Modern Synthetic Theory Evolution

The Modern Synthetic Theory of Evolution is an advanced explanation of how evolution occurs. It emerged in the 20th century when scientists combined insights from various fields like genetics, molecular biology, and paleontology. This theory emphasizes that evolution is not only the result of natural selection but also of genetic changes occurring within populations over generations. It builds upon the concept of Darwin’s theory of natural selection.

This Story also Contains

1. What is Modern Synthetic Theory?
2. Factors of Modern Synthetic Theory of Evolution
3. Key Elements of Modern Synthetic Theory
4. Evidence for Modern Synthetic Theory
5. Recommended Video for Modern Synthetic Theory of Evolution
6. MCQs on Modern Synthetic Theory of Evolution

By using the principles of genetics, the modern theory explains how inherited traits vary due to mutations, genetic recombination, and gene flow. It highlights how these genetic variations serve as raw material for natural selection to act upon. The theory plays a key role in modern biology, helping scientists understand the mechanisms of evolution in a more complete and scientific manner.

What is Modern Synthetic Theory?

Modern Synthetic Theory integrates principles of natural selection and Mendelian genetics as a single theory of evolution. This theory incorporates Darwin's model of the evolution of species through natural selection with our present understanding of genetic inheritance to present a comprehensive framework for studying biological evolution.

The theory is critical in biology as it explains what diversified life on Earth. It also shows how modifications in genetics and environmental conditions fuel evolutionary change. The compilation of knowledge of different biological sciences, the Modern Synthesis has changed the view of the evolution and adaptation of species over time. The modern synthesis began with the synthetic theory of evolution in the early twentieth century. It brought together some of Darwin's contributions and Mendel's findings, representing the biochemical and evolutionary points of view. The key contributions were made by scientists like Ronald Fisher, J.B.S. Haldane, and Sewall Wright provided mathematical models of genetic variation and selection pressures within populations.

Factors of Modern Synthetic Theory of Evolution

This theory is influenced by several biological factors that drive evolutionary changes over time. These include genetic variations, mutation, recombination, gene flow, and natural selection. Each factor plays a role in shaping the genetic makeup of populations.

Several factors lead up to the Modern Synthetic Theory of Evolution, all of which are equally important in the shaping of populations over time.

Genetic Recombination

• Reshuffling of alleles during stages of meiosis

• New combinations of genes

• Increased genetic variation

Mutation

• Changes in the DNA sequence

• Beneficial, neutral, or harmful

• Source of new genetic variation

Genetic Drift And Gene Flow

• Genetic drift: Random change in allele frequencies

• Bottleneck and founder effects

• Gene flow: Gene migration across populations

• Introduction of new genes, thus decreasing population differences

Natural Selection

• Variation in survival and reproduction

• Select for beneficial traits

• Adapts in time

Isolation

• Geographic, reproductive or behavioural barriers

• Prevents gene flow between populations

• This can lead to speciation

Key Elements of Modern Synthetic Theory

The theory combines classical Darwinian ideas with modern genetics. It focuses on how populations evolve, not individuals, and includes the role of reproductive isolation and speciation. It gives a detailed understanding of how new species arise.

Key elements of the Modern Synthetic Theory describe how evolution works through some mechanisms and processes.

Genetic Variation

• Sources of genetic variation include mutation, recombination, and gene flow.

• Necessary for evolution, as it provides the raw material for natural selection.

Natural Selection

• The process by which individuals who have positive traits are more likely to survive and reproduce.

• Examples: Peppered moths and antibiotic resistance in bacteria

Genetic Drift

• Random changes in the frequency of different alleles are significant in small populations.

• Examples: bottleneck effect and founder effect

Gene Flow

• Movement of genes from one population to another by migration.

• Reduces genetic variation among populations and increases genetic variation.

Speciation

• Formation of new species.

• Allopatric speciation, physical isolation due to geographic change.

• Sympatric speciation, no physical barriers to organism distribution.

Evidence for Modern Synthetic Theory

Various fields support this theory through consistent findings. Evidence comes from molecular biology, fossil records, comparative anatomy, and genetics. These collectively validate the mechanisms and predictions of the modern evolutionary framework.

The Modern Synthetic theory has significant amounts of evidence to back up its findings, showing the reason behind evolutionary theory.

Fossil Record

• Transitional fossils – species in intermediate form.

• Temporal patterns in evolutionary change.

Molecular Biology

• Similarities and differences in DNA and proteins reflect genetic relationships.

• Comparative genomics allows the establishment of evolutionary relationships.

Embryology

• Similarities in embryo development of species reflect common ancestry.

• Homologous structures in embryos indicate evolutionary relationships.

Biogeography

• The geographic distribution of species reflects evolutionary history.

• Adaptive radiation illustrates diversification from a common ancestor.

Recommended Video for Modern Synthetic Theory of Evolution

MCQs on Modern Synthetic Theory of Evolution

Q1. Who among the following scientists is not mentioned as a contributor to the modern synthetic theory of evolution?

1. T. Dobzhansky
2. R.A. Fisher
3. J.B.S. Haldane
4. Charles Darwin

Correct answer: 4) Charles Darwin

Explanation:

Cilia and flagella are critical to cell movement but differ in various key features. Cilia are small, hair-like protrusions that are significantly shorter (5-6 µm), much smaller in number on the surface of the cell and usually found in organisms such as fungi, protozoa, and epithelial cells in the respiratory tract. They manifest a paddle-like motion. On the other hand, flagella are whip-like protrusions that can measure up to 1000 µm, and in fewer numbers; they have the rotary motion of movement.

Hence the correct answer is Option 4) Charles Darwin.

Q2. Modern evolutionary theory consists of the concepts of Darwin modified by knowledge concerning:

1. population statistics
2. Mendel's laws
3. The idea of the survival of the fittest
4. Competition

Correct answer: 3) The idea of the survival of the fittest

Explanation:

The theory of evolution is first formulated by Darwin in his book “On the Origin of Species”. Evolution by natural selection is a process by which changes occur in an organism over time due to heritable physical or behavioural traits. The changes allow organisms to adapt to their environment which helps in survival and having more offspring.

The theory has 2 main points: all life on the earth is related and connected and this life diversity is due to natural selection. It is the best theory supported by evidence from a wide variety of scientific disciplines.

In the field of biology, evolution is a vital phenomenon as it is a central principle of all the life that exists. Evolution involves the elimination of weaker individuals and survival of the stronger individuals and in the aspect of biology, it is important for better-fit survival. Evolution is the basis of all the observations made by the biologist.

Hence, the correct answer is Option 3) the idea of the survival of the fittest.

Q3. Who proposed the theory of Germplasm

1. T.H.Morgan
2. Aristotle
3. Weismann
4. K.F.Wolf

Correct answer: 3) Weismann

Explanation:

In 1892, August Weismann started a Theory of Germplasm that explained heredity. According to this theory, germ cells (such as gametes: sperm and egg cells) are the only ones through which hereditary information is transmitted, but not by somatic cells. This theory helped establish that genetic material is conserved from generation to generation, thereby discrediting the idea of acquired characteristics. Work done by Weismann provided a basis for the modern version of genetics that followed and furthered our understanding of heredity.

Hence the correct answer is Option 3) Weismann.

Also Read:

• MCQ Practice on Modern Synthetic Theory
• Mutation Theory
• Origin and Evolution of Man