EVOLUTION
Evolution is considered a scientific theory, not a hypothesis. The theory
is based on a series of hypotheses that have been tested and verified over
time.
Terms to know:
1. Evolution is defined as a change in gene pool overtime.
2. Biological Evolution is a genetic change in a population that are
inherited over successive generations due to natural selection and
ultimately resulting in the formation of a new species.
3. Macro evolution is the development of new life forms or species from
earlier life forms over many generations (speciation).
4. Micro evolution is the variation that occurs within a species , small
changes that originate in a gene pool and result in small changes in
genotypes.
Variation within a species:
A species is a group of closely related organisms that have similar
characteristics and can interbreed and produce fertile offspring.
A population is the total number of individuals of a particular species
that live in a particular area at a specific time.
Variation in a species is caused by the following;
1. Meiosis
- crossing over involves the exchange of genetic matter during prophase of
meiosis 1 which leads to the formation of 4 gametes which are all unique in
gene combinations.
- Random assortment of homologous pairs on the equator during metaphase of
meiosis 1 results in greater variation of gametes.
2. Mutations
- mutations can change the DNA which leads to the formation of a new
characteristic which helps the organism adapt to the environment and
survive. Mutation has to occur in the gamete for it to be pass onto
offspring.
3. Chance fertilisation
- the combination of male and female gametes is random and results in more
gene combinations every time fertilisation occurs, which also leads to more
variation.
, 4. Random mating
- males and female mate randomly and this leads to a variety in gene
combinations and more variation within a species
Types of Variation:
1. Continuous variation which is there is are a range of phenotypes
for a particular characteristic e.g. Height.
2. Discontinuous variation which is the phenotypes fit into separate
categories with no intermediate forms e.g. Blood groups
Theories of Evolution;
1. Lamarck’s Theory
2. Darwin’s Theory
3. Punctuated Equilibrium.
1. Lamarck’s Theory of Evolution: (use or disuse)
Lamarck was a French biologist that proposed that evolution occurred
through the following mechanisms;
- Conditions in the environment of an organism often change
- to cope with new environments, organisms must develop new needs.
- the development for new needs requires the organism to use certain parts
of its body which it might previously not used.
- this use or disuse leads to either an enlargement of the specific body
part or causes the body part to shrink in the case of disuse.
- these newly acquired characteristics are past down from generation to
generation.
Evolution is considered a scientific theory, not a hypothesis. The theory
is based on a series of hypotheses that have been tested and verified over
time.
Terms to know:
1. Evolution is defined as a change in gene pool overtime.
2. Biological Evolution is a genetic change in a population that are
inherited over successive generations due to natural selection and
ultimately resulting in the formation of a new species.
3. Macro evolution is the development of new life forms or species from
earlier life forms over many generations (speciation).
4. Micro evolution is the variation that occurs within a species , small
changes that originate in a gene pool and result in small changes in
genotypes.
Variation within a species:
A species is a group of closely related organisms that have similar
characteristics and can interbreed and produce fertile offspring.
A population is the total number of individuals of a particular species
that live in a particular area at a specific time.
Variation in a species is caused by the following;
1. Meiosis
- crossing over involves the exchange of genetic matter during prophase of
meiosis 1 which leads to the formation of 4 gametes which are all unique in
gene combinations.
- Random assortment of homologous pairs on the equator during metaphase of
meiosis 1 results in greater variation of gametes.
2. Mutations
- mutations can change the DNA which leads to the formation of a new
characteristic which helps the organism adapt to the environment and
survive. Mutation has to occur in the gamete for it to be pass onto
offspring.
3. Chance fertilisation
- the combination of male and female gametes is random and results in more
gene combinations every time fertilisation occurs, which also leads to more
variation.
, 4. Random mating
- males and female mate randomly and this leads to a variety in gene
combinations and more variation within a species
Types of Variation:
1. Continuous variation which is there is are a range of phenotypes
for a particular characteristic e.g. Height.
2. Discontinuous variation which is the phenotypes fit into separate
categories with no intermediate forms e.g. Blood groups
Theories of Evolution;
1. Lamarck’s Theory
2. Darwin’s Theory
3. Punctuated Equilibrium.
1. Lamarck’s Theory of Evolution: (use or disuse)
Lamarck was a French biologist that proposed that evolution occurred
through the following mechanisms;
- Conditions in the environment of an organism often change
- to cope with new environments, organisms must develop new needs.
- the development for new needs requires the organism to use certain parts
of its body which it might previously not used.
- this use or disuse leads to either an enlargement of the specific body
part or causes the body part to shrink in the case of disuse.
- these newly acquired characteristics are past down from generation to
generation.
