35.2 Defenses Against Infection Texter

The section of pages that you should have read were section 35.2, pages 1014 to 1019. The book talked about how your body protects yourself from infectious diseases.

The first barriers of defense your body has for protecting you from disease is your skin. Your skin is a thick barrier that keeps most of the diseases out of your body. But, microbes can still find ways into your body through your eyes, nose and mouth. Fortunately, they too have their own way of defending you. Your eyes protect you by using lysozyme, which is an enzyme that breaks down bacteria cell walls. The nose creates mucus that traps pathogens and your stomach acid kills most of the things that you swallow. If a pathogen doe enter your body the immune system uses its secondary line of defense that includes raising your body temperature (fever), inflammation response and interferons.

The inflammatory response is when infected areas becomes inflamed and painful because of histamines which cause increased blood flow to the infected area. When this occurs the amount of white blood cells in the area greatly increase because they are destroying the invading bacteria. Interferons are certain cells that interfere with virus growth by producing proteins that don’t allow the viruses to grow. A fever is your body’s way of slowing down or stopping the growth of pathogens. It is caused when the immune system releases certain chemicals that increase body temperature.

The immune system defenses distinguish your body’s own cells from harmful other cells. A healthy immune system recognizes its own cells and knows that they are not harmful. Your immune system also recognizes harmful cells. When a harmful cell invades your body your body attacks it and then remembers it so that if it ever attacks again your body will recognize it faster, this is known as immune response. Antigens are a foreign substance on a harmful cell that the immune system recognizes and tags to be destroyed. When it senses antigens it increases the amount of cells that kill the invaders. Antibodies tag antigens for destruction. Each antibody is made specifically for one type of cell only.

B-lymphocytes are cells that travel to the invasive cells and are created in red bone marrow. T lymphocytes are the cells that are made in the bone marrow but mature in the endocrine gland. They work together to locate and destroy invasive cells. The humoral immunity depends on the response activated when antibodies embedded on B cells hold onto antigens of invading cells. An antigen binds to an antibody and then waits for a T cell to stimulate the division of the B cells.

Plasma cells produce antibodies that are moved throughout the bloodstream. These antibodies float around and mark cells of pathogens. Healthy adults produce around 10 billion different types of antigen that allows the immune system to respond to virtually anything that enters the body. Memory B cells are the cells that remember the pathogen that the body fought off. After an infection is gone the plasma cells that destroyed it die. The memory B cells remember it and if it ever comes back it will know which plasma to make. In the long term it allows your body to build up immunity to it.

Cell mediated immunity guards the body against viruses, fungi, and single celled pathogens that take over and use the bodies own cells. It also protects the body from itself if any of its cells become cancerous. If a cell is infected with a pathogen the cell displays a little of the antigen on the outer surface and marks it to be destroyed.

This activates cytotoxic T cells, which hunt down the infected cells and kill them by puncturing their membranes or apoptosis. The memory T cells help the immune system detect if the same pathogen enters the body again. Suppressor T cells help the immune system stay in check once the infection is under control and also inhibit autoimmune deficiencies. Although cytotoxic T cells are useful to the body, they make organ transplants difficult because they recognize the organ as not itself and it tries to attack it. This is why organ transplant patients usually have to take medications the rest of their lives.

Now that you read this you should have a good idea about how the immune system works, and what it does. Thank you for reading. 8^th Period Mr. Paek’s BIO Rocks!!!!!!!

5.1 Text - Growth Curves

Main Ideas:

The textbook pages that should have been read over the weekend were sections 5.1 and 5.2. In section 5.1, the book described how to read a “J-Curve” graph. It shows the point where the growth is of the highest rate, and it shows how the higher the population, the faster it will grow. The J-Curve shows how a population increases in a certain habitat, and gives you an idea of how the species survives in the habitat. Another name for the J-Curve is called Exponential Growth.

Key Point: under ideal conditions with unlimited resources, a population will grow exponentially.

Another important graph that was reviewed was the “S-Graph”, also known as the Logistic Growth. This graph shows phases 1, 2, and 3 of the growth of a population. The first phase shows the population growing rapidly, the second shows the slowing curve of the population growth, and the third phase shows the complete halt of population growth. The third phase shows the carrying capacity. The carrying capacity is the maximum number of individuals of a particular species that a particular environment can support.

Key Point: logistic growth occurs when a population’s growth slows and then stops, following a period of exponential growth.

Things of importance:

A population’s allocation in a specific environment can vary, too. Some environments will have sparsely populated inhabitants, while others will be closed concentrations of species, dotted along the specific environment. Some species are allocated in their environment randomly, so they can be all over the place. Another type of allocation of a species is uniform, where the species will be populated accordingly, and neatly, so there is no overcrowding. Most commonly, a species will be clumped together for purposes including safety, shelter, and resources.

The area inhabited by a population is called its geographic range. These areas are entirely controlled by that species, and its range extends until the area that is not inhabited by that species is found. For example, a bacterial population in a rotting pumpkin may have a range smaller than a cubic meter.

The growth rate of a population determines whether the population increases, decreases, or stays the same. Species that are in their original or natural habitats often have the same population over time. These populations have a growth rate close to zero. Populations can also decrease in size, depending on the habitat that they are in. That specific population would have a negative growth rate.

Limiting factors can also be introduced into an environment that ultimately limits the population of a certain species. A limiting factor could be things like predation, parasitism, and disease. These limiting factors do depend on the population density though. If there is a shortage of prey for predators, the predators will starve, and most likely die of starvation. If it was the opposite, and there was more prey than there are predators, than the predator’s population will most likely grow, making an onward cycle. These limiting factors are very important to control a fast growing population. These limiting factors are density-dependent.

Density-independent limiting factors affect all populations in similar ways, regardless of population size and density. Things like monsoons, hurricanes, tornadoes, or earthquakes will happen no matter what, and do not depend on the size of a population in that specific environment. In such events, populations will “crash”, and the population will fall rapidly. After the crash, a population will grow rapidly because there is an abundance of food and shelter, considering there is less of a population of that species than there was before.

All of this information can be found on pages 130-140 in the textbook. Do it if you haven’t done it, or else.