What are the three types of symbiotic relationships?
- parasitic (+/-)
- commenalistic (+/NA)
- mutualistic (+/+)
NA = not affected
What are the two types of symbiosis?
- obligate - one or both species depend on the other for survival
- facultative - optional, species can survive without each other
What are some examples of competiton?
- food
- mates
- resources (sunlight, water, etc.)
- space
What are the two types of competition?
- interspecific - different species
- intraspecific - same species, often results in a fight to the death
What is an ecological niche?
the role an organism plays in a community
What is stratification?
The vertical distribution of different species occupying different levels in an ecosystem
What is the law of tolerance?
- for each abiotic factor, an organism has a range of tolerance for which it can survive
- when abiotic factors get more extreme, the niche availability becomes more marginalised
What is zonation?
A gradual change in the distribution of species across a habitat
What is the difference between a fundamental and realised niche?
- fundamental niche is the full range of conditions and resources in which a species could survive and reproduce
- realized niche is the actual conditions and resources in which a species exists due to biotic interactions
What is the difference between abundance and distribution?
- abundance - number of individuals of a species in an area
- distribution - where species is found
What are the three types of distribution?
- clumped - in groups
- random
- regular - evenly spread
What are the advantages of clumping?
- prevent dessication
- maintain heat
- mutual defense
- hunting in packs
- swarming - e.g. for mating
What are the advantages of regular distribution?
- separates small groups of individuals
- keeping & defending territories ensures adequate food, resting sites, and protection of young
- limits population density
What are some ways that regular distribution can occur?
- through competiton/aggression - keeps organisms in territories they defend
- plants - may be due to shading or competition for food/water
What evidence does Aboriginal rock art provide for past ecoystems?
- evidence of megafauna & other extinct species
- from this we can infer changes in vegetation/climate
How is aboriginal rock painting dated?
Charcoal mud wasp nests can be used for carbon dating
What evidence do rock stuctures and formations provide for past ecosystems?
- banded iron formation - layers of iron rich and iron poor rock
- red stripes are oxidised iron - oxygen rich environment
What evidence does palaentology provide for past ecosystems?
- fossils
- stromatolites - mounds of photosyntheisising bacteria and sediment
- cynobacteria increased oxygen in atmosphere
- led to ozone and blocking of UV rays, allowing land-based oxygen-breathing organisms to develop
What evidence does ice-core drilling provide for past ecosystems?
- snowflakes crystallising around atmospheric particles - volcanic ash changes climate, pollen shows vegetation, greenhouse gases
- oxygen thermometer - less heavy oxygen isotopes=colder climate
- carbon isotopes - fossil fuel emmisions reduce carbon-14 in atmosphere
- Gas chromatography and mass spectrometry - analyses gases in air bubbles, carbon dioxide and methane, higher levels of carbon dioxide and methane = warmer air temperature
- thickness of annual layers - precipitation
How is ice-core drilling dated?
- radiometric dating
- Steno’s law of superposition
What are the theories for what caused the extinction of megafauna in Australia?
- drier climate due to Laschamp excursion
- dried up water - animals would get stuck in mud and die or die from dehydration
- smaller animals that could travel between water sources and not sink into mud survived
- drier climate reduced vegetation available
What is a Laschamp Excursion?
- Earth’s magnetic poles switch place
- last one was around 42,000 years ago, same time as when megafauna went extinct
- magnetic field was weakened & likely destroyed ozone layer - lots of UV rays entered atmosphere
- increase in clouds cooled & dried climate
What evidence is there that dates the last Laschamp excurison?
- rings of Kauri tree
- enrichment of radiocarbon around 42,000 years ago
- indicates more UV rays
What evidence is there that megafauna existed during a time where most of Australia was a rainforest?
- Welsby lagoon sediment
- sediment that is older is wetter and has more rainforest plant material
- in this layer there is also fungi from Megafauna dung
