EVOLUTION
WHAT IS EVOLUTION?
● cumulative change in the heritable characteristic of a population (i.e. biological change overtime)
○ characteristics are…
■ encoded by genes
■ transferred between generations as alleles
● change in the allele frequency of a population’s gene pool over successive generations
● allele
○ variant form of a gene (dominant or recessive)
○ creates diversity
FOSSILS.
● refer to the preserved remains or traces of organisms from the remote past
● fossils may act as evidence for…
○ physical changes (imprints, stamping, footprints)
○ behavioural changes (trace fossils, faeces, footprints, fossilized burrows)
● Fossil Record
○ provides a record of the order of physical and/or behavioural changes in certain species
over time
○ totality of discovered and undiscovered fossils
○ reveals that gradual changes occurred in ancestral organisms
○ different species appear in the fossil in a systematic order (law of fossil succession)
■ e.g. ferns appear before flowers
● Fossilisation
○ requires a rare set of circumstances → results in gaps in fossil record
○ evolutionary relationships are constantly being redefined
○ preserves hard body parts
■ soft parts may leave imprints
○ conditions required:
■ preservation of remains (i.e. no scavenging)
■ anoxic conditions (low oxygen conditions to prevent decomposition)
■ high pressure (turns the body parts into fossilized materials)
○ conditions are likely to occur as a result of rapid burial
, ● Law of Fossil Succession
○ fossils can be dated according to the age of the rock layer (strata) in which they were found
○ certain kinds of fossils are found in particular strata → indicates a sequence of
development
○ prokaryotes appeared before eukaryotes
○ invertebrates appeared before vertebrates
TRANSITIONAL FOSSILS
● demonstrate the intermediary forms that occur within an evolutionary pathway
● establish connections between species by exhibiting traits common to both an ancestor and its
predicted descendants
○ i.e. missing links
● e.g. Archaeopteryx
○ links dinosaurs (jaws, claws) to birds (feathers)
NATURAL SELECTION
● first published in the 19th century by Charles Darwin & Alfred Wallace
● occurs when species have variation
● certain traits are selected because they help the species to reach a reproductive age and pass on
their genes
● process that explains how a species evolves and survives as a consequence of its ability to adapt
○ depends on whether genetic variability is advantageous to species
ARTIFICIAL SELECTION
● occurs when humans select the favourability of a particular trait
● may involve selective breeding or transgenic techniques (DNA manipulation)
SELECTIVE BREEDING
WHAT IS EVOLUTION?
● cumulative change in the heritable characteristic of a population (i.e. biological change overtime)
○ characteristics are…
■ encoded by genes
■ transferred between generations as alleles
● change in the allele frequency of a population’s gene pool over successive generations
● allele
○ variant form of a gene (dominant or recessive)
○ creates diversity
FOSSILS.
● refer to the preserved remains or traces of organisms from the remote past
● fossils may act as evidence for…
○ physical changes (imprints, stamping, footprints)
○ behavioural changes (trace fossils, faeces, footprints, fossilized burrows)
● Fossil Record
○ provides a record of the order of physical and/or behavioural changes in certain species
over time
○ totality of discovered and undiscovered fossils
○ reveals that gradual changes occurred in ancestral organisms
○ different species appear in the fossil in a systematic order (law of fossil succession)
■ e.g. ferns appear before flowers
● Fossilisation
○ requires a rare set of circumstances → results in gaps in fossil record
○ evolutionary relationships are constantly being redefined
○ preserves hard body parts
■ soft parts may leave imprints
○ conditions required:
■ preservation of remains (i.e. no scavenging)
■ anoxic conditions (low oxygen conditions to prevent decomposition)
■ high pressure (turns the body parts into fossilized materials)
○ conditions are likely to occur as a result of rapid burial
, ● Law of Fossil Succession
○ fossils can be dated according to the age of the rock layer (strata) in which they were found
○ certain kinds of fossils are found in particular strata → indicates a sequence of
development
○ prokaryotes appeared before eukaryotes
○ invertebrates appeared before vertebrates
TRANSITIONAL FOSSILS
● demonstrate the intermediary forms that occur within an evolutionary pathway
● establish connections between species by exhibiting traits common to both an ancestor and its
predicted descendants
○ i.e. missing links
● e.g. Archaeopteryx
○ links dinosaurs (jaws, claws) to birds (feathers)
NATURAL SELECTION
● first published in the 19th century by Charles Darwin & Alfred Wallace
● occurs when species have variation
● certain traits are selected because they help the species to reach a reproductive age and pass on
their genes
● process that explains how a species evolves and survives as a consequence of its ability to adapt
○ depends on whether genetic variability is advantageous to species
ARTIFICIAL SELECTION
● occurs when humans select the favourability of a particular trait
● may involve selective breeding or transgenic techniques (DNA manipulation)
SELECTIVE BREEDING
