Biodiversity and Conservation Bio-3/13/25

Ecosystems and Global Ecology

• Biomass: flow of energy

• Ecosystem: community of interacting species

• Biosphere: thin zone of soil, water, and the atmosphere surrounding earth

Energy Flow

• Primary producer/autotroph: make their own food

  • Via energy in sunlight into chemical energy

  • Exception: areas in deep sea of hydrothermal vent: use methane 

• Primary production

  • Gross primary productivity: total amount of chemical energy produced 

  • Chemical energy can be used for: 

    • cellular respiration and 

    • anything else can be put into growth and reproduction (NPP)

      • NPP creates biomass

  • Fate of biomass

    • Consumers eat living organisms

      • Primary

      • Secondary

      • Tertiary

      • Decomposers

    • Trophic level: organisms that obtain energy from the same source occupy the same trophic level

    • Diagram on right: 

      • Black arrows get smaller going up to show energy given off as heat

  • Trophic Structure

    • Food chain: one possible pathway

      • Grazing food chain: composed of herbivores and organisms that eat them

      • Decomposer food chain: made up of species that eat detritus (primary decomposer)

      • Consumers can be part of multiple food chains

      • Consumers can feed on multiple trophic levels

      • Food web: sum of all trophic or feeding interactions in an ecosystem

  • Transfer of biomass

    • Productivity: biomass produced within an area over a period of time

    • Biomass declines as you move up trophic levels

    • 10% of biomass gets transferred up each trophic level

      • Reason: most consumed energy is used for cellular processes

      • Efficiency: amount of energy that moves from one trophic level to the next (in percent, about 10%)

        • Larger organisms: less surface area to volume so less heat lost

    • Biomagnification: the increase of a molecules at higher trophic levels

      • Common for molecules that don’t break down quickly 

      • Examples: mercury, organic pollutants

      • The greater the number of trophic levels, the higher the health impacts on top consumers

  • Nutrient Cycling

    • Cycling: energy transferred when one organism eats another

    • Nutrients that are essential to life are also transferred 

      • Carbon, nitrogen, phosphorus, sulfur, calcium

    • Biogeochemical cycle: the path an element takes as it moves from abiotic reservoirs to organisms and back again

    • Example: terrestrial cycling

      • Nutrient in the soil taken up into a plant

      • Plant transforms nutrients into organic form

      • When eaten, nutrients go to consumer

      • Waste and eventual death are taken up by decomposers

      • Decomposers convert into inorganic form

      • Ultimate source of nutrients for cycling comes from

      • the environment (can also be lost to it)

    • Nutrient loss examples

      • Co2 is released to the atmosphere during cellular respiration

      • An herbivore eating a plant and then leaving the ecosystem

      • Transport of the exosystem by flowing water or wind

      • Plant removals due to agriculture

    • Nutrient gain examples

      • Rocks being broken down or weathered

      • Transport into the ecosystem by flowing water or wind

      • Carbon is added when primary producers fix it during photosynthesis

    • Factors limiting nutrient cycling (3 factors)

      • Rate of nutrient decomposition

      • Abundance and diversity of detritivores

      • Quality of the detritus, some things are harder to breakdown than others

        • Detritus: waste or debris 

    • The Nitrogen cycle

      • Atmosphere is the largest nitrogen reservoir but is unavailable to plants

      • Nitrogen needs to be fixed before it is biologically usable

      • Can be fixed by 

        • Enzyme catalyzed reactions in bacteria

        • lighting -driven reactions in the atmosphere

    • The phosphorus cycle

      • Main reservoir is in earth’s crust

      • Available by the weather of rocks and deposition in soils

      • Humans mine phosphorus as a fertilizer and have increased its abundance in the global cycle by four times in the last 75 years

    • Carbon cycle

      • Largest reservoir is in the ocean

      • Atmosphere reservoir is not the largest but important because it can be cycled quickly from the atmosphere

      • Photosynthesis takes carbon out of atmosphere into tissues

      • Anthropogenic impacts: changes caused by human activities

        • Intensive agriculture, deforestation, etc

        • Burning fossil fuels

Climate change

• Terminology

  • Weather: short term and variable

  • Climate: long-term pattern of regional and global weather

  • Global warming: increase in the average temperature of the planet

  • Global climate change: sum of all the changes in local temperature and precipitation patterns that result from global warming

• Causes

  • The Greenhouse Effect

    • Solar radiation either reflects off the earth or is absorbed and warms it

    • Much of the heat reemitted gets trapped around the earth by the atmosphere, CO2 is really good at absorbing the heat

    • Increased CO2=Higher retention of heat around the earth

    • Biological effects

      • Range shifts: species moving towards poles as suitable habitat moves

      • Phenology shifts: changes in processes that happen on the seasonal cycle (ex. When organisms mate, migrate, etc.)

      • Evolutionary adaptation: climate change can impact allele frequencies by favoring certain traits over others (ex. Ladybugs with primarily black shield are selected against) 

      • Extinctions: rising temperatures can be too much for species and they cannot adapt or move quickly enough

      • Ocean acidification: increased CO2 in the atmosphere causes a lower pH in the ocean that can erode calcium carbonate shells

        • Co2 in atmosphere can be quickly brought into the carbon cycle

Biodiversity and Conservation

• Biodiversity: biological diversity

• Species richness and species diversity

  • Richness: # of species in the community

  • Diversity: richness and evenness both taken into account

• Genetic diversity: can also be used to measure diversity

  • Can be used to measure the adaptive capacity of a community

• Phylogenetic diversity: measure of diversity that is higher when species are more distantly related 

  • Measured by length of the branches in the phylogenetic tree

• Functional diversity: variation in ecological traits

• Ecosystem diversity: a measure of diversity that emphasized the complexity of species interactions 

• Distribution of biodiversity

  • Global trends

    • Higher diversity closer to the equator 

    • Higher diversity of land than on sea

      • Possible reasons: insects

    • Higher diversity in areas with greater geographical variation 

  • Biodiversity in peril

    • Rates of extinction are increasing

  • Threats to biodiversity

    • Habitat loss: MOST IMPORTANT FACTOR

    • Harvest overexploitation

      • Marine species most susceptible to this

      • Ex. overfishing

    • Climate change

  • Benefits of biodiversity

    • Direct and indirect benefit to humans

    • Ecosystem services

      • Est. $125 trillion per year

  • Preserving biodiversity

    • Sustainability

    • Management plans

    • Ecosystem restoration

    • Wildlife corridors