belief in evolution? (18.2) What are the Galapagos finches? How did they diverge from one another? Why are island chains a good place to observe evolutionary change? (18.3) What were Darwin’s observations made in the Galapagos Islands that led to his development of the theory of evolution? (18.3) Why is genetic diversity important for natural selection? How does genetic diversity arise? (18.3) How does fossil evidence support the theory of evolution? (18.4) How do shared developmental pathways support the theory of evolution? Why do you think they are so highly conserved across species? (18.4) Review questions continued How do anatomical similarities support the theory of evolution? (18.4) How does vestigiality support the theory of evolution? What are some examples of vestigiality? (18.4) How do DNA similarities support the theory of evolution? (18.4) Be able to explain why the following statements about evolution reflect misconceptions (18.5): o “Evolution is just a theory” o “Evolution explains the origin of life” o “Individuals evolve” o “Organisms evolve on purpose” How does sympatric speciation occur? Why is this type of speciation most likely to result in new species in organisms that are hermaphroditic? (18.6) Why are groups of islands common sites for adaptive radiation? (18.6) Be able to explain how the following types of reproductive isolation occur; is each one pre- or post-zygotic? (18.6): o Habitat isolation o Behavioral isolation o Gametic barrier isolation o Hybrid inviability o Hybrid infertility 2.1 introduction to population genetics and hardy- Weinberg Evolution happens to populations not individuals the graph shows average beak depth of finches before and after a drought Drought decreased availability of small, soft seeds; larger beaks that could eat larger seeds were favored However, individual finches did not change their beak length Population and gene pools a population is a group of individuals of the same species that live in the same area and can interbreed producing fertile offspring Allele is one version of a gene Allele frequency is the measure of how often that version of the gene appears in the population Gene pool is the # of different alleles that exist for a population including recessive alleles that may or may not be expressed Allele frequency say there is a population of 500 wildflowers with genotypes and phenotypes Our population has: 320 plants with red flowers (Cr Cr= 640 Cr alleles) 160 plants with pink flowers (Cr Cw= 160 Cr and 160 Cw alleles) 20 plants with white flowers (Cw Cw =40 Cw alleles) what is the allele frequency Co of alleles es : 40 = 02. p is the frequency of the more common allele, a the frequency of the less common allele If there are only two alleles in the population as in the previous example p+q =1 The Hardy-Weinberg equation the Hardy-Weinberg theorem states allele frequencies will remain stable in populations that meet the conditions: No mutations Large population size Random mating No migration (gene flow) No natural selection A population that meets these conditions is said to be in Hardy-Weinberg equilibrium The HW theorem is expressed as an equation p2 29p q2 1 + + = P and q are the frequencies of alleles in a population p2zq2 are the frequencies of individuals that are homozygous (AA or aa) 2pq is the frequency of hertozygous individuals (Aa)  Allele frequencies represent the likelihood of having sperm or egg with that allele 2.2 population genetics natural selection Genetic drift Gene flow Non-random mating Mutation Natural selection: individuals in a population exhibit variable and heritable traits If some of those traits confer a survival and reproductive advantage, the alleles responsiblity for them may increase in frequency over time Example: fruit flies have an allele that confers resistance to many insecticides including DDT The frequency of this allele was 0% in flies collected in the wild in the 1930s Today the frequency is 37% Some variation is not heritable memorial arizonaria caterpillars appear different due to differences in diet Phenotypes are influenced by both genes and environment Only genetic differences are heritable Genetic drift another mechanism of evolution Happens in smaller populations Chance events can cause fluctuations in allele frequencies: Genetic drift: the founder effect and bottleneck effect founder effect: when a few individuals become isolated from a larger population they will affect the allele frequency of the resulting population Bottleneck effect: when the population size suddenly drops allele frequency of the population can quickly change Gene flow the transfer of alleles into or out of a population due to movement of fertile individuals or their gametes Non-random mating humans do not choose mates randomly nor do many other species 1 example of this is assertive mating: individuals tend to choose partners with similar traits such as human height Overtime can exaggerate differences within a group  2.3 brief history of life on earth How can we determine historic rates of speciation the fossil record indicates that evolutionary change does not happen at a constant rate but instead represents punctuated equilibria, periods of little change followed by periods of rapid change The Cambrian Explosion, starting 541 million years ago is a major example of this change, likely caused by increased oxygen in the environment The scale of geological time Vertebrates arose in the Cambrian explosion they are chordates that have a backbone All except for hagfishes and lampreys also have jaws Humans are Chordates chordates have the following Tetrapods have limbs characteristics: have limbs with finger/toes Bilateral symmetry instead of pectoral and pelvic Notochord that provides skeletal support fins Hollow nerve cord along the dorsal side of Fossil Shown is “Tikaalik” a the body transitional fossil discovered Pharyngeal slits in 2004 that is 375 million Muscular tail years old Has some characteristics of fish and some tetrapods  2.4 From tikaalik to TikTok Amphibians: the first land-dwelling tetrapods animals did not start to live out of water until about 500 million years ago Includes frogs and salamanders Most lay eggs in water Reptiles (including birds) lay amniotic eggs eliminates the need to reproduce in water Allows parents to protect eggs better Mammals are amniotic that have hair and produce milk We belong to the order primates primates all have an especially mobile thumb; monkeys and apes have a fully opposable thumb This is an adaptation to living in trees, as all ancestral primates did All have large brains 2.5 Social Darwinism and eugenics The origins of social Darwinism Darwin’s foundational book, On the Origin of Species was published in 1859 and immediately became immensely popular and well known Some came to see Darwin’s ideas of natural forces contributing to human dominance as being applicable to power structures within human societies The term “Social Darwinism” first appeared in the 1870s and promoted the idea that class and racial differences were the result of inherent genetic superiority/inferiority among different human groups Scholars are conflicted over whether Darwin himself had any social Darwinist views Darwin was an outspoken abolitionist, and resisted attempts to use use evolution to explain differences between races Social Darwinism and eugenics the popularity of social Darwinism led to renewed interest in eugenics: the idea that humankind could be improved by selective breeding and removal of “undesirable” traits from the gene pool through sterilization or killing of certain people Does the theory of evolution explain differences between races? the term “race” is used to describe a combination of social class, culture, and genes We do see racial differences in medicine; can these be attributed to genetic differences resulting from evolution? Do racial differences = genetic differences? a study published in 2002 looked at human genetic differences across different regions of the world to see how much “racial” differences contributed to human genetic diversity Result: 93-95% of human genetic variation can be attributed to “within population” diversity; only 3-5% of human genetic variation can be attributed to differences between groups Many researchers now prefer to use the term “ancestry” rather than “race” to refer to genetic differences between different groups of humans 2.6 the evolution of modern humans Common misconceptions about human evolution humans are not descended from chimpanzees rather we shared a common ancestor several million years ago Many intermediate species fossils have been found, showing us how modern humans evolved Hominins pre-human species are referred to as hominins Multiple hominin species lived at the same time Modern humans and Neanderthals overlapped and bred together in Europe and Asia; many modern people of European and Asian descent have Neanderthal DNA “Being a self-described night owl and being prone to daytime napping were both traits positively influenced by Neanderthal variants, as were loneliness, low mood, and smoking.” A proposed timeline of some hominin species The earliest hominins “arid” the Skelton pictured here lived 4.4 million years ago Has a more upright stance than other apes based on location of the foremen magnum of the skull and the structure of the pelvic and leg bones Australopiths hominins from 2-4 million years ago Probably all have a single common ancestor “Lucy” is a famous Skelton from this genus Showed further evidence of bipedalism: walking on 2 legs instead of 4 Bipedalism important for tool use Other apes do use tools, like putting leaves on their feet to walk over thorns or using rocks to smash open food Oldest accepted evidence of tool use by hominins is 2.5 million year old cut marks on animal bones Early homo arose around 2.4 million years ago Main development is larger brain volume Also decreased sexual dimorphism(male gorillas are about 2x the size of females) Homo erectus was the first hominin to migrate out of Africa, probably around 1.8 million years ago Neanderthals First Homo neanderthalensis fossils were found in 1856 in Germany, and dated to 40,000 years ago Originally thought to be a human ancestor but no longer the case; we diverged about 400,000 years ago Had brains larger than modern humans, buried their dead, and made hunting tools from stone and wood Module 3: Intro to anatomy and physiology anatomy: the study of the structure of body parts in their relationships to another Physiology: the study of how the body normally functions Basic ideas in anatomy and physiology: exchange with the environment animal tissue types communication and homeostasis Thermoregulation and energy expenditure 3.1 exchange with the environment Basic ideas of anatomy and physiology : exchange with the environment all organisms need to absorb essential substances and secrete wastes Parts of our bodies are specialized for exchange These structures tend to be highly branched or folded (why?) 3.2 animal tissue types all animal bodies are made up of tissues: epithelial Connective Muscle Nervous Epithelial tissue Epithelial tissues cells covers the outer and inner cells are named by surfaces of the body (including shape and linings of hollow organs) arrangement Many subtypes Simple: 1 layer Regulates passage of Stratified: many substances in and out of the layers body Connective tissue provides physical structure to the body Many subtypes Very considerable in structure from solid (bone) to liquid (blood) Connective tissue cells loose connective tissue Fibrous connective tissue Adipose tissue Muscle tissue produces movement of the body and within the body Produces heat May be voluntary or involuntary The 3 types: Skeletal Smooth Cardiac Nervous tissue cells: Neurons: dendrites, cell body, axon Glia 3.3 communication and homeostasis How do our cells know how to work together? 2 communication systems in the body: Nervous system: electrical and chemical signals called neurotransmitters Endocrine system: chemical signals called hormones Hormones travel through the bloodstream to reach target cells Homeostasis regulation of conditions in the body’s internal environment Keeps the internal environment stable (though not always the exact same) Maintained via negative feedback  What is a feedback loop set point: the desired value ( or range of values) the system wants to maintain Stimulus: a change in conditions Sensor: something that detects the stimulus Response: a change attempting to bring the system back towards the set point Negative feedback: when the response shuts itself off when the set point is achieved Negative feedback maintains homeostasis Food is consumed and digested, causing blood level glucose to V T rise In response to the lower In response to higher concentration of glucose, glucose levels, the the pancreas stops pancreas secretes secreting insulin insulin into the blood Y In response to higher insulin levels, glucose is transported into Y cells and liver cells store glucose as glycogen. As a result, glucose levels drop Positive feedback, does not promote homeostasis needs something outside the feedback loop to shut it off - Do set points change yes, set points can change based on the environment and other factors Most living things exhibit circadian rhythms: changes in set points at different times of the day Do set points change? acclimatization: when changes in environmental conditions affect set points Example: mountain climbers adjust to lower levels of oxygen in many ways 3.4 thermoregulation and energy expenditure What is endothermy temperature is an important factor that determines the speed of chemical reactions Mammals and birds are endothermic: they maintain a fairly consistent body temperature regardless of external temperature (Note that most of life on earth lives in water, where temp varies a lot less on land) Endothermy is usually achieved through a combination of behavioral and physiological means Insulation prevents heat loss most endothermic animals have feathers or fur Effectiveness of these can be increased by fluffing up fur using arrector pili muscles (we don’t have fur but still get goose bumps when cold) Fat also provides insulation The circulatory system prevents heat loss under cold conditions blood is shunted away from the surface of body by constricting certain blood vessels In limbs and other body parts with high surface area, countercurrent exchange systems reduce heat loss How does the body lose and gain heat? radiation: emission of heat energy Evaporation: removal of water also removed heat Convection: transfer of heat from movement of air (this is why wind makes you feel cooler) Conduction: direct transfer of heat between objects in contract with each other What factors influence metabolic rate? physical activity is energetically demanding Animals can reduce energy demand through: Torpor: a physiological state of decreased activity and metabolism often occurs in response to starvation or extreme temps Hibernation: a seasonal decrease in activity Body composition: muscle tissue uses more energy than other tissue types Evaporative heat loss cools the body when water evaporates, heat energy is absorbed, resulting in cooling Human and horses can sweat but most mammals can’t Some mammals achieve evaporative cooling through panting How does the body make its own heat? heat is produced as a byproduct of all muscle contraction We tend to produce movement when cold (shivering) Mammals also have a specialized tissue, brown fat that produces heat using mitochondria Brown fat uses the mitochondrial proton gradient to generate heat rather than ATP How can we measure energy use? Metabolic rate: the sum of all the energy an animal uses in a period of time Can be measured using heat loss, oxygen consumption or methods What factors influence metabolic rate? body size: bigger animals have a higher metabolic rate, but also more efficient It takes more energy to maintain a gram of a mouse’s body than it does to maintain a gram of an elephant’s body