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

Tissues represent an organizational level above the cellular level. They are a set of similar cells that specialize in a particular function and are classified into four basic groups: epithelial, connective, muscular, and nervous.

1. Epithelial Tissue

Formed by epithelia, epithelial tissue has two main types based on its features:

• Epithelial tissue lining: Lines the body's surface and internal body cavities. This is further divided into two types:
  • Simple: Just one layer of cells.
  • Stratified: Many layers of cells.
• Glandular epithelial tissue: Builds secreting cells that are exchanged or clustered epithelial cells to form glands.

Examples of Epithelial Tissue:

• Simple squamous epithelium: Flattened cells, wider than they are high. Lines the heart and

Tabanidae: Horseflies and Deerflies

Life Cycle of Tabanus, Chrysops, and Haematopota

The life cycle of horseflies and deerflies (genera Tabanus, Chrysops, and Haematopota) is closely tied to water and is notably long, typically lasting 1-2 years.

• Oviposition: Females lay eggs on plants or stones located close to water bodies.
• Larval Stage: Upon hatching, the larvae enter the water. They are not swimmers but feed on organic matter and plankton. They undergo several larval stages.
• Pupation: The final larval stage burrows into the mud and transforms into a pupa.
• Adult Emergence: Orthorrhaphous adults emerge from the pupa.

Ecology and Ethology

These flies are commonly found in meadows and woodlands near water collections. Ethologically, they are highly... Continue reading "Horsefly and Deerfly Biology: Life Cycle, Health Impact, and Morphology" »

Understanding Nutrition

Nutrition is the set of processes that allows organisms to use and transform nutrients to stay alive. Food is the process by which these nutrients are obtained from the external environment. Food contains nutrients, which are essentially the biomolecules that make up our body.

Essential Nutrients

These include:

• Carbohydrates (Carbs): Energetic substances.
  • Simple Carbohydrates (Sugars): Sweet, crystalline, and water-soluble.
  • Complex Carbohydrates: Not crystalline, do not dissolve, and are formed by the bonding of many simple carbohydrate molecules.
• Lipids: A very diverse set of substances characterized by being insoluble in water and having an oily appearance.
  • Fats: Highly energetic molecules. Depending on their chemical composition,

Digestive System

Function

The digestive system is responsible for processing food, absorbing molecules, and eliminating waste.

Types of Digestion

There are two main types of digestion: mechanical and chemical.

System Interactions

The digestive system interacts with the nervous, endocrine, and circulatory systems.

Functional Structure

1. Mouth: Digestion begins in the mouth.
2. Esophagus: Food travels down the esophagus.
3. Stomach: Gastric digestion occurs in the stomach.
4. Small Intestine: Intestinal digestion and absorption take place.
5. Large Intestine: Final absorption and waste processing.

Excretory System Structure

The excretory system plays a crucial role in waste removal.

• Cecum: Follows the ileocecal valve.
• Colon: Divided into ascending, transverse, and descending

Virus Characteristics

Viruses are unique pathogens, not classified as living organisms. A virus particle, a submicroscopic infectious agent, has a single nucleic acid type (DNA or RNA) within a protein coat called the viral capsid, forming the nucleocapsid.

Some viruses have a lipid-protein envelope. The capsid's protein organization determines the virus's shape, usually helical or polyhedral. Viruses are genetic elements in transit, switching between extracellular and intracellular states.

Extracellular Phase (Virion)

In the extracellular phase, the virion is metabolically inert. It carries viral genetic material from one cell to another.

Intracellular Phase

Inside a cell, the virus replicates, using the cell's machinery to synthesize new viral... Continue reading "Virus Structure, Classification, and Replication Cycles" »

Understanding Human Sexuality

Human sexuality encompasses three fundamental aspects:

• Biological: The physiological and anatomical differences between sexes.
• Spiritual: The emotional and relational dimensions of sexuality.
• Socio-cultural: How society and culture shape sexual norms and behaviors.

Biological Foundations of Sex

The differentiation between the two sexes begins at the cellular level. In a zygote, if the 23rd pair of chromosomes has the characteristics XY, the individual is male; if XX, the individual is female. From that moment, primary sexual characteristics (reproductive organs) begin to form. At puberty, secondary sexual characteristics develop due to hormone production, leading to changes in body shape, voice tone, and hair growth.... Continue reading "Human Sexuality: Biology, Reproduction, and Health" »

1. Bacterial Antibodies

Which individual component of a bacterium should be injected into rabbits to generate effective antibodies against subsequent exposure to the same bacteria?
c. Bacterial chromosome DNA fragments

2. Lymphocytes

The lymphocyte, a type of leukocyte, is characterized by:
II. Providing long-term or short-term immunity to the body

3. Acquired Immunity

Acquired immunity, whether natural or artificial, is achieved by:
I. Suffering from an illness
II. Vaccination with an attenuated microbe
III. Administration of antibodies produced by another source

4. Natural Immunity

The term "natural immunity" refers to:
I. Immunity that develops during an individual's life as a result of the body's response to a pathogen
II. Immunity that is activated

**Functions of the Cell**

• Nutrition: Through nutrition, cells obtain the energy they need to create and maintain their structures and perform other vital functions. The molecules from which they obtain materials and energy are nutrients such as water, minerals, oxygen, and organic molecules.
• Relationship: By using this function, cells perceive physical and chemical changes that occur in the environment that surrounds them.
• Reproduction: Using this function, cells originate and divide into new cells.

**Types of Cells**

• Prokaryotes: They are characterized by a lower degree of complexity and a smaller number of organelles. These are single-celled organisms.
• Eukaryotes: They are characterized by a complex organization with many different compartments

Stages of Embryonic Development

A key feature that differentiates living things from non-living things is the ability to reproduce. Reproduction occurs through cell division. In more complex organisms, this includes sexual and asexual reproduction. The essential phenomenon is mitosis in plants and animals. Sexual reproduction involves meiosis, the process of gamete formation, or specialized cells for reproduction, with the participation of individuals of different sexes. Genetic and hormonal events, along with synchronization mechanisms, ensure the release of gametes for successful fertilization. This is followed by a series of events that characterize successive development and differentiation, transforming the egg or zygote into an adult individual.... Continue reading "Embryonic Development: Stages, Fertilization, and Processes" »

Eradication of Diseases Worldwide

If we tried to reach all the world, including countries that are not even developed, we could eradicate diseases.

The Relationship Between Diseases and Microorganisms

Pasteur established for the first time the relationship between certain diseases and the presence of microorganisms in the patient, but the mere observation of microorganisms with the disease does not guarantee that it will cause it.

Ebola Virus: A Highly Contagious Disease

The Ebola virus is the cause of Ebola viral hemorrhagic fever, an infectious, highly contagious, and very severe condition that affects both animals and humans. The virus is transmitted by direct contact with infected bodily fluids such as blood, saliva, sweat, urine, or vomit.... Continue reading "Understanding Common Infectious Diseases and the Immune System" »