Energy and living things
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Energy and Living Things - PowerPoint PPT Presentation

Energy and Living Things. Outline. Energy Sources Solar-Powered Biosphere Photosynthetic Pathways Using Organic Molecules Chemical Composition and Nutrient Requirements Using Inorganic Molecules Energy Limitation Food Density and Animal Functional Response Optimal Foraging Theory.

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Energy and Living Things

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Energy and Living Things

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  • Energy Sources

  • Solar-Powered Biosphere

  • Photosynthetic Pathways

  • Using Organic Molecules

  • Chemical Composition and Nutrient Requirements

  • Using Inorganic Molecules

  • Energy Limitation

  • Food Density and Animal Functional Response

  • Optimal Foraging Theory

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Energy Flows Through Living Systems


Plants= Autotrophs

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  • Autotroph: ‘self feeder’ - an organism that can gather energy (usually from light) … to store in organic molecules

    • Photosynthesis

    • chemosynthesis

  • Heterotroph: An organism that must rely on other organisms to capture light energy … must rely on breakdown of organic molecules produced by an autotroph as an energy source

    • Classified by trophic level

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Law of the minimum- ecosystems must adapt to it.

  • Light in ocean floor

  • Water in desert

  • Heat on mountain top

  • Matter is also limiting, thus have limiting nutrients that allow for life

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Flow of energy and nutrients

  • Photosynthesis

  • Metabolism

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Capture and transfer light energy to chemical bonds

Occurs in:



Certain Bacteria

Not a perfect process – some energy is lost - entropy

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How Photosynthesis Works

  • Light strikes leaf

  • Energy absorbed by chemical pigments

  • Absorbed energy drives chemical processes to convert CO2 into larger molecules

    • Energy absorbed in building larger molecules, released as they are broken down

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Only certain Wavelengths of Light are Used in Photosynthesis

  • Light Energy Used = ‘Photosynthetically Active Radiation’ or PAR

    • How Much is absorbed: Number of light energy (photons) striking square meter surface each second.

  • Chlorophyll absorbs light as photons.

    • Landscapes, water, and organisms can all change the amount and quality of light reaching an area.

  • Light not absorbed is reflected

    • Some in PAR + all in green and yellow wavelengths

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    Wavelengths most useful in driving photosynthesis

    Absorption spectra of chlorophylls and carotenoids

    Wavelengths not used - reflected

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    Fall color

    • In many plants production of chlorophyll ceases with cooler temperatures and decreasing light

    • other pigments become visible

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    C3 Photosynthesis

    CO2 enters passively so stomata have to be open for long periods of time

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    Why C3 Photosynthesis Doesn’t always work out - CO2 must enter though stomata

    • stomata (sing., stoma) are tiny holes on the undersides of leaves

    • CO2 enters and moisture is released

    • In hot, dry climates, this moisture loss is a problem

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    Food Web


    • Herbivores

      • Animals that eat plants

      • The primary consumers of ecosystems

    • Green plants and algae

    • Use solar energy to build energy-rich carbohydrates

    • Carnivores

    • Animals that eat herbivores

    • The secondary consumers of ecosystems

    • Omnivores are animals that eat both plants and animals

    • Tertiary consumers are animals that eat other carnivores

    • Detritivores

    • Decomposers

      • Organisms that break down organic substances

    • Organisms that eat dead organisms

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    • Total amount of energy kept constant

    • Energy can be converted

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    Transfer of Energy with Ecosystems

    • Board notes

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    • Three Feeding Methods of Heterotrophs:

      • Herbivores: Feed on plants.

      • Carnivores: Feed on animal flesh.

      • Detritivores: Feed on non-living organic matter.

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    Classes of Herbivores

    • Grazers – leafy material

    • Browsers – woody material

    • Granivores – seed

    • Frugivores – fruit

    • Others – nectar and sap feeders

      • Humming birds, moths, aphids, sap suckers …

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    • Substantial nutritional chemistry problems.

      • Low nitrogen concentrations – difficulty extracting needed protein/amino acids from source.

      • Require 20 amino acids to make proteins ~ 14 are must come from diet

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    How do plants respond to feeding pressures by herbivores?

    • Mechanical defenses – spines

    • Chemical defenses

      • Digestion disrupting chemicals – tannins, silica, oxalic acid

      • Toxins – alkaloids

        • More common in tropical species

          How do animals respond?

      • Detoxify

      • Excrete

      • Chemical conversions – use as nutrient

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    • Predators must catch and subdue prey - size selection.

      • Usually eliminate more conspicuous members of a population (less adaptive).

      • act as selective agents for prey species.

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    Adaptations of Prey to being preyed upon

    • Predator and prey species are engaged in a co-evolutionary race.

    • Avoid being eaten – avoid starving/becoming extinct

    • Defenses:

      • Run fast

      • Be toxic – and make it known

      • Pretend to be toxic

    • Predators learn to avoid

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    • Consume nutritionally-rich prey.

      • Cannot choose prey at will.

        • Prey Defenses:

          • Aposomatic Coloring - Warning colors.

          • Mullerian mimicry: Comimicry among several species of noxious organisms.

          • Batesian mimicry: Harmless species mimic noxious species.

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    Mullerian mimicry: Comimicry

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    Batesian mimicry: Harmless species mimic noxious species

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    Aposomatic Coloring - Warning colors

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    • Consume food rich in carbon and energy, but poor in nitrogen.

      • Dead leaves may have half nitrogen content of living leaves.

    • Fresh detritus may still have considerable chemical defenses present.

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    Detritivores and decomposers

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    • Refers to the production of food

    • Primary production = total gross primary production

    • Activity- Compare ecosystems p. 26

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    Optimal Foraging Theory

    • Assures if energy supplies are limited, organisms cannot simultaneously maximize all life functions.

      • Must compromise between competing demands for resources.

        • Principle of Allocation

    • Fittest individuals survive based on ability to meet requirements principle of allocation

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    Optimal Foraging Theory

    • All other things being equal,more abundant prey yields larger energy return. Must consider energy expended during:

      • Search for prey

      • Handling time

  • Tend to maximize rate of energy intake.

  • What would a starving man do at an all you can eat buffet?

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    Optimal Foraging in Bluegill Sunfish

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    Cycles of matter

    • Nitrogen

    • Carbon

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    Nutrient Cycling and Retention

    Chapter 19

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    Nitrogen Cycle

    • Includes major atmospheric pool - N2.

      • Only nitrogen fixers can use atmospheric supply directly.

        • Energy-demanding process.

          • N2 reduced to ammonia (NH3).

        • Once N is fixed it is available to organisms.

          • Upon death of an organism, N can be released by fungi and bacteria during decomposition.

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    Nitrogen fixation

    Biological Nitrogen Fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by a pair of bacterial enzymes

    • N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi

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    Microbes Denitrification NO3- (nitrate) → NO2- → NO → N2O → N2 gas

    Nitrogen Cycle

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    Carbon Cycle

    • Moves between organisms and atmosphere as a consequence of photosynthesis and respiration.

      • In aquatic ecosystems, CO2 must first dissolve into water before being used by primary producers.

      • Although some C cycles rapidly, some remains sequestered in unavailable forms for long periods of time.

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    Carbon Cycle

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    Animals and Nutrient Cycling in Terrestrial Ecosystems

    • Huntley and Inouye found pocket gophers altered N cycle by bringing N-poor subsoil to the surface.

    • MacNaughton found a positive relationship between grazing intensity and rate of turnover in plant biomass in Serengeti Plain.

      • Without grazing, nutrient cycling occurs more slowly through decomposition and feeding of small herbivores.

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    Animals and Nutrient Cycling in Terrestrial Ecosystems

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    Plants and Ecosystem Nutrient Dynamics

    • Fynbos is a temperate shrub/woodland known for high plant diversity and low soil fertility.

      • Two species of Acacia used to stabilize shifting sand dunes.

    • Witkowski compared nutrient dynamics under canopy of native shrub and introduced acacia.

      • Amount of litter was similar, but nutrient content was significantly different.

      • Acacia - N fixer

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    Biotic communities

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    Climate and weather

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