week 2 Flashcards
(26 cards)
what is alpha diversity
number of species in a certain area/ecosystem
what is beta diversity
- variation in species composition across/between different areas/habitats
- B = (S1 - c) + (S2 - c)
- S1: total number of species in first environment
- S2: total number of species in second environment
- C: total number of species appearing in both environments
what is gamma diversity
- number of taxa across areas/ecosystems
- can be global in extent
disparity
range of morphologies (shapes) among species
describe sampling
- it is impossible to get information about all individuals from a population - we therefore take a sample to get an estimate of information about the population
- these estimates deviate from the true value - this is known as bias
- the larger the sample, the smaller the sampling bias
types of fossil record bias
- taphonomic
- geological
- anthropogenic
describe taphonomic biases
- material
- size
- body part
- abundance/rarity
- taphonomic pathways
describe material bias
- hard body parts have a high likelihood of being fossilised.
- considering about 95% of organisms in a shallow marine environment are entirely soft bodied
- so we are losing an enormous amount of info about soft-bodied organisms
describe body size bias
- bones of large dinosaurs preserve very well - they’re big so can’t get moved about a lot and are less likely to get easily broken.
- bones of small dinosaurs are more fragile and likely to get broken
- we may know a lot more about large dinosaurs than small dinosaurs
describe geological biases
- rock area across space and time
- lithology
- palaeoenvironment
describe the bias of rock area across space
- species-area effect - the greater the habitable area, the more species there are
- therefore, variation in geographic spread of fossil localities also biases diversity reconstructions
- diversity changes could occur simultaneously across the globe but there could also be different patterns in each region, which are masked by the global pattern.
describe the bias of rock area through time and space
- plate movements mean that certain latitudes are preserved more commonly from different time intervals
- today, different numbers of species found at pole compared to equator (latitudinal biodiversity gradient)
- generally, there is an increased number of species at the tropics compared to at high latitudes
describe lithology bias
- different substrates impact preservation potential for different organisms
- organisms may also exhibit preferences for certain environments and lithologies will further impact preservation patterns
describe palaeoenvironment bias
- different environments have different preservation potential
- 84% of modern nonmarine land area lies outside of a sedimentary basin, in uplifted and eroding areas
- within sedimentary basins, typically low elevations recorded
describe anthropogenic biases
- disproportionate sampling.study of ‘key’ time intervals or organisms e.g. intervals before/after an extinction event, dinosaurs
- historical/geographic biases e.g. varying research intensity around the globe due to political/economic/colonial past
- analysis artefacts (taxonomic e.g. synonyms, misidentification or analysis dependent e.g. length of time intervals)
describe historical biases
- colonial history
- positively benefitting from colonialism has the largest impact on palaeontological research output
summarise taphonomic, geological and anthropogenic biases
taphonomic - intrinsic factors that impact preservation e.g. materials, size
geological - extrinsic factors that impact preservation e.g. area of rock available
anthropogenic - human-influenced factors that impact how we sample fossils
describe the great ordovician biodiversification ‘event’
thought to have been driven by a combination of biotic and abiotic factors including:
- heightened atmospheric oxygen levels
- increased nutrient supply
- diversification of shelly faunas
what are jawless fish
- fish that do not have paired upper and lower jaws
how did jaws form
it is thought that jaws evolved from gill arches of fish
non-extinct jawless fish
- hagfish and lampreys
- lots of teeth but they are not homologous to ours
what are conodonts
- the earliest vertebrates with hard tissues
- lived from the late Cambrian to end-Triassic
- important role in our understanding of vertebrate origins
what was the late Ordovician Mass Extinction
- 445 Ma
- thought to relate to a period of extreme glaciation
where did teeth originate from
- dermal scales which have dentine and enamel in them
- they share the same homologous structures
