Genetics and Evolution
| Chromosomes | - | Structures in the nucleus of a eukaryotic cell that consist of DNA molecules that contain the genes. |
| DNA | - | (deoxyribonucleic [dee-OX-see-rye-boh-new-CLAY-ik] acid) 1) A type of nucleic acid that contains the instruction set for life's machinery. Found in the nucleus of plant and animal cells and free in the cytoplasm of bacterial cells. 2) A nucleic acid composed of two strands wound around a central axis to form a double helix; the repository of genetic information. |
| Evolution | - | 1) the development and change of species through the accumulation
of changes in its genetic code over time. 2) The change in life over time by adaptation, variation, over-reproduction, and differential survival/reproduction, by a process referred to by Charles Darwin and Alfred Wallace as Natural Selection. |
| Gene | - | Specific segments of DNA that controls cell structure and function; the functional units of inheritance. Sequence of DNA bases usually coding for an amino acid sequence.Genes code for a specific trait, eg. ability to roll the your tongue. |
| Genetics | - | The study of the structure and function of genes and the transmission of genes from parents to offspring. |
| Lamarckism | - | a theory predating Darwin to explain evolution. Generally referred to as the inheritance of acquired characteristics. Shown to be incorrect. |
| Natural selection | - | 1) mechanism proposed by Darwin to explain how evolution works;
in nature more fit individuals are more likely to survive to reproduce and to reproduce in greater numbers. In
artificial selection the selection pressure is exerted by man and can result in rapid changes. 2) The process of differential survival and reproduction of fitter genotypes. Better adapted individuals are more likely to survive to reproductive age and thus leave more offspring and make a larger contribution to the next generation than do less fit individuals. The differential survival and reproductive successes of individuals in a variable population that powers the evolutionary process. When all individuals survive and reproduce (except for chance occurrences) natural selection works at a lower rate. |
| Protein | - | Large chain-like molecules that are made up of a series of smaller molecules call amino acids. |
| RNA | - | A type of nucleic acid that carries the DNA to the cytoplasm and directs the construction of proteins. |
What is DNA?
The stuff of life, the controller of heredity.
The DNA molecule is life's blueprint. It is the instruction set for all microorganisms, all plants, all animals;
for all life.
DNA Construction
Ladder or Zipper Like
Rungs of base pairs
Sides of alternating sugar and phosphate groups
Spiral twist, the DOUBLE HELIX
The number of chromosomes is different in different organisms. Humans have 23 pairs of chromosomes. Honey bees have 32 (females) or 16 (males) chromosome pairs. For organisms reproducing sexually, one half of each chromosome pair comes from the female parent, the other half of the pair from the male parent.
Honey bees don't reproduce exclusively by sexual means. Male bees have chromosomes from both parents, this is called diploid. Female honey bees, the queen and all workers, have only the chromosomes from the female parent, the queen. This is the haploid (half) condition.
All life is based on nucleic acids and use a triplet code to produce proteins. All life has similar metabolic processes and is carbon-nitrogen based. This is because all life is related and is the result of change over time, evolution. Species evolve into other types or die out.
Because species are related, even if the relationship is distant, we can apply what we know about a one species to another. This is what allows us to study cancer in sharks to develop cancer prevention in humans. This is what allows us to study genetic control of development in insects and use that knowledge to devise treatment for human disease. We can learn from one species and apply it to another because all life is related.
What is debated and not totally clear is the mechanism of evolution. Natural selection as proposed by Darwin is certainly part of it but it is not the whole story. It is more complex than originally thought.
An Example of Evolution in Action
This is an example of rapid, genetic change in a moth population. The English peppered moth has light and dark colored forms that are under genetic control. In pre industrial England the dominant form was white-colored with dark, "peppery" spots on its wings. The moth rests on the trunks of birch trees during the day where it blends against the similarly colored birch bark. As the industrial revolution began, factories emitted immense amounts of coal soot that settled on the tree trunks and turned them dark gray. In the peppered moth a few individuals had always been a dark, gray color. As the birch trees became darker, the white variants of the moth population became easy prey for birds and the population began to shift. Eventually, the dark form was p predominant and the white form rare. In recent times with modern pollution controls, the air in England is cleaner and the birch trees are again lighter in color. The frequency of light colored peppered moths is increasing.
The selection pressure was in the form of bird predation. The result was deferential reproduction between dark and light colored moths so that the dark forms were initially disfavored, then favored, and now with pollution controls, the light forms are again being favored.
Changes in the peppered moth population over time
% of Moth Population 1850
1950
1972
white colored 95
5
25
dark colored 5
95
75
Natural Selection the mechanism proposed by Darwin to explain how evolution works. While evolution is accepted by most scientists, natural selection is vigorously debated. Darwin proposed gradual natural selection whereby changes accumulated slowly over geological time. Other evidence suggests that at times evolution can proceed very rapidly. In reality, evolution probably proceeds slowly in most circumstances but in some situations can be rapid.
Artificial Selection is the deliberate attempt by man to change the genetic characteristics of plants, animals, or microorganisms. Artificial selection is practiced to make the organism more useful or more pleasing to man. For example, hundreds of varieties of dogs have been bred for various tasks from hunting, tracking, to guarding and for esthetic reasons. Similarly our domestic crops have undergone extensive breeding to make them more useful and productive. Corn has been bred to such an extent that is no longer capable of surviving in the wild.
Selection whether artificial or natural makes changes in the genetic code by differential survival and reproduction. The changes are are inherited by the offspring. Selection is the mechanism of making changes in an organisms heredity.
Genetics and Evolution Links:
ENTER EVOLUTION: Theory and History (7 Feb. 1998).
Teaching about Evolution and the Nature of Science (25 Jan. 2000).
| What is an organism? DNA's way of making more DNA. In other words, you and I, all plants and animals, everything we recognize as an organism, is a biological machine for making more DNA! |
| Steps | Insect Group | Examples |
| 1. Development of insect thorax and body plan from primitive Arthropod body | Apterygota - wingless insects | Silverfish |
| 2. Development of wings | Paleoptera - old winged insects | Dragonflies and mayflies |
| 3. Development of wing folding mechanism | Exopterygota - insects with folding wings | True bugs, roaches, grasshoppers |
| 4. Development of complete metamorphosis | Endopterygota - insects with internal wing buds | Flies, butterflies, beetles, wasps |
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Last updated Dec. 30, 2000