Patterns of Evolution Flashcards
What is the branching pattern of descent?
Speciation events or splits from a ‘lineage’ = MACROEVOLUTION
Changes within a species or within a ‘lineage’ = MICROEVOLUTION
What are the problems with the fossil record – a problem for the Modern Synthesis? Name two theories
In the fossil record new species appear suddenly but this could be due to;
*There being major gaps in the fossil record so gradual transitions are absent (Phyletic gradualism)
*Evolutionary changes happen suddenly in short bursts (Punctuated equilibrium)
What is the explanation for punctuated equilibrium?
Allopatric speciation
-Fossil record may not show speciation events if they occured in a small population
-Descendent species evolve in a different place from ancestors
and then they could have re-invaded and out-competed ancestors or are ecologically different from ancestor.
-Evolutionary changes happen in short bursts away from the main population, these short bursts, rather than prolonged transitions, are missing from the fossil record
Is Punctuated Equilibrium compatible with the Modern Synthesis?
Between speciation events there is a slow rate of evolution: ‘stasis’
Most of the time natural selection is stabilising
Evolution only occurs during speciation events
Evolution takes place in rapid ‘bursts’
Still compatible with the Modern Synthesis – New adaptations still result from a ‘gradual’ accumulation of changes – they just happen over a very short period of time
What are the different meanings for ‘Gradualism’
Adaptation – an accumulation of new characters; Darwin’s meaning and compatible with punctuated equilibrium
Pattern of evolution – means evolution has a constant rate; not Darwin’s meaning and not congruent with punctuated equilibrium
What is Adaptive radiation
It is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic interactions or opens new environmental niches.
What is Convergent evolution?
Convergent evolution occurs when species occupy similar ecological niches and adapt in similar ways in response to similar selective pressures but did not derive from common ancestor. Traits that arise through convergent evolution are referred to as ‘analogous structures’.
Explain co-evolution and give an example
Species don’t evolve in isolation from each other
Other species form part of the environment they are adapted for.
Co-evolution happens when two or more species directly influence each other’s evolution = exert selection pressure on each other
Insects and plants – may explain adaptive radiation in these two groups
What are co-adaptations?
Co-evolving species change together and speciate together
‘Mutualism’
What does the Neo-Darwinian theory of evolution explain?
summary
gradual change with time even though fossil record suggests sudden changes which could be due to rapid evolutionary events missed by the fossil record, rather than major gaps in the fossil record
Although similar structures can evolve in different species, evolution is not directed towards a ‘goal’
