Topic 3.1-3.4: Biodiversity Notes

Topic 3.1: An Introduction to Biodiversity

  • Biodiversity can be identified in three main forms:
    • Species diversity
    • Habitat diversity
    • Genetic diversity
  • More habitats create more unique combinations of biotic and abiotic factors, leading to more ecological niches.
  • More ecological niches allow for a greater diversity of species to live within.
  • Species genetic diversity means that a range of individuals may be more or less suited for a particular niche or habitat.
  • Biodiversity incorporates species, habitat, and genetic diversity.
  • Species richness: the number of different species found in an area.
  • Species evenness: how those species are distributed within an ecosystem.
  • Species diversity consists of both the number of different species (species richness) and their relative abundance or distribution across an ecosystem (species evenness).
  • Simpson's Diversity Index or Simpson's Reciprocal Index: a standard way to assess biodiversity in an area.
  • Habitat diversity: the range of different habitats found within an ecosystem.
  • Low diversity frequently indicates pollution (e.g., eutrophication) or other negative human impacts on the ecosystem.
  • Diversity levels change throughout the course of succession.
  • Habitat diversity leads to greater species diversity.
  • Genetic diversity results in greater variation within a single species.
  • Genetic variation leads to greater degrees of biodiversity because in different environments, different individuals have greater chances of successful reproduction.
  • Different environments can cause different camouflage appearances of the same species to be more prominent. This leads to speciation.
  • Conservation efforts depend on our ability to effectively measure or assess biodiversity.
  • Biodiversity hotspots are areas with a high degree of species, genetic, or habitat diversity.
  • Threats to biodiversity, such as human populations, impact biodiversity.
  • Biodiversity exists on three different levels:
    • Ecosystem or habitat diversity
    • Species diversity
    • Genetic diversity
  • The assessment of biodiversity is only as solid as the quality of the data collected.
  • Data describes patterns, which influences decision-making.
  • Factors affecting data quality include accessibility of areas and difficulty in counting certain species.
  • Threats to biodiversity include logging and agriculture.
  • Reliable data about habitat diversity, species diversity, and genetic diversity within an area helps decision-makers choose a course of action.

Topic 3.2: Origins of Biodiversity

  • Evolution: a gradual change happening over many generations; it is a genetic change that leads to changes in physical appearance or the phenotype of an organism, driven by natural selection.
  • Natural selection was originally published in The Origin of Species in 1859.
  • Evolution is supported by fossil examples, genetic evidence in mitochondrial DNA, and real-time observations.
  • Variation within populations: some variation benefits survival, some harms, and some has no impact.
  • Variations that harm survival are filtered out, while those that give a survival advantage are selected for, increasing their frequency in the gene pool over time.
  • The environment drives the process of evolution; it selects who lives and who dies.
  • English pepper moth example: before the Industrial Revolution, lighter moths were camouflaged on birch trees, but pollution darkened the trees, causing darker moths to become more camouflaged, so predators switched to eating the light moths.
  • If environmental pressure is great enough, a population will eventually become a new species because they can no longer successfully interbreed and produce fertile offspring.
  • Galapagos finches example: beak shape of birds correlated with the type of food on each island. There was one original species of finch that came to the islands, and as its offspring survived, the ones who had beak shapes were particularly adapted to finding food on certain islands gradually developed physical and behavioral differences until they became new species.
  • Adaptive radiation: new species adapted to new environments and radiated out from the original species.
  • Speciation is driven by isolation.
  • Pork fish example: populations could no longer interact and interbreed because that changed the movement of water in the oceans. It changed the ocean currents. The environment changed in the Caribbean compared to the Pacific, and over many generations, the pork fish split off from the panamic pork fish.
  • Plate activity has influenced evolution and biodiversity on Earth.
  • Landmasses continually move around our planet over many millions and billions of years, and as they move, they might migrate from the tropical zones into the temperate areas or into polar zones.
  • As landmasses move, migration routes change.
  • The movement of landmasses in and out of different climate zones, and as Earth's climate changes through ice ages and warm spells, this changes migration routes.
  • Fossil remains on landmasses that are currently very far apart from the exact same time period, showing that in the past, those landmasses were together.
  • Mass extinction events: periods in Earth's history where the number of species on the planet drops very precipitously.
    • Driven by rapid climate change.
    • KT event: happened 65 million years ago, knocking out the dinosaurs.
    • Extinction rates today have spiked, leading many scientists to conclude that we have entered the sixth great mass extinction event in Earth's history.

Topic 3.3: Threats to Biodiversity

  • Global biodiversity is decreasing rapidly due to human activities.
  • Species conservation status is assigned through the IUCN (International Union for the Conservation of Nature).
  • Quantifying biodiversity estimates of how many species there are on our planet vary widely.
  • Extinction rates are increasing rapidly beyond the historic background extinction rate.
  • Most extinctions are due to:
    • Habitat destruction
    • Introduction of invasive species
    • Pollution
    • Overharvesting and hunting
  • Current rates of extinction loss are really, really high, showing the world's sixth great mass extinction right now, called the Anthropocene.
  • Red List: the IUCN Red List showing extinction rates
  • Factors to determine the conservation status of species:
    • Red List population size
    • Speciation
    • Distribution
  • IUCN Labels:
    • Least concerned
    • Extinct in the wild
    • Critically endangered
    • Endangered
    • Vulnerable
      *
  • Population size: it's easier to wipe out small populations.
  • Species that are highly specialized for a very particular ecological niche are also at risk of extinction.
  • Species that are distributed very widely because they're in a wide range of habitats or ecosystems are less likely to go extinct.
  • Reproductive potential refers to reproduction rates.
  • Geographic range and how that range is fragmented also poses a risk.
  • The lower the trophic level, the lower the risk of extinction.
  • Factors are combined to reach a determination of conservation status.
  • Tropical biomes contain some of the most biodiverse areas because of their high primary productivity due to Earth's climate.
  • A popular area for people to live, means they are being unsustainably used or exploited.
  • Discuss the case histories of three species:
    • One that is already extinct due to human activities
    • One that is currently critically endangered
    • One that has previously been threatened but whose status has improved due to conservation efforts
  • Describe threats to biodiversity from human activities in a given natural area.
  • Evaluate the impact of human activity in tropical biomes.
  • Conflict between exploitation, meeting the needs of people, sustainable development while ensuring that those needs of future generations can still be met, and conversation.

Topic 3.4: Conservation of Biodiversity

  • The loss of biodiversity is what's driving efforts to conserve it, and those efforts to conserve biodiversity are greatly influenced by one's environmental value system.
  • Differing approaches to the conservation of biodiversity:
    • Target the habitat
    • Focus on specific species
  • Arguments about species and habitat preservation can be based on aesthetic, ecological, economic, ethical, and social justifications.
  • Differing approaches to the conservation of biodiversity use different governmental and organizational strategies.
  • The International Union for Conservation of Nature (IUCN) publishes the Red List, which is considered the comprehensive guide to the conservation status of many species on Earth, and that list is used to guide decision-making.
  • The United Nations has a global spread and influence, but they're also quite bureaucratic, which restricts their effectiveness.
  • Smaller grassroots organizations have a much smaller scale of operation, but because they are small and they operate only in one or two areas, they tend to be locally effective but minimally effective on a larger scale.
  • International conventions on biodiversity create collaboration among nations.
  • CITES (Convention on the International Trade of Endangered Species): This came into effect in the 1970s and has actually been quite successful, particularly in combating the poaching of elephants and rhinos in East Africa.
  • Habitat-based approaches versus species-based approaches to biodiversity conservation:
    • The habitat approach focuses on protecting the entire habitat and all of the species that live there.
    • The species-based approach is very narrowly focused on target species, generally ones that are very critically endangered or near extinction.
    • Most conservation efforts fall somewhere in the middle, where we call a mixed approach, using the strengths of each to offset the weaknesses of the other.
  • Factors to evaluate protected areas:
    • Size of the area; a large area is better than a small area.
    • Shape of the area; a round shape that reduces what we call the edge effect.
    • Area has not been split or fragmented by roads or infrastructure.
  • Conservation criteria for evaluating protected areas include looking at the shape of the protected area.
    *When you have long, narrow, skinny shapes, the core becomes very small, and the edge space becomes quite large.
  • If it's not possible to design one big core area, the next best approach is to design several smaller core areas and connect them through corridors to allow wildlife to migrate back and forth between the protected areas.
  • Species threatened, endangered, critically endangered categories of the IUCN Red List show up on the CITES list.
  • Species based conservation strategies include captive breeding programs.
    *Reintroduction: the idea here is that we remove individuals of the target species, we bring them into a protected area, raise them, increase their populations, and then take them back to their original habitat and release them into the wild.
  • Species-based conservation is frequently based on the use of a flagship species.
  • Flagship Species: one that is considered charismatic or famous; it draws people's attention and makes people feel warm and fuzzy.
  • Keystone Species: critically important for the functioning of an entire ecosystem.
  • People will look out for themselves first, so if the surrounding communities don't benefit from the conservation effort, a protected area is likely to enjoy less success.
  • If people don't benefit from conservation efforts, they will fail.
  • Habitat-based approaches will be better because they are more holistic and they actually protect the entire ecosystem and more than just one species. They conserve all biodiversity or a larger proportion of biodiversity, whereas species-based conservation may benefit one or two target species but tend to be more expensive and overall less successful in the long run unless also combined with habitat-based conservation efforts.