BIOLOGICAL CLASSIFICATION

Importance of Classifying Organisms

1. It makes the study of organisms convenient.

2. It helps in the specific identification of any given organism.

3. The study of each distinct group of organisms helps is to integrate life as a whole.

4. It provides information about the organisms, which occur in specific geographical regions.

5. Indicates the evolutionary relationship by establishing the gradually increasing complexity of forms and structures in different groups of organisms.

Levels of Classification

"Kings Play Chess On Fine Glass Sets"

Major Characteristics of the Six Kingdoms

Some Organisms and Their Uses

• Button mushroom (fungi) are famous taste when cooked. Several species of edible mushrooms are being successfully cultivated
• Most plants are cultivated for food like potato, corn, rice, carrots, and other roots crops
• The fungi genus, Penicillium is used not only for medicine, but also in cheesesmaking
• Escherichia coli, Bacillus, and Streptomyces produce vitaminB12, and roboflavin they are when placed in a meduim with coconut water. Bacillus and Streptomyces species in the same medium also produce antibiotics
• Bacteria, aside from their medical uses, are also aids in digestion and fermentation. They also decompose dead plants and animals into forms used by the environment
• Some fungi, like yeast and those belonging to the genus Streptomyces, are indispensable in bread-making.
• Ficus elastica, commonly known as the rubber plant, provides raw materials for the rubber industry.
• Abaca plant (Musa textilis) is known for its strong and durable fibers in making ropes, fabrics, and many other.
• Econimically, animals are as useful as plants.Meats sold markets come from pigs, cattle, goats, and poultry. Many clothing materials like leather and wool come from animal skin.
• Humans, animals, plants, and microorganisms are interdependent. People need plants and animals for food, clothing, and shelter. Plants need animals for carbon dioxide; animals need plants for oxygen. Each cannot exist without the other.

FOSSILS AND EVIDENCES OF EVOLUTION

Fossil
- any preserved part or trace of an organism that once lived.
- it is formed when substance in the soil replace the soft, easily decomposed part of a dead organism.
- Other organisms like mosquitoes and spiders are sometimes covered with resin. The resin hardens, forming amber.

Fossil Reconstruction
- Scientists gather pieces of fossils, reconstruct them to form a complete structure, and compare them with structures of living organisms.
- Scientists work with other artists who compare the shape of the skeleton to determine an ancients organism's posture ans style of walking.
- Some may even determine the shape of the preserved organism by detecting muscle attachments and using clay molds.

Types of Fossils
1. Imprints - are formed when soft body structures such as feathers and leaves form impressions on sedimentary rocks.

2. Molds - are depressions on the rock and are shaped like the part of the organism such as teeth, shells, and bones.

3. Cast - it is formed when a mold is filled with another material.

4. Petrified Fossils - are formed when minerals replace the hard parts of organisms.

Fossils can be formed in 3 processes:

1. Replacement - is the process through which the original mineral is replaced by other minerals that seep in from the environment.

2. Molds and Casts

3. Recrystallization - only outline of the original material is preserved.

Evidences of Evolution

1. Embryonic Development
- organisms in their early stages of development are called embryo.
- embryonic development among species reveal similarities with their "ancestors".
- during development process embryos look alike because organisms may have the same ancestral roots.

2. Homologous and Analogous Structures

Homologous structures - some organisms of different groups have body parts that are similar in structure but have different functions.
Analogous structure - are those that have similar functions but different anatomical structures. Example butterfly's wings have the same function as the bat's wings.
3. Vestigial Structures - are parts of the body with no particular function. The existence of these structures indicates that the changes have taken place through time and that the ancestral roots of the organisms with these structures may be the same.

4. Biochemical Evidences - indicates that living organisms share a common ancestor. Variation is formed in the protein structure of one group of organisms as they evolve into another group.The greater are the similarities in the protein structures, the closer is the relationship between the organisms.

Mechanisms of Evolutiom

Mechanisms of Evolution

· Evolution does not occur in individual but in populations.

· A population is an interbreeding group of individuals of one species in a given geographic area.

· A population evolves because the population contains the collection of genes called gene pool. As changes in the gene pool occur, a population evolves.

                    

                        1. Mutation

· is a random change in the gene pool of a population. It is a change in the nature of the DNA in one or more chromosomes.

· Gives rise to new alleles; therefore, they are the source of variation in a population.

· It may be harmful but may be also beneficial. For example, mutation may permit organismsin a population to produce enzymes that will allow them to use certain food materials. Over time, these types of individuals survive, while those not having the mutations perish. Therefore, natural selection tends to remove the less fit individuals, allowing more fit individuals to survive and form a population of fit individuals.

2. Gene Flow

· Refers to change in the allele frequencies due individuals entering or leaving a population

· When migrating individuals interbreed with the new population, they contribute to the gene pool of the local population. This establishes gene flow in the population.

· Gene flow occurs, for example, when wind carries seeds far beyond the bounds of the parent plant population. As another example, animals may be driven off from the herd. This forces them to migrate to a new population, thereby bringing new genes to a gene pool. Gene flow tends to increase the similarity between remaining populations of the same species because it makes gene pools more similar to one another.

                      

                        3. Genetic Drift

· Occurs when a small group of individuals leaves a population and establishes a new one in a geographically isolated region.

· Example, when a small population of fish is placed in a lake, the fish population will evolve into one that is different from the original. Fitness of a population is not considered in genetic drift, nor does genetic drift occur in a very large population.

4. Natural Selection

· The most important influence on evolution is natural selection.

· In natural selection, an organism is subject to its environment. The fittest survive and contribute their genes to their offspring , thereby producing a population that is better adapted to the environment. The genes of less-fit individuals are eventually lost. The important selective force in natural selection is the environment.

· Environmental fitness may be expressed in several ways. For example, it may involve an individual’s ability to avoid predators, it may imply a greater resistance to disease, it may enhance ability to obtain food, or it may mean resistance to drought. Fitness may also be measured as enhanced reproductive ability, such as in the ability to attract a mate. Better-adapted individuals produce relatively more offspring and pass on their genes more efficiently than less-adapted individuals.

· Types of natural selection:

1. Stabilizing Selection – occurs when he environment continually eliminates individuals at extremes of a population.

2. Disruptive Selection – here, the environment favors extreme types in a population at the expense of intermediate forms, thereby splitting the population into two or more populations.

3. Directional Selection – The environment acts for or against an extreme characteristic, and they likely result is the replacement of one gene group with another gene group. The development of antibiotic resistant bacteria in the modern era is an example of directional selection.

Species Development

· The evolution of species is called speciation.

· Speciation can occur when a population is isolated by geographic barriers, such as occurred in the isolation of Australia, New Zealand, and the Galapagos Islands. The variety of life forms found in Australia but nowhere else is the characteristic result of speciation by geographic barriers.

· Speciation can also occur when reproductive barriers develop. For example, when members of the population develop anatomical barriers that make mating with other members of the population difficult, a new species can develop. The timing of sexual activity is another example of a reproductive barrier. Spatial difference, such as one species inhabiting treetops while another species occurs at ground level, is another reason why species develop.