Adaptive Radiation and Extinction Flashcards
what are the two views on the Cambrian Explosion
‘Cone of increasing diversity’
‘Decimation and diversification’
what does the Cambrian explosion show?
adaptive radiation (increasing diversity)
extinction (loss of diversity)
diversity is determined by the rate if each process
adaptive radiation definition
a small number of ancestral species increases to give a large number
where can adaptive radiation be observed?
a variety of taxonomic scales
examples of adaptive radiation
Darwin’s finches, Galapagos!!!
fruit flies, Hawaii
lemurs, madagascar
causes of adaptive radiation
adaptive breakthrough
colonisation of a new area free of competitors
extinction of competition
replacement of competitors
Evidence for extinction
direct observation
fossil records
‘small scale extinction’ meaning
local and occur over a short period of time
‘mass extinction’ meaning
global or continental occur over long stretches of time
Causes of small scale extinctions
biotic (parasites, pathogens, competitors)
physical – change in climate
Developmental constraints prevent adaptations to change
Extinction happens because environmental changes happen faster than the rate of adaptation
what factors affect the chance of extinction?
population size- small more likely to go extinct
longevity- short lifespan more susceptible
rate of increase- few young and reproduce irregularly more susceptible
stability of environment
% of species lost in the ‘End Permian’ extinction
80-96%
% of species lost in the the K-T extinction
60-75%
what groups were affected in the K-T Extinction
all
where is the best evidence from the K-T Extinction given from?
given by microfossils- Foraminifera
what went extinct in the K-T Extinction?
dinosaurs and ammonites
cause of K-T Mass extinction?
large asteroid collided with earth
(high levels of rare metals)
Asteroid impact of K-T Extinction
global dust cloud blocked sunlight for several years
- Global warming
* Acid rain
* Vulcanisation
* Global fires
Four pieces of evidence support the asteroid-impact theory
Iridium anomaly
Chicxulub crater
Rock structures
Simultaneous extinction (Amonites, Bivalves, Brachiopods, Vertebrates (dinosaurs))
other causes of mass extinction
changes in sea level/ climate
changes in shape of continents
high levels of volcanic activity
NOT MUTUALLY EXCLUSIVE
Anthropogenic threats to bio- diversity: The ‘sixth extinction’?
Overexploitation
habitat destruction (e.g. deforestation)
disruption of earth processes (e.g climate change)
introduction of alien species
accumulation of toxins
non-density dependence of human ecology
passive replacement meaning
gene pool of a species/population changes as a result of natural selection in favour of the genes that increase survival and reproduction.
