Post on 27-Jan-2017
OriGin And Exintiction In PHANEROZOIC EON
By: VARUN DURGE Roll No:33
Outline I. Geological time scaleII. Jack SepkoskiIII.Rates of origination and extinctionIV.Generalist species and specialist
speciesV. Imp terms : Degree of ecological
specialization Population dynamics Geographic range
Geological Time Scale
BIG BANG
HADEAN ARCHEON PROTEROZOIC PHANEROZOIC
PALEOZOIC MESOZOIC CENOZOIC
CAMBRIAN
ORDOVICIAN
TRIASSIC
JURASSIC
CRETACEOUS
10-20 billion
Jack sepkoskicompiled
dataon the
stratigraphic ranges
What did he exactly do? He studied over 4000marine
skeletonized families
.20000Genera
So,what did he conclude?
Rates of Origination And Extinction
TRIASSICORIGINATION
RESULTS
DIVERSITY
MESOZOIC&
CENOZOIC
✘ The rates of origination was highest in recorded animal evolution in
CAMBRIAN ORDOVICIAN
Generalist species Specialist species
Can survive on wide variety of resources. Can tolerate harsh conditions of environments. Most of them are Omnivores
Can thrive only in narrow range of environment. which subsists almost entirely on eucalyptus leaves. Mostly these are Herbivores
1)Degree of ecological specialization: Ecologically specialized species are likely to be more vulnerable than generalized species to changes in their environment. They may also be more likely to speciate because of their more patchy distribution, and newly formed species may be more likely to persist by specializing on different resources and thus avoiding competition with other species.
A)Population Dynamics:Species with low or fluctuating population sizes are especially susceptible to extinction. Some authors believe that speciation is also enhanced by small or fluctuating population sizes, although this hypothesis is controversial..
3)Geographic Range:1)Species with broad geographic ranges tend to have a lower risk of extinction because they are not extinguished by local enviromental changes. They also have lower rates of speciation,probably because they have a high capacity for dispersal.
Mike Foote
Prone to extinction
Fluctuate great in diversity
Stabilize diversity
Fluctuate great in diversity
• 107 stages of Phanerozoic • Origination increases diversity and Extinction decreases
diversity BUT
• In Paleozoic diversity increases when extinction had a stronger effect than origination
• In Cenozoic and Mesozoic Origination had a stronger effect than extinction
`THANK YOU!