Key Theories and Evidence of Evolution
Evolutionary Theories: Lamarck, Darwin, and Beyond
Evolutionary theories propose that species undergo evolution over time, transforming one into another new species. Among these, the evolutionary theories of Lamarck and Darwin are particularly emphasized.
Lamarck’s Theory and Lamarckism
Jean-Baptiste de Monet, Comte de Lamarck (1809), attempted the first systematic explanation of how species evolve. He considered evolution a slow and gradual process in which changes in the environment caused changes
Read MoreUnderstanding Biological Evolution and Speciation
Evolution: Key Concepts and Mechanisms
Evolution is defined as a change in a population over time, resulting in new organisms or extinction.
Homologous structures are similar structures in two organisms that indicate a common ancestor.
Jean-Baptiste Lamarck’s Hypothesis
- Organisms strive to improve themselves.
- Inheritance of Acquired Characteristics: He believed that traits acquired during an organism’s lifetime could be passed on to its offspring. For example, he thought children of blacksmiths naturally
Darwin’s Evolution: Genetics, Speciation, and Evidence
Evolution After Darwin
Mendel’s Discoveries and the Synthetic Theory of Evolution
Gregor Mendel discovered some of the basic laws of inheritance. Darwin’s proposals were enriched and updated with new knowledge of genetics, leading to the Synthetic Theory of Evolution. Key contributions include:
- The evolutionary unit is not the individual, but the population. Natural selection acts on the genetic wealth of the population.
- The origin of variability is mutation: a sudden change in DNA. Organisms carrying
Evolutionary Biology: Essential Terms and Processes
Key Concepts in Evolutionary Biology
Founder Effect
The founder effect is the loss of genetic variation that occurs when a new population is established by a small number of individuals from a larger population.
Genetic Bottleneck
A genetic bottleneck is a sharp reduction in the size of a population due to environmental events (such as earthquakes, floods, fires, or disease).
Directional Selection
Directional selection is a mode of natural selection in which an extreme phenotype is favored over other
Read MoreDarwin’s Theory of Evolution: Natural Selection and Variability
Darwin’s Theory of Evolution
Evolution according to Darwin’s theory: The next step in the evolutionary theories of Charles Darwin, who made his work public in his 1859 Origin of Species, in which he formulated his theory of the evolution of living beings called Darwinism. Darwin conceived his theory after a trip to the coast of South America and the Galapagos Islands, which are about 960 km from the continent.
Darwin’s Observations
Darwin’s observations: Plants and animals on the east coast of South
Read MoreEvolutionary Theories: From Fixism to Biodiversity
Evolutionary Theories
Fixism: The theory that existing species have not changed since creation.
Creationism: The theory that species were created by God. Creationism is associated with fixism because it also defends the immutability of species.
Early Evolutionary Thought
Lamarckism (Theory of Acquired Characteristics):
- Environmental conditions change over time.
- Environmental changes create new needs, causing individuals to alter their habits or behaviors.
- New habits lead to the greater or lesser use of