Topic 5: Ecology

1. Topic 5: Ecology Also topic G.5

2. Readings • IB Book pages 112 – 133, 142 – 150, 589 – 595

3. Topic 5.1 Communities and Ecosystems

4. 5.1.1 Key Terms • Species • Habitat • Population • Community • Ecosystem • Ecology

5. 4 main components of the environment • Hydrosphere – water • Atmosphere – air • Lithosphere – rocks/soil • Biosphere – all living organisms • The first 3 are abiotic (nonliving) and include things such as light, heat, minerals, humidity, oxygen • Biosphere is biotic (living)and includes plants, animals, bacteria, fungi, protists

6. Feeding methods • Autotroph – synthesize organic molecules from simple inorganic substances. • Involves photosynthesis as well as chemosynthesis (a process found in a few extremophile bacteria) • Because they make food that other organisms use they are known as producers. Ex) plants, algae, cyanobacteria

7. Heterotrophs – obtain organic molecules from other organisms (autotrophs or other heterotrophs) • Referred to as consumers • Include parasites, omnivores, carnivores, herbivores, detritivores, saprotrophs • Detritivores eat nonliving organic matter such as feces. carcasses, dead leaves • Saprotrophs live on or in non-living organic matter. Secrete enzymes into the organic matter and absorb products of their digestion. AKA decomposers. Ex) bacteria, fungi

8. Food Chains • A sequence showing the feeding relationships and energy flow between species. • Arrows show who gets eaten by whom • Ex) herring  seal herring gets eaten by seal • Food web – an interconnecting series of food chains. • Food webs illustrate the fact that an animal may eat (or be eaten by) more that one animal.

11. Trophic Levels • T1 - producer • T2 – primary consumer • T3 – secondary consumer • T4 – tertiary consumer • T5 – quaternary consumer • Typically only 10% of the energy from one trophic level is incorporated into the next

12. Pyramid of Energy IMPORTANT!! Correct IB unit for this pyramid is kilojoules per square meter per year, kJ/m-2y-1. Use this if you have to draw a pyramid of energy!!!!

13. Why is energy lost? • 100% of the food source may not be swallowed (bones etc…) • Not all of the food is digestible • Not all organisms are eaten. They may just die and decay • A great deal of energy is lost as heat during cellular respiration

14. Identify the trophic level of each organism in the food webs on slides 9 and 10. • Most food chains have 4 trophic levels although they can have as many as 6. • Click on the link below to create your own food web. After placing the animals in the correct trophic level DO NOT view the web until you have drawn it! http://www.gould.edu.au/foodwebs/kids_web.htm

15. Some last words about energy! • Producers are the most important organism in the food chain. Sunlight is the initial source of energy for all communities. • Sunlight is converted into chemical energy by producers and transferred to consumers in the various trophic levels. • Remember that most of the energy fixed by producers is lost as heat as it passed from one trophic level to the next.

16. Nutrients • Organisms must recycle the C, N, S, and other elements necessary for life to exist. These elements as well as others are trapped in the cells of the organisms body. • Decomposers (saprotrophs and detritivores) break down dead organisms and their wastes and make recycling of the nutrients possible

17. 5.2 – The Greenhouse Effect

18. Where is carbon found • In the biosphere? • In the lithosphere? • In the atmosphere? • In the hydrosphere?

19. Carbon cycles between these 4 locations • Photosynthesis – fixes atmospheric carbon into the bodies of plants and algae. This carbon is converted directly into glucose and then into proteins, lipids, and carbohydrates • Cellular Respiration – organic molecules are broken down and carbon dioxide is released. • Feeding – carbon is moved from one part of the food chain to another • Fossilization – carbon is trapped in sediment as coal and oil • Combustion – burning of biomass and fossil fuels.

20. 5.2.1 • Draw and Label a diagram of the carbon cycle to show the processes involved.

22. 5.2.3 • Explain the relationship between rises in greenhouse gases and the enhanced greenhouse effect.

23. Carbon dioxide levels have been rising: • Use of machines, factories, transportation • Burning of forests to clear land for farming • Burning of wood or coal for energy • In general, CO2 levels have risen as much as 25% since the industrial revolution. • Look at the graph on page 124. What causes the fluctuations in the graph?

24. Greenhouse gases • Carbon dioxide – produced from burning of fossil fuels • Methane – produced from cattle ranching, decomposition of organic waste, production and distribution of natural gas • Oxides of nitrogen – made from burning fossil fuel, use of organic and commercial fertilizers, industrial processes

25. How a greenhouse works • As light penetrates the walls of a glass greenhouse the light strikes the plants and is transformed into heat. • Heat has longer wavelengths than light • Greenhouse glass is not as transparent to heat energy as it is to light energy so heat is trapped inside keeping air inside the greenhouse warmer that that outside. • Carbon dioxide and water vapor are the “glass” of the earth’s atmosphere. • See page 125 for an explanation!

26. The greenhouse effect a) Short wave solar radiation (light) b) light penetrates the atmosphere and passes through the molecules of the atmosphere c) Absorption by the ground and conversion to long wave infrared radiation (heat) d)This warms the planet e) Some infrared is lost to space as heat f) Atmospheric gases particularly water vapour, carbon dioxide, methane and CFC's g) Greenhouse gases absorb infra-red radiation and scatter this rather than letting it escape to space. In effect this traps the heat energy. h) Some light reflects off the outer surface of the atmosphere and never enters

27. Enhanced greenhouse effect • The increase in greenhouse gases will intensify the Earth’s natural greenhouse effect. • The Earth’s average temperature will rise • What impact does the enhanced greenhouse effect have on the planet?

28. The impact of greenhouse gases • As human activity generates more greenhouse gases, more heat is retained causing earth’s temperature to rise.

29. 5.2.4-5.2.5 Precautionary Principle • http://click4biology.info/c4b/5/eco5.2.htm#four This link has a great explanation of the precautionary principle. Read it AND the supplemental reading at the links on the page. • Basically this is an ethical theory which states that we should always attempt to prevent harm even if there is not sufficient data to prove that the activity will have severe negative consequences. • Without this principle industry proceeds with activities until it becomes clear that harm is being done.

30. 5.2.6 Arctic Ecosystems • http://click4biology.info/c4b/5/eco5.2.htm#six • Read both your book (pages 129-130) as well as the article at click 4 biology. I also have a link to the article at our wiki. • Your assessment statement says you must OUTLINE the consequences of a global temperature rise on arctic ecosystems.

31. 5.3 Populations

32. 5.3.1 Population Dynamics • Population size is affected by four main factors: • Natality – number of new members due to reproduction • Mortality – number of deaths • Immigration – members arriving from other places • Emigration – members leaving the population

33. 5.3.2 Population Growth Curve This sigmoid curve shows the changes in population size vs. time. In this model the population is expanding into a habitat offering initial low resistance or low limiting factors. Note the 3 stages in population growth: exponential, transitional, and plateau. __________________________K

34. Causes of exponential phase • Under ideal conditions population growth would be exponential (2n where n= number of generations or 1,2,4,8,16,32,64….) • Causes: • Plentiful resources • Little or no competition from others • Favorable abiotic factors such as T, dissolved oxygen • Little or no predation or disease

35. Causes of transitional phase • Increasing competition for resources • Predators attracted to the growing food supply in the area • More disease due to crowding in limited space • There will not just be a reduced rate of population growth but also a selection (survival and reproduction) of these individuals within the population best suited to using, accessing the resources. Natural Selection is occurring.

36. Carrying capacity • The maximum number of individuals a habitat can support. Is represented by the letter K. • Carrying cappacity is defined by limiting factors which may include: • Availability of resources • Build up of wastes (excrement and CO2) • Predation • Disease

37. What is the carrying capacity of the earth? • It seems that the human population is continuing to increase. Is there evidence that the earth is nearing its carrying capacity for humans? Explain your answer in a 3-5 paragraph essay. Be sure to cite sources that you use.

38. G5 – Population Ecology G.5.1 – G.5.4

39. r and K strategists • r strategy refers to species who produce “disposable offfspring!” Most invertebrates and “lower” vertebrates can be classified as r strategists. Offspring are many, require little or no care, mature rapidly. Die quickly. Opportunistic. Ex.) bacteria • K strategy refers to species who produce few offspring and nurture them. The time and effort invested in the young increases the probability that they will survive • Study the life history table on pg. 590 of your text and be able to compare r and K strategy species.

40. In unstable environmental conditions, is it better to be a r or K strategist? Why? • Ecological disruption favors r strategists. The organisms that can successfully survive the disruption are often considered pests by humans. Invasive species are also typically r strategists.

41. Estimating population size • Scientists use the capture-mark-release-recapture method to do this. • Animals are captured and marked in some way then released. A second sample is captured in which some of the animals will be marked and others will not be marked. • See formula on page 591 to calculate population size • Lab!!!

42. G.5.4 Estimating size of commercial fish stock • How do scientists gather quantitative data about commercially important fish? • Survey fishermen • Research vessels • Random sampling • Echo sounding • Measuring age of caught fish – otoliths, scales • Coded tags • Mathematical models

43. Maximum sustainable yield • The highest proportion of fish that can be removed from the total population without jeopardizing the maximum yield in the future. • What problems exist if the fish stock is too small or too large?

44. Promoting fish conservation • Fish stocks are declining. Commercial fishing may become nonexistent. Read page 594. • NOAA Fishwatch link from Hotlink 18.25a http://www.nmfs.noaa.gov/fishwatch/ • Example: Brown shrimp http://www.nmfs.noaa.gov/fishwatch/species/brown_shrimp.htm • Marine stewardship link from Hotlink 18.25b http://www.msc.org/