Option C: Ecology and Conservation

C1 Species and Communities

• Survival factors 

  • U: The distribution of species is affected by limiting factors
  • Limiting factor = a component of an ecosystem which limits the distribution or numbers of a population
    • Defines optimal survival conditions according to its effect on a species when in deficiency or excess
    • Can be biotic or abiotic
    • Biotic factors include interactions between organisms
      • Either intraspecific (within a species)
      • Or interspecific (between species)
    • Abiotic factors include environmental conditions
      • E.g. light, temperature, salinity (concentration of salts in water or soils), rainfall, wind velocity, soil pH, etc.
    • Typical abiotic limiting factors for plants within a community
    • Temperature
      • Plants can only survive within a narrow range of temperatures to which they are adapted
      • High temperatures will increase the rate of water loss by evaporation and may also denature metabolic enzymes
      • Low temps may cause plant sap to freeze
      • The expansion of frozen water in xylem can cause trunks to split
      • Certain species of woody plants synthesis antifreeze protein to prevent crystal formation in frozen cells
      • E.g. maple trees
    • Water availability
      • Water is needed for photosynthetic processes + maintaining cell turgor
      • Xerophytes are plant species that are adapted to survive in dry and arid environments such as deserts
      • E.g. cacti
      • Hydrophytes are plant species that are adapted to survive in frequently waterlogged soils
      • E.g. rice
    • Light availability
      • Light is essential to the process of photosynthesis whereby plants produce organic molecules
      • Low-growing plants will typically possess darker leaves in order to optimize their light conversion
      • Dark = more chlorophyll
      • Certain seaweeds have pigments adapted to absorbing blue wavelengths
      • E.g. kelp
      • Red does not easily penetrate water
    • Typical abiotic limiting factors for animal within a community
    • Temperature
      • Animal survival typically relies on narrow temperature range
      • Few animals can survive temperature extremes
      • Poikilotherms cannot maintain thermal homeostasis and must occupy environments according to temperature needs
      • Homeotherms can regulate their own internal body temperatures and hence can occupy a wider range of habitats
      • Body size will play a fundamental role in determining an animal’s capacity to retain heat
      • The surface area to volume ratio
    • Territory
      • Territorial boundaries may determine an animal's capacity to attract mates, rear young, forage for food and avoid predators
      • Territories may be temporary (e.g. migration, breeding sites) or alternatively may be permanent
      • In certain species, juveniles may have different environmental requirements to adults
      • E.g. tadpoles and frogs
      • Establishment of territories can lead to intraspecific and interspecific competition
    • Food availability
      • Availability of food supply is a critical determinant in influencing population size and distribution
      • Animals may require a particular plant or animal species as a food source
      • This limits their spread to certain regions
      • Seasonal or geographic variations may directly affect food availability within a population
        • E.g. seasonal migrations
  • Law of Tolerance
    • The Law of Tolerance was proposed by Victor Ernest Shelford (American zoologist) in 1911
    • States that populations have optimal survival conditions within critical minimal and maximal thresholds
    • When populations are exposed to the extremes of a particular limiting factor (too much or too little), the survival rates drop
    • The distribution of species in response to a limiting factor is a bell-shaped curve with 3 distinct regions
    • The optimal zone 
      • Central portion of a curve which has conditions that favor maximal reproductive success and survivability
    • Zones of stress
      • Regions flanking the optimal zone where organisms can survive but with reduced reproductive success
    • Zones of intolerance
      • Outermost regions in which organisms cannot survive 
      • Represents the extremes of the limiting factor
    • Example:
    • 
  • A: Distribution of one animal and one plant species to illustrate limits to tolerance and zones of stress
  • Plant example 
    • Plant growth varies greatly in response to salinity levels (concentrations of salt within the soil)
    • Plants that are not salt tolerant are called glycophytes
    • They are easily damaged by high salinity 
    • Most plant species are considered glycophytes
    • Plants that are salt tolerant are called halophytes
    • They may become stressed in freshwater environments
    • Less than 2% of all plants are halophytes
    • Cultivation of land for agriculture causes the water table to rise and concentrates salt at the roots
    • Such cultivation includes irrigation and grazing
    • This makes it harder for glycophytes to extract water from the soil and the uptake of salt can be toxic to the plant
    • Understanding salt tolerance for different plant species is therefore critically important to effective crop farming
  • Animal example
    • Coral species form connected reefs → these are greatly impacted by changes in oceanic temperature
    • Coral polyps receive nutrition from photosynthetic zooxanthellae that lives within the polyp’s endodermis
    • Zooxanthellae = an algae
    • Endodermis = an inner layer of cells in the cortex of the root
    • The Zooxanthellae cannot survive in lower ocean temperatures 
    • Below 18 degrees Celsius
    • Increases in ocean temperature cause Zooxanthellae to leave the coral tissue → this leads to coral bleaching
    • Above 35 degrees Celsius
    • Reef-building coral species therefore have a typical optimal growth range in temperate waters between 20 and 30 degrees Celsius
    • This correlates to the tropical and sub-tropical regions of the world (near the equator)

• Species distribution

  • S: Use of a transect to correlate the distribution of plant or animal species with an abiotic variable
  • Quadrats and transects can measure the distribution of a plant or animal species in response to an incremental abiotic factor
    • Incremental = happening gradually
    • Quadrats = rectangular frames of known dimensions than can be used to establish population densities 
    • Transects = a straight line along an abiotic gradient from which population data can be recorded to determine a pattern
    • Quadrats and transects are used together
  • Quadrats are placed at regular intervals along the transect line to generate population data
    • Basically, placing a quadrat down regularly and observing/counting the difference in distribution of X species based on the change of Y abiotic variable
    • The quadrats will show the changing distribution pattern of a species in response to a change in an abiotic variable
    • This data can be used to identify optimal conditions + zones of stress and zones of tolerance
  • Sampling with Quadrats and Transects
    • Quadrat counting method: count all variables mostly inside the quadrat (not mostly out)
    • Line transects: find a line, place quadrat every x meters
    • Transect data
    • Transects are used to assess species distribution in correlation with any abiotic factor that varies across a measurable distance
      • These factors could include elevation, elemental exposure, temperature, light levels, pH, humidity and more
    • A kite graph with the transect data can be used to represent changes in species distribution in a clear and effective fashion
    • The relative width of each kite represents the abundance of an organism at a particular point along a transect
    • Example:

• Ecological niche

  • U: Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species
  • Ecological niche = the functional position and role of an organism within its environment
    • Consists of all physical and biological conditions which determine the organism’s survival and reproductive prospects
    • Is comprised of various components, including:
    • The habitat in which an organism lives
    • The activity patterns of the organism
      • E.g. periods of time during which it is active
    • The resources it obtains from the environment
      • E.g. food sources, territorial boundaries, etc.
    • The interactions that occur with other species in the community 
      • E.g. predator prey relationships, competition, etc.
  • U: Two species cannot survive indefinitely in the same habitat if their niches are identical 
  • If two distinct species share an identical niche, there will be interspecific competition for available space and resources 
    • This competition will result in the fitness of one being lowered by the presence of the other
    • The less well-adapted species will struggle to survive and reproduce
    • Eventually it will be eliminated from the niche
  • Interspecific competition within a shared niche will typically prompt one of two responses 
    • Competitive exclusion → one species uses the resources more efficiently, driving the other species to local extinction
    • Resource partitioning → both species alter their use of the habitat to divide resources between them
    • Niche separation
  • Niche differentiation diagram:
  • S: Analysis of a data set that illustrates the distinction between fundamental and realized niche
  • Some species may not be able to occupy their entire niche due to the presence or absence of other species 
    • Hence, a species may occupy a small subset of their niche than is theoretically possible 
    • This creates fundamental vs. realized niche
  • Fundamental niche = the entire set of conditions under which an organism can survive and reproduce (where it could live)
    • The theoretical habitat 
    • Example: in a rocky shore environment, the Chtalamus barnacle can potentially occupy the entire rocky shore, if in isolation
  • Realized niche = the set of conditions used by an organism after including interactions with other species (where it does live)
    • The actual habitat that is completely occupied by an organism in the presence of competing species
    • Example: the Chtalamus barnacle only occupies regions where the Semibalanus barnacle is absent
  • Diagrams:
    • Niches
    • Experimental data
    • Types of barnacles

• Species interactions

  • U: Interactions between species in a community can be classified according to their effect
  • In nature, no species exist in total isolation → all organisms interact with both the abiotic environment and other organisms
    • The interactions between species can be classified according to their effect on the organisms involved
  • Herbivory
    • The act of eating only plant matter
    • That’s why primary consumers are called herbivores
    • Herbivores ay employ different feeding strategies
      • E.g. mucivores feed on plant sap while granivores feed on seeds, etc.
    • Herbivory can be either harmful or beneficial to plant species as a whole
    • Harmful: Certain types of beetle may feed voraciously on the leaves which causes crop failure 
    • Beneficial: Fruit-eating animals spread the seeds from a fruit in their feces, which promotes overall seed dispersal 
    • Examples of herbivores: Rabbit, cow
  • Predation
    • A biological interaction whereby one organism hunts and feeds on another organism
    • Predator and prey
    • The dependance of the predator on the prey as a food source intertwines their population levels
    • If the prey population drops, the predator numbers will fall as well as intraspecific competition has to increase
    • If the prey population rises, predator numbers will increase as a result of the ober-abundance of a food source
      • No intraspecific competition necessary = even the weakest survives
    • Diagram:
  • Symbiosis 
    • Close and persistent long-term interaction between two species
    • Can be obligate (required for survival)
    • Or facultative (advantageous without being strictly necessary)
    • Symbiotic relationships can be beneficial to either one or both organisms in the partnership
    • Mutualism – both species benefit from the interaction
      • Example: how anemone protects clownfish and clownfish provides fecal matter for food
    • Commensalism – one species benefits, the other is unaffected
      • Example: barnacles are transported to plankton-rich waters by whales
    • Parasitism – one species benefits to the detriment of the other species
      • Example: ticks or fleas feed on the blood of their canine host
    • Diagram:
  • A: Local examples to illustrate the range of ways in which species can interact within a community
  • Mutualism 
    • Ongoing interaction between two species whereby both species benefit from the interaction
    • Examples:
    • Honey bees gather nectar from flowers and distributes pollen between plants 
      • This mediates the plant life cycle 
    • Plover birds pick food morsels from between the jaws of crocodiles, cleaning their teeth in the process
    • Zooxanthellae photosynthesise within the protective environment of the polyp’s endodermis 
      • This feeds the coral
  • Commensalism
    • Ongoing interaction between two species whereby one benefits and the other is unaffected
    • Examples:
    • Remora attaches to the underside of larger predatory fish and feed off the uneaten food scraps
    • Monarch butterflies can safely store poisonous chemical produced by milkweeds discourage predators from eating it
    • Decorator crabs remove small fragments of tissue from sea sponges and uses them as a source of camouflage 
  • Parasitism 
    • Ongoing interaction between two species whereby one species benefits at the other’s expense
    • Examples:
    • Ticks infest the skin and fur of host animals, feeding off the host and potentially causing disease
    • Leeches attach to the skin and drinks the blood of the host animal until fully engorged
    • Tongue-eating louses eat the tongue of a fish and may still later ingested food
  • A: The symbiotic relationship between Zooxanthellae and reef-building coral reef species
  • Reef-building coral will form a mutualistic symbiotic relationship with the photosynthetic unicellular algae Zooxanthellae
    • Coral are colonial organisms made up of individual polyps that are connected by a layer of living tissue
    • The algae lives within the cells of the coral’s endodermis (the innermost lining of the animal)
  • The coral provides the algae with a protective environment and source of inorganic compounds
    • Coral polyps secrete calcium carbonate to build a stony skeleton which encases the polyps and the Zooxanthellae
    • Coral polyps also recycle the waste products of the algae and supplies the Zooxanthellae with CO2
  • The Zooxanthellae in turn provides the coral polyps with a necessary source of nutrition
    • The alage supplies the coral with oxygen, glucose and other organic molecules that it produces via photosynthesis 
    • The algae also helps the coral remove necessary waste products 
  • Diagram of their mutualistic relationship:
  • Coral bleaching
    • It is the Zooxanthellae that gives the coral its vibrant pigmentation
    • When there is a large scale loss of Zooxanthellae from the coral due to environmental stress, bleaching of the coral occurs
    • This causes the coral to starve and die unless the Zooxanthellae are restored
    • Conditions which can cause coral bleaching include:
    • Changes in light availability
      • E.g. sedimentation may increase the opacity of the oceanic waters
    • Temperature increases
      • Water temperatures in excess of 30 degrees Celsius can irrevocably stress the Zooxanthellae
    • Ocean acidification 
      • The buildup of CO2 concentrations in the ocean can lower pH and stress the Zooxanthellae

• Keystone species

  • U: Community structure can be strongly affected by keystone species
  • Keystone species = a species that has a disproportionately large impact on the environment relative to its abundance 
    • Name comes from the keystone in an arch → it fundamentally supports the whole structure and prevents it from collapsing
  • Keystone species may influence communities in a number of ways:
    • Predators can exert pressure on lower trophic levels to prevent them from monopolizing certain resources
    • Mutualists can support the life cycle of a variety of species within a community
    • E.g. pollinators and seed dispersal 
    • Engineers can refashion the environment in a manner that promotes the survival of other species
    • Engineer = any species that creates, significantly modifies, maintains and/or destroys habitats
  • Numerous examples of keystone species within different communities, such as:
    • Sea stars (predators) prey on urchins and mussels, which prevents mussel overpopulation and coral reef destructions by urchins
    • Honey bees (mutualist) pollinate a wide variety of plant species, ensuring the continuation of the plant life cycle
    • Beavers (engineer) build dams that transform the environment in a manner that allows certain other species to survive
  • Keystone species are not the dominant species (most numerous) within a community nor do they have to be apex predators 
  • Diagram of consequences of removal of keystone species:

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C2 Communities and ecosystems

•  Trophic levels
  • U: Most species occupy different trophic levels in multiple food chains
  • Trophic level = the position an organism occupies within a feeding sequence 
    • Producers occupy the first trophic level in a feeding sequence
    • Primary consumers feed on producers → second trophic level
    • Secondary consumers feed on primary → third trophic level
    • Further consumers occupy the subsequent levels
    • Diagram:
  • Food chain = shows linear feeding relationships between species in a community
    • Arrows represent the transfer of energy and matter
    • This transfer happens as one organism is eaten by the other
    • The arrows point in the direction of energy flow
    • Goes from the producer to the consumers
    • Most species’ feeding requirements means they will be in multiple food chains where they may occupy a different trophic level 
    • As few species only feed on one other species
    • E.g.:
  • U: A food web shows all the possible food chains in a community
  • Links food chains together into more complex and interrelated feeding relationships
  • More representative of actual feeding pathways within an ecosystem because
    • Organisms can have more than one food source
    • Organisms can have more than one predator 
    • Hence, organisms can also occupy more than one trophic level 
  • Tip! When constructing food webs, position organisms at their highest trophic level (from left to right) as it keeps all arrows pointing in the same directions
  • Example:
  • EC: Ecological Pyramids
  • Ecological pyramids show the relative amounts of a specific component at the different trophic levels of an ecosystem
    • The three main types measure species numbers, biomasses and energy
  • Pyramid of Numbers
    • Shows the relative number of organisms at each stage of a food chain
    • Are usually shaped like pyramids → higher trophic levels cannot be sustained if there are more predators than prey
    • However, the shape may be distorted if a food source is disproportionately large in size/biomass compared to the feeder
      • E.g. a large number of caterpillars may feed on a single oak tree
  • Pyramid of Biomass
    • Shows the total mass of organisms at each stage of a food chain
    • Almost always upright in shape as biomass diminished along food chains as CO2 and waste is released
    • An exception to this rule is found in marine ecosystems where zooplankton have a larger total biomass than phytoplankton
      • Because phytoplankton replace their biomass at such a rapid rate and can therefore support a larger biomass of zooplankton
  • Pyramid of Energy
    • Shows the amount of energy trapped per area in a given time period at each stage in a food chain
    • Always upright in shape as energy is lost along food chains
    • Either used in respiration or lost as heat
    • Each level in the pyramid is roughly one tenth the size of the preceding level as energy transformations are ca. 10% efficient
  • Examples of pyramids:
• Energy conversions
  • U: The percentage of ingested energy converted to biomass is dependent upon the respiration rate
  • Ecological production/productivity refers to the rate at which biomass is generated in an ecosystem
    • Usually expressed in units of mass per area per time 
    • km m^-2 day^-1
  • Biomass = total dry weight of organic matter in organisms or ecosystems
    • The entirety of all biologically produced organic matter 
    • E.g. proteins, carbohydrates, etc.
  • The percentage of energy that is converted into biomass is dependent upon a number of factors that lose energy
    • Energy is lost as inedible materials (bones, teeth, hair)
    • Energy is lost via excretion of undigested or unabsorbed materials
    • Energy is lost as heat from cellular respiration 
    • The higher respiration rate results in more heat lost
  • Primary production = the production of chemical energy in organic compounds by producers
    • The main source of energy for primary production is sunlight
    • Sometimes chemosynthesis by lithotrophs 
    • Can be categorized as one of two types:
    • Gross primary production (GPP) → the amount of chemical energy as biomass that a producer creates in a given length of time
    • Net primary production (NPP) → the amount of chemical energy that is not consumed by respiration
      • GPP - respiration
  • Secondary production ? the generation of biomass by heterotrophic organisms (consumers)
    • Biomass generation is driven by the transfer of organic compounds between trophic levels via feeding
    • Secondary production may also be categorized according to gross and net amounts of biomass
    • Gross = total
    • Net = usable 
  • Diagram explaining how ingested energy converted to biomass depends on respiration:
• Feed Conversion Ratio
  • A: Conversion ratio in sustainable food production practices
  • Feed Conversion Ratio (FCR) = mass of feed/mass of desired output
    • FCR measure the efficiency of an animal in converting food into a desired output
    • The lower the FCR the more efficient the method of food production
  • Low FCR is achieved by minimizing the potential losses of energy for the animal stock
    • Restricting animal movement will reduce energy lost to cell respiration
    • Optimizing feeding practices so that food is ingested and digested more effectively 
    • Slaughtering animals at a young age
    • As older animals tend to grow more slowly and have a higher FCR
  • Theoretically the most efficient FCR is best as it lowers cost, however there are a number of potential ethical issues involved
    • Is it ethical to restrict animals and kill them early?
  • Diagram displaying the FCRs of different species:
  • EC: Sustainable food practices
  • Most of the protein found in Western human diets comes from farmed animal meet
    • E.g. cattle and poultry
    • These animals must be fed and housed → this creates an ecological footprint, the size of which depends on the FCR
  • Sustainable food practices provide food for the consumer while minimizing the environmental impact of the food source
    • The benefits of lowering food production costs must be balanced against ethical considerations regarding animal treatment
  • One sustainable food practice is the use of crickets as a protein source (as opposed to cattle)
    • Crickets have a substantially lower FCR → minimizes feed costs
    • They require significantly less water → minimizes water usage
    • They can reproduce much faster and require less space
    • Produce far less methane
    • For these reasons, certain health professionals are advocating the introduction of crickets into normal diets
    • The advantages of crickets as a food source is still debated though, so implementation is likely to be slow
• Types of Ecosystems
  • U: In closed ecosystems energy but not matter is exchanged the with the surroundings
  • Ecosystems can either be open or closed, depending on whether matter moves into and out of the system
    • A closed ecosystems exchanges energy with its surrounding, but not matters
    • It is self-contained 
    • E.g. a mesocosm
    • An open ecosystem changes both energy and matter with surrounding environments
    • A natural ecosystem such as a forest
  • U: The type of stable ecosystem that will emerge in an area is predictable based on climate
  • Ecosystem = the interaction of living and non-living things within an area
    • A community and its abiotic environment
  • Particular types of stable ecosystems will emerge in a given geographical area according to its climate conditions
  • Biome = a geographical area that has a particular climate and sustains a specific community of plants and animals
    • Basically a specific type of natural ecosystem, created from its climate and environment
    • The main factors affecting the distribution of biomes is temperature and rainfall 
    • These factors vary according to latitude, longitude, altitude, proximity to ocean, etc.
  • Many different biomes are found across continents, including: 
    • Tropical rainforests
    • Hot and humid environments
    • Near the equator
    • Dense vegetation
    • High biodiversity
    • Taiga
    • Coniferous forests
    • Near the poles 
    • Have cold temperatures
    • Little precipitation 
      • Moisture trapped as snow or ice
    • Deserts
    • Dry and arid environments
    • Display extreme temperature conditions (hot and cold)
    • Picture examples:
  • EC: Types of Biomes
  • Biomes are geographical area that have a particular climate and sustain a specific community of flora and fauna 
    • The total area where all living things are found is called the biosphere
    • The totality of biomes
    • Certain biomes are named and recognized according to their specific characteristics
  • Tropical rainforest
    • Hot climate → 25-30 degrees Celsius 
    • Very high levels of precipitation → > 250 cm per year
    • Large diversity in species
    • Vegetation includes epiphytes, tall trees and undergrowth
    • Epiphytes: organisms that grow on the surface of plants
  • Temperate forest
    • Also called deciduous forests
    • Moderate temperatures and clear seasonal changes
    • Growing period of around 200 days during 4-6 frost free months
  • Boreal forest (Taiga)
    • Coniferous forests
    • Cold and icy → 0-15 degrees Celsius
    • Only small amount of precipitation
    • Coniferous trees are densely packed and there is little variation in species
  • Tropical Grassland (Savannah)
    • Warm → 20-30 degrees Celsius 
    • Medium amounts of moisture, although seasonal droughts are common
    • Trees are intermittent and widely spaced
    • Occasional fires prevents thicker vegetation from encroaching
  • Temperate Grassland
    • Moderate temperatures and amounts of rainfall
    • Trees and shrubs are largely absent
    • Grass is the dominant vegetation
  • Mediterranean (Chaparral)
    • Moderate temperatures → 15-25 degrees Celsius
    • Rainy winters and dry summers
    • Vegetation consists of dry woody shrubs that are quick to grow
  • Desert
    • Extreme temperature conditions → > 30 degrees Celsius during the day, < 0 degrees at night)
    • Very low precipitation
    • < 30 cm per year
    • Dominant plant species are xerophytes which are adapted for water conservation
  • Tundra
    • Freezing temperatures → < 0 degrees Celsius
    • Very little precipitation 
    • Vegetation is low growing
    • E.g. mosses
    • Perennial plants may grow during the summer
  • Mountain ranges
    • Found all over the world at high attitudes → > 10 000 feet
    • Temperatures are typically low due to the altitude
    • Weather conditions may change rapidly
  • Distribution of biomes in the biosphere: 
    • 
• Ecosystem Analysis
  • S: Analysis of a climograph showing the relationship between temperature, rainfall and the type of ecosystem.
  • Climograph = graphical representation of basic climate parameters at a given geographical location
    • Shows a combination of monthly average temperature and precipitation at a certain location
    • Precipitation = rainfall
    • Provides a quick overview of the climate of a region and can be used to identify seasonal patterns and changes
    • Examples: 
    • 
  • Whittaker’s climograph
    • In 1975, ecologist Robert Whittaker developed a holistic climograph that allowed for the classifying of 9 distinct biomes
    • Biomes distinguished according to their average yearly temperatures and precipitation
    • Deserts typically have high average temperatures but low precipitation
      • Hot and dry
    • Rainforests typically have high average temperatures and high precipitation 
      • Hot and wet
    • Taigas typically have low average temperatures and reasonably low precipitation
      • Cold and icy
    • 
  • S: Comparison of pyramids of energy from different ecosystems
  • Pyramids of energy (PoE) = diagram of the flow of energy between trophic levels
    • Measures in units of energy per area per time
    • Standard units are kJ m^-2 and y^-1
    • Triangular and never inverted as 90% of energy is lost between trophic levels
  • PoEs differ between ecosystems due to the effect of climate on primary productivity 
    • Warmer temperatures speed up enzyme reactions required for photosynthesis 
    • High precipitation also increases photosynthesis as the photolysis of water is essential for non-cyclic photophosphorylation 
    • Higher (optimal) rate of photosynthesis = more energy transferred
  • Tropical rainforests have a high NPP whereas deserts have a low NPP
    • Higher NPP = more energy supplies to consumers hence more trophic levels can exist
    • Tropical rainforests PoE has a wider base and more levels than a desert
  • Types of species within a particular biome may also affect how efficiently energy is transferred between trophic levels
    • Example: Homeotherms will use more energy maintaining a stable body temperature compared to poikilotherms
  • Diagram:
  • S: Construction of Gersmehl diagrams to show the interrelationships between nutrient stores and flows between taiga, desert and tropical rainforest
  • Gersmehl diagrams show the differences in nutrient flow and storage between different types of ecosystems
  • Nutrients are stored in one of three nutrient sinks
    • Biomass → the total mass of living organisms in a given area
    • Mainly plant tissue
    • Litter → any organic matter in and on the soil
    • Includes humus and leaf litter (defoliation)
    • Soil → the top layer of the earth that is composed of disintegrated rock particles 
  • Nutrients can be transferred between nutrient sinks and may also be cycled via environmental inputs and outputs
    • Transfer from biomass to litter → fallout
    • Transfer from litter to soil → decay
    • Transfer from soil to biomass → uptake
    • Litter can additional gain nutrients via precipitation and lose nutrients in surface runoff
    • Soil can gain nutrients from the erosion of rocks via weathering and lose via leaching
  • Standard: Gersmehl diagram
  • Comparing Gersmehl diagrams
    • The inter-relationships between nutrient stores and flows will be affected by climatic factors
    • Such as temperature and rainfall
    • Therefore Gersmehl diagrams will differ between biomes
    • Tropical rainforest
    • Most nutrients are stored as biomass
      • Litter is rapidly decomposed and vast roots quickly draw nutrients from soil 
    • There is a fast rate of transfer between stores
      • Hot and wet conditions promote precipitation, runoff, weathering and leaching
    • Taiga
    • Most nutrients are stored as litter
      • Low temperatures slow decomposition which delays nutrient transfer to soil and biomass
    • There is little nutrient gain from precipitation or weathering due to low levels of precipitation 
      • Cold temperatures produce snow instead
    • There is little nutrient loss via leaching due to low precipitation
      • But surface runoffs may be high at certain times if the snow melts
    • Desert
    • Most nutrients are stored in the soil
      • Few plants exist to store nutrients as biomass nor to produce litter
    • There is little nutrient gain from precipitation and little nutrient loss via runoff → both due to the dry climate
    • The amount of weathering and leaching is insignificant
    • 
• Primary Succession 
  • S: Analysis of data showing primary succession
  • Ecological succession = the process by which a sequence of increasingly complex communities develop over time
    • Climax community = when succession has ended and the community has all of its characteristics
  • Primary succession = when communities develop on entirely new land without any established soil
    • May occur at river deltas, glaciers, sand dunes or on exposed rock
    • First organisms to colonize the region are called pioneer species
    • Typically consist of lichen or moss
      • When they die, they decompose which creates the first organic soil capable of sustaining plant growth
  • As plant species colonize a new area, the litter produced by their growth and decomposing remains will cause changes
    • Soil depth will increase because plants add humus to the soil
    • Soil pH will become altered by the additions
    • Soil mineral content will increase and rocks will begin to be broken down by the action of roots
    • The soil will become aerated and water retention increases
    • Drainage is reduced 
    • These changes will allow for growth of larger plants, which will reduce erosion through the binding action of their roots
    • Not all plant species will thrive in unison → larger plants will eventually outcompete smaller shade intolerant plants
  • Overview of primary succession:
  • Primary succession data
    • A primary succession sequence can be identified according to the distribution of plants 
    • This applies for any location where a new community may emerge from uninhabitable land
    • The regions closer to the site of development will be in the earlier chronological stages of succession 
      • E.g. Glacial retreat exposes bare rock for colonization, so regions further from the glacier have had more time to develop life
    • Diagram example:
• Ecological Disturbance 
  • U: Disturbance influxes the structure and rate of change within ecosystems
  • Environmental disturbances may cause fluctuations to the structure and rate of change within ecosystems
    • Such disturbances may be natural or artificial (human-induced)
    • E.g. bushfire, earthquake
  • Natural disturbance
    • A natural environmental disturbance may give rise to secondary succession
    • Secondary succession = one ecosystem is replaced by another
    • Occurs when succession starts on existing soil following the upheaval (change) of a pre-existing ecosystem
      • This upheaval results in the removal of existing biota and allows a new ecosystem to develop on the site of the old
    • Because the soil is already developed during secondary succession, dominance is usually achieved by the fastest growing plants
    • The progression of secondary succession can be summarized as follows:
    • An environmental disturbance destroys the pre-existing climax community
    • Grasses and herbaceous plants are the first to grow back as the soil is already present
      • Soil = no pioneer species required
    • Fast growing trees will develop to their fullest while shade tolerant trees will develop in the understory
      • Eventually the fast-growing trees may be overtaken by larger, slower-growing trees as the ecosystem reverts to its prior state
    • Diagram:
  • A: Consideration of one example of how humans interfere in nutrient cycling
  • Deforestation is the permanent destruction of a forest via the removal or clearance of trees
    • Human-induced degradation of forests
    • Driven primarily by a need for timber and cleared land for agricultural purposes
  • Deforestation disturbs the normal nutrient cycling within the region in a number of ways
    • Less trees means there is less evapotranspiration  meaning there is less moisture/precipitation in the air
    • Fewer trees means less litter 
    • Due to less defoliation (leaves falling off a plant)
    • This reduces the production of humus, so there will be less nutrients in the soil
    • Rapid loss of nutrients from leaching
    • Less chemical weathering of rock, due to less water in soil
    • The soil will become more acidic and release iron and aluminum to form an infertile ferralitic soil 
    • Ferralitic soil = nutrient poor
    • The soil layer will become increasingly thin and eroded 
    • The infertile soil will prevent vegetative growth, reducing biodiversity and nutrient cycling
    • Logging operations may also alter the distribution of plant species by removing the canopy and increasing light exposure
    • Canopy = the upper layer of habitat zone, usually formed by mature tree crowns
    • Removal of the canopy also results in an increases loss of nutrients from the soil via runoff
  • The effect of deforestation on nutrient cycling:
  • S: Investigation into the effect of an environmental disturbance on an ecosystem
  • Environmental disturbances are caused by natural or artificial disruptions to a normal ecosystem
    • Examples:
    • Fire breaks in bush lands or regions damaged by bushfires
    • Outer boundaries of population settlements or regions bordering roads
    • Dams and artificial rivers and creeks
      • E.g. irrigation sites
  • The effect of an environmental disturbance on an ecosystem can be measured in a number of ways
    • Population density
    • Using the Lincoln index via the capture-mark-recapture technique
    • Species diversity and richness
    • Using the Simpson’s reciprocal index
    • The presence and distribution of indicator species 
    • To measure levels of pollution
    • Canopy coverage and relative light intensity
    • Could measure with a lux meter
    • Biomass
    • Via the average width of tree stems at a specified height
    • Edaphic factors such as soil erosion (via depth), water retention (via drainage), pH and nutrient content
  • Measurements taken from a disturbed area need to be compared against measurements taken from an undisturbed control area
    • This enables the investigator to statistically calculate both the effect and magnitude of the environmental disturbance

C3 Impacts of humans on ecosystems

•  Invasive species
  • U: Introduced alien species can escape into local ecosystems and become invasive.
  • The species within any given ecosystem can be broadly described as either endemic or alien
    • Endemic = native species to a defined geographic region
    • E.g. koalas in Australia
    • Alien = species that have been transferred from their natural habitat into a new environment
    • If an introduced alien species has detrimental effects on the pre-existing food chains, it is classified as invasive 
    • Invasive species typically threaten the biodiversity of the ecosystem they are introduced into by displacing native species
  • Example: invasive species in Australia → cane toad, European rabbit, red fox, camel, feral cat
  • U: Competitive exclusion and the absence of predators can lead to reduction in the number of endemic species when alien species become invasive 
  • Competitive exclusion principle = two species cannot occupy identical niches within a community
    • One species will have a competitive advantage and survive at the expense of the other
    • Evolution via natural selection results in adaptations that function to minimize direct competition between species in nature
  • Invasive species possess several advantages that allow them to displace endemic species via competitive exclusion:
    • Typically possess a large fundamental niche
    • = can occupy a wider area than endemic species
    • Commonly lack a predator capable of limiting their survival
    • As they are introduced into a foreign environment
    • May possess certain features that are suited to the new environment
    • E.g. more aggression, better foraging, etc.
  • Diagram:
  • A: Study of the introduction of cane toads in Australia and another local example of an introduced alien species
  • Case study one: Cane toads (Bufo marinus)
    • Cane toad was introduced in Australia in 1935 by humans to control the spread of the sugar cane beetle that was damaging crops
    • Failed to limit the beetle population → beetles live at the tops of sugar canes where the toads could not reach
    • The cane toad has reproduced rapidly and is now classified as an invasive species that endangers native wildlife
    • It has a wide diet → depleted the prey population for native insectivores 
    • Secretes a toxic chemical from its skin that has poisoned native predators
    • Carries diseases that have been transmitted to native species of frogs and fish
    • The cane toad has spread across the northern fringes of Australia 
    • Now numbers in the millions
    • Proven difficult to eradicate as there are no natural predators in Australia to reduce its population size
  • Case study 2: Wild rabbits
    • European rabbits were introduced in Australia with the arrival of the First Fleet
    • Ostensibly for recreational hunting
    • Australian conditions promoted a population explosion
    • Mild winters allowed rabbits to breed the entire year
    • Fastest spread ever recorded for any mammal anywhere in the world
    • Rabbits have had a devastating effect on native Australian ecology
    • Killed native plant species by ringbarking 
      • Ringbarking = removing a strip of bark that prevents future growth beyond that point
    • Loss of native plants has left the topsoil exposed and vulnerable to extensive erosion from wind and rain
    • Various strategies have been employed to control rabbit populations with varying effect
    • ‘Rabbit-proof’ fences were built to try and contain rabbit populations
    • Methods of hunting and poisoning have been utilized 
      • Also efforts to destroy rabbit warrens (burrows)
    • Rabbit-borne diseases have been released with moderate success
      • E.g. myxomatosis virus
• Biological control
  • S: Evaluation of eradication programmes and biological control as measures to reduce impact of alien species.
  • Controlling the population of invasive species once they have become established is difficult and typically very expensive
    • Three main methods: physical, chemical, biological
  • Physical control
    • Involves removal or restriction by manual or mechanical measures
    • May include:
    • Installation of barriers and fences 
    • Removal of habitat by excavation or trimming
    • Population numbers may be reduced by hunting, trapping and culling
      • Although this is labor intensive
    • Physical methods to contain invasive species are not usually species specific and can also impede endemic wildlife 
  • Chemical control
    • Involves the use of chemical agents to limit population numbers and spread
    • Chemical agents = poisons and toxins 
    • Chemical agents may include:
    • Herbicides for plants
    • Pesticides for insects
    • Other compounds such as rat poison
    • Chemical agents may have moderate specificity, but can also detrimentally affect local wildlife + are costly
    • The effect may become more pronounced in high trophic levels due to biomagnification
  • Biological control
    • Involves using living organisms or viruses to control an invasive species
    • Biological control may eat the invasive species or cause it to become diseased
    • Biological agents mut be carefully assessed before release to ensure they do not become invasive themselves
    • Examples:
    • The Vedalia beetle feeds on citrus plant invertebrates
    • The Myxoma virus that affects rabbits
    • Biological control agents must be monitored for unintended side effects
    • E.g. development of immunity in invasive species
    • Biocontrol case study: The Vedalia Beetle (ladybug)
    • The cottony cushion scale is an invertebrate pest from Australia that was accidentally released in California
      • Spread and fed on citrus plants such as orange trees
      • Devastated the Californian citrus industry
    • The Vedalia beetle is a predatory insect from Australia that was introduced into California as a means of biological control
      • It worked to limit the numbers of the cottony cushion scale
      • Minimized the economic impact on the citrus industry
    • Diagram:
• Biomagnification
  • U: Pollutants become concentrated in the tissues of organisms at higher trophic levels by biomagnification
  • Biomagnification = the process in which chemical substances become more concentrated at each trophic level
    • Bioaccumulation = the build up of a chemical substance in the tissues of a single organism 
  • Biomagnification occurs because organisms at higher trophic levels must consume more biomasse to meet feeding requirements
    • Energy transformations are only ca. 10% efficient, so higher order consumers must eat more to meet energy demands
    • This means higher order consumers will experience increased contamination from a chemical substance
  • Diagram of effect:
  • S: Analysis of data illustrating the causes and consequences of biomagnification
  • Dichloro Diphenyl Trichloroethane (DDT) is an example of a chemical substance which is biomagnified
    • DDT = a chemical pesticide that is sprayed on crops to eliminate mosquito larvae and washed into waterways at low concentrations
    • Taken up by algae and passed on to primary consumers
    • DDT is fat soluble and selectively retained within the tissues of an organism instead of being excreted 
  • At each subsequent trophic level DDT is passed on through the algae, the concentration of DDT stored in the body increases
    • Increased trophic level = increased food uptake = increased DDT 
    • Very high levels of DDT were discovered in birds that preyed on fish
  • Birds exposed to high levels of DDT through feeding on fish that fed on algae were found to produced thinner shells as a consequence
    • This decreased survival rates of fledglings
  • Diagrams we may encounter for such data analysis
  • A: Discussion of the trade-off between control of the malarial parasite and DDT pollution
  • DDT was widely employed as a chemical pesticide in the 1940s and 1950s to control insect-borne diseases like malaria
    • Agricultural insecticide
    • Led to complete eradication of malaria in many high socioeconomic world regions
    • Less effective in low socioeconomic tropical regions where eradication programs could not be sustained
  • Eradication programs were curtailed by the World Health Organization (WHO) in 1969
    • For safety and environmental concerns
    • DDT can bioaccumulate to toxic levels and poses a significant threat to high trophic levels due to biomagnification
    • Current interventions for malaria now focus on non-spraying strategies
    • E.g. the use of bednets soaked in insecticides
  • Malaria vs. DDT
    • Arguments for DDT spraying:
    • DDT spraying is an affordable and effective means of killing mosquitos that carry disease
      • E.g. malaria, dengue fever, etc.
    • Where the use of DDT has been discontinued, the incidence of malaria and associated deaths have increased
    • Health costs associated with the treatment of malaria are reduced when DDT spraying is implemented 
    • Alternative strategies are not as cost-effective or successful 
    • Arguments against DDT spraying
    • It is associated with adverse health effects in humans
      • E.g. cancer, birth defects, reduced fertility, etc.
    • Persists in the environment for long periods of time
      • More than 15 years
    • DDT is biomagnified in higher order consumers which has adverse consequences on ecosystems
• Plastic pollution
  • U: Macroplastic and microplastic debris has accumulated in marine environments
  • Plastic = a type of synthetic polymer 
    • Found in certain types of clothes, bottles, bags, food wrappings, containers, etc.
    • Most plastics are not biodegradable → persist in the environment for many centuries
  • Macroplastic = large visible plastic debris
    • > 1 mm 
    • Macroplastic debris can be degraded and broken down into microplastic debris by UV radiation and the action of waves
  • Microplastic = smaller plastic debris
    • < 1 mm
  • Ocean currents will concentrate plastic debris in large oceanic convergence zones called gyres
  • Plastic debris in the ocean will leach chemical into the water + absorb toxic contaminants called persistent organic pollutants
    • Microplastics will absorb more persistent organic pollutants (POPs) due to their smaller size 
    • More surface area available
  • Both macro- and microplastic debris is ingested by marine animals, which mistake the debris for food
    • This leads to the bioaccumulation and biomagnification of POPs within marine animals
    • It may also damage the stomach of animals or cause them to stop feeding
    • By taking up space in the digestive tract
  • Diagram:
  • A: Case study of the impact of plastic debris on Laysan albatrosses and one other named example
  • Case Study 1: Laysan Albatross
    • Nests on islands found in the North Pacific gyre where large amounts of plastic debris is found
    • Feeds by skimming the ocean surface with their beak → this causes them to ingest large quantities of plastic too
    • Adults can regurgitate (throw up) the plastic they have swallowed, but chicks are unable to
    • Instead, it fills up their stomachs
    • The mortality rate in albatross chicks is very high
      • Estimated 40% die before fledgling
  • Case Study 2: Sea turtles
    • Will commonly mistake plastic bags for jellyfish
    • Jellyfish = one of their primary food sources
    • Ingestion of the plastic can be fatal
    • It can become lodged in the esophagus and cause future feeding problems
    • Plastic debris can also become wrapped around the turtle → restricting movement and developmental growth
    • It is estimated plastic pollution harms ca. 100 000 sea turtles and other marine animals each year
• EC: Cholorfluorocarbons 
  • Chlorofluorocarbons (CFCs) = chemicals widely used as refrigerants, propellants and solvents in the past
  • Contribute to ozone depletion in the upper atmosphere
    • Therefore their manufacture and use is being phased out
  • Ozone layer = stratospheric region composed of ozone (triatomic oxygen)
  • CFCs are broken down by UV radiation to release chloride ions that react with ozone 
  • The ions breaks the ozone down into oxygen
  • One chloride ions can destroy 100 000 ozone molecules 
  • Diagram of the process:
  • Ozone in the stratosphere absorbs UV radiation, however there is a limit to how much radiation ozone can absorb 
  • Regions where the ozone layer is thinner will experience higher terrestrial UV levels
    • Thinning caused by for example CFCs
  • UV light penetrates tissues and damages DNA → this causes gene mutations and cancer
  • Can also damage the ability of plants to carry out photosynthesis + kill phytoplankton → this reduces productivity
• EC: Earth spheres
  • The Earth is made up of four distinct and connected spheres
  • Lithosphere, hydrosphere, atmosphere, biosphere
  • 
  • Lithosphere = all the rocks, minerals and molten magma found on or in the Earth
  • Also called geosphere
  • Hydrosphere = all the water on Earth 
  • Liquid water such as oceans and rivers
  • Precipitation and vapor 
  • Atmosphere = the layer of gasses surrounding the Earth 
  • Divided into further sections 
  • E.g. stratosphere
  • Biosphere = all the living organisms on the planet
  • Including plants, animals, bacteria, etc.
  • As the four spheres are interconnected, human impact on one sphere will potentially affect other spheres
  • Examples:
    • The release of plastic pollution into the hydrosphere (oceans) will impact the biosphere (marine life)
    • The production and release of CFCs into the atmosphere will impact how much UV radiation the biosphere is subjected to

C4 Conservation of biodiversity

• Indicator species
  • U: An indicator species is an organism used to assess a specific environmental condition
  • Indicator species are sensitive to specific environmental conditions → limited range of tolerance
    • Reduction or growth of their population therefore indicates changes in the environment
    • Useful means of monitoring change
  • Examples of indicator species and their environmental conditions
    • Lichen and mosses are susceptible to air-borne pollutants dissolved in water
    • E.g. sulfur dioxide
    • Tubifex worms are sensitive to concentrations of heavy metals
    • Mayfly larva and certain aquatic invertebrates are sensitive to dissolved oxygen levels in water
  • Diagram:
  • U: Relative numbers of an indicator species can be used to calculate the value of a biotic index
  • Biotic indices compare the relative frequency of indicator species 
    • + Provide an overall assessment of environmental health
  • Calculating a biotic index involves multiplying the population size of each indicator species by its pollution tolerance rating
    • 
  • The following conclusions can be drawn from a biotic index:
    • A high biotic index = the presence of many pollution-sensitive organisms
    • Denotes an unpolluted environment
    • A low biotic index = the absence of pollution-sensitive organisms + abundance of pollution-tolerant organisms
    • Indicates a polluted environment
    • A change in the biotic index over time marks a change in the environmental conditions within a given ecosystem
  • Pollution tolerance rating
    • 
  • Environmental pollution levels
    • 
• Biodiversity
  • U: Richness and evenness are components of biodiversity
  • Biodiversity = the variety and variability of all living organisms within a given ecological area
    • Can be used to refer to the number of species, their genetic diversity or habitat variety
    • Habitat variety = ecological variations
  • 2 main components contribute to biodiversity
    • Species richness → the number of different species present in an area
    • More species = greater richness
    • Species evenness → the relative abundance of the different species in an area
    • Similar abundance = more evenness
    • Richness vs. evenness
  • S: Analysis of the biodiversity of two local communities using Simpson’s reciprocal index of diversity
  • Simpson’s reciprocal index can be used to measure the relative biodiversity of a given community
    • It takes into account both the number of species present (richness) and the number of individuals per species (evenness) 
    • A higher index value is indicative of a greater degree of biodiversity within the community
  • 
  • Simpson’s reciprocal index can be used to compare communities to identify intrinsic values
    • Intrinsic value = something we value for itself, not its consequences
    • A high index value = a stable site with many different niches and low competition
    • High richness and evenness
    • A low index value = a site with few potential niches where only a few species dominate
    • Low richness and evenness 
    • The index value may change in response to ecological disturbance
    • E.g. human intervention, natural disasters, etc.
• Biogeographic factors
  • U: Biogeographic factors affect species diversity
  • Biodiversity within a given ecosystem will be affected by a number of biogeographic factors
    • Larger habitats tend to promote biodiversity better than smaller ones
    • More available niches = less competition
    • Ecology at the edges of ecosystem is different from central areas
    • E.g. more sunlight, more wind, etc.
    • This is known as the edge effect, whereby species distribution is influenced by divergent environmental conditions
    • Edges tend to have greater biodiversity as different habitats with different abiotic factors exist in close physical proximity
    • However, edges tend to have more competition than central regions → may restrict survival prospects of certain species
    • Habitat corridors between parts of a fragmented habitat can connect disparate regions to improve genetic diversity
  • These principles of biogeographic factors are routinely applied when setting aside land as a nature reserve to improve the conservation of biodiversity
    • 
  • A: Analysis of the impact of biogeographic factors on diversity limited to island size and edge effect
  • Island size
    • The biodiversity of an island is typically proportionate to island size
    • Larger island = greater biodiversity
      • Larger islands support a greater range of habitats
      • Hence more available niches for species to occupy → more survival + diversity
      • Larger islands can sustain higher population numbers for each species
      • Increases species evenness
      • Larger islands have greater productivity at each trophic level
      • Leads to longer + more stable food chains
    • Smaller island = less biodiversity
    • Diagram depicting the relationship between island size and biodiversity
  • Edge effect
    • The diversity of species within a given environment changes with proximity to the ecosystem’s boundaries 
    • Biodiversity may be greater at the border between two ecosystems as different abiotic factors favor certain species
    • However, certain species may not be able thrive under these conditions
    • Instead must occupy more central regions
    • The effect of edges on biodiversity will be greatly influenced by the particular conditions caused by the ecological disturbance
    • Diagram:
• Conservation
  • U: In situ conservation may require active management of nature reserves or national parks
  • Conservation = the careful preservation, protection and maintenance of natural resources
    • Such as trees, water, wildlife, etc.
    • Can be either in situ or ex situ
    • On site or off site
  • In situ conservation is the preservation of plant and animal species within their natural habitat
    • Typically involves the designation of protected areas of land as either nature reserves or national parks
  • These areas may require active management to ensure that an appropriate and sustainable ecological balance is maintained
    • Ecological monitoring of a species may be required to ensure viable population levels are maintained
    • Interventions may be required to prevent habitat degradation or competition from invasive species 
    • Legislation may be necessary to ensure adequate funding for policing and education
  • In situ conservation offers several advantages when protecting endangered species from extinction
    • It allows species to live in the environment to which they are adapted 
    • + to occupy their natural position in the food chain
    • It maintains the animal’s normal behavior
    • Offspring usually acquire skills from parents and peers around them
    • Retaining the natural habitat prevents its eventual loss + ensures it remains available for other endangered species
    • Such areas provide a place to return animals from breeding programs as they provide realistic conditions for reintegration
    • Reserves in different areas can share information and provide a place for scientific study and developing public awareness
  • U: Ex situ conservation is the preservation of species outside their natural habitats
  • Ex situ conservation involves the preservation of plant and animal species outside their natural habitats
    • May typically be required for critically endangered species when urgent intervention is necessary
  • There are several advantages associated with ex situ conservation 
    • It allows for greater control of essential conditions
    • E.g. climate control, dietary intake, veterinary care, etc.
    • It can improve the chances of successful breeding by utilizing artificial methods
    • E.g. embryo transfer, IVF, etc.
  • Ex situ conservation is also associated with several disadvantages
    • They do not prevent the potential destruction of their natural habitats
    • Species raised in captivity are less likely to be successfully reintroduced into the wild
    • Loss of autonomous survival
    • Increases inbreeding by restricting the gene pool → restricts the evolution of the species
  • Some examples of ex situ conservation measures employed around the world:
    • Captive breeding → animals are raised and bred in containment to ensure survival prospects
    • E.g. zoos
    • Botanical gardens → areas devoted to the collection, cultivation and display of a wide variety of plant species
    • Seed banks → secure sites that store and catalog seeds in order to preserve plant genetic diversity
  • A: Case study of the captive breeding and reintroduction of an endangered animal species
  • Case Study 1: Indian rhinoceros 
    • An endangered species with only ca. 3500 rhinoceros living in the wild
    • This number was as low as 2000 in the early 1990s → increased due to successful captive breeding programs
    • In addition to habitat loss, the Indian rhinoceros is threatened by poachers 
    • Their horn is considered potent in some cultures
    • It is listed as vulnerable on the IUCN red list + the majority of the species is situated in Indian protected areas (reserves)
  • Case Study 2: Mountain Chicken Frog
    • A species of frog native to the Carribean islands of Dominica and Montserrat
    • The population of this frog has declined i81% in the last 10 years 
    • Due to the fungal disease chytridiomycosis
    • Also threatened by human consumption → local delicacy said to taste like chicken
    • Considered critically endangered with fewer than 8000 individuals existing in the wild
    • The frog has been artificially bred in laboratories in England prior to being reintroduced into the wild
• EC: Endangered species
  • Endangered species = categorized by the International Union for Conservation of Nature (IUCN)  as likely to become extinct
  • Conservation status = likelihood of becoming extinct
  • Currently 3000 endangered species according to IUCN
  • Factors for determining a species’ conservation status
  • Rate of decline
  • Population size
  • Area of geographic distribution 
  • Degree of population fragmentation
  • IUCN has a red list which classifies species into nine groups
  • Extinct (EX)
    • No surviving individuals
    • E.g. tasmanian tiger
  • Extinct in Wild (EW)
    • Captive individuals survive, but there is no wild population
    • E.g. barbary lion
  • Critically endangered (CR)
    • Faces an extremely high risk of extinction in the near future
    • E.g. red wolf
  • Endangered (EN)
    • Faces a high risk of extinction in the near future
    • E.g. snow leopard
  • Vulnerable (VU)
    • Faces a high risk of endangerment in the medium term
    • E.g. Indian rhinoceros
  • Near Threatened (NT)
    • May be considered threatened in the near future
    • E.g. tiger shark
  • Least Concern (LC)
    • No immediate threat to species survival
    • E.g. giraffe
  • All other organisms may be listed as Data Deficient (DD) or Not Evaluated (NE)
• EC: Extinction
  • Extinction = the complete cessation of a species or higher taxon level, reducing biodiversity
  • Can occur gradually as one population of organisms evolves into something else
  • Phyletic extinction
  • Can be sudden without any identifiable descendents → cease to exits
  • Abrupt extinction
  • Can be very difficult to determine the moment of extinction → most categorizations are usually done retrospectively
  • Occasionally species thought to be extinct can be rediscovered after a period of time
    • E.g. lazarus taxa
  • 99% of all species that ever lived on Earth are considered to be extinct
  • Estimated to amount over 5 billion species
  • Natural catastrophes may cause mass extinction events
    • Large scale loss of species in relatively short period
  • Case Study: Tasmanian Tiger
  • Thylacinus cynocephalus
  • Became extinct after the arrival of European settlers to Australia
  • Tasmanian tigers would feed on introduced sheep → therefore hunted and poached 
  • The loss of habitat due to human development + lack of successful breeding programs = population numbers dwindling
    • Aboriginal rock paintings suggest the Tasmanian tiger once lived on the mainland, but died out from predation and/or competition
  • Last Tasmanian tiger died in captivity in 1936
    • Declared extinct by international standards in 1986

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