TOPIC 5: EVOLUTION AND BIODIVERSITY
5.1 Evidence for Evolution
Evolution: The cumulative change in the heritable characteristics of a population
There are various pieces of evidence that can be provided for evolution:
o Fossil Record – provides a snapshot of organisms over a long period of time allowing
scientists to compare fossils from different eras, showing evolution of species over time.
Fossil record is incomplete & can be damaged/altered by geological processes
Fossils can be dated by determining the age of the rock layer (strata) in which
the fossil is found
o Selective Breeding (artificial selection) – process by which humans change the
phenotype (physical appearance) of species over many generations. This is done through
the breeding of certain plants/animals that display favourable characteristics (e.g.
breeding larger breasted chickens). Different to natural selection which occurs naturally
rather than as an outcome of human intervention
o Homologous Structures – Anatomical features
showing similarity in shape (not function), evidence
that living things originated from a common
ancestor. For example, the pentadactyl limb all
contain the same key bones but have been adapted
to individual animals
Divergent Evolution – Process whereby a population of organisms with a recent common
ancestor develop different adaptations as a result of changed habitats (can result in speciation
– formation of different species)
o This results in homologous structures (features of organisms with the same basic
structure but have been adapted for different functions (e.g. pentadactyl limbs)
Adaptive Radiation – A form of divergent evolution where a group of organisms (with a recent
common ancestor) may evolve different adaptations in response to a
Divergent
Divergent Convergent
range of different environmental pressures
Evolution
Evolution Evolution
o New species are formed through selection into new ecological
niches
o Darwin’s Finches are an example of this with birds undergoing
adaptive radiation to produce a range of species each with its
own unique niche (role and position a species has in its
environment)
Convergent Evolution – Process in which two distict lineages evolve a
similar characteristic (but different structures) independently of one another
o This often occurs becauase both lineages face similar environmental challenges and
selective pressures
o For example both bats and insects have wings, however have evolved from very
different original structures
5.2 Natural Selection
Natural Selection can only occur if there is variation among members of the same species
o Variation can be caused by: mutation, meiosis and sexual reproduction
41
, Adaptations: characteristics that make an individual suited to its environment and way of life
Natural Selection: the process whereby organisms better adapted to their environment tend to
survive and produce more offspring. It occurs in the stages:
o Overproduction: Species tend to produce more offspring than the environment can
support (populations generally remain stable)
o Variation: Mutation, meiosis and sexual reproduction cause variation between
individuals in a species
o Competition: Individuals that are better adapted tend to survive and produce more
offspring while the less well adapted tend to die or produce fewer offspring
o Changes in Allele Frequency: Natural selection increases the frequency of characteristics
that make individuals better adapted and decreases the frequency of other
characteristics
Characteristics acquired during an individual’s lifetime are NOT heritable
Darwin’s Finches provide an example of natural selection (+ adaptive radiation)
o 13 current species now found on the island evolved from a small flock of 30 birds
o As the population grew, finches started to adapt their feeding habits to avoid
competition (resulting in variation in beak length)
o On the island Daphne Major a serious drought caused large beak birds to thrive as they
could feed on larger seeds (environmental pressures)
o Natural selection acted on the population w/ beak length increasing by 3% the next year
The peppered moth is another example of natural selection
o The pollution from the industrial revolution caused trees to blacken and resulted in the
white peppered moth dying out and the black moth becoming more common
o When the Clean Air Act became a law white the peppered moth increased in numbers
again with the black phenotype becoming less frequent
Natural Selection is evident in the evolution of antibiotic resistance in bacteria
o The bacterium Staphylococcus Aureus has two forms: Methicillin Resistant
Staphylococcus Aureus (MRSA) and Methicillin Susceptible Staphylococcus Aureus
(MSSA)
MRSA has evolved to be resistant to antibiotics (arisen partly as a result of the
overuse of antibiotics and incomplete course of medication), and has become
more frequent
MSSA can still be controlled by the use of Methicillin
5.3 Classification of Biodiversity
Universal binomial system of names for species has been agreed upon among biologists
o Genus must be capitalised, species must be in lowercase
o Must be underlined when handwritten or italicised when typed
o Followed by the name of the person who discovered the species
Species are given scientific names by taxonomists using a hierarchy of taxa
o Natural classifications help in identification of species and allow the prediction of
characteristics shared by species within a group
All organisms are classified into three domains: Archaea, Eubacteria and Eukaryote
42
5.1 Evidence for Evolution
Evolution: The cumulative change in the heritable characteristics of a population
There are various pieces of evidence that can be provided for evolution:
o Fossil Record – provides a snapshot of organisms over a long period of time allowing
scientists to compare fossils from different eras, showing evolution of species over time.
Fossil record is incomplete & can be damaged/altered by geological processes
Fossils can be dated by determining the age of the rock layer (strata) in which
the fossil is found
o Selective Breeding (artificial selection) – process by which humans change the
phenotype (physical appearance) of species over many generations. This is done through
the breeding of certain plants/animals that display favourable characteristics (e.g.
breeding larger breasted chickens). Different to natural selection which occurs naturally
rather than as an outcome of human intervention
o Homologous Structures – Anatomical features
showing similarity in shape (not function), evidence
that living things originated from a common
ancestor. For example, the pentadactyl limb all
contain the same key bones but have been adapted
to individual animals
Divergent Evolution – Process whereby a population of organisms with a recent common
ancestor develop different adaptations as a result of changed habitats (can result in speciation
– formation of different species)
o This results in homologous structures (features of organisms with the same basic
structure but have been adapted for different functions (e.g. pentadactyl limbs)
Adaptive Radiation – A form of divergent evolution where a group of organisms (with a recent
common ancestor) may evolve different adaptations in response to a
Divergent
Divergent Convergent
range of different environmental pressures
Evolution
Evolution Evolution
o New species are formed through selection into new ecological
niches
o Darwin’s Finches are an example of this with birds undergoing
adaptive radiation to produce a range of species each with its
own unique niche (role and position a species has in its
environment)
Convergent Evolution – Process in which two distict lineages evolve a
similar characteristic (but different structures) independently of one another
o This often occurs becauase both lineages face similar environmental challenges and
selective pressures
o For example both bats and insects have wings, however have evolved from very
different original structures
5.2 Natural Selection
Natural Selection can only occur if there is variation among members of the same species
o Variation can be caused by: mutation, meiosis and sexual reproduction
41
, Adaptations: characteristics that make an individual suited to its environment and way of life
Natural Selection: the process whereby organisms better adapted to their environment tend to
survive and produce more offspring. It occurs in the stages:
o Overproduction: Species tend to produce more offspring than the environment can
support (populations generally remain stable)
o Variation: Mutation, meiosis and sexual reproduction cause variation between
individuals in a species
o Competition: Individuals that are better adapted tend to survive and produce more
offspring while the less well adapted tend to die or produce fewer offspring
o Changes in Allele Frequency: Natural selection increases the frequency of characteristics
that make individuals better adapted and decreases the frequency of other
characteristics
Characteristics acquired during an individual’s lifetime are NOT heritable
Darwin’s Finches provide an example of natural selection (+ adaptive radiation)
o 13 current species now found on the island evolved from a small flock of 30 birds
o As the population grew, finches started to adapt their feeding habits to avoid
competition (resulting in variation in beak length)
o On the island Daphne Major a serious drought caused large beak birds to thrive as they
could feed on larger seeds (environmental pressures)
o Natural selection acted on the population w/ beak length increasing by 3% the next year
The peppered moth is another example of natural selection
o The pollution from the industrial revolution caused trees to blacken and resulted in the
white peppered moth dying out and the black moth becoming more common
o When the Clean Air Act became a law white the peppered moth increased in numbers
again with the black phenotype becoming less frequent
Natural Selection is evident in the evolution of antibiotic resistance in bacteria
o The bacterium Staphylococcus Aureus has two forms: Methicillin Resistant
Staphylococcus Aureus (MRSA) and Methicillin Susceptible Staphylococcus Aureus
(MSSA)
MRSA has evolved to be resistant to antibiotics (arisen partly as a result of the
overuse of antibiotics and incomplete course of medication), and has become
more frequent
MSSA can still be controlled by the use of Methicillin
5.3 Classification of Biodiversity
Universal binomial system of names for species has been agreed upon among biologists
o Genus must be capitalised, species must be in lowercase
o Must be underlined when handwritten or italicised when typed
o Followed by the name of the person who discovered the species
Species are given scientific names by taxonomists using a hierarchy of taxa
o Natural classifications help in identification of species and allow the prediction of
characteristics shared by species within a group
All organisms are classified into three domains: Archaea, Eubacteria and Eukaryote
42
