Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

Cell Biology Fundamentals

• Cell Membrane: A thin layer surrounding the cell.
• Cytoplasm: The cellular material excluding the contents of the nucleus.
• Cell Nucleus: A spherical structure which is in the center of the cell.

Cell Organelles

• Mitochondria: They provide energy to the cell.
• Vacuoles: Store products or waste materials.
• Lysosomes: Transform complex substances into simpler ones.
• Cytoskeleton: Is the structural framework (backbone) of the cell.
• Centrioles: Direct the movement of the cytoskeleton.
• Golgi Apparatus: Its function is secretion.

Structure of the Nucleus

• Nuclear Envelope: A double membrane pierced by pores that permit the exchange of substances.
• Nucleoplasm: The contents within the nucleus.
• Chromatin: Very long filaments formed by coiled structures

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Health, Disease, and Prevention

Core Definitions

Health

A state of complete physical, mental, and social well-being.

Illness (Malady)

A state of poor health or sickness, often characterized by symptoms like difficulty sleeping due to a malfunction of the body.

Infectious Diseases

Are those caused by pathogenic microorganisms such as bacteria, viruses, fungi, and protozoa.

Non-Infectious Diseases

Are not produced by pathogenic microorganisms and therefore are not contagious. The causes include:

• Bad habits.
• Environmental factors.
• Deterioration of the body (e.g., age, trauma).
• Genetic abnormalities.

Disease Transmission Routes

Direct Contact Transmission

Causes skin diseases, digestive diseases, and sexually transmitted diseases.

Transmission via Contaminated

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DNA Structure and Genetic Information

Genes are the carriers of biological information, found inside every cell. Their precise location was not known until their discovery within chromosomes. The chromosome number in sex cells is half that which exists in other somatic cells. Genes are contained within chromosomes, and each gene is made up of the molecule known as DNA (Deoxyribonucleic Acid).

DNA Replication: Ensuring Genetic Continuity

Each time a cell divides into two, the two resulting cells must receive the same genetic material. For this to happen, it is essential that DNA copies itself, a process known as replication or duplication.

RNA: Types and Functions

RNA (Ribonucleic Acid) is typically single-stranded. In RNA, the sugar deoxyribose...

The Genetic Code

The genetic code is degenerate, meaning several triplets code for the same amino acid. Some triplets act as stop signals, indicating the end of synthesis. The genetic code is read exclusively from RNA.

Transcription and Translation

• Transcription: Occurs in the nucleus; it is the process of creating an RNA molecule, specifically messenger RNA (mRNA), from DNA.
• Translation: Involves linking amino acids in a specific order determined by mRNA information. Since nucleotides and amino acids do not correspond directly, adapter molecules (tRNA) are required. Each tRNA binds to a specific amino acid and recognizes the corresponding triplet on the mRNA.

Chromosome Morphology

DNA is not isolated but associated with proteins, forming a substance...

Types of Biological Reproduction

Sexual reproduction is performed by specialized cells called gametes. This process involves two individuals, where each one contributes sex gametes from the progenitor. In contrast, asexual reproduction involves no gametes and only one parent from which the offspring originate.

The Role of Genetic Information

Certain cellular components contain the instructions for each organism to develop its own characteristics of its kind. This information, known as genetics, is contained in a substance called deoxyribonucleic acid (DNA), which is localized in chromosomes within the cell nucleus. DNA is the material carrier of genetic genes.

Chemical Composition of DNA

DNA is a chemical that belongs to the group of nucleic acids....

Physiology of Digestion

The transformation process experienced by food within the digestive tube consists of two primary processes:

• Mechanical: Grinding and motion.
• Chemical: Digestive enzymes in gastric juices break down macromolecules into molecules that can be absorbed in the intestine into the blood as nutrients.

Location of Mechanical Digestion

• Mouth: Crushing and deglutition.
• Stomach: Mixing food with gastric juice.
• Intestine: Peristaltic movements to propel food forward.

The Respiratory System

This system is responsible for circulating air between the organism and the environment through external respiration. The ducts that circulate air are called the respiratory tract.

Upper Respiratory Tract

Includes the nose, pharynx, and larynx.

Lower Respiratory

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The Human Heart and Circulatory System

The heart is a hollow organ, approximately the size of a fist, composed of specialized muscle tissue called myocardium. It acts as a pump, ensuring the continuous movement of blood through the circulatory system.

Heart Anatomy

The heart consists of four chambers: two upper chambers called atria and two lower chambers called ventricles. Key structures include:

• Aorta
• Superior and inferior vena cava
• Right and left atria
• Right and left ventricles
• Tricuspid, mitral, and semilunar valves
• Pulmonary arteries and veins

Chamber Functions

• Right Atrium: Receives deoxygenated blood from the vena cava, which returns blood from the entire body.
• Left Atrium: Receives oxygenated blood from the pulmonary veins.

Valves control the blood...

Characteristics of the Human Circulatory System

• It is closed: The blood flows within blood vessels. When a blood vessel breaks, bleeding occurs.
• It is double: There are two circuits: the systemic circuit (general) that travels around the body and the pulmonary circuit (smaller) that targets the lungs.
• It is complete: There is no mixing of oxygen-rich blood with oxygen-poor blood in the heart.

Lymph and Interstitial Fluid

Lymph: This consists of plasma and lymphocytes. The liver forms urea from uric acid. Interstitial fluid is the plasma medium located in the spaces between cells.

Functions of Blood

The blood carries nutrients and oxygen to the cells and collects waste products formed in cell metabolism, such as urea, uric acid, and CO2. It also handles...

Hybridization (general technique for detecting a specific gene, allowing a labeled probe with the complementary sequence to bind to the target molecule)

Recombination of DNA (the technology to transplant genes from one species to the genome of another)

Abiogenesis (study of how new biological life would arise from inorganic matter through natural processes)

Lamarck:

His theory considered that species proceeded one from another through transformation.

Causes of transformation:

1. Species are constantly making an effort to adapt to their environment, which leads to the transformation of their organs.
2. New acquired characteristics are hereditary and passed on to descendants.

Darwin:

In 1859 he published The Origin of Species, which explained the theory of...

Meiosis: A mechanism of sexual reproduction that combines and enriches genetic information from parents to offspring, creating genetic diversity that helps the species adapt to environmental changes.

Chromosome structure: Each chromosome consists of two identical chromatin filaments called sister chromatids, joined by a centromere. Both chromatids contain duplicated genetic information. The centromere divides each chromatid into two regions called arms.

Key Differences Between Mitosis and Meiosis

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