Themes in Biology – Regulation

2010/05/03
By Andrew

Regulation, by definition, is the adaptation of form or behavior of an organism to changed conditions.

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.

Photo by Duncan

Photo by Leo Reynold

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.

Photo by I Need Coffee

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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