Understanding Biodiversity

Biodiversity

• The variety of life on Earth

Scales of Biodiversity

• Biodiversity is measurable at different scales
• Species: different species occupy same habitat simultaneously
• Genetic diversity (within species): Genotype differences among individuals of a species
• Plasticity (phenotypic plasticity): different phenotypes among individuals with the same genotype
• Variation can occur within an individual or among individuals with the same genotype due to environmental factors
• Higher taxa: groupings of species by evolutionary relatedness such as genera, orders, phyla
• Functional groups: grouping of species by ecological role, for example predators and primary producers
• Habitat/Ecosystem diversity: Grouping of species by physical environment like forest, lake, ocean
• Diversity exists at the habitat level, considering different environments and inhabitants
• Ecosystem diversity: the diversity of an ecosystem is directly proportional to the amount of different organisms inhabiting it

Measuring Biodiversity

• Species richness: the total number of different species present
• Species evenness: relative abundance of each species
• Species diversity: a combination of species richness and species evenness
• Species accumulation curves: Used to estimate species richness by sampling progressively larger areas
• Plots the relationship between sampling effort and the number of species

Distribution of Biodiversity

• Patterns of species diversity across geographic space
• Biodiversity hotspots: places with many endemic species that do not occur in other regions
• These regions have a high concentration of species
• Endemic species: species are only found in a particular place

Factors Influencing Biodiversity Across Geographic Space

• Historical factors (legacy of geological and past evolutionary events)

• Continental movements (continental drift): cause isolation and create opportunities for migration

• The movement of continents occurs over millions of years

• Gondwanaland: Supercontinent once joining South America, Africa, Antarctica, India and Australia

• Wallace's line: separates Asiatic and Australian species despite similar climates, due to historical geological connections

• Biotic interchange: the movement of species between regions

• Contemporary factors (present-day influences): Present-day ecological interactions with other species and the environment

• Climate: The average and annual variation in temperature and precipitation in a region over the long-term

• Serves as a major driver for plant biodiversity

  • Weather: temperature and precipitation over a short period of time (days or weeks)
  • Climate: Average and seasonal temperature/precipitation patterns over longer periods of time (years or longer)
  • Climatographs: single graph describing both temperature and precipitation, showing average conditions and seasonality
  • Global precipitation patterns: Driven by differential heating and cooling Rising air cools/condenses, leading to rainfall near the Equator, sinking air warms/absorbs moisture, leading to dry conditions at 30 degrees N/S
  • Hadley cell: drives high rainfall near the equator and low rainfall at 30 degrees north and south
  • Regional precipitation patterns (Orographic Uplift and Rain shadows):
    • Orographic uplift: air driven aloft by mountains
    • Rain shadow: reduced rainfall on the leeward side of mountain ranges
    • Windward side: side of a mountain facing the wind where precipitation occurs as air rises and cools
    • Leeward side: side of a mountain opposite the windward side, which is dry

• Ecological interactions: Interaction with other species and environment

Classification of Life

• Organizing and classifying biodiversity
• Latin binomial (genus species): unique two part name for each species
• Genus: group of closely related species
• Species: group of individuals that can interbreed and produce fertile offspring
• Hierarchical Categories (Taxonomic Hierarchy): classification of life based on similarity in morphology or genetics
• Species, genus, family, order, class, phylum, kingdom
• Evolutionary tree (phyletic tree): Branching diagram showing how species are related, based on genetic similarity
• Species closer on the tree are more closely related

Assessing the Number of Species

• Extrapolation from limited sampling: Using species area curves or other estimates based on limited sampling
• Terry Erwin's Beetle Study: Used small scale sampling in a single habitat type to estimate global insect diversity through fogging
• Specialist species: species only found on a specific host
• Generalist species: species that can utilize a variety of resources or hosts

Adaptation

• Structure, physiological process, or behavior arising through natural selection which improves an organism's survival or reproduction Functional diversity: adaptations of organisms to their environment that groups species by shared evolutionary history/functional roles

Principle of Allocation

• Each organism has a limited amount of resources for all life processes
• Resources allocated to one function can't be applied to another, resulting in trade-offs
  • Trade-off: Relationship between the benefits of a trait in one context and its costs in another
  • Excelling in one aspect results in poor performance in another
• Resource allocation: how organisms distribute their limited resources among different life functions
• Root to shoot ratio: ratio of below ground (roots) to above ground (shoots) biomass in plants and indicates plant needs
• High ratio suggests need for more water and nutrients
• Low ratio suggests need for more carbon
• Lifetime trade-offs: trade-offs that occur throughout an organism's lifetime

Resource Acquisition

• Fundamental ways in which energy and other resources are acquired
  • Autotrophs (self-feeding): Organisms living exclusively on inorganic sources of carbon, nitrogen, and other essential resources. They produce their own food, such as plants
  • Photoautotrophs: use light as the energy source
  • Photosynthesis: the process by which light energy converts carbon dioxide and water into glucose and oxygen
  • Chlorophyll: Primary light harvesting pigment of green plants, absorbs most colors except green
  • Plant adaptations for light capture: increasing surface area, increasing chloroplast packing, altering chloroplast structure, adjusting pigment size
  • Plant nutrient acquisition: uptake of nutrients from the soil, role of clay particles, CO2 release, carbonic acid formation, ion displacement, root surface area
  • Rhizobia: Bacteria converting atmospheric N2 into ammonia for plants
  • Mycorrhizal fungi: fungi enhancing nutrient and water uptake in plants
  • Liebig's Law of the Minimum: Growth is determined by the most scarce resource compared to how much the plant needs
• Heterotrophs (other-feeding): organisms using organic molecules formed by other organisms as source of carbon, nitrogen, energy, etc
• Herbivores: consume plant material, adaptations of long guts, detoxification enzymes and grinding dentition
• Carnivores: attack and consume animal material, adaptations for pursuit and subdual of prey like sharp teeth
• Omnivores: consume both plant and animal matter, adaptations include generalist morphologies
• Detritivores: consume dead plant/animal matter, adaptations for subsisting on low quality foods
• Specialization vs Generalization in consumers: specialists use a small number of resources, whereas generalists use a wide range
• Optimal foraging behavior: Foragers often aim to maximize energy intake per unit of time by choosing prey that maximizes the ratio of rewards to costs

Ecology

• The study of relationships between living things (biotic interactions) and between living things and their non-living environment (abiotic interactions)
  • Biotic interactions: interactions between living things
  • Abiotic interactions: interactions between a living thing and a non-living environment

Evolution

• Genetic change across generations (small or large scale)
  • Development of the theory of evolution:
    • Aristotle and Scala Naturae: stair step hierarchy of organisms
    • Arab and muslim scholars: introduced ideas about whether and how organisms change
    • Alexander von Humboldt: biogeographer who studied similarities between distant ecosystems
    • Charles Lyell: geologist who emphasized long, slow processes of change
    • Mary Anning: prolific fossil worker
    • John Edmonstone: taught darwin taxidermy and sparked interest in biodiversity
    • Charles darwin and voyage of the beagle: observations and hypothesis development during the voyage
    • Darwin's breeding experiments: experiments with pigeons that showed varied traits in offspring
    • Darwin's phyletic tree: first illustration of lineage divergence
• Eclipse of Darwinism: the 40-year period after Darwin's "Origin of Species" where natural selection was just one of many ideas about species change
• Modern Synthesis: integration of population genetics, mendelian inheritance and darwin's natural selection
• Natural Selection: Produces genetic change/evolution and can be driven by species interactions or ecology

Properties of Life

• Characteristics shared by all living things
• organization, energy processing, growth and development, evolutionary change, homeostasis, response to stimuli

Biomes

• Habitats characterized by a particular type of vegetation and plant life
• Climate is a major determinant of the types of plants in locations, thus influencing biomes
• Tropical rainforest, desert, temperate grassland, temperate deciduous forest, boreal forest, tundra, mediterranean
• Seasonality: variation in temperature and precipitation throughout the year, influenced by Earth's tilted axis and revolution around the sun

Earth's Energy Budget

• The balance between incoming solar radiation and outgoing radiation from earth and is altered by the concentration of the gases in the atmosphere
  • Greenhouse gases: gases in atmosphere that allow light to pass through but trap longer wavelength infrared heat energy
  • increases in these gases lead to a warming of the atmosphere
  • Anthropogenic-driven climate change: evidence that earth's climate is changing due to human activities increasing greenhouse gas concentrations
  • Infrared radiation: heat energy radiated back out to space, greenhouse gases absorb certain wavelengths and increase temperatures

Scientific Discovery

• Iterative nature of scientific discovery: the scientific process is not linear; more questions arise
• Scientists lean on previous ideas and theories and assumptions can be wrong