Ecosystems & biodiversity

1. Ecosystems & biodiversity Feedbacks through biota Chapters 9, 13, & 18

2. Evolution of life & biogeochemistry • Biota mediate the cycles of many elements that cycle between various reservoirs with different residence times • Biology – transfer energy through food chains/webs • Geochemistry – lead to steady state systems far from chemical equilibrium • Records on Earth – atm composition, sediments • Diversity of microbial metabolisms • Higher organisms mostly aerobic • Present day cycles can deviate from rock record

3. Complex processes cycle elements among different reservoirs - involves biology - has geochemical consequences Different communities store and cycle material and energy differently - diversity differences - different biogeochemical results - different storage of biomass

4. What it means to be Alive • Auto conservation • The main function of every living organism is making sure that it can continue it's existence. • Auto reproduction • Any living system can reproduce or proceeds from a reproduction. • Storage of information • Each organism contains genetic information. This appears stored in DNA, and is read and translated by proteins according to a universal genetic code, which is common to all creatures. • Breathing-fermentation • Every living being must have a metabolism that will transform energy and matter taken from the environment into energy and compounds that can be used by the different parts of the living organism. • Stability • Through the creation and control of it's own internal environment, all creatures remain stable in front of the perturbations of the external world. • Control • The distinct parts of an organism contribute to the survival of a group and, therefore, to the conservation of it's identity. • Evolution • The mutations in the hereditary material and natural selection permit the perfection, adaptation and complexity of living beings. For many, life is a mere product of evolution. • Death

5. What it Means to be Alive • Capable of transforming energy • Photosynthesis and respiration • For homeostasis • For growth • For reproduction • Life and the second law of thermodynamics • Transformation of energy leads to disorder • Life requires the maintenance of order • Homeostasis, growth and reproduction occur at the expense of increased disorder (entropy) of the whole system • Life is characterized by: • Cells • Common metabolic pathways • Common genetic code • Living things include • Bacteria • Algae • Plants • Animals • Non-living things include • Viruses • Prions • Organic molecules • Proteins and amino acids • Nucleic acids • Fats • Sugars

6. The Origin of Life on Earth • The earth is 4.6 billion years old • Life on earth has existed for more than 3.8 billion years • All life requires liquid water • The basic molecules of life can be made from a primitive reducing atmosphere • Methane, ammonia water, hydrogen, and energy • No oxygen - anoxic

7. The Origin of Life • Growing evidence supports the idea that the emergence of catalytic RNA was a crucial early step. How that RNA came into being remains unknown. • Catalysts are essential for the chemistry of life • RNA acts as a genetic ‘messenger’ in modern cells • The ‘Central Dogma’ of Modern Biology • DNA makes RNA, RNA makes protein, proteins are the common biological source of enzymatic catalysis

8. Two Critical Steps in the Origin and Evolution of Life • Organic catalysis and self-replication • Catalytic RNA? • Photosynthesis • A mechanism for capturing energy and converting it into food

9. Structure of the biosphere • Hierarchy • Species – reproductive group • Population – members of a single species that live in a given area • Community – assemblage of interacting species in a given area • Biome – a region with a characteristic plant community (e.g. rainforest, desert) • Ecosystem – a community of animals, plants, microbes, etc, together with the physical environment that supports it

10. Structure of the biosphere • Ecosystem • Assemblage of organisms that interact with each other and the environment • Some can be defined by their environment (rain forest, desert) • Interactions between organism and environment • Daisyworld example • Alteration of environments can impact ecosystems • ENSO events – food web effects • Cessation of upwelling – food web effects • Physiological versus ecological growth optima • Not always the same – optimal niche versus realized niche • High productivity oceanic regions are often high latitude or upwelling • Related to ocean physics and nutrient availability rather than growth optima; compromise between mixing (promoting nutrient availability) and temperature (promoting stratification)

11. Fig. 9-1

12. Environments • Many ecosystems defined by the environment • Organisms subdivide that environment • Organisms that share habitats find niches within those habitats • Strategies and living habits

14. Productivity • High productivity • Upwelling; low latitudes • Low productivity • Central gyres; downwelling

15. ENSO Upwelling – productive No upwelling - collapse La Nina El Nino Western Fig. 15-13 & 14

16. Productivity • Nt = Noekt • Add resource limitation to set limits to population size (Nt) • Oh, and life pollutes…

17. Phytoplankton growth in the ocean 0 Temperature optima in the lab are 20-25 deg

19. Highest productivity at higher latitudes! Ecological growth optimum is 8 deg C – due to ocean physics and nutrient availability

20. Phytoplankton productivity • Related to physics, light, & nutrient supply • If surface waters are too warm, water stratifies & limits nutrient resupply from bottom waters • High turbulence increases mixing up of nutrients • Compromise between nutrients & temp

21. Light • On land, photosynthesis proceeds just above ground level • In water, communities may be vertically stratified • In the water, photosynthesis proceeds to considerable depths, depending on • Water clarity • Sun angle • Sea state

22. Light • Unlike the atmosphere, water attenuates light, especially green and red • The depth to which light penetrates depends on the amount and nature of dissolved and suspended constituents • Oceanic waters contain few particles and are blue • Coastal waters contain high phytoplankton populations and are green • Estuarine waters contain lots of suspended sediments and look brown

23. Light penetrates deepest in oceanic waters • Blue light penetrates best • Red light is rapidly attenuated

24. Light penetration is shallower in plankton-rich coastal waters • Phytoplankton absorb blue light for photosynthesis • Water absorbs red light • Coastal ocean looks green

25. Light Penetration in Coastal Waters

26. Photosynthesis • Depends on the amount of light up to saturation • Depends on the color of light – not all photons are equivalent • Most efficient with blue and red light, least efficient with green light

27. Layers of the ocean defined by light

28. Temperature • Ocean temperature varies with • Depth • Latitude • Temperature controls rate of chemical reactions • Slower at low temperature because molecules carry less energy • Fewer collisions • Less energy per collision • Metabolism is defined by chemical reactions • Most organisms are ectothermic – don’t regulate body temperature • Some organisms are endothermic – regulation of body temperature requires • lots of energy • good insulation

30. Salinity • Salinity can vary with rainfall and evaporation • Changes in salinity (up or down) can affect metabolic function, energy consumption and cell viability. • Different organisms have very different salinity tolerances

31. Marine Communities are Highly Productive

32. Marine Communities Store Less Organic Carbon and Turnover Rates are Faster than Terrestrial Communities

33. Ocean Productivity Observed from Space

34. Trophic Relationships • Energy Transfer • Primary Producers are Autotrophs • harvest sunlight • Heterotrophs are Consumers • eat organic matter

35. The Trophic Pyramid:A Model of Consumption

36. Food Webs Illustrate Complex Trophic Relationships

37. Exploitation efficiency • Autotroph – plants & microbes • Photosynthesis or chemosynthesis • Produce organic matter from inorganic C sources • Heterotroph – accelerate chem reactions to gain energy • Herbivores - ~ 20% • Carnivores - ~ 0.2% (not very efficient at converting food to biomass!)

39. Symbioses • Mutualism – both organisms benefit

40. That’s biology but… biodiversity • Linked to ecosystem health and stability • Number of species per unit area or ecosystem • Often think of deforestation • Destruction of tropical habitats

41. Biodiversity • Number of species in a community • Diversity indices • Simpson diversity = 1 – [(proportion of species A)2 + (proportion of species B)2 + …..]

42. Biodiversity over time • Natural changes in diversity due to evolution and extinction of species • General increase in diversity over time • Interupted by extinction events • 26 my periodicity in extinction events? • Extraterrestrial cause? • Extinction is natural • Over 90% of species that have evolved are extinct

43. 26 my periodicity etc. Figs. 13-4 & 13-10

44. Recent changes in biodiversity • Present day rates exceed geological rates of extinction • Present day extinction is across the board – affects many groups • Other extinction events affected species within particular groups – other groups survived • Example is K-T extinction of dinosaurs; mammals and plants survived to reradiate • Modern extinction associated with spread of human populations • Over hunting/fishing • Habitat destruction – deforestation & coral bleaching

45. Fig. 18-1 - Extinction of large mammals and birds corresponds to the spread of human populations

46. Deforestation & biodiversity • Poster child • The tropics is the area of greatest rate of species loss • Concern for more than biodiversity • Addition of CO2 • Loss of CO2 uptake mechanism • Impact on regional climate

47. Deforestation and soil nutrients • Distinct differences in storage of biomass & nutrient cycling between temperate & tropical forests • Temperate forests have thick, rich topsoils • Humus layer of organic detritus on top of subsoil • Nutrients stored in soils • Tropical soils are highly weathered (lots of rain) • Lateritic clays depleted in nutrients • Thin humus layer • Nutrients stored in biomass

48. Tropical above ground storage of biomass & nutrients

50. Model results – decrease forest cover, increase albedo, decrease winter temperatures, increase sea ice, increase albedo, decrease temperatures….