Neo-Darwinism vs. Saltationism: Evolution Theories
Neo-Darwinism vs. Saltationism (Punctuated Equilibria)
Neo-Darwinism:
- The variability of populations is genetic and is due to two processes: mutation and genetic recombination.
- The gene pool is defined as the sum of all genes (each with their different alleles) present in all individuals of a population.
- Natural selection acts on genetic variability. Each individual in a population carries different alleles responsible for their phenotype.
- Natural selection leads to changes in the set of alleles of the population. The alleles which confer an advantageous phenotype on the individuals will increase in frequency in the population.
- The unit of selection is the population, not the individual. Populations evolve. A population is defined as a group of individuals of the same species that share an area and can interbreed, leading to fertile offspring.
- Evolution occurs gradually. Evolution is the result of small changes in the frequencies of different alleles in the population. The process to create a new species is very long.
Saltationism (Punctuated Equilibria):
- An alternative to the synthetic theory to explain the great extinctions seen in the fossil record and the sudden appearance of new forms.
- Not all evolutionary changes are gradual.
- Throughout Earth’s history, there have been long periods of apparent stability in which species have not changed, known as periods of stasis.
- These periods of stasis alternate with short periods, called speciation events, in which there are rapid changes and many new species arise from existing ones. These are periods of explosion of biodiversity.
Microevolution vs. Macroevolution
Microevolution is the occurrence of small-scale changes in allele frequencies in a population over a few generations. It is also known as change at or below the species level.
These changes may be due to several processes: mutation, natural selection, gene flow, and genetic drift.
Macroevolution refers to major evolutionary changes, as opposed to the small and progressive changes of microevolution.
Identifying Individuals of the Same Species
To identify whether two individuals are of the same species, perform the following tests:
- Biochemical
- Anatomical
- Embryological
- Biogeographical
- Paleontological
Speciation Mechanisms
Speciation can occur through various mechanisms, and one of the primary ways is through reproductive isolation. Reproductive isolation can occur in various ways, including geographical isolation of populations.
Anthropomorphic Characteristics of the First Primates
- Bipedalism: They always move upright. This is because the foramen magnum is shifted to the base of the skull.
- Double articulation of the skull on the atlas.
- The vertebrae are more circular and therefore better support the weight.
- The spine has three curvatures.
- The pelvis is wider and shorter.
- Lengthening of the leg bones.
- Shortening of the thumb of the lower extremities.
- U-shaped Palate: Round-arched palate.
- Small teeth.
- Skull with a voluminous brain, associated with a high-energy diet.
Chronological Order of Hominid Species Discovered
- Homo habilis
- Homo ergaster
- Homo erectus
- Homo antecessor
- Homo neanderthalensis