Notes, summaries, assignments, exams, and problems for Biology

• In the pyramids of numbers, the lengths of the steps are proportional to the number of individuals of all species in each trophic level per unit area or volume.

  Biomass in the lengths of the steps are proportional to the dry weight of all individuals in each trophic level per unit area or volume.

  These pyramids best describe the trophic relationships of the ecosystem as they indicate the amount of organic matter that can be eaten at each trophic level, but do not express the amount transferred from one level to another.

  Energy in the lengths of the steps are proportional to the energy produced per unit time of all individuals in each trophic level per unit volume or surface.

  These pyramids provide a better overall picture of trophic relationships

Cholera

Pathogen: Vibrio cholerae

Methods of Transmission:

• Foodborne
• Waterborne

Note: 3/4 of infected people may be asymptomatic carriers and pass large numbers of bacteria in their feces.

Global Distribution: Asia, Africa

Incubation Period: 1-5 days

Site of Action: Wall of the small intestine; secretes a toxin called choleragen

Clinical Features:

• Severe diarrhea
• Loss of water and salts
• Weakness

Note: Can be fatal if not treated within 24 hours.

Method of Diagnosis: Microscopic analysis of feces

Annual Incidence Worldwide: 5.5 million

Annual Mortality Worldwide: 120,000

Treatment: Antibiotics

Tuberculosis

Pathogen: Mycobacterium tuberculosis

Transmission:

• Airborne droplets
• Infected meat

Global Distribution: Worldwide

Incubation Period: A few weeks or months

Site of

Infection: Pathogen Penetration and Host Response

Infection is the penetration of a pathogen into the body of an animal or plant, causing changes in organs and their functions. It is essential for the microbe to possess pathogenicity (the ability to cause disturbances in the body), which depends on its invasiveness and toxin production. For an infection to develop, the host organism must be receptive to the microbes (i.e., susceptible to invasion).

Organic Defense Mechanisms: Protecting the Body

Nonspecific Defense (External Barriers)

These are the body's first lines of defense, acting as external barriers:

• Structural: Skin and mucous membranes. These are common entry points for pathogens when compromised.
• Mechanical: Tears, urine, coughing, and

Genetic Mutations

A mutation is an alteration of genetic material. Key characteristics include being detectable and heritable.

Types of Mutations

• Chromosome Mutations

  These are visible under light microscopy and affect large fragments of chromosomes or entire chromosomes, thus involving many genes. They can impact the structure or number of chromosomes.

  • Structural Alterations: Changes in chromosome structure resulting from broken chromosomes and the rejoining of fragments.
  • Numerical Abnormalities: Changes that alter the normal chromosome number of a species.

• Gene Mutations

  These are not observable by light microscopy and typically involve only a few nucleotides.

Genetic Engineering

Genetic engineering encompasses the study and techniques for the manipulation... Continue reading "Genetic Mutations, Engineering, and Biotechnology Applications" »

Understanding Health and Disease

Key Definitions

• Disease: A part of our body that changes and ceases to perform its function well.
• Health: Your mental or physical condition.
• Symptoms: A physical or mental feeling experienced by someone with a disease or illness.
• Diagnose: To study symptoms of an illness or disease and to decide what is wrong with a person.
• Sign: A symptom of a disease or illness that is recognized by others.
• Treatment: Medical care or attention given to a person who is ill (curative or symptomatic).
• Convalescence: The period needed for returning to health after illness.

Factors for Maintaining Good Health and Preventing Diseases

• A Healthy Environment: Free of anything harmful to health.
• Healthy Habits and Lifestyles.
• Personal Characteristics.

Diarrheal Diseases

Diarrheal diseases are among the most serious health problems worldwide. Key diseases in this category include cholera, dysentery, and salmonellosis. These are caused by organisms that reside in the intestines of infected individuals, sometimes without causing apparent symptoms. Regardless of whether the person exhibits symptoms, their feces contain large amounts of pathogenic microorganisms.

The disease spreads via the digestive tract through the consumption of contaminated food or drink. Contamination can occur directly or indirectly, such as through flies, or via contact with the hands or skin of individuals living without proper sanitation. Intense diarrhea is often accompanied by vomiting, leading to significant loss of... Continue reading "Understanding Common Infectious Diseases and Their Management" »

Divisions of the Nervous System

Central Nervous System

Consists of the brain and spinal cord. It is responsible for receiving and processing information to control bodily functions.

Peripheral Nervous System

Consists of a set of nerves that connect the central nervous system with other organs of the body.

Components of the Central Nervous System

The brain is housed in the skull. The main parts are the cerebrum, the cerebellum, and the medulla oblongata.

The Cerebrum

Appears divided into two hemispheres. The outer part consists of gray matter that receives information from sense organs. The inner zone contains white matter.

The Cerebellum

Located below the cerebrum. The cerebellum coordinates movements such as walking and allows us to maintain balance.... Continue reading "Nervous System: Structure, Function, and Health" »

Infectious Disease Prevention and Treatment

Infections can be treated with antiseptics, which kill microorganisms but can only be applied to the skin's surface. Antibiotics are substances that selectively attack bacteria and can be ingested or injected. Penicillin was the first known antibiotic. The English physician Jenner invented vaccines, which involve injecting small amounts of dead or fragmented pathogens.

Healthy Habits

• Eat in moderation at least three times a day, always including breakfast.
• Eat a balanced diet with the appropriate proportion of nutrients.
• Sleep eight hours a day.
• Exercise moderately to maintain muscle tone.
• Maintain a proper weight for your age, sex, and build.
• Practice proper hygiene.
• Avoid snuff, alcohol, and other drugs.

The Human Genome Project (HGP)

The Human Genome Project (HGP) aimed to map and sequence all the genes of human beings.

Key Genetic Concepts

• Genome: The complete set of genes of an individual organism.
• Proteome: The entire set of proteins originating from the genome.

The human genome contains fewer than 30,000 genes. The genetic differences between humans and other species are lower than initially expected.

Present and Future Applications of HGP Discoveries

The possibilities offered by these discoveries include:

• Genetic Testing: To determine the likelihood of developing specific diseases.
• Gene Therapy: Techniques used to correct defective genes.
• Genetic Diagnosis: Essential for pre-transplantation screening.
• Knowledge of Human Evolution: Providing deeper

Muscle Contraction Physiology and Rigor Mortis

The Mechanism of Rigor Mortis

Rigor mortis occurs when muscles become rigid a few hours after death. This rigidity results because muscle cells run out of ATP and can no longer pump calcium back into the sarcoplasmic reticulum.

Calcium ions, upon leaving the reticulum, bind to accessory proteins, allowing the formation of cross-bridges. Without ATP, contraction cannot occur, but calcium remains present, and cross-bridges persist, preventing the muscles from stretching. Rigor mortis typically disappears 15 to 20 hours later, when muscle cells begin to break down.

Skeletal Muscle Contraction Control

The nervous system controls the contraction of skeletal muscle. Motor neurons activate specialized synapses... Continue reading "Muscle Contraction Physiology: Skeletal, Cardiac, Smooth, and Rigor Mortis" »