The Theory of Evolution

Mutations  All species show genetic variation  The original source of genetic variations are mutations.  Mutations create new genes that may be neutral, harmful or beneficial  Beneficial mutations can change an individual’s phenotype (outward appearance) that can give them an advantage.  Example: Colorado potato beetle evolved to be resistant to insecticides.  All species show genetic variation  The original source of genetic variations are mutations.  Mutations create new genes that may be neutral, harmful or beneficial  Beneficial mutations can change an individual’s phenotype (outward appearance) that can give them an advantage.  Example: Colorado potato beetle evolved to be resistant to insecticides.

Selective Breeding  Artificial Selection: directed breeding in which individuals that exhibit a particular trait are chosen as parents of the next generation.  Used commonly to produce new plants and animals  Example: all dogs have descended from wolves.  Example: wild sea cabbage has produced different vegetables such as brussel sprouts, cabbage, cauliflower, broccoli, kale.  Very slow process where you pick the traits you want and breed them generations after generations.  Artificial Selection: directed breeding in which individuals that exhibit a particular trait are chosen as parents of the next generation.  Used commonly to produce new plants and animals  Example: all dogs have descended from wolves.  Example: wild sea cabbage has produced different vegetables such as brussel sprouts, cabbage, cauliflower, broccoli, kale.  Very slow process where you pick the traits you want and breed them generations after generations.

Artificial Selection and Mutations  Artificial selection methods can reduce genetic diversity within a population.  Breeders favour only selected traits, so the genes become more alike.  Low diversity means it could be more vulnerable to disease.  Example: some dogs are prone to hip dysplasia or cancer because the genes are inherited along with the favoured trait genes.  Artificial selection methods can reduce genetic diversity within a population.  Breeders favour only selected traits, so the genes become more alike.  Low diversity means it could be more vulnerable to disease.  Example: some dogs are prone to hip dysplasia or cancer because the genes are inherited along with the favoured trait genes.

Evolution of an Idea  Back in 380 BCE, most people believed that all living things on Earth had been created in their present form and were immutable (species cannot change) based mainly on religious and philosophical beliefs)  A French scientist Buffon ( ) studied anatomy closely.  He was puzzled by anatomical features that seemed to serve no purpose.  Example: pigs have extra toes that don’t reach the ground  He believed that species were created in perfect form but DID change over time.  Carl Linnaeus and Erasmus Darwin (around the same time) also proposed that life changed over time. And E.Darwin suggested that all life came from a single original source.  Back in 380 BCE, most people believed that all living things on Earth had been created in their present form and were immutable (species cannot change) based mainly on religious and philosophical beliefs)  A French scientist Buffon ( ) studied anatomy closely.  He was puzzled by anatomical features that seemed to serve no purpose.  Example: pigs have extra toes that don’t reach the ground  He believed that species were created in perfect form but DID change over time.  Carl Linnaeus and Erasmus Darwin (around the same time) also proposed that life changed over time. And E.Darwin suggested that all life came from a single original source.

 Lamarck ( ) proposed that evolutionary change resulted from two distinct principles:  Use and disuse: structures that organisms used, became longer and stronger; structures they did not use became smaller and weaker  The inheritance of acquired characteristics: individual can pass on their traits that they have acquired during their lives to their offspring. Example: giraffe  Today we know that this theory is flawed because these things do not change in your DNA.  We can use Lamarck’s discoveries though: all species evolve over time, species can adapt to their environment, and changes are passed on from generation to generation.  Lamarck ( ) proposed that evolutionary change resulted from two distinct principles:  Use and disuse: structures that organisms used, became longer and stronger; structures they did not use became smaller and weaker  The inheritance of acquired characteristics: individual can pass on their traits that they have acquired during their lives to their offspring. Example: giraffe  Today we know that this theory is flawed because these things do not change in your DNA.  We can use Lamarck’s discoveries though: all species evolve over time, species can adapt to their environment, and changes are passed on from generation to generation.

Patterns of Change  The first real evidence scientists found were that fossils demonstrated change in species.  Most fossils are hard impressions in solid rock of once living organisms.  Fossils are formed when buried organisms are gradually replaced by mineral deposits  usually the body will decompose, but if it sinks to the bottom of a body of water and is quickly buried by sediments, it can prevent decomposition and compress the body leading to mineralization.  The first real evidence scientists found were that fossils demonstrated change in species.  Most fossils are hard impressions in solid rock of once living organisms.  Fossils are formed when buried organisms are gradually replaced by mineral deposits  usually the body will decompose, but if it sinks to the bottom of a body of water and is quickly buried by sediments, it can prevent decomposition and compress the body leading to mineralization.

 Necessary conditions for fossils are rare  Oxygen present: body decomposes too quickly to fossilize  Usually just aquatic organisms  Dinosaur fossils are well known but rare in comparison to clams, snails and other marine organisms.  Fossils can be formed from footprints, burrows, fecal remains.  Can be trapped in amber (fossilized tree sap) and preserved  Necessary conditions for fossils are rare  Oxygen present: body decomposes too quickly to fossilize  Usually just aquatic organisms  Dinosaur fossils are well known but rare in comparison to clams, snails and other marine organisms.  Fossils can be formed from footprints, burrows, fecal remains.  Can be trapped in amber (fossilized tree sap) and preserved

Reading Fossil Records oObservations of fossils are tough because: oMany fossils are unusual and of unknown organisms oNo fossils of currently living species oOften buried very deep oFound in unexpected locations. oPaleontology: investigation of prehistoric live through the study of fossils. oPaleontologist Cuvier ( ) and geologist Lyell ( ) began to provide new evidence on how species evolved over time. oObservations of fossils are tough because: oMany fossils are unusual and of unknown organisms oNo fossils of currently living species oOften buried very deep oFound in unexpected locations. oPaleontology: investigation of prehistoric live through the study of fossils. oPaleontologist Cuvier ( ) and geologist Lyell ( ) began to provide new evidence on how species evolved over time.

Georges Cuvier noted:  Fossils of simple organisms are found in all depths  Fossils of more complex organisms found only at shallower depths (more recent)  Fossils at shallow depths resemble living species more  Rock layers contain fossils of many species that do not occur in layer above or below them.  Theory of Catastrophism: the pattern of fossils could be accounted for by a series of global catastrophes that wiped out many species on Earth.  But why are they increasingly more complex?  Fossils of simple organisms are found in all depths  Fossils of more complex organisms found only at shallower depths (more recent)  Fossils at shallow depths resemble living species more  Rock layers contain fossils of many species that do not occur in layer above or below them.  Theory of Catastrophism: the pattern of fossils could be accounted for by a series of global catastrophes that wiped out many species on Earth.  But why are they increasingly more complex?

Charles Lyell:  Theory of Uniformitarianism:  Earth has been changing by the same processed in the past that are occurring presently.  Geological change is slow and gradual, not fast and catastrophic  Ideas were radical for his day since people still believed in a relatively young Earth… and his theory would disprove that since everything happened so slowly.  Theory of Uniformitarianism:  Earth has been changing by the same processed in the past that are occurring presently.  Geological change is slow and gradual, not fast and catastrophic  Ideas were radical for his day since people still believed in a relatively young Earth… and his theory would disprove that since everything happened so slowly.