Molecular Level – Operon

The operon is a region of bacterial DNA that regulates gene expression in bacteria. The operon consists of four major parts: structural genes, regulatory gene, the promoter gene, and the operator. Structural genes are genes that code for enzymes needed in a chemical reaction and these genes will be transcribed at the same time to produce specific enzymes. The regulatory gene codes for a specific regulatory protein called the repressor, which is capable of attaching to the operator and blocking transcription. The promoter gene is the region where the RNA polymerase binds to begin transcription. The operator is the region that controls whether or not transcription will occur.

 
Cellular Level – Nucleus

The nucleus is considered to be the control center of the cell; it controls everything that occurs inside the cell, including the cell’s ability to reproduce. The nucleus is also the home to the cell’s DNA, which is packaged into chromosomes. It is found in the cells of all multicellular living things such as: plants and animals.

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Organismal Level – Pituitary Gland

The pituitary gland is in charge of releasing many hormones that reach other glands to stimulate and secrete their hormones. The pituitary gland has two parts: the anterior and the posterior, each with their own set of hormones.

The anterior pituitary secretes six hormones, three for regulating growth and three for regulating the reproductive systems. The six hormones include: the growth hormone (GH), the adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin. GH stimulates the growth throughout the body, specifically targeting bones and muscles. ACTH is the hormone that stimulates the adrenal cortex to secrete glucocorticoids and mineralocorticoids. Lastly, TSH stimulates the thyroid to secrete thyroxine. FSH stimulates follicle to grow in females and spermatogenesis in males. The anterior pituitary is actually regulated by the hypothalamus.

The posterior pituitary, secretes only two hormones: the antidiuretic hormone also known as vasopressin as well as the hormone oxytocin. The antidiuretic hormone regulates the water intake by nephrons. Oxytocin stimulates the contraction of the uterus and the ducts of the mammary glands.  

Photo by Reigh LeBlanc

Populations – Hardy Weinberg

The Hardy-Weinberg law states that even with all the shuffling of genes that occur, the approximate frequencies of genotypes in a population still prevail over time. The frequency of alleles is depicted in this equation: p + q = 1. This can also be calculated by determining the frequency of the genotypes in a population using the equation: p^2+2pq+ q^2. In these equations, p stands for dominant allele, while q is for the recessive. The law states that populations will be in genetic equilibrium only if it meets the five conditions: there is a large population, there are no mutations, no immigration or emigration occurs, random mating occurs, and that no natural selection occurs. Through this, the Hardy-Weinberg Law regulates variation in a population.

Population – Growth Characteristics

There are two different types of population growth and regulation, r-selected and k-selected. The characteristics of r-selected growth include: late maturation, fewer offspring, larger young, longer life spans, more parental care and intense competition for resources. Then there is also the is the K-selected population, whose characteristics include: early maturation, a large number of offspring, smaller young, shorter life spans, less parental care and little competition for resources. Still though, biological and environmental factors can affect these characteristics. These two regulate the growth of an animal.

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Community Level – Decomposers

Decomposers are organisms that break down organic matter into simple products. The most common decomposers are fungi and bacteria and they serve basically as the “garbage collectors” of the community. Eventually in a community everybody will yield to a decomposer. Now, the reason this has to do with regulation is that decomposers regulate or help clean up our communities, making them capable of living comfortably in them.

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Biosphere – Ozone Layer

The ozone layer is a layer in the earth’s atmosphere made up of O3 that absorbs 93 to 99 percent of the sun’s ultraviolet rays, thus protecting us from them. The ozone layer is mainly located in the stratosphere and the thickness of the layer depends on the area on earth.

Photo by Nasa Goddard Photo and Video

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In a sequence of experiments from 1909 to 1911, Ernest Rutherford discovered that the majority of an atoms weight was concentrated in the center called the nucleus. He discovered this by completing and analyzing a gold foil experiment. Rutherford fired alpha particles, relatively massless particles consisting of two protons and two neutrons, at a thin sheet of gold foil. Rutherford wanted to measure how much the alpha particles were deflected because the alpha particles have a positive charge and the electrons have a negative charge. The electrons were expected to slightly alter the trajectory of the fired alpha particles. Contrary to Rutherford’s hypothesis, the alpha particles were hardly deflected. After analyzing the experiment, Rutherford concluded that the mass of the atom was not evenly distributed as previously thought. The mass of the atom, in fact, was highest in the center of the atom called the nucleus. Rutherford’s hypothesis for this experiment was disproved, a key part of Science as a process. It is acceptable in science to hypothesize incorrectly as long as you can explain the correct outcome of the experiment.

Tangerine fruit stalk; Photo by Tatcher a Hainu

 In 1838, Theodor Schwann and Matthias Schleiden were sitting together speaking about their study of cells. Schleiden described plant cells as having a nucleus in the center. This directly correlated with Schwann’s observation of animal cells. The two immediately looked at each others slides and came up with a cell theory which stated:

1) The cell is the unit of structure, physiology, and organization in living things.   

2) The cell retains a dual existence as a distinct entity and a building block in the construction of organisms.

3) Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation).

In this case, Schwann and Schleiden used many different processes of Science. They Experimented, inferred, and collaborated in order to come to their conclusion.

Louis Pasteur; Photo by Euclid vanderKroew

Louis Pasteur, a French scientist, disproved the theory of spontaneous generation. This theory stated that living organisms could be made from non-living matter. In order to disprove this, Pasteur boiled meat broth into a flask and shaped the flask into an S shape. Air could enter the S shaped flask, but small microorganisms could not. After many days, as expected by Pasteur, no organisms grew in the broth. In the broth that Pasteur left in a regular open flask, however, organisms grew. This proved that organisms couldn’t just appear. Pasteur hypothesized correctly and accurately conducted an experiment to prove his hypothesis. This was one of the landmark experiments at the time, disproving a common theory.

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Karl von Frisch, an Austrian ethologist, studied honeybees and showed that they use dance to communicate food locations to other bees. Von Frisch noticed that when one honeybee found food, others appeared around the food. He then studied the bee’s movements when it found the food. He observed two different movements or dances. A round dance, which tells other bees to search for food close to the hive and a waggle dance which told other bees the direction and distance to fly toward the food. This study on a population of honeybees helped scientists further understand the movement and food searching methods of the bees. Von Frisch mainly used the scientific process of observation and analysis to reach his conclusions on honeybee dances.

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Recently, Harvard University has conducted studies on invading, nonnative plant species, especially those in Massachusetts. The Alliaria petiolata, a common invader in Massachusetts’s forests. This plant threatens other local plants such as sugar maple and breech in the forest. They also studied that the Alliaria petiolata spreads in low light areas. The study of the population of plants in Massachusetts forests help Harvard scientists figure out how to get the nonnative species out and how to help the native plants survive. These scientists observed the plants for hours in order to come up with a hypothesis on what the invading species is doing and a way to help the native species survive.

Photo by KTVee

In 1988 James Lovelock published a book speaking about his Gaia hypothesis. This hypothesizes that all living things have a regulatory effect on the earth’s environment that promotes life. Lovelock came upon this hypothesis while looking at the atmosphere of Mars in its equilibrium. He analyzed that the earth’s atmosphere was never in equilibrium. This highly controversial hypothesis has not been proven. Most scientific discoveries start out as unproven hypothesis. Scientists then conduct experiments to prove or disprove hypothesis and eventually come to a final conclusion.

1.Each species produces more offspring than can survive.
2.These offspring must compete with each other for limited resources required to survive.
3.Organisms in all populations vary in alleles and are different.
4.The individuals with the most favorable traits or variations are the most likely to survive and therefore produce more offspring.

Molecular

Genes are the units that help code for proteins within an organism. Evolution has seen the selection of specific genes that code for specific proteins over less desirable genes. For instance, the gene that codes for blindness in the blind cavefish is chosen over the gene for eyesight. The reason for this is that one of the two genes involved in senses of the fish must be traded for the others. In easier terms, the eyesight of the fish must be sacrificed so that the jaw and taste buds can develop. In this case, the pleitrophy gene that controls this development is slightly inhibited by another gene. The only reason the inhibiting gene is selected is because while it inhibits eyesight, the fish can rely on its other sensory organs, which proves to be successful.

Cellular

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On a cellular level, eukaryotic cells are complex in comparison to prokaryotic cells. According to the endosymbiotic theory, the evolution of organelles originated from a prokaryotic cell that joined with separate prokaryotic cells. The organelles in the cell proved to be exceptionally helpful, such as the mitochondria, which supplied it with energy. The earliest mitochondrion is believed to have begun as a very primitive bacterium. With a source of internal energy, the eukaryotic cell was more favorable and through natural selection, became more frequent.

Organismal

Photo by Kaptain Kobold

The kidneys are responsible for filtering the wastes of the blood and reabsorbing nutrients during the process. Some animals have evolved to have excretory systems to compliment the environment that they live in. For instance, in dry and arid environments, many animals have an extra complex collecting duct, where the most water is reabsorbed during excretion, to maximize the amount of water conserved. Those organisms that have the systems to do this can survive longer and are favorable to the environment because of their success in retaining water, which is a necessity in their environment.

Population

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One of the easiest examples to observe since it reproduces so quickly, bacteria helps explain genetic drift in populations. If you were to put a culture of bacteria in a nutrient rich environment, they would reproduce. But if you added an antibiotic into the environment that killed most of the bacteria, only the bacteria that had alleles that made them resistant to the antibiotic would survive. Since the bacteria that died did not have a high fitness, they were not able to continue contributing their genes to the pool. Only the surviving bacteria will be able to pass on their genes, which include resistance. This, in time, will lead to a whole generation of antibiotic resistant bacteria that has evolved from the original population to one made of resistant genes.

Community

Photo by Thomas Hawk

The predators and prey evolve together, the prey trying to stay one step ahead of the predator, and the predator trying to catch up. In the case of wolves and rabbits, wolves evolve mechanisms to help them survive by obtaining food such as speed, stealth, camouflage, and excellent sensory senses. Likewise, the prey, rabbits, develop similar mechanisms to aid in avoidance and escape of a predator. Any trait such as long legs to run or hop faster will enable the prey to escape its predator, and pass its genes to its offspring. Those that are eaten obviously were not fit to their environment and their genes, which did not help them, will not be passed on.

Biosphere

Photo by Brent Danley

The globe is made up of many different climates and geographic features, each factors of a specific biome. With in a biome, an ecosystem of organisms exists which specifically suit that particular biome. Producers within the biome have evolved features that give them high evolutionary fitness. The consumers that feed off of these producers are also well suited to their biome, as discussed in population. With the combination of all of the organisms well suited to their environment in one biome, there is an ecosystem that is specifically designed to survive there. If you were to take a kangaroo and place it in the arctic, the kangaroo would not be able to find the resources it needs to survive. The food that it lives off of, the habitat it is used to and the mates it needs to reproduce are not there. That is why each biome is made up of biotic and abiotic factors that specially suit the surrounding ecosystem.