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

Taste and the Tongue

Flavors are perceived by the tongue through chemoreceptors known as taste cells. There are four basic tastes from which others are derived: sour, bitter, sweet, and salty.

The Ear and Hearing

Hearing allows us to perceive sound waves. These waves are collected by the pinna, penetrate the ear canal, and vibrate the eardrum. This membrane transmits vibrations to the ossicles, which move another small membrane located in the cochlea. The vibration is transmitted through the liquid filling the cochlea, traveling in waves to the cochlear nerve, which sends signals to the brain to be interpreted as sound.

Balance and Equilibrium

Balance allows us to perceive turns, accelerations, and the positioning of our body; this process occurs...

Photosynthesis: Converting Inorganic to Organic Matter

Photosynthesis is essential not only for plants but for all living organisms. Heterotrophs rely on the organic matter produced by autotrophs. This process converts light energy into chemical energy, utilizing ambient carbon dioxide and producing the oxygen necessary for respiration. Furthermore, the oxygen released contributes to the formation of the ozone layer, which absorbs harmful ultraviolet radiation.

Cellular Respiration: Energy Production

Cellular respiration involves the oxidation and breakdown of organic substances to release stored energy in the form of ATP.

• Fermentation: Glucose is processed without oxygen, yielding 2 ATP.
• Aerobic Respiration: Glucose is fully oxidized, yielding

The Circulatory System

The circulatory system is responsible for delivering nutrients and oxygen to all cells, collecting the waste substances produced, and conducting these to the organs responsible for eliminating them.

Composition and Properties of Blood

Blood is a thick, viscous red liquid that circulates through the blood vessels, responsible for transporting substances. It is formed by a liquid part called plasma, where cells are in suspension: red blood cells, white blood cells, and platelets.

Blood Plasma

Plasma is a transparent yellow liquid in which blood cells float. It is composed of 90% water and 7% proteins, of which the most important factors are related to coagulation and antibodies related to defense against infections.

Red Blood

The Human Digestive System

The digestive system is responsible for processing food and transforming it so nutrients can be absorbed and distributed to every cell in the body.

The Respiratory System

The respiratory system captures the oxygen needed by cells and removes the carbon dioxide (CO2) produced during cellular metabolism.

The Circulatory System

The circulatory system transports nutrients and oxygen to cells and removes waste substances.

The Urinary System

The urinary system handles debris and waste products ejected from cell metabolism, which are carried by the circulatory system to be filtered and expelled.

Key Components of the Digestive System

• Digestive Tract: Measures about 8 meters and varies in diameter along its length. It begins in the

Anatomy and Function of Key Body Systems

Organs and Parts of the Digestive System

• The **Digestive Tract** includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
• **Accessory Glands** include the salivary glands, the pancreas, and the liver.

Maintaining Digestive Health

• Wash hands thoroughly before meals.
• Brush teeth after meals using a fluoride toothpaste. Brushing should take at least three minutes.
• Chew food well and maintain correct posture while sitting at the table to ensure adequate intake.
• Ensure that eating is a moment of relaxation, shared with people with whom you can maintain a peaceful and pleasant conversation.

The Respiratory System

Organs of Respiration

• **Airways:** The nose, pharynx, larynx, trachea,

Interstitial Fluid

Interstitial fluid: the liquid that surrounds the cells, which renews constantly and contains nutrients, oxygen and other substances for exchange.

Blood

Composition: ^{Plasma sanguini} (H₂O + molecules), including proteins, hormones, salts, minerals, nutrients and substances for exchange.
^{Cèl·lules sanguínies:} formed in the interior of the bones, from the bone marrow.

• Red blood cells: contain haemoglobin, a protein that carries oxygen.
• White blood cells: take part in the body's defence against and phagocytosis of microbes.
• Platelets: fragments of cells that help coagulate the blood and heal wounds.

Types of Blood Vessels

1. ^Arteries: A. Carry blood away from the heart. B. Branch into smaller arteries and arterioles; prone to arteriosclerosis.

Plant Metabolism: Vital Processes

Like all living organisms, plants perform essential functions to facilitate growth, development, and reproduction.

The primary metabolic processes include:

• Absorption
• Circulation
• Respiration
• Transpiration

Absorption: Nutrient Uptake

Plants acquire nutrients not only from the soil but also from the air, primarily through their leaves, absorbing oxygen and carbon dioxide.

Water and dissolved minerals enter the roots via diffusion. Plants then convert these substances into organic molecules, such as:

• Glucose
• Fructose
• Starch
• Proteins
• Lipids (fats)

This conversion of minerals into organic compounds is unique to plants, certain bacteria, and microscopic algae. Consequently, wildlife, fungi, and protozoa rely on plants as their...

Understanding Genetics: Key Concepts

Genetics is the branch of biology that studies the laws governing the transmission of traits.

Basic Genetic Terms

• Gene: The unit of genetic transmission.
• Genotype: The complete set of genes of an individual.
• Phenotype: The observable characteristics of an individual.
• Allele: A variant form of a gene.
• Dominant Allele: An allele that prevents the manifestation of the alternative allele for the same trait.
• Recessive Allele: An allele that is only manifested when the dominant allele is not present.

Mendel's Laws of Inheritance

1. 1st Law (Law of Segregation): When two heterozygous individuals are crossed, all descendants of the first filial generation are equal in both genotype and phenotype.
2. 2nd Law (Law of Independent Assortment)

Concept of the Cell

A cell is a structure formed by a plasma membrane, cytoplasm, and genetic material (DNA), which has the ability to perform three vital functions: nutrition, interaction, and reproduction. Of these three functions, the most important is reproduction, which characterizes a living being. Viruses are also capable of reproducing, but they need to invade a living cell to do so.

Structure of the Cell

The Plasma Membrane

The plasma membrane is formed by a lipid double layer in which proteins are embedded. The lipid membrane acts as an insulating barrier between the internal aqueous environment and the external environment. The proteins allow the entry and exit of substances.

The Cytoplasm

The cytoplasm contains the internal liquid and...

Reproduction

The biological process of producing offspring.

Sexuality

A human reproductive process involving two distinct sexes.

Menstruation

The final stage of the 28-day menstrual cycle where an unfertilized egg is released. This is the conclusion of the ovarian cycle.

Gametes and Gonads

• Gametes: Reproductive cells (Sperm in males; Ova in females).
• Gonads: Glands that produce gametes.

Fertilization and Nesting

• Fertilization: The union of the nuclei of the sperm and the egg.
• Nesting (Implantation): The process where the zygote (fertilized egg) attaches to the uterine wall.

Gestation

The period of development from embryo or fetus to birth, typically lasting 36 to 40 weeks.

Male Genital Anatomy

External Organs

• Penis: The copulatory organ.
• Scrotum: The sac containing