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LU2: THE COMPLEXITY OF LIFE STF1054 BIODIVERSITY

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Evolution of life Complex processes cycle elements among different reservoirs - involves biology - has geochemical consequences

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Evolution of life (cont.) Different communities store and cycle material and energy differently - diversity differences - different biogeochemical results - different storage of biomass

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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.

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What it means to be Alive (cont.) 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 deviation 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. Death

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What it means to be Alive (cont.) Capable of transforming energy Photosynthesis and respiration For homeostasis (regulation and balance) 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

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What it means to be Alive (cont.) Life is characterized by: Cells Common metabolic pathways Common genetic code Living things include Bacteria Algae Plants Animals

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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. 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

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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 Ecosystem a community of animals, plants, microbes, etc, together with the physical environment that supports it Biome a region with a characteristic plant community (e.g. rainforest, desert)

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Structure of the biosphere (cont.) Interactions between organism and environment Eg. rainforest Alteration of environments can impact ecosystems Cut the trees?

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

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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

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Light (cont.) The depth of water 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

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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

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Temperature Ocean temperature varies with Depth Latitude Temperature controls rate of chemical reactions Slower at low temperature Metabolism is defined by chemical reactions

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

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The Trophic Pyramid: A Model of Consumption

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Food Webs Illustrate Complex Trophic Relationships

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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!)

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

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Biodiversity over time Natural changes in diversity due to evolution and extinction of species General increase in diversity over time Interupted by extinction events Extinction is natural Over 90% of species that have evolved are extinct

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Recent changes in biodiversity 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

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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 materials 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

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Deforestation and recovery Rainforests loss of rainforest trees leads to loss of nutrients & changes in the water cycle Temperate forests recover because nutrients retained in the soils

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Deforestation & water cycle & climate Elimination of tropical rainforests disrupts regional water cycle Minimizes evapotranspiration (source of H2O to atm) Decreases soil moisture and increases runoff Increases erosion rates General circulation models to predict Net temperature increase Decrease in soil moisture

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The water cycle

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Biodiversity and deforestation in tropical areas Half of the living species are found in rainforests Forest plants have medical value Treatment of diseases Forest plants have agricultural value Need genetic diversity for long-term health Need variety to limit vulnerability to diseases and pests Modern agricultural practices limit diversities Centers of genetic diversity for crops come from areas threatened by development, population pressures, deforestation Seed banks

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Biodiversity and ecosystem stability Relationship is complex In some settings environmental stability leads to high diversity In others, high diversity is thought to result from disturbances of intermediate frequency and intensity How does loss of biodiversity impact ecosystem? Remove enough species and ecosystem collapses System maintained by a few keystone species

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Causes of deforestation Social, political, and economic drivers Economic arguments people and countries need hard currency (Nepal) Motivation not to Who will bear the costs of not exploiting resources? Earth will recover, will humans survive?

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The Elements of Life In addition to energy, life requires certain material substances All organisms require 23 basic elements Availability of these elements can limit growth and survival

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The Carbon Cycle A basic building block of life Largest of all biogeochemical cycles Availability rarely limits marine productivity

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The Nitrogen Cycle N is a critical component of proteins, nucleic acids and pigments (e.g. chlorophyll) Traditionally viewed as the most limiting nutrient in the sea Liebigs Law of the Minimum Growth is limited NOT BY THE TOTAL RESOURCES AVAILABLE but by the single resource in shortest supply,

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The Nitrogen Cycle Free N 2 comprises 80% of the atmosphere Not generally biologically available Biological availability requires FIXATION Most of the anthropogenically fixed N ultimately winds up in our rivers, estuaries & coastal waters where it promotes HARMFUL ALGAL BLOOMS

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