Theories and Evidence of Biological Evolution

Posted on Mar 2, 2025 in Biology

Theories of Biological Evolution

Punctuated Equilibrium (PUNT): The theory suggests that there are certain periods of intense speciation which interrupt the equilibrium of normal adaptation.

Fixism (FIXIST): Upholds the idea that species on Earth were created by God.

Catastrophism (CATAS): Proposed by Cuvier, maintained that fossils were the remains of extinct species that had died out as a result of catastrophes.

Evolutionism (EVOL): Maintains that species undergo a process of transformation which results in the appearance of new species.

Actualism (ACTUAL): Holds that events in Earth’s distant past were caused by the action of forces identical to those operating today.

Homologous and Analogous Structures

Homologous Structures: Have the same origin and same basic structure, although their shape is different.

Analogous Structures: Have a different origin, but a similar shape.

Adaptation Types

Adaptation Types:

  • Structural: Affects the organs (e.g., extremities of vertebrates adapted to swim).
  • Physiological: Affects the function of organisms (e.g., dromedaries).
  • Behavioral: Related to reproduction, food, etc. (e.g., migrations).

Miller’s Experiment

Miller’s Experiment:

  1. They introduced gases.
  2. Then, they ran electrical currents through it to simulate energy from lightning.
  3. The products created in the chamber were collected in a container.
  4. When they extracted the liquid, they analyzed the biomolecules.

Biological Evolution

Biological Evolution: Refers to the process that led protocells to become different types of cells, and resulted in all the different organisms ever to have inhabited the Earth.

Endosymbiotic Theory

Endosymbiotic Theory:

  1. A primitive prokaryotic cell folds its membrane and creates a cell nucleus.
  2. The cell engulfs other prokaryotic cells:
    • A. A prokaryotic cell creates the mitochondria.
    • B. A prokaryotic cell creates the flagellum.
    • C. A prokaryotic cell creates the chloroplast.

Embryological Evidence

Embryological Evidence: During the 19th century, Haeckel suggested that the different shapes that an organism’s embryo shows during development reflect the different shapes that its ancestors had during the evolutionary process. When studying the development of the embryos of some of the vertebrate species, we see something that can only be explained if all vertebrates had a common ancestor. They exhibit many similarities; these similarities disappear as they develop further and begin to acquire the different traits that evolution has provided them.

Darwin’s Hypothesis

Darwin’s Hypothesis:

  • The world is not static.
  • The process of change is gradual and continuous.
  • Organisms share a common ancestor.
  • Evolutionary change is the result of natural selection.

Natural Selection

Natural Selection: A process that favors individuals in populations that are best adapted to the environment and which, over time, will lead to the appearance of new species.

Neo-Darwinism

Neo-Darwinism: Is a revised version of the theory of natural selection enriched by contributions from various studies.

Embryological Evidence

Embryological Evidence: During the 19th century, Haeckel suggested that the different shapes that an organism’s embryo shows during development reflect the different shapes that its ancestors had during the evolutionary process. When studying the development of the embryos of some of the vertebrate species, we see something that can only be explained if all vertebrates had a common ancestor. They exhibit many similarities; these similarities disappear as they develop further and begin to acquire the different traits that evolution has provided them.

Darwin’s Hypothesis

Darwin’s Hypothesis:

  • The world is not static.
  • The process of change is gradual and continuous.
  • Organisms share a common ancestor.
  • Evolutionary change is the result of natural selection.

Natural Selection

Natural Selection: A process that favors individuals in populations that are best adapted to the environment and which, over time, will lead to the appearance of new species.

Neo-Darwinism

Neo-Darwinism: Is a revised version of the theory of natural selection enriched by contributions from various studies.

Embryological Evidence

Embryological Evidence: During the 19th century, Haeckel suggested that the different shapes that an organism’s embryo shows during development reflect the different shapes that its ancestors had during the evolutionary process. When studying the development of the embryos of some of the vertebrate species, we see something that can only be explained if all vertebrates had a common ancestor. They exhibit many similarities; these similarities disappear as they develop further and begin to acquire the different traits that evolution has provided them.