Biotechnology, Evolution, and Taxonomy: A Comprehensive Overview
Biotechnology and Its Applications
Biotechnology is a collection of laboratory techniques that involve the direct manipulation of an organism’s DNA to change its phenotype.
Applications of Biotechnology:
- Cheaper and more effective drugs
- Correction of genetic mutations
- Creation of cells that can clean up environmental messes
- Increase in agricultural productivity
DNA Fingerprinting and Its Uses
DNA fingerprinting is a technique that uniquely identifies individuals based on DNA fragment lengths. Because no two people have the same nucleotide sequences, they do not have the same lengths of DNA fragments.
Uses/Applications of DNA Fingerprinting:
- Identifying deceased individuals from skeletal remains
- Identifying perpetrators of crimes from blood or other body fluids
- Determining the genetic makeup of long-dead individuals or extinct organisms
- Resolving paternity cases by determining the biological father of a child
Human Genome Project
The Human Genome Project was a massive collaborative effort to determine the sequence of DNA in all human chromosomes.
Key Aspects:
- Started with physical maps of chromosomes
- Determined the location of specific markers on the chromosomes
- DNA sequencing determined the exact nucleotide sequence between each marker
Applications of the Human Genome Project:
- Disease diagnosis
- Discovery of new families of proteins
- Better understanding of basic biology
- The project revealed that there are far fewer genes in the human genome than previously predicted (each gene can be alternatively spliced to code for several proteins)
Genetically Modified Organisms (GMOs)
Applications of GMOs:
- Producing human insulin
- Generating “Golden rice” with beta-carotene, which is missing in normal rice
- Producing interferon, an antiviral agent
- Producing human growth hormone
Gene Therapy
Gene therapy involves manipulating genes to cure or treat a genetic disease.
Gene therapies must be specifically designed for each situation. If the mutant gene is not functional, then a functional gene must be inserted. If the mutant gene is overactive, then it must be deleted or altered. This usually involves mutating the part of the gene that controls its activation.
Evolution
Evolution is the change in the frequency of genetically determined characteristics within a population over time.
Types of Evolution:
- Microevolution involves changes in allele frequencies between populations of the same species.
- Macroevolution involves major genetic changes that occur over long periods, generating new species.
Natural Selection
Natural selection is the process in which individuals with certain traits have greater survival and reproduction rates than individuals lacking these traits, resulting in an increase in the frequency of successful alleles and a decrease in the frequency of unsuccessful ones.
Natural selection works on individuals, but only populations evolve.
Factors Influencing Population Change:
- Environmental factors affecting individuals
- Sexual reproduction among individuals
- Genetic diversity within the gene pool
Survival of the Fittest:
Survival is a prerequisite for reproduction. Individuals that do not survive cannot reproduce.
Example: Darwin’s Finches
The finches’ beak size correlated with the type of seeds they ate.
- Small beaks: softer seeds
- Larger beaks: harder seeds
During drought, as soft seeds became scarce, only birds with larger beaks survived.
Patterns of Selection
Natural selection changes allele frequencies in a population, reducing genetic diversity. Over time, individuals become more alike. Selection can favor different phenotypes in different situations, leading to three forms of selection: stabilizing, directional, and disruptive.
Stabilizing Selection:
Occurs when individuals at the extremes of the range of a characteristic are selected against, favoring “average” individuals.
Example:
Brown mice are selected for, while white and black mice are selected against because they are more likely to be noticed and eaten by predators. Over time, the population will have mostly brown mice. Stable environments favor stabilizing selection.
Directional Selection:
Occurs when individuals at one extreme of the range of a characteristic are selected for. This usually occurs when the environment is changing.
Example:
Insecticide use will select for resistant individuals. Originally, there were probably only a few resistant individuals. After several generations, the population will contain mostly resistant individuals.
Disruptive Selection:
Occurs when both extremes of a range of a characteristic are selected for, while the intermediate is selected against.
Example:
Insects that live on plants with dark green or light green leaves. Medium green insects will be noticed and eaten by predators.
Genetic Drift
Genetic drift is due to random shifts in gene frequency. The smaller the population, the more likely random events can determine the genetic information passed to the next generation. Genetic drift involves a significant change in allele frequency that is not a result of natural selection.
Genetic drift is more likely to impact small populations.
Example:
In a population of 100 plants, 10 have red spots on their leaves. If these 10 are randomly trampled by an animal or killed by a late frost, the red spot allele would be lost, but not due to natural selection.
Example: Florida Panther
The Florida panther has many unusual characteristics. Many endangered species can experience genetic drift because of their small populations.
Speciation
Speciation is the process of generating new species. It has occurred continuously over the history of life on Earth. The fossil record shows that huge numbers of new species have originated, and most have gone extinct.
Definition of Species and Population:
- Species: A group of organisms whose members have the potential to interbreed naturally and produce fertile offspring.
- Population: A group of organisms of the same species located in the same place at the same time.
Mechanisms of Speciation:
- Geographic isolation
- Polyploidy
Geographic Isolation:
Occurs when a portion of a population becomes totally isolated from the rest. If followed by genetic divergence (changes in allele frequencies), then reproductive isolation can result, and the isolated population becomes a new species.
Mechanisms of Geographic Isolation:
- Colonization of a distant area: A few individuals emigrate and establish a population far from their original home. The distance prohibits gene flow with the original population; the new population becomes reproductively isolated.
- Appearance of a geographic barrier: Uplifting of mountains, rerouting of rivers, or formation of deserts can subdivide a population. This barrier prohibits gene flow between the divided subpopulations; they can become reproductively isolated.
- Extinction of intermediate populations: Occurs when a population that exists between other populations dies out, eliminating gene flow between the remaining distant populations. The other populations can become reproductively isolated.
Speciation will only happen if the genetic changes accumulated during the period of reproductive isolation generate two populations that can no longer interbreed and produce fertile offspring. After a geographical separation, the two subpopulations will likely experience different environmental conditions, and different phenotypes will be selected for in each subpopulation. Over time, genetic differences that accumulate may result in structural, physiological, and behavioral differences that may prohibit interbreeding, thus resulting in speciation.
Polyploidy:
Polyploidy is a condition of having multiple sets of chromosomes (more than haploid or diploid). It is the primary mechanism of speciation in the absence of geographical isolation.
Polyploidy can result from abnormal events in mitosis or meiosis where chromosomes do not separate properly. The resulting organism cannot mate with its original population but can self-fertilize and generate a new species. It can also result from the mating of two different species, where the hybrid ends up with a novel number of chromosomes and cannot mate with either of the parent populations but can self-fertilize and generate a new species.
Cotton, potato, sugarcane, broccoli, and wheat are all species that resulted from polyploidy.
Evolutionary Patterns
Divergent Evolution:
An evolutionary pattern in which individual speciation events cause successive branches in the evolution of a group of organisms.
Example:
The evolution of horses
Extinction:
The loss of a species. Most species that have ever existed are now extinct. Ever-changing environments lead to the generation of new species and the elimination of others. Divergence is accompanied by a great deal of extinction.
Example:
Gray wolves, passenger pigeons, black-footed ferrets, and spotted skunks were once abundant species but are now extinct in the United States as a result of human activity.
Adaptive Radiation:
A special evolutionary pattern that involves a rapid increase in the number of kinds of closely related species. A kind of evolutionary explosion of new species in a short amount of time.
Example:
A particular organism invades a previously unexploited environment, such as animals moving to land or the Galapagos finches.
Convergent Evolution:
A special evolutionary pattern in which similar characteristics develop in unrelated groups of organisms. The characteristics serve a similar purpose in the particular environment but have very different ancestors.
Example:
Spines in desert plants, eating while flying in bats, dragonflies, and swallows, and the body shape of whales, sharks, and tuna.
Homologous and Analogous Structures:
- Homologous structures have different appearances and functions but arose from a common ancestor. These structures result from divergent evolution.
- Analogous structures have similar structures and functions but arose from different ancestors. These structures result from convergent evolution.
Taxonomy
Taxonomy is the science of naming organisms and grouping them into logical categories (taxis = arrangement).
Scientific names of organisms are in Latin and follow the binomial system of nomenclature, which uses two Latin names (e.g., Artemia parthenogenetica): the genus and the specific epithet.
- A genus is a group of closely related organisms.
- A specific epithet identifies the particular species to which the organism belongs.
Binomial names are italicized or underlined. The first letter of the genus is capitalized; the specific epithet is not.
Rules of Nomenclature:
- International Rules for Botanical Nomenclature
- International Rules for Zoological Nomenclature
- International Bacteriological Code of Nomenclature
Hierarchical Classification:
Organisms are organized into logical groups that are hierarchical: domain, kingdom, phylum, class, order, family, genus, species (Dear King Philip Came Over From Germany – So?).
Three Domains:
- Eubacteria
- Archaea
- Eucarya
Eubacteria and Archaea are prokaryotic, while Eucarya is eukaryotic.
Order of Appearance:
- Eubacteria evolved first.
- Archaea arose from Eubacteria.
- Eucarya evolved most recently.
Phylogeny
Phylogeny is the science that explores the evolutionary relationships among organisms, seeking to reconstruct evolutionary history.
Taxonomists use phylogeny to classify organisms whenever possible.
Data Used to Establish Evolutionary Relationships:
- Fossils
- Comparative anatomy studies
- Life cycle information
- Biochemical and molecular studies