Evolutionary Processes and Theories: A Comprehensive Overview

MICROEVOLUTION

Changes that lead to the appearance of new species and groups that are closely related to each other.

MACROEVOLUTION

Leads to large groups of organisms after drastic change.

PUNCTUATED EQUILIBRIUM

The appearance of major groups of organisms took place as a result of drastic changes and the accumulation of gradual variations.

PHYSIOLOGICAL TREES

Visual representation of the evolutionary history of a group of organisms. A simplified diagram that, using a series of branches, shows the relationship between organisms.

SPECIATION

Two or more distinct species.

GEOGRAPHICAL BARRIERS

Examples are lakes, mountain ranges, and seas.

SEXUAL BARRIERS

Caused by anatomical changes that prevent mating from occurring.

PHYSIOLOGICAL BARRIERS

Incompatibilities in the way the gametes work that prevent fertilization.

CHROMOSOMAL BARRIERS

Changes in the number or structure of chromosomes which prevent the affected individuals from having offspring with the rest of the population.

ETHOLOGICAL BARRIERS

Caused by the appearance of new types of behavior that result in the rejection of some individuals by others.

BIODIVERSITY

Refers to the wide variety of living things that live on our planet.

SELF-REPLICATING

Molecules that were able to self-replicate and that were surrounded by a lipid layer were formed, creating the first prokaryotic cells.

METABOLISM

Lipid bubbles that were able to carry out chemical reactions were formed and later developed the ability to self-replicate.

FIXISM

Claimed that living things do not change and always have the same characteristics.

NATURAL SELECTION

Characteristics that help their survival in a certain environment.

INHERITANCE OF ACQUIRED TRAITS

Characteristics developed or lost organs are transmitted to the next generation.

LAMARCK

French naturalist expert on fossils who had many arguments with Cuvier. He observed fossils with an intermediate appearance between older and present-day organisms, one might have developed from another. He was the first to propose a reasoned theory of evolution.

LAMARCKISM

Organisms developed structures and organs they need to adapt to their environment. These new characteristics developed or lost organs are transmitted to the next generation.

PANSPERMIA THEORY

This theory claims that life came from outer space as microorganisms trapped inside meteorites and all other living things evolved from these microorganisms.

GEORGES CUVIER

Major figure in comparative anatomy and paleontology. He repeatedly emphasized that the fossil record did not prove any kind of gradual change into new species. When confronted with the evidence provided by fossils, he proposed the theory of catastrophism.

DARWINISM

In any population, individuals present variations which are produced randomly. Some variations are favorable while others are unfavorable. These characteristics are inheritable.

CHARLES LYELL

Foremost geologist of his time. Author of Principles of Geology. Popularized Hutton’s concept of uniformitarianism. The Earth was shaped by the same processes still in operation today. One of the first to believe that the planet was older than 300 million years.

ANATOMICAL EVIDENCE

About three groups: 1. Homologous that come from the same descendant and have the same structure but are not used for the same thing, 2. The analogous that is the opposite of homologous, 3. Vestigial says that if those organs are not used, they disappear.

EMBRYOLOGICAL EVIDENCE

Based on the comparative study of the embryonic development of different animals. By comparing the early stages of embryonic development of many animals, it is observed that there are certain similarities that go disappearing as the process progresses.

FOSSIL EVIDENCE

Based on the study of fossils, which are remains of beings that lived in the past or of its activity that have been preserved. Many fossils bear some resemblance to current species. Sometimes they can also present intermediate forms that relate species current with other older fossils.