5. Ecology and evolution


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5. Ecology and evolution

  1. 1. IB DIPLOMA PROGRAMMETHE IB LEARNER PROFILE:-Inquires: They develop their natural curiosity. They acquire theskills necessary to conduct inquiry and research and showindependece in learning.They actively enjoy learning and thislove of learning will be sustained troughout their lives.-Knowledgeable: They explore concepts, ideas and issues thathave local and global significance. In so doing, they acquire indepth knowledge and develop understanding across a broadand balanced range dsciplines.-Thinkers: They excercise initiative in applying thinking skillscritically and creatively to recognize and approach complexproblems, and make reasoned,ethical decisions.
  2. 2. THE IB LEARNER PROFILE:Communicators: They understand and express ideas and information confidently and creatively in more than one language and in a variety of modes of communication. They work effectively and willingly in collaboration with others-Principled: They act with integrity and honesty, with a strong sense of fairness, justice, and respect for the dignity of the individual, groups, and communities.They take responsibility for their own actions and the consequences that accompany them.-Open minded: They understand and appreciate their own cultures and personal histories, and are open to the perspectives, values, and traditions of other individuals and communities. They are accustomed to seeking and evaluating a range of points of view, and are wiling to grow from the experience.-Caring: They show empathy, compassion, and respect towards the needs and feelings of others. They have a personal commitment to service, and act to make positive difference to the lives of others and to the environment.
  3. 3. THE IB LEARNER PROFILE:- Risk takers: They approach unfamiliar situations and uncertainty with courage and forethought, and have the independence of spirit to explore new roles, ideas, and strategies. They are brave and articulate in defending their beliefs.- Balanced: They understand the importance of intellectual, physical, and emotional balance to achieve personal well-being for themselves and others.- Reflective: They give thoughtful consideration to their own learning and experience. They are able to assess and understand their strenghts and limitations in order to support their learning and personal development.
  5. 5. 2.1.- COMMUNITIES AND ECOSYSTEMSWORD DEFINITIONHabitat: The environment in which a species normally lives, or the location of a living organism.Species: A group of organisms that can be interbreed and produce fertile offspring.Population: A groups of organisms of the same species who live in the same area at the same time.Community: A group of populations living and interacting with each other in an area.Ecosystem: A community and its abiotic environment.Ecology: The study of relationships between living organisms and between organisms and their environment.
  6. 6. ECOLOGY:• Living organisms do not live in isolation. If we study organisms in their natural habitat, we invariably find that they live with other members of their species and with populations of other species, in what ecologists refer to as a community.• Living organisms depend on their environment, whether it consists of air, water, soil or rock. There are many types of relationships between organisms and their environment.• The community of organisms in an area and their non-living environment can be considered to be a single higly complex interacting system, known as ecosystem
  7. 7. 2.1.1.- Food SourcesWORD DEFINITIONAutotroph: An organism that synthesizes its organic molecules from simple inorganic substancesHeterotroph: An organisms that obtains organic molecules from other organismsConsumer: An organism that ingests organic matter that is living or recently killedDetritivore An organism that ingests non-living organic matterSaprotroph: An organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion
  8. 8. 2.1.1.- Food SourcesAll organisms need a supply of organic molecules, such as glucose and aminoacids. They are needed for growth and reproduction.Methods of obtaining organic molecules:1.- Some organisms make their own organic molecules from carbon dioxide and other simple inorganic substances: Autotroph organisms (self feeding)2.- Some organisms obtain their organic molecules from other organisms and of digesting it so that it can be absorbed: 2.1.: By ingesting organisms and digesting them inside the gut, these organisms are called consumers 2.2.: By ingesting dead organic matter derived from living organisms and by digesting it inside the gut, these organisms are called detritivores 2.3.: By secreting digestive enzymes into dead organic matter derived from living organisms and by absorbing the products of externl digestion, these organisms are called saprotrophs
  9. 9. 2.1.2.- Food chains• A food chain is a sequence of organisms, each of which feeds on the previous one.• There are usually between 2 and 5 organisms in a food chain• Producers are autotrophic. They are usually photosynthetic organisms, such as terrestrial green plants and phytoplankton. As theydo not obtain food from other organisms, producers are always the first organisms in a food chain.• The subsequent organisms are consumers. Primary consumers feed on producers, secondary consumers feed on primary consumers, tertiary consumers feed on secondary consumers and so on.• Consumers obtain energy from the organic matter of the organisms on which they feed. The arrows in a food chain therefore indicate the diretion of energy flow
  10. 10. 2.1.3.- Trophic levels• The categories of organism, producer, primary consumer, secondary consumer and so on, are called TROPHIC LEVELS.• The word trophic means “nourishment” in old Greek.• Trophic levels: - Producer - Primary consumer - Secondary consumer - Terciary consumer …..
  11. 11. Trophic levels- FOOD WEBS
  12. 12. 2.1.3.- Food webs• Trophic relationships within ecological communities tend to be complex and web-like. This is because most species fed on by more than one species and most consumers feed on more than one species.• When a food web is constructed, organisms at the same trophic level are often shown at the same level in a web. This isn’t always possible, as some organisms feed at more that one trophic level.
  13. 13. Food webs
  14. 14. Alaska’s Food web
  15. 15. 2.1.4.- Energy flow in food chains• For most biological communities, the initial source of energy is LIGHT captured by plants undergoing photosynthesis.• Plants convert light into chemical energy.• A portion of this energy is used by the plant in cellular respiration and is ultimately released as waste heat to the environment.• Energy stored in plant tissues is passed to the next trophic level, if plant matter is eaten by primary consumers.• Also a portion of the plant’s material may become detritus, in which case stored energy can be passed on to Saprotrophs or Detrivores.
  16. 16. • The energy stored in plant matter eaten by primary consumers can be used directly as a source of energy for cellular respiration. This energy can also be released as waste heat, from the primary consumers.• The alternative is that organic matter containing stored energy in the primary consumer can be eaten by a secondary consumer.• In addition, undigested plant matter released as feces by the primary consumer contains available energy for saprotrophs and detrivores to use.
  17. 17. • Energy is passed from consumer to consumer in a food chain, but with every transformation energy is lost from the community in heat generated by respiration.• One of the laws of physics states that energy transformations are never 100% efficient. Further, when an animal eats, a portion of its food is never absorebed and is egested as feces.• Some material such as bones or air, may not be eaten. That energy can be used by decomposers.
  18. 18. 2.1.5.- Pyramids of energy• The amount of energy converted to new biomass during a given time period by each trophic level, in an ecological community, can be represented by a pyramid of energy.
  19. 19. • The width of the bars is proportinal to the energy in that trophic level.• There’s always loss of energy trough the food chain.• To be more accurate, the boxes should be drawn to have relative widths that match the relative energy content at each trophic level.• Pyramids of energy show how much energy is lost between trophic levels. Typically only between 5% and 20% of the energy in one trophic level is passed on to the next.• As a result there is less and less energy available to each succesive trophic level. Eventually there is too little energy to sustain a population, that is why food chains are limited in lenght.
  21. 21. 2.2. POPULATIONS• 2.2.1. POPULATION GROWTH:• Population studies, often focus on variables such as population size, density, growth and the interaction of the population with the biotic and abiotic factors of the habitat it occupies
  22. 22. Sigmoid S-Shaped growth curve
  23. 23. Sigmoid S-Shaped growth curve• The figure, shows the population growth of a group of organisms, kept in controlled conditions, including a constant supply of food. The figure illustrates a pattern called the Sigmoid or S- Shaped, growth curve.• The S-curve is representative of what happens when a population colonizes a new habitat. With limited environmental resistance, a population will growth exponentially. At this stage, birth rate (natality) is higher than death rate (mortality).
  24. 24. • As population density increases, various density- dependent factors begin to limit population growth.• Examples of such limiting factors include: 1.- Competition for resources 2.- toxic products of metabolism 3.- Increase in predation 4.- Increase in the incidence of disease. The initial result is that natality slows in relation to mortality. This is the transition phase of the curve.
  25. 25. • The maximum size of a population that and environment can support is its carrying capacity *• In the sigmoid growth pattern, when a population reaches its carrying capacity, the population will stop growing and natality and mortality will be equal. This is referred to as the plateau phase on the S-curve.* The carrying capacity of a biological species in an environment, is the population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment.
  26. 26. • Some populations can overshoot the carrying capacity of the environment. The result is a “boom-and-bust” pattern. DATA BASES IN ECOLOGICAL RESEARCH:Advances in technology have meant that the creation and publication of data is increasingly exceeding the rate at which it can be analysed. Hypothesis testing is increasingly possible by extracting data from a database rather than the researcher directly collectong the data themselves.
  28. 28. • Unlike energy, which flows through an ecosystem and must be constantly replenished, nutrients are recycled within ecosystems. Nutrients are chemicaql elements such as carbon, nitrogen and phosphorus. The basic pattern of nutrient cycles involves three stages:1.- There is an inorganic reserve of each element in the ecosystem, for example carbon dioxide in the atmosphere. Autotrophs abosrb the element from this reserve and convert it into organic compounds, for example nitrate is converted into amino acids.
  29. 29. 2.- Consumers obtain the element in organic form, by feeding on autotrophs or other consumers.For example, elephants obtain amino acids, containing nitrogen, from the plants that they eat.3.- Dead organic matter, containing the element is released when organisms excrete or egest waste material or they die. The element would remain locked up in the organic matter if it were not for the activity of saprothophs (fungi, bacteria) or detritivores. These organisms therefore, have a crucial role in recycling.For example: saprotrophs release nitrogen in the form of ammonia, which is converted by bacteria into nitrates.
  30. 30. Generalized nutrient cycle
  31. 31. 2.3.1.- THE CARBON CYCLE• As life is based on carbon compounds, the carbon cycle is especially important. In marine and aquatic ecosystems, the inorganic reserve of carbon is: dissolved cabron dioxide and hydrogen carbonate, which is absorbed by producers, and by various means is released back into the water.
  32. 32. 2.3.2.- THE GREENHOUSE EFFECT• In a greenhouse, light enters and warms up the solid surfaces.The glass prevents the heat from escaping and the temperature inside the greenhouse rises. A similar sequence of events happens inside an automobile with its windows closed, when it has been parked in full sunlight. The rise in temperature is known as the greenhouse effect. It also occurs in the Earth’s atmosphere.
  33. 33. • Much of the light from the sun has short wavelenghts and high energy, and it passes through the atmosphere, to the Earth’s surface.• The warm surface of the Earth re-emits energy, but with much longer wavelenghts, and lower energy than the light from the sun.• Most of this re-emitted energy is infrared radiation. Certain gases in the atmosphere absorb infrared radiation and re-emit it, some towards the Earth.
  34. 34. • Certain gases in the atmosphere absorb infrared radiation and re-emit it, some towards the Earth. The effect is GLOBAL WARMING and makes the Earth habitable.• Without the Greenhouse Effect it is estimated that the mean temperature at the Earth’s surface would be about -18ºC.• The main gases that contribute to the global warming, known as greenhouse gases, are carbon dioxide, methane and oxides of nitrogen.
  35. 35. 2.3.3.- The enhanced greenhouse effectThere is a considerable evidence that the Earthis becoming warmer.
  36. 36. • An obvious explanation for the global warming is an enhanced greenhouse effect caused by human additions of greenhouse gases to the atmosphere, mostly trough fossil fuel burning.• Now we know that the atmospheric levels of carbon dioxide have grown since the past century; due to the increase of industralization.• Carbon dioxide is not the only greenhouse gas and the concentrations of others, including methane and nitrogen oxides, have also been rising as a result of human activities.
  38. 38. 2.3.4. The precautionary principle• Governments are responsable for protecting when assessing new techonolgies. This requires a balance between encouraging innovation and minimizing risk. Scientists are often asked to advise governments about risks. BUT HOW SHOULD GOVERNMENTS ACT WHEN SCIENTISTS OFFER INCOMPLETE INFORMATION OR CONTESTED KNOWLEDGE?
  39. 39. • Traditional risk analysis involves assessing the likelihood that new technologies will harm the public. This puts the burden of proof on those who are concerned about the risk. However, damage may already have been done long before evidence harm exists.• A contrasting approach is the precautionary approach. In the late 1970s, when private landowners in Germany observed that significant tracts of forest were being killed. There was not yet scientific proof that ACID RAIN was the cause, but the government acted to regulate power- plant emissions. more strictly anyway
  40. 40. Precautionary principle vs. Anti-precautionary principleEXAMPLE:In 1997, The European Union banned the import of products from cattle that had been treated with bovine somatotropin (BST), a hormone that when given to cattle, increases milk yields by about 10%. The USA inmediately appealed to the World Trade Organization (WTO). They argued that there was no known example of humans being affected by BST. The WTO gave EU a year to privide evidence of harm to humans. If they could not do this, the ban would have be lifted. The WTO was applying what we might call the anti-precautionary principle: it is for society to show that something is dangerous, instead of requiring the perpetrator to show it is safe.
  41. 41. Excersice: Thinking about science DRUG TESTING• The precautionary principle argues that the action to protect must precede certainty of risk. The principle is particularly relevant when the potential consequences of the activity are catastrophic. Some drugs have had catastrophic effects when they were introduced without effective testing.• In some jurisdictions, a relatively conservative protocol has emerged for approval of drugs so that they become available for later than in other jurisdictions. Patient advocacy groups often exert pressure for the process to be expedited. Tests and trials make drugs less risky, but the risk is never removed entirely. Urging that drugs be made available earlier is equivalent to urging that grater levels of risk be accepted.
  42. 42. QUESTIONS:• 1) Can it be argued that there is a scientific standard for acceptable levels of risk?• 2) If there were a shortage of milk produced globally, would that make the possible risk from BST more acceptable?• 3) If there are no effective treatments forb a disease, does that make it more acceptable to release a drug for use, before it has been subjected to all normal testing protocols?
  43. 43. The precautionary principle applied to the grenhouse effect• The UN Framework Convention on Climate Change made the case in 1992 that: Parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse affects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures.
  44. 44. • Given the dependence of current economic systems on fossil fuels, others argue that the data to support the benefit of significant reductions in carbon dioxide emissions is insufficient to justify the economic consequences. It is not certain that adverse effects on the environment would occur if no such action was taken, neither can we be certain that limiting emissions would be sufficient to slow current global warming trends.• Those who support the precautionary principle argue that there ir enough preliminary evidence of both the likely harm of emissions continuing to increase and the benefits of limiting emissions, to promt action. Most reasonable scientist agree that the impacts of greenhouse gas emissions on climate change are significant and potentially catastrophic.
  45. 45. • One politician representing the island state of Vanuata, Ambassador to the UN Robert van Lierop, puts it as follows:For us, the precautionary principle is much more than a semantic or theoretical excercise. It is and ecological and moral imperative. We do not have the luxury of waiting for conclusive proof, as some have suggested in the past. The proof we fear will kill us.
  46. 46. 2.4. EVOLUTION• The word EVOLUTION, has several different meanings.1) Biological meaning: evolution is the process by which living organisms are formed, by gradual change, from previous organisms.As currently understood, the process takes many generations and works at the level of a population. Individual organisms cannot evolve because the characteristics that they acquire during their lifetime cannot be inherited by the next generation.
  47. 47. Charles Darwin12 February 1809 – 19 April 1882; was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection
  48. 48. Charles Darwin• Charles Darwin proposed a mechanism for evolution: NATURAL SELECTION. He probably developed this theory in the late 1830s, but did not publish it for 20 years.• Historians of science have claimed that the delay was due to Darwin being nervous about hostile reactions, but his letters and other writings do not suggest this.• The real reasons are probably that he wanted to amass as much evidence for natural selection as he could before publishing, and also that Darwin was very busy with other work!
  49. 49. • It was a letter from Alfred Wallace, suggesting a similar theory, that finally stimulated Darwin to make public his ideas.• Darwin and Wallace presented their papers jointly to a learned society in London in July 1858, and in the following year he published his great work, THE ORIGIN OF SPECIES.• Much of it, is concerned with evidence for evolution by natural selection: These are the main types of evidence:1) Breeding of domesticated animals and crop plants2) Fossils3) Homologus structures4) Geographical distribution of animals and plants.
  50. 50. Darwin’s caricature from Punch’s Almanack- 1882
  51. 51. 2.4.1.- Evidence for evolution• 1) DOMESTICATED ANIMALSHumans have deliberatly bred and used particular animal species for thousands of years. If modern breed of livestock are compared with the wild species that they most resemble, the differences are often huge.Consider the differences between modern egg-laying hens and the jungle fowl of Southern Asia, or between Belgian Blue cattle and aurochs of Western Asia. There are also many different breeds of sheep, cattle and other domesticated livestock, with much variation between breeds.
  52. 52. • It is clear that domesticated breeds have not always existed in their current form. The only credible explanation is that the change has been achieved simply by repeadly selecting for breeding the individuals most suited to human uses. This process is called artificial selection.• The effectiveness of artificial selection is shown by the considerable changes that have occured in domesticated animals over periods of time that are very short, in comparison to geological time. It shows that selection can cause evolution, but it does not prove that evolution of species has actually occured naturally, or that the mechanism for evolution is natural selecion.
  53. 53. 2) FOSSIL RECORD:In the first half of the 19th century, the sequence in which layers or strata of rock were deposited was worked out and the geological eras were named. It became obvious that the fossils found in the various layers were different; there was a sequence of fossils. In the 20th century, reliable methods of radiosotope dating revelaed that ages os the rock strata an of the fossils in them. There has been a huge amount of research into fossils, which is the branch of science called paleontology. It has given us the strong evidence that evolution has occured.
  54. 54. Fossil evidence:The sequence in which fossils appear matches the sequence in which they would be expected to evolve:- Bacteria and simple algae appearing first- Fungi and worms later- Vertebrates then: fish  amphibians  reptiles birds  mammals.
  55. 55. Fossils and rock layers
  56. 56. 3) Homologus structures
  57. 57. 3) Homologus structuresDarwin pointed out in the Origin of the species that some similarities between organisms are superficial.Similarities like those between the tail fins of whales and fishes are known as analogus structures. When we study them closely we find that these structures are very different. An evolutionary interpretation is that they have had different origins and have become similar because they perform the same or similar function. This is called CONVERGENT EVOLUTION.
  58. 58. Homologus structures are the converse of this. They are structures that may look superficially different and perfomr a different function, but they have a “unity type”. These limbs, include the same bones, in the same relative positions, despite on the surface appearing completely different.The evolutionary explanation is that they have had the same origin, from an ancestor that had a pentadactyl or 5 digit limb, and that they have become different because they perform different functions. This is called adaptive radiation.
  59. 59. There are many examples of homologus structures. They do not prove that organisms have evolved or had a common ancestry and do not reveal anything about the mechanism of evolution; But they are difficult to explain without evolution.Particulary interesting are the structures that serve no function. They are called VESTIGIAL ORGANS, and examples of thme are the beginning of teeth found in embryo baleen whales; despite adults being toothless.Another example is the appendix in human being.These structures are easily explained by evolution as structures that have lost their function and so are being gradually lost.
  60. 60. NATURAL SELECTION• Darwin developed his understanding of evolution over many years after returning to Englad from his voyage around the world.• He probably developed the theory of natural selection in 20 or 30 years.• Observations and deductions of this theory:
  61. 61. Observation  Deduction1)Populations tend to reproduce rapidly and if every individual survived, there would be a geometrical or exponential increase in the population. On the other hand, when natural populations are studied, they tend to remain stable. There are natural checks to increases in population, for example, food supplies for animals. There is a limit to the size of population of a species that the environment can support  THERE IR A STRUGGLE FOR EXISTANCE, IN WHICH SOME INDIVIDUALS SURVIVE AND SOME DIE.
  62. 62. 2) Organisms vary- there are differences between individual organisms even if they are members of the same species. These differences affect how well suited of fiited and organism is to its environment and model of existence. This is called adaptation. Some individuals are better adapted that others because they have the favourable variations.  IN STRUGGLE FOR EXISTENCE, THE LESS-WELL ADAPTED INDIVIDUALS WILL TEND TO DIE AND THE BETTER ADAPTED WILL TEND TO SURVIVE. THIS IS NATURAL SELECTION.
  64. 64. Linked concepts in Darwin’s theory of evolution1.- Population growth2.- Resource limitation3.- A struggle for existence4.- Variation5.- Adaptation6.- Differential reproduction7.- Natural selection8.- Descent with modification9.- Origin of species10.- Extinction of species.
  65. 65. GALAPAGOS FINCHES- Evolution in action
  66. 66. • Darwin visited the Galápagos Islands in 1835 and collected specimens of small birds, which were subsequently identified as finches. There are 14 species in all. Darwin observed that the sizes and shapes of the beaks of the finches varied, as did their diet.• From the overall similarities between birds and their distribution over the Galàpagos islands, Darwin hypothesized that “ one might really fancy that from an original paucity of birds in this archipielago, one species had been taken and modified for different ends”
  67. 67. • Characters and diet are closely related and when one changes, the other does also.• Variation in the shape and size of the beaks is mostly due to genes, though the environment has some effect.P=G+EThe proportion on the variation due to genes is called the heritability
  68. 68. Antibiotic resistance Evolution in action• After an antibiotic is introduced and used on patients, bacteria showing resistance appear within a few years.• Resistance to the antibiotic spreads to more and more species of pathogenic bacteria.• In each species the proportion of infections that are caused by a resistant strain increases• Strains of bacteri appear that are resistant to more and more different antibiotics; this is called MULTIPLE RESISTANCE.
  69. 69. • There has been very widespread use of antibiotics, both for treating diseases and in animal feeds used in farms.• Bacteria can reproduce very rapidly, with a generation time of less than an hour.• Populations of bacteria are often huge, increasing the chance of a gene for antibiotic resistance being formed by mutation.• Bacteria can pass genes on to other bacteria in several ways, including useing plasmids, which allow one species of bacteria to gain antibiotic resistance genes from another species.
  70. 70. Antibiotic resistance
  71. 71. 2.5.- CLASSIFICATION• It is natural for humans to recognize the features of living organisms and to use these features to put organisms into groups. At a basic level, simple observation shows that there are often many organisms of the same type.• If we agree on a name for a groups of organisms, we can the talk about them.• Naming organisms is called NOMENCLATURE.• The idea of a group of organisms of the same type has developed into the biological concept of the species.• In every language, names have been chosen for species, but science is an international venture and so names are needed to be understood throughout the world.
  72. 72. Biological systemThe system that biologists use is called BINOMIAL NOMENCLATURE  scientific name of 2 words: Linnaea borealis.1) First name: Genus name  Genus is a group of species that share the same characteristics.2) Second name: Species or specific name
  73. 73. Binomial Nomenclature’s Rules:1) The genus name begins with an upper-case (capital) letter and the species name with a lower-case (small) letter.2) In typed or printed text, a binomial is shown in italics.3) After a binomial has been used once in a piece of text, it can be abbreviated to the initial letter of the genus name with the full species name. Ex: L. borealis.4) The earliest published name for a species, from 1753 onwards, is the correct one.
  74. 74. 2.5.1.- The hierarchy of taxaTaxon: things that are arranged into a groupTaxa: Plurarl of taxon1) KINGDOM: Animalia2) PHYLUM: Chordata3) CLASS: Mammalia4) ORDER: Carnivora5) FAMILY: Canidae6) GENUS: Canis7) SPECIES: lupusCanis lupus.
  75. 75. Dichotomus keys: How to classify organisms
  76. 76. Kingdom: PlantaeCharacteristics:Photosynthetic, Chlorophyll, Cellulose, cell wall, Vacuoles permanent,Store starch