Week 1 Flashcards
What is natural selection?
The process whereby certain genetically inherited characteristics increase the chances of their carriers surviving and reproducing in a particular environment. These individuals will pass on their beneficial characteristics to the next generation
What does selection lead to?
Selection leads to the accumulation of favoured variants which over a long period produce new life forms, the origin of species.
When we study evolution which two interlinked areas are we concerned with?
pattern and process
What is pattern?
Is what we see in the fossil record, in DNA sequences or other data
What is process?
From pattern we can make inferences about the process of evolution
Where are fossils most likely to occur?
Sedimentary rock in seas rivers lakes or after floods
What are the 2 fossilisation processes?
Permineralisation
Natural cast process
Describe permineralisation
Organic material in the bones decays and is replaced by minerals from water percolating through the sedimentary rocks.
Describe the natural cast process
The bones dissolve to leave a hollow mould which may be filled later with minerals to form a solid replica of the bone
What is bad about the fossil record?
It is incomplete.
It is a chance event and some animals live in places that are less conductive to fossilisation
Species with small population sizes will be poorly represented
What are the 2 types of dating for fossils and explain them.
Absolute dating - the item itself is dated
Relative dating - strata above and below are dated and the item is expressed relative to these
What are the 2 modes of evolution?
Punctuated and gradualism
Punctuated is where there are long periods of stasis and then rapid change.
Gradualism neo darwinism is where there is gradual change
What is macroevolution?
Evolution of higher taxa.
What are the 4 major environmental drivers of evolution?
Bolide impact
climate change
vulcanism
continental movement
What are the 4 consequences of the major drivers of evolution?
Large scale migrations
Speciation
Mass extinction events
Adaptive radiation
what is the order of the 11 time periods?
COSDCPTJKTQ Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Tertiary Quarternary
What are the 5 mass extinctions?
Ordovician Devonian Permian Triassic KT boundary
What are the two mass extinctions that are particularly important from the point of view of mammal evolution and why?
End permian - mammal like reptiles are superseded by the dinosaurs. A few mammal-like reptiles remained and evolved into true mammals.
End cretaceous - see the rise of the mammals following the extinction of the dinosaurs
What more recently has influenced mammal evolution with particular implications for hominids?
cycles of ice ages and glaciation
Changes in the _____ ______ have had major influences on the history of life on earth. These changes acting via ______ ______ have shaped the evolution of life on earth by mechanisms which involve ______, ____ ____ or both.
The mass extinctions at the end of the _____ paved the way for the radiation of mammals
physical environment natural selection gradualism punctuated equilibrium cretaceous
what are the 5 main characteristics of mammals?
mammary glands characteristic teeth (heterodont dentition) Single lower jawbone Three bones in the middle ear Possess hair, sweat to cool, endotherms
When did the major adaptive radiation of mammals occur?
began after the KT extinction of dinosaurs
Late Proterozoic 650mya
southern polar region frozen
not a great deal of land mass
no complex life
Late cambrian 514mya
Explosion of multicellular life
Trilobites common
first chordate
