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

Internal Environment

The internal environment is the set of surrounding cells and liquids of an organism. Cells extract the nutrients and oxygen they need from it, and discharge waste and carbon dioxide produced during metabolism. The interstitial fluid originates from blood that has been filtered through the thin walls of blood capillaries.

Homeostasis

Homeostasis is a set of mechanisms whose mission is to maintain a constant internal environment, meaning that its properties do not vary. The maintenance of these properties is called homeostasis, and the task is performed by different devices and systems of the organism.

Veins and Arteries

Arteries and veins differ in that arteries carry blood from the heart to the various organs of the body, and... Continue reading "Understanding the Human Body: Internal Environment and Blood Circulation" »

Eukaryotic Cell Reproduction:

Mitosis Phases:

1) Prophase:

Key occurrences:

• Disappearance of the nucleolus. The genes that synthesize 45S ribosomal RNA (rRNA) are located on chromosomes 13, 14, 15, 21, and 22 (in humans).
• The nuclear envelope disappears due to water entering the cytosol.
• The mitotic spindle forms from the centriolar microtubule organizing center.
• Duplication of the centrosome.

2) Metaphase:

Key occurrences:

• The spindle is completely formed.
• Chromosomes, which appeared as filaments in prophase, are now fully compacted and consist of two chromatids (each containing a DNA molecule).
• Kinetochore microtubules form and push the kinetochores on the chromosomes to align them in the equatorial plane of the cell.

3) Anaphase:

Key occurrences:

• Shortening

Protein Structure, Properties, and Functions

Quaternary structure: The association of multiple polypeptide chains, resulting in a cluster of subunits. Only some proteins have this level. Formed by several polypeptide chains, each unit is called a protomer.

Properties of proteins:

1. Solubility: Proteins have high dispersion and form colloidal solutions.
2. Denaturation: Increased temperature or pH changes alter the links that stabilize the protein structure, causing it to lose its biological activity.
3. Specificity: Each species has its own unique set of proteins, and there is even individual specificity, which can lead to transplant rejections and allergies.
4. Buffer capacity: Proteins, being amphoteric, can help neutralize pH variations.

Classification of

Plant Responses: Tropisms

Tropisms are directional growth responses by plants to external stimuli (anything that induces a response).

Types of Tropisms

• Phototropism: Response to a light stimulus. Can be positive (+) (towards light) or negative (-) (away from light).
• Geotropism: Response to the stimulus of gravity. Can be positive (+) (towards gravity) or negative (-) (away from gravity).
• Chemotropism: Response to a chemical substance stimulus.

Photosynthesis: The Process

Photosynthesis is a biochemical process unique to chlorophyll-containing organisms that requires light and occurs in chloroplasts. It releases O2 (oxygen) to the environment and consumes CO2 (carbon dioxide) from the environment (gas exchange with the atmosphere).

Nutrient Transport

Anisakiasis: A Parasitic Infection from Seafood

Anisakiasis is a parasitic infection caused by the accidental consumption of Anisakis larvae (white) and Pseudoterranova (yellowish-brown-red) in raw fish meat. These are parasitic nematodes (roundworms) with a transversely striated cuticle. They have a terebrant tooth with the opening of the excretory pole (front of the head), a lipless mouth, and an esophagus divided into a long muscular pre-ventricle and a short, oblique one joined to the intestine. They also have three anal glands near the rectum and a spine or mucron at the end of the tail. The definitive host is marine mammals.

Cycle

When sperm whales defecate, unfertilized eggs are removed. These eggs need to form into larvae first. Mature... Continue reading "Anisakiasis and Ascariasis: Parasitic Infections" »

Diseases Caused by Microorganisms

Diseases caused by microorganisms are a significant public health concern. These tiny organisms, including bacteria, viruses, protozoa, and fungi, can cause a wide range of illnesses.

Common Examples of Infectious Diseases

• Malaria
• Diarrheal Diseases
• Tuberculosis (TB)
• AIDS
• Influenza (Flu)
• SARS, Measles, Poliomyelitis
• Ebola and Marburg Hemorrhagic Fevers

Malaria

Cause and Transmission

Malaria is caused by Plasmodium protozoa, which infect erythrocytes (red blood cells).

It is transmitted by Anopheles mosquitoes, which act as vectors.

Prevention and Treatment

Prevention includes antimalaria drugs and avoiding mosquito bites.

Mosquito control methods like crop spraying with insecticide are also used.

Distribution

Malaria is prevalent... Continue reading "Common Infectious Diseases and Prevention" »

Mendelian Heredity

Gregor Mendel's experiments on pea plants revealed that inheritance is transmitted through heredity, following simple statistical norms.

Mendelian Inheritance

These are the rules governing the transmission of characteristics from one generation to the next.

1st Law (Uniformity)

In the first generation, all offspring are identical if one of the parents is homozygous dominant and the other is homozygous recessive.

2nd Law (Segregation)

Hereditary factors separate during gamete formation, leading to new combinations.

3rd Law (Independent Assortment)

Characters are transmitted independently, as long as the genes are located on different chromosomes.

Post-Mendelian Heredity

Mendel's laws were extended to animals, and it was later discovered... Continue reading "Mendelian & Post-Mendelian Heredity: A Comprehensive Overview" »

Digestive System

Main Function

The main function of the digestive system is the digestion and absorption of nutrients.

Layers of the Digestive Tract

• Mucosa: Formed by different types of epithelium depending on the zone.
• Muscularis Mucosa: Smooth muscle tissue, predominantly circular.
• Submucosa: Formed by connective tissue, blood vessels, and nerves.
• Muscularis: Formed by 2 or 3 layers of muscle tissue.
• Adventitia/Serosa: Consists of loose connective tissue or peritoneum depending on the zone.

Parts of a Tooth

• Root: Within the alveolar bone cavity.
• Crown: External, visible part of the tooth.
• Neck: Separates the root from the crown.
• Pulp Chamber: Formed by pulp, connective tissue, blood vessels, and nerves.
• Dentin: Hard tissue surrounding the pulp, covered

Sensory Receptors and Organs

Receptors gather outside information. Exterorreceptores are sensory structures that make up the organs.

Eye

The eye is composed of 3 layers: sclera, choroid, and retina. The eyeball contains aqueous liquid and vitreous. The cornea bends light, and the lens focuses images. The retina receives inverted pictures, and fotorreceptors convert images into impulses.

Ear

The ear has 3 parts: external ear, middle ear, and inner ear. It is responsible for hearing and balance.

Touch

The skin has two layers: epidermis and dermis. It contains various receptors for pressure, cold, heat, and contact.

Nose

The nose contains mucosa and pituitary, which are responsible for olfactory receptors and heating the air.

Taste

There are 4 flavors on... Continue reading "Sensory Receptors and Coordination Systems in the Human Body" »

Mendel's First Law: The Law of Uniformity

Mendel started his experiments by crossing two individuals homozygous for a particular trait. The first law, or the law of uniformity, states that if you cross two pure individuals differing in one character, the offspring is uniform, all showing the dominant character.

Mendel's Second Law: The Law of Segregation

For the F2 generation, Mendel allowed plants with the Aa genotype from the F1 generation to self-fertilize. The second law, the law of segregation, states that the recessive traits that do not occur in the first generation reappear in the second generation in the proportion of three dominant to one recessive.

Mendel's Third Law: The Law of Independent Assortment

The third law, the principle of independent