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

The Digestive System

The digestive system is made up of the organs that break down food. Nutrients cannot be used directly by cells, so food must be transformed into simple substances that the body can absorb.

The Gastrointestinal Tract

The gastrointestinal tract is a tube about 10 meters long, with walls of muscle, that runs from the mouth to the anus. Along this tract, different parts perform different functions.

• Mouth: Digestion begins here. Teeth grind food, the tongue mixes it with saliva, and the result is a mass that is swallowed.
• Pharynx: A cavity that connects the mouth to the esophagus.
• Esophagus: A tube of about 25 cm that conducts food down to the stomach.
• Stomach: A muscular, expandable organ with a capacity of about 2.5 liters. When

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Intestinal Juice and Nutrient Absorption

Intestinal juice is produced by cells in the small intestine and acts upon nutrients to break them down into their simplest components. As a result of digestion in the small intestine, chyme transforms into chyle, a slurry that is significantly more liquid and milky. The inner wall of the small intestine features numerous folds, which in turn present villi and microvilli. These structures greatly increase the absorbing surface area of the intestine, facilitating the passage of nutrients into the bloodstream.

Functions of the Large Intestine

The unabsorbed chyle passes through the large intestine, which measures approximately 1.5 meters and is divided into three main parts:

• Cecum (including the appendix)
• Colon

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Fundamentals of Food and Nutrition

Food

We consume foods that make up our diet and are essential for proper nutrition.

Nutrition

The set of processes by which the body obtains the material and energy needed to build its own tissues and perform vital functions.

Organic Nutrients: Structure and Function

The primary organic nutrients required by the body are carbohydrates, lipids, and proteins.

• Carbohydrates

  Carbohydrates are the most abundant nutrients in food. The simplest forms are sweet, including glucose and sucrose.

• Lipids (Fats)

  Lipids are nutrients that are not dissolved in water (hydrophobic). They provide concentrated energy. Vegetable lipids are typically liquid and are called oils. Solid lipids are known as fats or tallow.

• Proteins

  These are

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DNA and Chromosomes

DNA is the biomolecule that contains genetic information to make proteins in the cell.

The chromosomes are composed of chromatin (DNA + protein).

Before cell division the DNA is duplicated. Each chromosome is formed by two chromatids joined together.

Karyotype and Genome

Karyotype: chromosome set ordered by pairs. Humans have 23 pairs.

Genome: the complete set of genes.

Genes and Genetic Information

A gene is a segment of DNA containing information to produce a given necessary protein. Genes together make up the genome.

Cell Cycle and Division

Cellular division is the process by which a cell is divided into two daughter cells.

Interphase

Interphase is the stage of growth: the cell increases in size, the cytoplasm grows, and routine...

Understanding Human Reproduction:
The process of human reproduction involves sexual reproduction. Females produce female gametes (eggs) and males produce male gametes (sperm). These two types of cells unite to form a zygote.
Fertilization is internal; the egg and sperm unite in the reproductive tract of women.
The reproduction process includes the following events:

• Production of gametes in specialized reproductive organs.
• Fertilization, which is the union of two gametes within the female reproductive tract to form the zygote.
• Development of the zygote within the female reproductive tract, where the zygote becomes an embryo and then a fetus.
• Birth of a fully formed baby.
• Development of children, including the maturation of their sexual organs

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Arachnids

Arachnids, such as spiders, scorpions, and mites, are terrestrial animals that typically live in dry regions. Their bodies are divided into two regions: the cephalothorax and the abdomen.

• Anatomy: They possess two chelicerae for feeding, two palps for defense, and four pairs of legs.
• Physiology: They breathe through tracheae and are primarily carnivorous.
• Reproduction: They are equipped with poison glands to capture prey, have separate sexes, and are oviparous or ovoviviparous.

Crustaceans

Crustaceans include lobsters, shrimp, barnacles, and crabs. While most are marine, some species, such as freshwater crabs or terrestrial woodlice, inhabit different environments.

• Body Structure: The body is divided into the head, thorax, and abdomen, though

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Theme: Health and Illness

1. Definitions of Health and Disease

• Health: The quality of a body in which all organs and systems function adequately.
• Disease: A continuing alteration in the normal functioning of the body.

2. Pathogenic Microbes

Microbes that act as pathogens and viruses cause disruption based on two factors: toxic capacity and ability to invade.

Viruses are entities that lack cellular organelles and must parasitize other cells to reproduce.

3. Sexually Transmitted Diseases (STDs)

STDs are a group of infectious diseases transmitted through sexual contact, caused by molds, bacteria, or viruses.

4. Phagocytic Cells

Phagocytes are a type of white blood cell present in the blood and tissues that identify and destroy microorganisms.

Topic: Nutrition

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Circulatory System

1. Define the circulatory system

The circulatory system is constituted by the heart, blood, and blood vessels by which blood is distributed throughout the body.

2. What is blood plasma?

Plasma is a yellowish liquid composed of about 91% water and the remaining ~9% consisting of salts, proteins, lipids, glucose, and urea.

3. Origin and types of blood cells

Blood cells originate in the bone marrow. The main types are:

• Red blood cells (erythrocytes)
• White blood cells (leukocytes)
• Platelets (thrombocytes)

4. Anemia

The main symptoms are fatigue and loss of vitality; these are direct consequences of decreased oxygen delivery to the body's cells. The most common form is iron-deficiency anemia. It is usually corrected by a sufficient and balanced...

Phagocytic Cells

These are defenses found after the first line. Some of these responses are nonspecific; that is, they attack a variety of microbes. One type of response involves cells with phagocytic capacity. Among these are macrophages, neutrophils, and NK cells.

Plasma Proteins

The last barrier participating in the processes of natural immunity involves specific proteins called cytokines, interleukins, or lymphokines. These are involved in inducing the response of white blood cell production.

Other proteins in the blood involved in the innate defense of the organism include:

• Interferons: Proteins released by cells in the body that have been infected by viruses.
• Complement System Proteins: Consists of twenty plasma proteins that bind to membranes

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The Excretory System

The excretory system is responsible for removing toxic substances and waste from our body. The excretory system consists of the urinary tract, lungs, and skin. The system is formed by the kidneys and the urinary tract.

The Urinary System

Function: It is responsible for ridding the body of harmful substances that form in the cells and helps maintain blood alkalinity.

Structure: It is formed essentially of two kidneys that drain their contents into a receptacle called the bladder. The bladder, in turn, empties its contents to the outside through a tube called the urethra.

The Kidneys

The kidneys are two bean-shaped, brown organs located on both sides of the body below the waist. Through the renal artery, blood carrying waste substances...