Ocean Origins, Endosymbiosis, and Disease Types

The Origin of the Oceans

When edges diverge from the same continent, rift valleys form.

If the gap in these valleys continues to widen and connects to an ocean, it floods, creating a new ocean.

The ocean floor will have a dorsal ridge where the lithosphere is created, producing intense volcanism.

Borders with Lateral Movement

Edges with lateral movements separate plates that slide laterally with respect to each other. These are broken, called transform faults, which are usually interspersed along the different edges, allowing the accommodation of plate fragments that move at different speeds.

As these borders neither create nor destroy lithosphere, they are called passive. They are highly unstable areas, with frequent and strong earthquakes.

Endosymbiosis Theory

According to the theory of endosymbiosis, or symbiogenesis, eukaryotic cells originated from small prokaryotes that were engulfed by larger ones. These smaller prokaryotes were not digested but transformed into symbionts within organelles.

Proposed by Lynn Margulis in 1967, this theory suggests that a large anaerobic prokaryotic cell capable of phagocytosis engulfed other prokaryotes at different times. Instead of being digested, these survived in symbiosis inside the host, eventually forming different organelles of the aerobic eukaryotic cell. The main foundations of this theory are based on the fact that mitochondria and chloroplasts have the following features:

1. Size and shape similar to those of bacteria
2. Ribosomes the size of bacterial ribosomes
3. Own circular DNA, like bacteria, and enzymes necessary for transmission to RNA.

Diseases

A disease is a physical or mental disorder that causes changes in the normal functioning of the body, either physically or psychologically. Pathology refers to the changes that occur in the body due to disease.

Non-Infectious Diseases

Non-infectious diseases disrupt the normal operation of the body and its systems. Depending on their causes, characteristics, and site of action, several groups are distinguished:

1. Hereditary or Genetic Diseases: These are inherited from parents. Many are chronic and remain for life. Genetic predisposition is considered a risk factor for other diseases, like cancer.
2. Mental Illness: These are characterized by abnormal behavior or undue disturbance of personality. Various psychotropic drugs, therapy, and counseling can be used in their treatment.
3. Diseases of Specific Organs and Systems: These affect different organs and body systems, such as diseases of the respiratory, circulatory, or peripheral systems.
4. Autoimmune Diseases: These are due to a failure of the immune system, resulting in the production of molecules that harm the body itself.
5. Diseases Caused by Accidents: Including diseases caused by traffic accidents, domestic accidents, work accidents, etc.

Infectious Diseases

The prevalence of a disease is the number of patients at a given time, while the incidence is the number of new cases of a disease in a population.

An infection is transmitted from a source of infection to a susceptible host, which is a healthy individual who may become ill after contact with the infectious agent. The relationship between the pathogen and the host can be distinguished by:

1. Contagiousness: The transmission capacity of the organism.
2. Infectivity: The ability of the infectious agent to settle and multiply.
3. Pathogenicity: The ability of the pathogen to produce disease.
4. Virulence: The degree of pathogenicity.

Reservoirs of Infection

Prior to infecting humans, all pathogens have locations, called reservoirs of infection, where they are produced and/or contained and from which they are transmitted to humans. The reservoir is usually an animal.

Phases of Infectious Diseases