Lecture 8 - biodviersity and palaeodiversity Flashcards
definition of biodiversity
biodiversity is the variety of life, in all its manifestations, it encompasses all forms, levles and combinations of natural variation
what are the two types of taxic approach when measuring extant organisms?
1) examine rate of discovery curves
2) extrapolate from intensive local sampling
describe the discovery curve of new mammal species
curve has plateaued out - is now very rare to discover new mammal species - can confidently say we know about 95% of extant mammal species
describe the discovery curve of new insect species
on average an excess of 7000 new species of insect are described each year - with them constantly increasing it is impossible to know the biodiversity of them in the living world let alone fossils
give an example of extrapolation from local sampling
there is 163 beetles exclusive to an individual tropical tree, times that by 50,000 species of tropical tree = 8,150,000 canopy dwelling tropical beetles
what do the estimates of modern biodiversity range between?
2-3 million to 30-100 million
what is the most used way to measure diversity
simply count taxa/number of individuals and record richness, density, evenness etc
what are the 3 problems with identifying biodiversity of fossil organisms?
1) fossil record is incomplete and bias
2) problem with recognition in the fossil record
3) are linnean hierarchies the same for different groups of organisms i.e. are we splitting the groups correctly KPCOFGS
what are 5 problems with recognition in the fossil record?
- species - are we recognising true species?
- ontogenetic stages - as species grow from juveniles to adults they look very different
- sexual dimorphism
- diseased individuals
- ecophenotypes - different ecologies can have different morphologies
can over-inflate numbers of species because we are not understanding
how do you we measure fossil biodiversity?
at prescribed intervals of time measure: -
1) morphological diversity (disparity) (new line of work - some taxa have very similar features while others are more spread out with different features)
2) number of taxa (species, genera, families etc) - best to work with groups well known in the extant biota, groups well represented in the fossil record and use higher taxa as proxies
- overall the taxic approach is most used
what is the estimated percentage of extant species to those that have ever lived
- 2-5% - based on average species durations and various bifurcating models of evolution - this suggests that 25-75 million past species have existed
what are the 3 models of theoretical consideration of biodiversity increase?
1) linear model = additive
2) exponential curve
3) logistic curve
( look in book at graphs)
does theory mirror reality?
- compare the models to past accounts and see if any of them make sense with mass extinctions added in
what does data show about mass extinctions effect on the biodiversity of plants and marine invertebrates?
shows mass extinctions has little effect on the plants - much more obvious when you look at the biodiversity pattern of marine invertebrates over time
- plants dont tend to be wiped out
when did plants increase and diversify?
when there is a period of innovation or a change in reproductive strategy e.g. moving from sea to land and they became better at reproducing on land
describe the pattern of non-marine tetrapods compared to marine invertebrates
the non-marine tetrapods were massively affected by mass extinctions, then there is a huge diversification driven by birds and mammals
- genera have longer lives in the ocean than on land - evolution works differently
describe the plateaus in the expansion of marine inverts?
one at the end of the cambrian
expansion in the ordovician
plateau after the mass extinction
- predicted the next plateau will be in 100 million yrs
describe the expansions in diversity of marine inverts
- initial diversification in biota at beginning of cambrian after explosion - most die out very quickly with most extinct by end permian
- great ordovician diversification event - things start to borrow down more deeply into the marine substrate and a whole new complexity of ecology occurs in the oceans
- end permian - life nearly dies on the planet
- KT doesn’t rock the diversification much
most patterns are governed largely by mass extinctions - end permian has the biggest effect on diversification of marine inverts
why is life 5-6 times more diverse on land than in the oceans but why doesnt the fossil record demonstrate this?
- largely due to insects and soil microbes e.g. plants
- however when we look at the fossil record 95% of fossils are marine
- most rock is marine - less likely to get deposits on land
what is the ‘pull of the recent’?
More of the discoverable rock is recent because rock can easily be buried or destroyed so most exposed rock is recent - i.e. mostly recent fossils and therefore not a fair representation
what are the 2 models for explanation of patterns of diversity?
1) equilibrium models (biodiversity ceiling due to diversity damping factors or limiting equilibrium factors e.g. competitive exclusion, carrying capacity etc)
2) expansion models ( no biodiversity ceiling)
have to go back in time to understand these patterns, cant work out by just looking at the modern world
describe fatovskys (2004) paper on dinosaur diversity
- did genera counts and broke them down into where the animals were found and the time stages they were around in
- very basic study
- model shows increasing diversity up until the KT boundry
- exponential increase based on new innovation of behavioural strategies
describe wang and dodson (2006) paper on dinosaur diversity
- looked at the availability of rock
- based on counts
- suggested 70% of dinosaur genera is still unknown
- massively biased by rock volume
- concluded that end of cretaceous decline is not real
describe lloyd et al paper on dinosaur diversity
- cladistic approach
- worked out ghost ranges of dinosaurs
- counted fossils that werent found yet
- concluded pattern was largely due to sampling bias and that diversity slows down with equal rates model
- decline at end of Cretaceous
- dinosaurs appear, diversify massively, fill ecospace then gradually decline
describe barret (2010) paper on dinosaur diversity
- cladistic approach
- looked at rock record in alot of detail
- limited themselves by only looking at 3 clades
- compared diversity to the amount of available rock for each period of time
- suggested huge rock megabias
- very difficult to interpret but did think there was a marked decline at the end cretaceous
