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ADAPT OR DIE Topic 5.7 CHANGING HABITATS A species lives there because it is specially adapted to survive and reproduce there- in the conditions in that habitat determined by the biotic and abiotic factors. It has a competitive/selective advantage Increased temperature (abiotic factor) may decrease size of habitat, organisms in the Arctic and surrounding sea may Emigrate Face local or worldwide extinction Adapt over many generations Climate change is a selection pressure for natural selection EVOLUTION AND NATURAL SELECTION Evolution: The change in an anatomical, physiological or behavioural feature over generations. Also the change in allele frequency in a population over time. Natural selection: The mechanism by which organisms change over time as they adapt to their changing environment. POPULATION GROWTH CURVES. Limiting factors are any factor that would limit the population growth. e.g. competition for/limited supply of food or space, predation, disease, light intensity- biotic and abiotic factors The carrying capacity is the maximum population size the habitat can support. ACTIVITY 5.22B POPULATION GROWTHLag phase - Slow increase due to low birth rate, becoming accustomed to the environment. Log phase - Exponential increase as there are very few limiting factors- high birth rate, low death rate. Slower increase in population- There are more limiting factors increasing the death rate and decreasing the birth rate. Stationary phase - Population size remains more or less constant with fluctuations- birth rate and death rate are equal. CHARLES DARWIN • Observed – • Concluded – • There is a struggle for existence Observed – • Organisms overproduce but population numbers stay the same. There is variation within species Concluded – The best adapted survive And they pass on their characteristics DARWIN’S OBSERVATIONS- 1 Organisms produce more offspring than survive and reproduce Numbers in natural population stay approx. the same over time Can you explain these two observations in terms of limiting factors? As the populations increase limiting factors increase (predation, competition for food and territory, rapid spread of disease due to overcrowding). What term is given in natural selection to the limiting factors ( or environmental factors) which limit population growth Selection pressures. Remember- climate change can be a selection pressure. DARWIN’S OBSERVATIONS- 2 There is a huge amount of variation within a species What are Darwin’s Conclusions ? Survival of the fittest- some characteristics are selected for (have a selective advantage) due to the selection pressure (environmental factor which causes this selection) Organisms with these characteristics are more likely to survive and reproduce passing on the advantageous allele to the next generation. Fitness- ability to survive and reproduce. Therefore the advantageous allele frequency will increase with every generation . Checkpoint 5.6 ACTIVITY 5.22C THEORY OF NATURAL SELECTION- BY CHARLES DARWIN Over-production of offspring- more offpring were produced than necessary to replace the adult population. There is variation within a speciesHow does it arise? Crossing over during prophase 1 of meiosis Independent assortment during metaphase/anaphase 1 of meiosis Random fertilisation Mutations- source of new alleles • Struggle for existence: not all offspring will survive. Predation, competition, disease, extreme environmental conditions…etc limit the population growth. Factors limiting population growth result in selection pressure. • A change in the environment result in a change in the selection pressure. • Survival of the fittest- some characteristics which were selectively neutral are now selected for (have a selective /competitive advantage) due to the change in the selection pressure. Organisms with these characteristics are more likely to survive and more likely to reproduce passing on the advantageous allele to the next generation. Fitness- ability to survive and reproduce • Some characteristics are now selected against (have a selective disadvantage) due to the change in the selection pressure. Organisms with these characteristics are less likely to survive and less likely to reproduce • From one generation to the next the frequency of the advantageous allele will increase. NATURAL SELECTION IN A NUTSHELL Suggest the source of the variation in colour. What is the selection pressure? Which organisms are selected for? What is the advantageous allele? Predict what the population will look like after a few generations. Why? WHAT EVIDENCE DID DARWIN HAVE? Biogeography Comparative embryology Paleontology Comparative anatomy EVIDENCE FOR EVOLUTION Darwin’s evidence. Observations of similarities and differences between organisms and their geographical location and fossil record BUT Darwin did not understand how the variation could be inherited. Mendel’s pea plant experiments were the first to show characteristics could be inherited in a predictable manner. PEER REVIEW PAGE 57 Q 5.42- Define the word gene. Include following terms in definition- nucleotides, polypeptide, allele, phenotype, genotype, dominant, recessive, expressed, polygenic, mutations Q 5.43-5.45 5.43- Authors can’t influence reviewers- e.g. bribery 5.44- Advantages-faster exchange of ideas. Disadvantage- poorly conducted studies can be publisized online, misleading people 5.45- Audience can question scientist presenting(immediate peer review) - Scientist receive immediate feedback and open discussions - Funding bodies can assess outcomes of project ACTIVITY 5.22, DEBUNKING THE MYTH OF POLAR BEAR HAIR What makes something black……or white? Reflection or absorption of the different wavelengths of light What is UV light? Shorter wavelength, higher energy than visible light and infrared. Discuss cards in small groups Read the article over the page and then answer Questions 1-3. MOLECULAR EVIDENCE What further evidence of evolution came AFTER Darwin’s time? Genomics: the study of DNA (the number and order of bases) Proteomics: the study of proteins (the number and order of amino acids) Techniques used to study and analyse DNA. DNA hybridisation, DNA profiling, DNA and protein sequencing, DNA molecular clocks. MOLECULAR EVIDENCE What information could we find out by studying DNA and proteins from different species? How closely related organisms are to one another. If there are FEWER differences between the DNA/Protein then the two species have evolved from a common ancestor MORE RECENTLY. Activity 5.23a DNA Hybridisation http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter14/animation_quiz_4.html How do high temperatures cause DNA to separate into single strands? Increased kinetic energy breaks the H- bonds between the complementary base pairs What is meant by the following terms in the context of this animation? Anneal- Combine, in this case H-bonds to reform between complementary base pairs DNA hybridisation- DNA strands from different sources anneal Homologous DNA strands- Double stranded DNA strands which have identical base sequences or at least are very similar Pure chimp DNA will separate at a higher temperature than a hybrid of chimp and human DNA because the two strands are completely complementary • Heat up DNA from Humans, Chimps and gorillas so that the DNA strands separate • Cool and mix DNA single strands from human and chimps, then human and gorilla. This allows hybridisation to happen. • To find out which hybrids are more similar heat them up to find out at which temperature the strands separate. • The denaturation temperature is measured of the hybrid and compared with that of non-hybrid human DNA. The higher the difference in denaturation temperature the bigger the difference in DNA. DNA PROFILING Use restriction enzymes to cut the DNA strand at specific points to produce different sized segments. Example: ECOR1 recognises the following sequence GAATC and makes a staggered cut between G and A If there are genetic differences the restriction enzymes will not cut at the same sections and will produce different sized segments. Write your own DNA sequence with 50 base pairs. They must include the above sequence (the one recognised by ECOR1) at least once (as many times as you want and where you want) DNA AND PROTEIN SEQUENCING http://www.mwit.ac.th/~deardean/link/All%20Co urse/pic/secuencia.swf Complete The Sanger Method DNA MOLECULAR CLOCKS PCR produces millions of copies of a DNA molecule. Automated DNA sequencing machines work out base sequences-by the Sanger Method As species evolve they accumulate random mutations at a regular rate- (this is an assumption) e.g. one every 10,000 years The more genetically different two species are the more mutations there were, so the longer in the past they shared a common ancestor. E.g. 10 mutations means they shared a common ancestor 100,000 years ago. Activity 5.23 Evolution Revealed horse horse zebra rabbit chicken duck snake moth zebra rabbit chicken duck snake moth rice 1 6 11 10 21 29 47 5 10 9 19 28 46 8 6 16 24 46 3 18 29 48 17 27 47 29 46 45 rice Q1-5. NOTE: Q4 is not just about sequencing but also about using DNA as a molecular clock EVOLUTION OBSERVED AND NATURAL SELECTION AND CLIMATE CHANGE The niche of polar bears: They cannot hunt for seals because the sea is unfrozen during late summer and early fall. Polar bears fast living off fat reserves then Polar bears also eat a wide variety of other wild foods, including muskox, reindeer, birds, eggs, rodents, shellfish, crabs, and other polar bears, plants, including berries, roots, and kelp, however none of these are a significant part of their diet. The polar bear's biology is specialized to require large amounts of fat from marine mammals, and it cannot derive sufficient caloric intake from terrestrial food. EVOLUTION OBSERVED Why is the population of polar bears decreasing? http://dsc.discovery.com/videos/global-warmingwhat-you-need-to-know-polar-bear-signs.html http://www.youtube.com/watch?v=axRX9_UyUOc http://www.youtube.com/watch?v=Kv9v9ALV3yk &feature=related Q 5.47-5.48 Natural Selection and Climate changeWhat are the major effects of climate change? Give specific examples Milder winter temps, earlier springs, later autumns, effect is greatest nearer poles where the length and severity of the winter is shorterlength of growing season is longer What is the major selection pressure resulting from climate change? Increased length of growing season In great and blue tits which characteristics were selected for? Selected against? Which allele frequency changed? How? Q 5.49 SPECIATION Define speciation: Formation of a new species What has to happen first before speciation? Reproductive Isolation What might cause isolation? Eg. A lake drying out, mountain range forming = Geographical Isolation REPRODUCTIVE ISOLATION Physical incompatability Behavioural isolation EXAMPLES OF THE DIFFERENT TYPES OF ISOLATION geographical ecological temporal sterility Behavioural Physical incompatability ACTIVITY 5.24 SPECIATIONDefine Species: Organisms which have similar morphology, behaviour and physiology and which are able to produce fertile offspring when they reproduce Reproductively isolated: Unable to interbreed and produce fertile offspring Write a detailed explanation of how isolation can lead to speciation. Use the interactive tutorial and textbook Brainstorm key words needed to answer questionIsolation, geographical isolation, gene pool, different random mutation, different selection pressure, natural selection, different alleles, selected for, survive, reproduce, pass on alleles, reproductive isolation, interbreed, sterile offspring, species EXTENSION 5.7 What are the four basic viewpoints? (note that this is oversimplistic) Where do you see yourself? Do you fit perfectly to one viewpoint? A mixture/ between two or more viewpoints? Another viewpoint? Underline the key words which describe each each viewpoint. What might make a creation scientist not able to accept the theory of evolution by natural selection? Not enough evidence for evolution leading to the formation of new species. Do NOT beleive in macroevolution Read the Bible as one might read a historical/scientific document written in the present day- literal interpretation. Believe that the earth is about 10,000 years old and most species or at least families were created as they were today. A flood destroyed many species. This is called Creationism.