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Topic 5: Ecology and Evolution


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IBSL Biology topic 5. Students testing out of standard level bio should study up on these points.

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Topic 5: Ecology and Evolution

  1. 1. Topic 5Ecology and Evolution
  2. 2. Using Keys to Identify Organisms• Species Identification: Finding out whatspecies of organism there are in the areabeing studied• Keys: Method of species identification
  3. 3. Binomial Nomenclature• Species: group of organisms with similarcharacteristics, which can interbreed andproduce fertile offspring• Genus: group of similar species• Nomenclature: the naming of a species• Binomial Nomenclature features:– First name is the genus name (Capitalized)– Second name is the species name (lowercased)– Underlined (handwritten) or italicized (typed)
  4. 4. Hierarchy of Taxa• Hierarchy of Taxa: species are classified intoa series of species, each level containing awider range of species than the one below it1. Kingdom2. Phylum3. Class4. Order5. Family6. Genus7. Species
  5. 5. Plant ClassificationType Roots, leaves, stems Max height ReproductionBryophates:mossesHave no rootsSimple leaves andstems0.5 meters Spores are produced in acapsule with develops atthe end of the stockFilicinophytes:fernsHave roots, leaves andshort non-wood stemsLeaves are pinnate(divided) buds15 meters Spores are produced insporangia, usually on theunderside of leavesConiferophytes:conifersHave roots, leaves,woody stemsLeaves have thick, waxycuticles100 meters Seeds are produced onfemale cones; male conesproduce pollenAngiospermo-phytes:flowering plantsFlowering plantsHave roots, stems,leaves100 meters Seeds are produced fromovaries; fruits develop fromovaries to disperse theseed
  6. 6. Animal ClassificationPorifera:• No clear symmetry• Attached to a surface• Pores throughout bodyExample: spongesPlatyhelminths:• Bilaterally symmetric• Flat bodies• Unsegmented• Mouth but no anusExample: tapewormsMollusca:• Muscular foot andmantle• Shell usually present• Segmentation notvisible• Mouth and anusExample: snailCnidaria:• Radially symmetric• Tentacles• Stinging cells• Mouth but no anusExample: jellyfishAnnelida:• Bilaterally symmetric• Bristles often present• Segmented• Mouth and anusExample: leechArthropoda:• Bilaterally symmetric• Exoskeleton• Segmented• Jointed appendagesExample: crab
  7. 7. Changes to the Size of a Population• Population: group of organisms of thesame species, who live in the same areaat the same time• Increases population:– Natality: offspring are produced– Mortality: individuals die• Decreases population:– Immigration: individuals are added in– Emigration: individuals leave
  8. 8. Population Growth Curvesa. Exponential phase:• Natality rate is higher thanmortality• Resources are abundant• Diseases/predators rareb. Transitional phase:• Natality rate starts to fall ormortality rate starts to rise• Natality is still higher thanmortality• Population slowly risesc. Plateau phase:• Natality and mortality are equal• Population size is constant• Carrying capactiy: when thepopulation is limited by ashortage of resources in area
  9. 9. Evolution of Populations• Evolution: the cumulative change in theheritable characteristics of a population• Three types of evidence for evolution:1. Homologous anatomical structures2. Fossil records3. Selective breeding
  10. 10. Homologous Anatomical Structures• There are remarkable similarities instructure between some groups oforganisms• Organisms could share a commonancestor• Homologous structures: structures thathave developed from the same part of acommon ancestor
  11. 11. Fossil Record - Palaeontology• Existing fossils show animals that are notidentical to any existing organism• Suggests change has taken place overtime
  12. 12. Selective Breeding of Domestic Animals• Domesticated animals are related to wildspecies and can often interbreed• These domesticated animals aredeveloped from their wild species bybreeding individuals with desirable traits• The differences in heritable characteristicsof different breeds of the same animalshow proof of evolution
  13. 13. Natural Selection• Charles Darwin created the theory ofevolution as published in his book TheOrigen of Species in 1859• Alfred Wallace suggested very similarideas
  14. 14. Explaining the Theory of EvolutionObservations: Deductions:• Populations of living organisms tendto increase exponentially• Yet, the number of individuals inpopulations remain nearly constant• More offspring are produced than theenvironment can support• There is a struggle for existence• Some die and some survive• Living organisms vary• Some individuals havecharacteristics that make them welladapted to their environment; someare not well adapted• Better adapted individuals tend tosurvive and reproduce more thanthose not as well adapted• This is called natural selection• Much variation is heritable – it can bepassed on to offspring• Better-adapted individuals pass ontheir characteristics to more offspringthan those not as well adapted• The species characteristics evolve asone generation follows another
  15. 15. Environmental Change and Evolution• Evolution acts in response toenvironmental change• Changes add to the evidence of evolution
  16. 16. Sexual Reproduction and Evolution• Variation is essential for natural selection,and therefore evolution• Sexual reproduction promotes variation byallowing the formation of new combinations ofalleles– Meiosis allows a variety of genetically differentgametes to be produced by each individual– Fertilization allows alleles from two differentindividuals to combine in a new individual• Without sexual reproduction the variation andthe capacity for evolution is less
  17. 17. Trophic Levels• Communities: group of populations livingtogether and interacting with each other inan area• Trophic Levels: where one population oforganisms feed on another population• Food chains: sequences of trophicrelationships, where each member in thesequence feeds on the previous one
  18. 18. Food Chains• First organism in afood chain does notfeed on others; mustbe a producer• Other organisms areprimary, secondary,tertiary, etc consumers• Trophic level: anorganism’s position inthe food chain
  19. 19. Autotrophs• Autotrophs: organisms that synthesizetheir own organic molecules (food) fromsimple inorganic substances• Called producers because they producetheir own food (usually by photosynthesis)• Light is the initial energy source for thewhole community as it provides energy forphotosynthesis
  20. 20. Heterotrophs• Heterotrophs: organisms that obtain organicmolecules (food) from other organisms• Three types of heterotrophs:1. Consumers:• Ingest organic matter that is living or recently killed• Example: lion2. Detritivores• Ingest dead organic matter• Example: earthworm3. Saprotrophs• Live on or in dead organic matter, secreting enzymesinto it and absorbing the products of digestion• Example: bread mold
  21. 21. Food Webs• Food web: diagram that shows all thefeeding relationships in a community• Arrows indicate direction of energy flow
  22. 22. Energy Pyramids• Energy pyramids: diagrams that show howmuch energy flows through each trophiclevel in a community• Each level is smaller than the one below it• Less energy flows through eachsuccessive trophic level• 10-20% of energy passes on to nextorganism
  23. 23. Example of Energy Pyramid
  24. 24. Ecosystems, Ecologists and Ecology• Ecosystem: a community and its abioticenvironment• Ecology: the study of relationships inecosystems – both relationships betweenorganisms and between organisms andtheir environment
  25. 25. Nutrient Recycling in Ecosystems• Energy is supplied to ecosystems in theform of light, flows through food chainsand is lost as heat• Nutrients must be recycled– Nutrients such as: carbon, nitrogen,phosphorus
  26. 26. Carbon Cycle
  27. 27. Saprotophs in Recycling Nutrients• Saprotrophs: feed by secreting digestiveenzymes into dead organic matter– These enzymes break down organic matter andrelease nutrients– Saprotrophs absorb the substances that theyneed from the digested organic matter• Without saprotrophs, nutrients wouldremain locked up permanently in deadorganic matter– Nutrients would soon become deficient
  28. 28. Rising Carbon Dioxide Levels• Before 1880 the carbon dioxideconcentration of the atmosphere remainedfairly constant at ∼ 270 parts per million• From 1880 onwards the concentrationrose• Overall upward trend
  29. 29. Greenhouse Gases• Group of gases that cause heat to beretained in Earth’s atmosphere:– Carbon dioxide– Methane– Oxides in nitrogen– Sulfur dioxide• Greenhouse effect: heat retention by gases• Global warming: rising temperatures on Earth
  30. 30. Rising Global Temperatures• Statistically significant changes intemperature• Most likely due to increased greenhouseeffect
  31. 31. Habitats• Habitat: the environment in which aspecies normally lives or the location of aliving organism
  32. 32. Consequences of Global Warming• Glaciers will melt and polar ice sheets will break up andeventually melt• Permafrost will melt during the summer increasing the ratesof decomposition; causing greater release of carbon dioxide• Species adapted to temperature conditions will spread north;altering food chains• Marine species that are sensitive to arctic watertemperatures may be killed• Polar bears will lose their ice habitat• Pests and diseases may become more prevalent in warmtemperature• Sea levels will rise; causing flooding• More frequent extreme weather events
  33. 33. The Precautionary Principle• Precautionary Principle: People planning todo something must prove that it will not doharm, before actually doing it– Should be followed when the possibleconsequences are very large• Many scientists argue that the precautionaryprinciple should be followed to stop anyoneadvocating the continuation of emittinggreenhouse gases at current or higher levels