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

Types of Digestion

Digestion is the process by which complex molecules are broken down into simpler ones. There are two methods of digestion:

• Intracellular Digestion: This takes place inside cells. Each cell functions as a complete digestive system:
  • Food capture (pseudopodia, cilia, or flagella)
  • Food inclusion (endocytosis)
  • Food digestion (lysosomes)
  • Expulsion of undigested material (exocytosis)
  Typical of sponges.
• Extracellular Digestion: This is performed inside the digestive systems consisting of one tract and specialized glands. The nutrients pass into the bloodstream and are distributed to reach all cells. Typical of most animals.

Some animals combine both types of assimilation:

• The food comes in the form of large fragments.
• The inner wall of the

Protein Definition

A protein consists of amino acids linked together. Each amino acid has a central carbon atom attached to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable radical group (side chain).

Protein Classification

Proteins can be classified based on their composition:

• Holoprotein: Composed solely of amino acids.
• Heteroprotein: Composed of amino acids along with other non-amino acid molecules (prosthetic groups).

Amino Acids

Amino acids are organic compounds characterized by having both a carboxyl group (-COOH) and an amino group (-NH2). They are typically solid, crystalline substances with high melting points, soluble in water, and possess optical activity. Their chemical behavior is amphoteric, meaning they... Continue reading "Protein Essentials: Structure, Properties, and Functions" »

Mendel's Laws of Inheritance

Gregor Mendel's foundational work established the basic principles of heredity:

• 1. Law of Uniformity (First Law)

  If you cross two pure strains that differ in a single character, the first filial generation (F₁) will be uniform, presenting only the dominant character.

• 2. Law of Segregation (Second Law)

  The recessive character, which is not expressed in the F₁ generation, reappears in the F₂ generation in a ratio of 3 dominant to 1 recessive (3:1).

• 3. Law of Independent Assortment (Third Law)

  In heterozygotes for two or more characters, each character is transmitted to the next generation independently of any other character. This results in all possible combinations for these traits.

Functions of DNA

Deoxyribonucleic Acid... Continue reading "Essential Biology: Genetics, Cell Division, Ecology" »

Non-Infectious Diseases

Cardiovascular Diseases

Cardiovascular diseases affect the heart and blood vessels, and their incidence is higher in adults and the elderly.

• Atherosclerosis: An enlargement of the walls of the arteries due to the deposition of cholesterol, platelets, and fibrous tissue. The arteries can become calcified and hardened, resulting in a loss of elasticity.
• Thrombus: A blood clot that occurs in an artery or vein, leading to its obstruction (thrombosis). When the clot forms in a vein, it can be released and easily move to another place (embolism).
• Aneurysm: A weakening of the arterial wall, which promotes dilation of the artery. This can rupture and form a hemorrhage.
• Stroke: Interruption of blood supply to the brain.
• Coronary Artery

Emerging and Reemerging Diseases

Emerging diseases are caused by previously unknown germs. These germs may have been hidden or have mutated. An example is Ebola.

Reemerging diseases are those that reappeared after a period of decline. Examples include cholera, tuberculosis, dengue, and malaria.

Outbreaks and Spread

An epidemic outbreak is the rapid spread of an infectious disease affecting many people in a limited area and time.

A pandemic is an epidemic affecting many parts of the world.

Key Concepts

A syndrome refers to the complex and variable damage caused by infectious agents.

A reservoir is an animal that harbors infectious agents transmissible to humans, such as rodents.

A vector is an animal that transmits germs to a healthy person, such as... Continue reading "Infectious Diseases: Emergence, Spread, and Immunity" »

Male Reproductive System Components

Sperm Production and Testicular Hormones

Spermatogonial: Embryonic cell producing sperm.

Testosterone: A hormone produced by the testis; its function is the development and maintenance of male sexual characteristics.

Hormones Synthesized by the Testis: Testosterone acts on the maturation of testicular germ cells.

Luteinizing Hormone (LH): Stimulates the secretion of testosterone by the Leydig cells.

Follicle-Stimulating Hormone (FSH): Stimulates the Sertoli cells.

Epididymis and Vas Deferens Function

Epididymal Function: Allows the passage of spermatozoa and facilitates their maturation.

Role of the Vas Deferens: Its function is to allow sperm to leave the epididymis and transport them to the ejaculatory duct.

Male

Stages of Childbirth

Expulsion (Second Stage of Labor)

The fetus is pushed outward by uterine contractions and by the force exerted by the mother pushing her diaphragm. This stage usually lasts about 15 to 30 minutes. It concludes when the baby is born and takes its first breath.

Placental Delivery (Third Stage of Labor)

Between 5 to 15 minutes after the baby's birth, the placenta is expelled, along with the remaining uterine lining.

Childbirth Complications

Inadequate Dilation of the Cervix and Vagina

To alleviate this problem, the mother may be given the hormone oxytocin, which causes uterine contractions and cervical dilation.

Umbilical Cord Clamping

If the umbilical cord is compressed, the blood flow between the mother and fetus is cut off. If this... Continue reading "Human Reproduction: Conception, Childbirth, and Family Planning" »

Understanding Species in Biology

A taxonomic category, a species is defined as a set of natural populations that can interbreed, either in reality or potentially, and which are reproductively isolated from other similar groups. When individuals can cross, it means their descendants are also fertile. The term "potentially" relates to natural conditions that might prevent crossing between two populations of the same species. All individuals of a species share similar anatomical and morphological features.

The Monera Kingdom: Prokaryotic Life

The Monera kingdom is constituted by the vast majority of prokaryotes. Their cells are bacteria, tiny living things. They are the most abundant organisms and have spread throughout the biosphere. There are species... Continue reading "The Monera Kingdom: Prokaryotic Life and Classification" »