Biodiversity, Ecosystem Services, Island Biogeography, Ecological Tolerance, Natural Disruptions, Adaptation, Ecological Succession

2.1 Introduction to Biodiversity

  • Biodiversity: Encompasses genetic, species, and habitat diversity within an ecosystem (ERT-2.A.1).

    • Genetic Diversity: The range of different genes within a population.
    • Species Diversity: The number of different species in an ecosystem.
    • Ecosystem Diversity: The variety of habitats available in a given area.

  • Importance of Biodiversity (ERT-2.A):

    • Genetic Diversity: A population's capacity to withstand environmental pressures increases with its genetic diversity (ERT-2.A.2).
      • A population bottleneck can reduce genetic diversity.
    • Species Diversity: Ecosystems with a high number of species are more likely to recover from disruptions (ERT-2.A.3).
    • Habitat Loss (ERT-2.A.4):
      • Leads to a decline in specialist species first, followed by generalist species.
      • Reduces the population of species requiring large territories.

  • Species Richness (ERT-2.A.5):

    • The number of different species found in an ecosystem.

  • Genetic Variation:

    • Determined by the amount of genetic variation within each species and the number of species present.

  • Examples of Biodiversity across Ecosystems:

    • Coastal chaparral, coniferous forest, desert, prairie, deciduous forest, grassland, and scrub forest

Biodiversity Basics

  • Measured on 3 different levels:
    • Genetic diversity: how different the genes are of individuals within a population (group of the same species)
    • Species diversity: the number of different species in an ecosystem and the balance or evenness of the pop. sizes of all species in the ecosystem
    • Ecosystem diversity: the number of different habitats available in a given area
  • Higher biodiversity = higher ecosystem/population health

Species Richness & Evenness

  • Richness (r) is just the total number of different species found in an ecosystem
  • Evenness is a measure of how all of the individual organisms in an ecosystem are balanced between the different species
  • High (r) is generally a good sign of ecosystem health (more species means more quality resources like H_2O & soil)
  • Evenness indicates if there are one or two dominant species, or if pop. sizes are well balanced

Genetic Diversity

  • Genetic diversity in all pops. Because random mutations in copying of DNA & recombination of chromosomes in sex cells of parents leads to new gene combinations & new traits in offspring
  • Genetic diversity = measure of how different the genomes (set of genes) are of the individuals within a population of a given species
  • The more genetic diversity in a pop. the better the population can respond to env. Stressors like drought, disease, or famine
  • More gen. div. = higher chance that some of the individuals in a pop. have traits that allow them to survive the env. stressor

Bottleneck Event

  • Bottleneck events reduce genetic diversity
  • An env. disturbance (natural disaster/human hab. destruction) that drastically reduces pop. size & kills organisms regardless of their genome
  • Surviving pop. is smaller and because individuals died randomly, it doesn’t represent the genetic diversity of the original pop.
  • Because the pop. is smaller & less genetically diverse, it’s even more vulnerable to future env. disturbances

Ecosystem Resilience

  • Resilience = the ability of an ecosystem to return to its original conditions after a major disturbance (wind storm, fire, flood, clear-cutting, etc.)
  • Higher species diversity = higher ecosystem resilience
  • High sp. div means more plant species to repopulate disturbed ground, anchor soil, and provide food & habitat for animal species

Generalist vs. Specialist

  • Habitat loss leads to loss of specialist species and then generalist.
  • Habitat loss and fragmentation is likely to lead to an increase in invasive species.
  • Habitat loss decreased the stability of an ecosystem and habitat fragmentation increases the edge-to-interior ratio or edge effect, leading to the ecosystem being more susceptible to the threat of invasive species. Examples include open corridors cleared for roads in woodlands and hedgerows established in grasslands.

Reasons for Biodiversity Loss

  • Primary drivers: Habitat loss, invasive species, overexploitation, pollution, and climate change
  • Influencers: Human population growth, increasing consumption, and reduced resource efficiency
  • Biodiversity loss is the reduction in the number of genes, individual organisms, species, and ecosystems in a given area

2.2 Ecosystem Services

  • Ecosystem Services: Encompasses provisioning, regulating, cultural, and supporting services (ERT-2.B.1).
  • Anthropogenic Activities (ERT-2.C.1): Disrupt ecosystem services, potentially resulting in economic and ecological consequences.
  • Regulating Nat. ecosystems regulate climate/air quality, reducing storm damage & healthcare costs
  • Provisioning Goods taken directly from ecosystems or made from nat. resources (wood, paper, food)
  • Supporting Nat. ecosystems support processes we do ourselves, making them cheaper & easier(bees pollinate crops)
  • Goods and services provided by natural ecosystems that are beneficial to humans (often monetarily of life-sustaining)
  • Money generate by recreation (parks, camping, tours) or scientific knowledge

Provisioning Services

  • Goods/products directly provided to humans for sale/use by ecosystems
  • Goods/products that are made from natural resources that ecosystems provide
  • Ex: Fish, hunting animals, lumber (wood for furniture/buildings) naturally grown foods like berries, seeds, wild grains, honey
  • Ex: paper, medicine, rubber
  • Disrupted by overharvesting, water pollution, clearing land for ag/urbanization

Humans Disrupt Ecosystem Services

  • Human activities disrupt the ability of ecosystems to function, which decreases the value of ecosystem services they provide
  • This has ecological (natural) and economic (money-based) consequences
    • Clearing land for ag./cities removes trees that store CO2 (more CO2 in atm. = more CC = more storm damage & crop failure)
    • Overfishing leads to fish pop. collapse (lost fishing jobs and lower fish sales in the future)

Regulating Services

  • Benefit provided by ecosystem processes that moderate natural conditions like climate and air quality
  • Examples
    • Trees in a forest sequester (store) CO_2 through photosynthesis which reduces rate of climate change & lessens damage caused by rising sea level & reduces crop failure from drought
    • Trees filter air by absorbing air pollutants which reduces health care costs for treating diseases like asthma and bronchitis
  • Disrupted by deforestation

Supporting Services

  • Natural ecosystems support processes we do ourselves, making them less costly and easier for us
  • Examples
    • Wetland plant roots filter pollutants, leading to cleaner groundwater that we don’t have to pay as much to purify with expensive water treatment plants
    • Bees & other insects pollinate our ag. Crops, leading to more crop production & higher profits
  • Disrupted by pollinator hab. loss & filling in wetlands for development

Cultural Services

  • Revenue from recreational activities (hunting/fishing licenses, park fees, tourism- related spending) & profits from scientific discoveries made in ecosystems (health/ag./educational knowledge)
  • Examples
    • Beautiful landscapes draw tourists who pay to enter parks, spend money at local stores/restaurants, or camping fees
    • Fishermen pay for fishing licenses to catch fish in clean rivers
    • Scientists learn about plant compounds that can lead to creation of new medicines which are sold for profit
  • Disrupted by deforestation, pollution, urbanization

2.3 Island Biogeography

  • Island Biogeography (ERT-2.D): Study of the ecological relationships and distribution of organisms on islands and their community structures (ERT-2.D.1).
  • Colonization (ERT-2.D.2): Islands have been colonized by new species arriving from elsewhere.
  • Island Species (ERT-2.E.1): Many have evolved to be specialists due to limited resources. Their survival is threatened by invasive generalist species.
  • The larger the island, the greater the ecosystem diversity
  • Greater ecosystem diversity = more food & hab. resources
  • More niches, or “roles” organisms can play in the ecosystem
  • Islands closer to the “mainland” support more species
  • Islands can be actual islands in a body of water or figurative habitat islands such as central park in New York City or National Parks (nat. habitats surrounded by human developed land)
    • Easier for colonizing organisms to get to island from mainland
    • More colonizing organisms = more genetic diversity in new pop.

Larger Islands support more total species

  • Larger islands =
    • higher ecosystem diversity
    • More available “niches” or roles
    • Larger pop. sizes (more genetically diverse and more resistant to env. disturbance)
    • Lower extinction rate (species less likely to die off)
  • Positive correlation between island size & species richness

Distance to Mainland

  • Closer to mainland = higher species richness
    • Easier for more species to migrate to island from mainland (swim/fly)
    • More continual migration of individuals to the island habitat
    • Frequent migration brings more genetic diversity & larger pop. size
  • Inverse relationship between island distance from mainland & species richness
    • The further away from mainland, the fewer species

Problems

  • Generalists (invasives) get introduced
  • Leads to drop in specialists
  • Outcompete the specialists
  • Specialists have limited defenses

2. 4 Ecological Tolerance

  • Ecological Tolerance (ERT-2.F): The range of conditions an organism can endure before injury or death (ERT-2.F.1).
  • Application (ERT-2.F.2): Applies to individuals and species.
  • Species and individual organisms both have a range of tolerance for all the different environmental conditions of their habitat
  • Range of conditions such as temperature, salinity, pH, or sunlight that an organism can endure before injury or death results
    • Ex: Salmon have a basic range of tolerance for temperature from 6^o to 22^o C. But some individual salmon have adaptations that give them a range of tolerance that is outside the basic range for the species. Due to genetic biodiversity
  • Makes populations of salmon more resistant to disturbances, like global warming

Ecological Range of Tolerance

  • Optimal range: range where organisms survive, grow, and reproduce
  • Zone of physiological stress: range where organisms survive, but experience some stress such as infertility, lack of growth, decreased activity, etc.
  • Zone of intolerance: range where the organism will die
    • Ex: thermal shock, suffocation, lack of food/water/oxygen

Writing Tips

  • On FRQs about human activities or natural events that cause environmental disturbance, connect answer to ecological range of tolerance
  • If possible, connect human activity to climate change
    • (electricity generation, transportation, agriculture) all release CO_2 which causes climate change and global warming
    • Global warming shifts temperature outside the range of tolerance for many tree species, causing their populations to decline
    • Global warming warms the ocean, shifting temperature outside range of tolerance for many fish species causing die-offs
  • Try to connect a shift in range of tolerance to a specific kind of physiological stress
    • Ex: suffocation, thermal shock, lack of water/food/nutrients/oxygen
    • Global warming warms the ocean, shifting temperature outside range of tolerance for many fish species. Since global warming increases ocean temperature and warm water holds less oxygen, fish may suffocate due to lack of oxygen.
    • Global warming warm can increase droughts. With increased droughts, rainfall patterns may shift outside the range of tolerance for many plant species. Without enough rainfall, these species may suffer population decline as their roots are unable to absorb enough water from the soil.

2.5 Natural Disruptions to Ecosystems

  • Natural Disruptions (ERT-2.G): Impact ecosystems with environmental consequences as great as or greater than human-made disruptions (ERT-2.G.1).
  • Earth System Processes (ERT-2.G.2): Operate on periodic, episodic, or random scales.
  • Climate Change (ERT-2.G.3): Earth's climate has changed over geological time.
  • Sea Level Variation (ERT-2.G.4): Sea level has varied significantly with changes in glacial ice.
  • Habitat Changes (ERT-2.G.5): Major environmental changes result in habitat changes.
  • Wildlife Migration (ERT-2.G.6): Wildlife migrates in response to natural disruptions.
  • A natural event that disrupts the structure and or function of an ecosystem Ex: Tornados, hurricanes, asteroids, forest fires, drought
  • Natural disturbances can be even greater than human disruptions
  • Can occur on periodic, episodic, or random time frames
    • Periodic: occurs with regular frequency (ex: dry-wet seasons)
    • Episodic: occasional events with irregular frequency (ex: hurricanes, droughts, fires)
    • Random: no regular frequency (volcanoes, earthquakes, and asteroids)
  • Earth’s climate has varied over geologic time for numerous reasons
    • Ex: Slight changes in earth’s orbit & tilt cause mini ice ages & warmer periods as earth shifts slightly closer to & further from sun
  • Major environmental disturbances result in widespread habitat changes and or loss Ex: Rising sea level floods coastal & estuary habitats
  • Env. Change = Hab. Disruption
  • Wildlife may migrate to a new habitat as the result of natural disruptions Ex: wildebeests migrating to follow rain patterns of African savanna

2.6 Adaptations

  • Adaptation (ERT-2.H): Organisms adapt to their environment over time via genetic changes (ERT-2.H.1).
  • Environmental Changes (ERT-2.H.2): May threaten species' survival, requiring behavioral changes, movement, or causing extinction.
  • All populations have some genetic diversity, or variability in genomes of individuals; Genetic diversity exists because:
    • Random mutations while DNA is being copied create new traits
    • Crossing over in parent chromosomes creates new combinations of genes (and therefore traits)
  • Adaptation: a new trait that increases an organism’s fitness (ability to survive and reproduce)
  • Natural selection: organisms that are better adapted to their env. survive and reproduce more offspring
  • Individuals with adaptations pass them on to offspring & individuals without adaptations die off, which leads to the entire population having the adaptation over time (evolution)
  • Selective pressure/force: the environmental condition that kills individuals without the adaptation
    • Predation (hawk) = selective pressure
  • The environment an organism lives in determines which traits are adaptations
  • As environments change, different traits may become adaptations & old traits may become disadvantages
    • Ex: a drought can kill off finches with smaller beaks, making larger beaks for cracking harder seeds an adaptation
  • If the pace of env. change is too rapid, many species may migrate out of the env. or die-off completely
    • Ex: if the ocean warms too quickly, many species of fish may not be able to migrate before they run out of oxygen and suffocate
  • The more genetic diversity in a population, the better they’re able to adapt to env. change (higher chance that some individuals have good mutations)
  • The longer the lifespan of the organism, the slower the rate of evolution
    • Ex: bacteria & viruses can adapt and evolve in days
    • Humans evolution = thousands-mil. years

2.7 Ecological Succession

  • Ecological Succession (ERT-2.J): A series of predictable stages of growth that a forest goes through.
  • Types of Succession (ERT-2.I.1): Primary and secondary succession.
  • Keystone Species (ERT-2.I.2): Its activities have a significant role in determining community structure.
  • Indicator Species (ERT-2.I.3): Indicates a distinctive aspect of an ecosystem.
  • Pioneer species: first species to move into an unoccupied habitat
  • Intermediate species: Species that show up after the pioneer species
  • Climax community: Point where biodiversity is highest in the area
  • Biomass: Living matter in a biological community
  • Species Richness: Number of species in a biological community
  • Net Productivity: Energy available to an ecosystem after respiration

Primary Succession

  • Starts from bare rock in an area with no previous soil formation
  • Moss & lichen spores carried by the wind grow directly on rocks, breaking them down to form soil
  • Moss and lichen (spores dispersed by wind) are able to grow directly on rock by secreting acids that break down rock & release minerals containing nutrients they need (N/P/K)
  • Chemical weathering of rocks by moss & lichen combined with organic matter from moss & lichen dying form initial shallow soil
  • Ex: volcanic rock, rock exposed after glacial retreat
  • Occurs in an area that hasn’t previously been colonized by plants (bare rock)

Secondary Succession

  • Starts from already established soil, in an area where a disturbance (fire/tornado/human land clearing) cleared out the majority of plant life
  • Grasses, sedges, wildflowers, and berry bushes have seeds dispersed by wind or animal droppings
  • Pioneer species are still wind-dispersed seeds of plants that are fast-growing and sun tolerant, but grasses/wildflowers/weeds instead of moss/lichen
  • Soil is already established & sometimes even enriched by nutrient-rich ash from fire; overall more rapid process than primary succession
  • Occurs in an area that already has established soil, but has had most plant life removed by a disturbance