DIVERSITY, CHANGE AND
CONTINUITY
1
,THE THEORY OF EVOLUTION
Evolution is loosely defined as a process by which populations change over time and
many generations (modification with descent: Darwin) to remain adapted to changes
in the environment.
The theory of evolution claims that species are not fixed, unchanging things, but have
evolved through a process of gradual change from pre-existing different species. It
implies that:
❖ The number of species multiplies over time
❖ All species are related and have shared a common ancestor at some point in their
history
❖ Increasingly complex living things have developed, or evolved, over time.
Why is evolution seen as a ‘theory’? Pg. 212/3
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_____________________________________________________________________
_____________________________________________________________________
What is biological evolution?
The process of change during the course of time because of the change in the gene
pool of a population due to processes such as mutation, natural selection and genetic
drift (random changes in the frequency of specific genes in a population).
Micro-evolution: Small scale evolution – typically in allele frequencies - adaptation
of existing species/ populations by changes of inherited characteristics from one
generation to the next.
Macro-evolution: Large scale evolution at or above species level - development of
new life forms from pre-existing ones over many generations.
2
,ORIGIN OF AN IDEA OF ORIGINS
Development of the theory of evolution – roles of Erasmus Darwin, Lamarck,
Charles Darwin and Alfred Wallace
Before 1700 most scientists accepted that species were unrelated and remained
unchanged; and that the earth was young (about 6000 years old). From 1700 to 1800 a
few scientists including Erasmus Darwin (Charles Darwin’s grandfather) and Jean-
Baptiste Lamarck began to challenge these ideas. They became convinced that
species had changed over time and that the earth was millions of years old, based on
fossil records and the huge diversity of living organisms they observed.
The role of Erasmus Darwin in the development of a theory of evolution
Erasmus Darwin - Grandfather of Charles Darwin (1731 – 1802) wrote a book
called Zoonomia in which he discussed the evolution of species. Some of his
hypotheses were:
• New species evolve from older species.
• Life has progressed as if up a ladder, from micro-organisms to human.
• An individual organism is able to improve (become better adapted to its
environment) through its own activities.
• An organism can pass on to its offspring improvements acquired during its
life.
.
Jean-Baptiste Lamarck (1774-1829)
Jean Baptiste Lamarck (1744–1829) was a French zoologist who accepted evolution
and, like Erasmus Darwin, he suggested how it happens. His books were translated
into English and his ideas were influential in England for more than a century. Here
are some of Lamarck’s hypotheses:
• Species evolve from older species.
• If organisms use a structure often, it becomes bigger.
If they don’t use it at all, it becomes smaller and may
disappear. He called this the ‘law of use and disuse’.
• The offspring of organisms inherit the characteristics
their parents acquired during their lifetimes. Lamarck
called this the ‘inheritance of acquired characteristics’.
• Forces within organisms drive species to evolve up a
ladder of progress.
3
, In a nutshell, Lamarck (1744-1829) accepted the idea that life forms evolve from
simpler to more complex forms. His theory as to how it happened was based on two
conditions:
1. Use and disuse of body parts
If certain organs were used more they would increase in size and efficiency. If not
they would get smaller and eventually disappear. He suggested that changes in the
environment could lead to new ways of behaving which would alter parts of the body
during the course of the organism’s life.
2. Inheritance of acquired characteristics
These physical changes or characteristics acquired by parents during their life time
could then be passed on to their offspring.
The theory was known as the Inheritance of acquired characteristics.
EXAMPLES:
1. Giraffe necks - There are fossils of extinct, short-necked giraffes in the Western
Coast Fossil Park.
Using Lamarck’s hypotheses, here is an explanation of how
they evolved long necks.
• Short-necked giraffes ate low-growing leaves and buck
competed with them for these leaves.
• The giraffe avoided competition with buck by
stretching to eat leaves higher up in trees. This made
their necks longer (the law of use and disuse).
• Baby giraffes inherited their parents’ long necks (the
inheritance of acquired characteristics).
• Eventually all giraffes had such long necks that they
didn’t have to compete with buck for leaves.
2. The toes of water birds. He proposed that from years of straining their toes
to swim through water, these birds gained elongated, webbed toes to better
their swimming.
3. The legs of snakes have been reduced due to disuse.
4. The eyes of moles stopped functioning due to disuse.
WAS HIS THEORY CORRECT?
Characteristics acquired during a lifetime cannot be transmitted to offspring.
For example body building exercises will increase the size of muscles, but this
acquired characteristic, whilst affecting the phenotype, does not affect the egg or
sperm cells, which carry the characteristics that are passed on to the next generation.
• NOTE: The understanding that characteristics are transferred by genes only became
known much later in the 1930s thanks to work done by Mendel in the late 1800s.
• EPIGENETICS SUPPORTS HIS THEORY]
4
CONTINUITY
1
,THE THEORY OF EVOLUTION
Evolution is loosely defined as a process by which populations change over time and
many generations (modification with descent: Darwin) to remain adapted to changes
in the environment.
The theory of evolution claims that species are not fixed, unchanging things, but have
evolved through a process of gradual change from pre-existing different species. It
implies that:
❖ The number of species multiplies over time
❖ All species are related and have shared a common ancestor at some point in their
history
❖ Increasingly complex living things have developed, or evolved, over time.
Why is evolution seen as a ‘theory’? Pg. 212/3
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
What is biological evolution?
The process of change during the course of time because of the change in the gene
pool of a population due to processes such as mutation, natural selection and genetic
drift (random changes in the frequency of specific genes in a population).
Micro-evolution: Small scale evolution – typically in allele frequencies - adaptation
of existing species/ populations by changes of inherited characteristics from one
generation to the next.
Macro-evolution: Large scale evolution at or above species level - development of
new life forms from pre-existing ones over many generations.
2
,ORIGIN OF AN IDEA OF ORIGINS
Development of the theory of evolution – roles of Erasmus Darwin, Lamarck,
Charles Darwin and Alfred Wallace
Before 1700 most scientists accepted that species were unrelated and remained
unchanged; and that the earth was young (about 6000 years old). From 1700 to 1800 a
few scientists including Erasmus Darwin (Charles Darwin’s grandfather) and Jean-
Baptiste Lamarck began to challenge these ideas. They became convinced that
species had changed over time and that the earth was millions of years old, based on
fossil records and the huge diversity of living organisms they observed.
The role of Erasmus Darwin in the development of a theory of evolution
Erasmus Darwin - Grandfather of Charles Darwin (1731 – 1802) wrote a book
called Zoonomia in which he discussed the evolution of species. Some of his
hypotheses were:
• New species evolve from older species.
• Life has progressed as if up a ladder, from micro-organisms to human.
• An individual organism is able to improve (become better adapted to its
environment) through its own activities.
• An organism can pass on to its offspring improvements acquired during its
life.
.
Jean-Baptiste Lamarck (1774-1829)
Jean Baptiste Lamarck (1744–1829) was a French zoologist who accepted evolution
and, like Erasmus Darwin, he suggested how it happens. His books were translated
into English and his ideas were influential in England for more than a century. Here
are some of Lamarck’s hypotheses:
• Species evolve from older species.
• If organisms use a structure often, it becomes bigger.
If they don’t use it at all, it becomes smaller and may
disappear. He called this the ‘law of use and disuse’.
• The offspring of organisms inherit the characteristics
their parents acquired during their lifetimes. Lamarck
called this the ‘inheritance of acquired characteristics’.
• Forces within organisms drive species to evolve up a
ladder of progress.
3
, In a nutshell, Lamarck (1744-1829) accepted the idea that life forms evolve from
simpler to more complex forms. His theory as to how it happened was based on two
conditions:
1. Use and disuse of body parts
If certain organs were used more they would increase in size and efficiency. If not
they would get smaller and eventually disappear. He suggested that changes in the
environment could lead to new ways of behaving which would alter parts of the body
during the course of the organism’s life.
2. Inheritance of acquired characteristics
These physical changes or characteristics acquired by parents during their life time
could then be passed on to their offspring.
The theory was known as the Inheritance of acquired characteristics.
EXAMPLES:
1. Giraffe necks - There are fossils of extinct, short-necked giraffes in the Western
Coast Fossil Park.
Using Lamarck’s hypotheses, here is an explanation of how
they evolved long necks.
• Short-necked giraffes ate low-growing leaves and buck
competed with them for these leaves.
• The giraffe avoided competition with buck by
stretching to eat leaves higher up in trees. This made
their necks longer (the law of use and disuse).
• Baby giraffes inherited their parents’ long necks (the
inheritance of acquired characteristics).
• Eventually all giraffes had such long necks that they
didn’t have to compete with buck for leaves.
2. The toes of water birds. He proposed that from years of straining their toes
to swim through water, these birds gained elongated, webbed toes to better
their swimming.
3. The legs of snakes have been reduced due to disuse.
4. The eyes of moles stopped functioning due to disuse.
WAS HIS THEORY CORRECT?
Characteristics acquired during a lifetime cannot be transmitted to offspring.
For example body building exercises will increase the size of muscles, but this
acquired characteristic, whilst affecting the phenotype, does not affect the egg or
sperm cells, which carry the characteristics that are passed on to the next generation.
• NOTE: The understanding that characteristics are transferred by genes only became
known much later in the 1930s thanks to work done by Mendel in the late 1800s.
• EPIGENETICS SUPPORTS HIS THEORY]
4
