Macro And Micro Evolution

SYNOPSIS:–

1. Introduction

2. What is Micro Evolution

3. Mechanism of Micro Evolution

4. What is Macro Evolution

5. Evidences of Micro Evolution

6. Conclusion

1. Introduction :-

Evolution is a process that results in changes in the genetic material of a population over time. Evolution reflects the adaptation of organisms to their changing environments and can new species. Evolutionary processes depend on both change in allele frequencies over time.

2. What Is Micro Evolution?

Micro Evolution is a change that occurs in time in a population due to changes in allelic frequencies. This happens due to four reasons, genetic drift, mutation, gen flow, natural and artificial selection.

The time for a microevolutionary change is relatively shorter as compared to macroevolutionary changes. It is not visible to a casual observer. However, these changes can be mathematically proved by the Hardly - Weinberg equilibrium. Microevolution causes speciation which makes a way for macroevolution. 

The best example of microevolution can be seen in bacterial strains that have acquired antibiotic resistance.

Some more examples of microevolution:-

Some examples of microevolution through the process of natural selection are herbicide resistance, pesticides resistance, antibiotic resistance and so on. Few other generally noticeable evolutionary instances of microevolution are the bacterial strains incorporating the property of resistance to antibiotics.

Few other examples are as listed below :- 

1) Resistance to pesticides by whiteflies.

2) Resistance to DDT by mosquitoes.

3) HIV strains developing resistance to antiviral medicines.

4) Gonorrheal bacteria strains developing resistance to penicillin.

3. MECHANISM OF MICROEVOLUTION.   :-

Microevolution occurs due to variation in the ''GENE POOL''.

GENE POOL - All the alleles (alternative forms of a gene) in all the individuals that make up a population. It is the "pool" from which the next generation draws it's genes.

Hardy Weinberg Equilibrium :-

1. Population that do not undergo change to there gene pools are not evolving.

2. They are in a condition known as hardly Weinberg Equilibrium.

3. However, populations rarely remain in H - W equilibrium for long, because any can change a gene pool.

Factors that cause change in the gene pool :-

1) Genetic Drift

2) Gene Flow

3) Mutation

4) Natural selection

1) Genetic Drift - Changes in the gene pool due to chance is called genetic drift. The smaller the population, the greater chance for random changes in frequencies.

Two Examples of Genetic Drift :-

1. Bottleneck Effect:- Drastic reductions in populations due to natural disasters or hunting leave very small population, with different frequencies of genes Ex. Cheetah.

2. Founder Effect:- When a few individuals colonize an island, lake or new habitat, the population of the original larger population.

Gene Flow :- Gene flow is caused by migration of individuals or their gametes between neighbouring populations

3. Mutation :- Mutation are random changes in an organism's DNA. If the DNA is carried by a gamete, it enters the population's gene pool. The vast majority of mutations are very minor changes such as the one pictures here.

4. Natural selection :- This is the major force that leads to adaptation.I t is a sorting among all the variations in the population for the "fittest". Fitness means the " Contribution an individual makes to the gene pool of the next generation compared to the contributions of other words, production of more healthy fertile offspring than others.

What is Macroevolution?

Macroevolution brings bigger, large - scale and visible changes above species level. It is inter-specific in nature. The new changes are often as big as development of new structures or organs.

Macroevolution Takes millions of years to take place and hence cannot be observed easily. Studying the fossils and other specific methods have to be employed to study these changes.

Examples of macroevolution include evolution of bat wings and loss of limbs in snakes and lizards.

Some more examples of macroevolution :-

1. The emergence of mammals, flowering plants, Vertebrate fish, and multicellular organisms as distinct groups.

2. The diversification of African cichlid fish into more than 1,600 species.

3. The development of wings, feather, lungs, and heart from modified structures in ancestral forms.

4. The reproductive isolation of Asian and African elephants.

5. The convergent evolution of similar traits in different primate lineages.

Evidence of macroevolution :-

1. Fossil

2. Molecular (Biochemistry and Genetics)

3. Comparative anatomy

4. Vestigial structures

5. Comparative embryology

Evidence of macroevolution :- 

1. Fossil record :- The study of fossils provides the strongest evidence of evolution.

What is fossil?

A trace or remains of an organism that has been preserved by natural processes.

By studying fossils, scientists can compare the remains of ancient organisms with organisms living today.

Whale Evolution based on the fossil record :-

2. Comparative Biochemistry and Genetics :-

The closer the relationship between organisms based on anatomy, the more alike the structure of their DNA and protein molecules.

A chain of amino acids is a protein :- Our hemoglobin shares only this many differences with these animals, seems to agree with the DNA evidences we just saw.

3. Comparative anatomy :- The presence of certain types of similarities in anatomy offers evidence for the evolutionary relationship between species.

Homologous Structures :- 

Parts of different organisms that have similar structures but may have different forms and functions.

4. Vestigial organs :- 

Small or incomplete structures with no apparent function. Example - Coccyx, appendix, Whale leg bones.

5. Comparative embryology :- Development of embryo tells an evolutionary story similar structures during development.

Conclusion :- 

1) Microevolution refers to small changes over short period time within a population.

2) Microevolution refers to larger changes over a long time scale. Macro evolution can result in speciation or the emergence of new species.

3) It is important to note that micro and macro evolution are not different processes , both relate to genetic changes in a population across generations, the only difference is the timescale on which the two operate.

References :- 

Evolution 4th Edition - Douglas J.

Futuyma and Mark Kirkpatrick

The Blind Watchmaker  - Richard Dawkins

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