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

The Cell Nucleus Structure

Nuclear Envelope

The nuclear envelope is a double membrane structure:

• The outer nuclear membrane is continuous with the Endoplasmic Reticulum (ER) and may have ribosomes.
• The inner nuclear membrane has a fibrous lamina, known as the nuclear lamina.

Nuclear Pore Complex

The nuclear pore is formed by the union of the two membranes and a set of ribonucleoproteins forming the Nuclear Pore Complex (NPC). The NPC regulates the passage of molecules into and out of the nucleus.

Nucleoplasm

The nucleoplasm is the internal environment of the nucleus. It contains a network of fibrillar proteins (the nuclear matrix), which remains fixed and organizes the nucleolus and chromatin.

Nucleolus

The nucleolus is a dense, almost spherical structure...

Types of Illness

• Physical Diseases: Caused by injury, infection, or degenerative processes in the body. They are classified into infectious and non-infectious diseases.
• Mental Illness: Provoked by a malfunction of the brain.
• Social Ills: Caused by the existence of a social environment with serious violent, economic, or educational deprivation.

Health vs. Illness

• Health: A state of complete physical, mental, and social well-being.
• Illness: The state in which a person's health is disturbed.

Violence as a Social Disease

Violence is a terrible social disease that kills many people every year. It is a disease that is incubated in childhood.

Viruses

Viruses are not living creatures but protein capsules containing DNA or RNA that is injected into a cell.

Infectious

The Journey of Pregnancy: From Conception to Birth

Gestation, commonly known as pregnancy, commences with fertilization and culminates in childbirth. This remarkable process brings about profound changes. What begins as a single cell, the zygote, progressively develops into an embryo, then a fetus, and ultimately a fully formed human being.

Typically lasting around nine months, pregnancy involves significant physiological transformations for the mother. These changes are driven by the fetus's development and growth, the vital exchange of nutrients and waste through the placenta, and the mother's body preparing for childbirth and lactation.

Early embryonic development is primarily regulated by estrogen and progesterone, initially produced by the...

Endocrine Glands and Hormones

What are Exocrine Glands?

Exocrine glands are specialized structures with specific functions, releasing chemicals to regulate life processes.

Types of Exocrine Glands

Major exocrine glands in the human body include the pituitary, thyroid, parathyroid, adrenals, testes, and ovaries.

What are Hormones?

Hormones are complex substances produced by endocrine glands, released directly into the bloodstream to regulate various cells and organs.

The Pituitary Gland

The pituitary gland is a small mass of cells located at the base of the brain, in the sella turcica of the sphenoid bone.

The Sex Glands

• Testes: The male sex glands, located in the scrotum beneath the penis.
• Ovaries: The female sex glands, located in the lower abdomen.

The

Human Tissue Types

Connective Tissue

Connective tissue consists of specialized cells embedded in an intercellular substance containing fibers like collagen. Key types include:

• Connective Tissue Proper: Binds and supports other tissues and organs, such as tendons and ligaments.
• Adipose Tissue: Composed of adipocytes filled with fat, providing lipid reserves, organ protection, and thermal insulation.
• Cartilage: Made of chondrocytes within a solid intercellular substance, forming structures like the nose, trachea, and ear cartilage.
• Bone Tissue: Composed of osteocytes that develop a strong intercellular substance with mineral salts of calcium and phosphorus, forming bones.
• Blood: Considered by many as a connective tissue with plasma as its intercellular

Chromatin

Chromatin consists of strands of DNA at different degrees of condensation associated with proteins and scattered throughout the nucleoplasm. When the cell is going to divide, the chromatin filaments are organized and condensed to form thicker structures called chromosomes.

Genes

A gene is a unit of hereditary material. It is a fragment of nucleic acid that carries genetic information for a character, a protein, or a polypeptide chain. It corresponds to what Mendel called a hereditary factor.

Centriole

In animal cells, centrosomes present two small cylinders and consist of protein tubules.

Mitotic Spindle

The mitotic spindle forms when the nuclear membrane and nucleolus disappear.

Karyotype

A karyotype is a set of chromosomes from one species....

Biological Evolution: Species Change Over Time

Biological evolution is the process of change in species over time.

Theories of Evolution

• Evolutionism: Species change and generate others (Lamarckism, Darwinism, synthetic theory, punctuated equilibrium).
• Fixism: Belief that species remain invariant over time.
• Creationalism: Explains the origin of species as creations of God, maintained immutable in the Bible.

Carolus Linnaeus established the binomial classification of species.

Catastrophism: Explains the existence and disappearance of species; species become extinct due to natural disasters.

Lamarckism: Species Change Over Time

• Organisms show a tendency toward greater complexity.
• Repeated use of an organ leads to its development (function creates the organ)

Food Composition and Nutrients

Simple and Compound Foods

• Simple: These consist of a single type of substance. Examples include oil and table sugar.
• Compounds: These are composed of different substances. Examples include bread and milk.

Inorganic Substances

These are not unique to living matter.

• Water: The most abundant compound in living things and the medium in which life develops within cells.
• Minerals: Chlorides, carbonates, and phosphates, along with sodium, potassium, and calcium, are found in bones and teeth, providing hardness. They are also dissolved in all body fluids, such as blood, tears, and sweat.

Organic Substances

Carbohydrates

The simplest carbohydrates, such as glucose and maltose, have a sweet taste. Glucose is a sugar that cannot be...

The circulatory system is made up of a pump, the heart, a liquid, blood, and a series of ducts, blood vessels, through which blood is pumped throughout the body.

The Circulatory System: Components and Function

What is Blood? Composition and Volume

Blood is composed of a liquid part (plasma) and different types of blood cells. If you separate the two components, the volume is typically 55% plasma and 45% blood cells.

Blood Plasma: The Liquid Component

The liquid of blood plasma is fundamentally formed by yellowish water (91%) in which a variety of dissolved substances are present.

Blood Cells: Formed Elements

Blood cells are formed in the red bone marrow that fills the inside of some bones. They are of three types:

• Red Blood Cells (Erythrocytes)

  These

Cell Structure and Function

Cells are the structural and functional units that make up our organisms. Their structure consists of:

• Centrioles: Formed by nine groups of three microtubules. Every cell contains a centrosome comprising two centrioles intersecting at right angles.
• Flagella: Long prolongations that allow for cell movement.
• Golgi Apparatus: A set of flat sacs that receive and process small vesicles.
• Cell Membrane: The boundary that surrounds and limits the cell.
• Cytoskeleton: Features three types of protein fibers: microfilaments, intermediate filaments, and microtubules. It provides structure to the cell and is responsible for its movements.
• Mitochondria: The powerhouses of the cell. They consist of five parts: matrix, cristae, internal