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

The Human Heart: Structure and Function

The heart is a muscular organ approximately the size of a fist, situated in the center of the chest, between the two lungs.

Primary Function

Its main function is to pump blood through the blood vessels.

External and Internal Structure

Externally, it is formed by a muscle that contracts involuntarily. Internally, it consists of two halves separated by a partition. Each half is comprised of two chambers (atria at the top and ventricles at the bottom).

The Cardiac Cycle

The heart operates through two alternating movements: contraction (systole) and dilation (diastole). Each complete cycle consists of four distinct stages:

1. Diastole (Filling Phase)

• Blood from different parts of the body enters the atria, causing

Understanding Biological Tissues

Tissue: A tissue is a collection of cells of the same type, with a very similar structure that performs the same functions.

Epithelial Tissue

Epithelial tissue is composed of cells that are very close together, often having geometric shapes and appearing together forming units or layers. Two groups are distinguished:

• Surface epithelium: This covers and protects external surfaces or internal cavities of the organism. Notable examples include: the mucous lining of the oral cavity, pharynx, and esophagus; the endothelium lining the inside of blood vessels; and the heart epithelium.
• Glandular tissue: This is the way glands are formed. Its function is to secrete substances. They are distinguished as:
  • Exocrine Glands: If

Understanding Nutrition

Nutrition is the set of processes that allows organisms to use and transform nutrients to stay alive. Food is the process by which these nutrients are obtained from the external environment. Food contains nutrients, which are essentially the biomolecules that make up our body.

Essential Nutrients

These include:

• Carbohydrates (Carbs): Energetic substances.
  • Simple Carbohydrates (Sugars): Sweet, crystalline, and water-soluble.
  • Complex Carbohydrates: Not crystalline, do not dissolve, and are formed by the bonding of many simple carbohydrate molecules.
• Lipids: A very diverse set of substances characterized by being insoluble in water and having an oily appearance.
  • Fats: Highly energetic molecules. Depending on their chemical composition,

1. Theories of Evolution

Anti-evolutionist Theories

• Fixism: Defends that species have remained unchanged since their emergence.
• Creationism: Similar to fixism, but attributes the origin of species to divine creation as described in the Bible.

Evolutionist Theories

• Lamarckism: The environment creates specific needs; characters are acquired or lost based on use and disuse.
• Darwinism: Based on diversity between individuals, limited resources, and the process of natural selection.
• Neodarwinism: Incorporates genetics; natural selection acts on mutations: favorable (remain), unfavorable (disappear), and neutral.

2. Mechanisms of Natural Selection

3. Evidence of Evolution

• Paleontological: Comparing current species with living fossils.
• Biogeographical: Comparing

Understanding Food and Nutrients

Food is any substance with nutritive properties that can be processed and absorbed by the digestive system. Nutrients are chemical compounds that provide the matter and energy required for all bodily functions.

Food Classification by Origin

Foods are classified according to their origin:

• Minerals: Found in water and mineral salts.
• Plant: This group includes cereals, legumes, vegetables, fruits, oils, and sugars.
• Animal: Derived from meats of mammals, birds, fish, mollusks, crustaceans, and other animal products.

Nutrient Classification by Energy Contribution

Nutrients are categorized based on their energy contribution:

• Energy-Yielding Nutrients: Carbohydrates, lipids (fats), and proteins. These provide calories for the

Cellular Structure and Function

Cells are the fundamental structural and functional units of all living organisms. The structure of a cell consists of the following components:

• Centrioles: Composed of nine groups of three microtubules. Each centrosome comprises two centrioles intersecting at right angles.
• Flagellum: A long extension that allows for cell movement.
• Golgi Apparatus: An assembly of flattened sacs that produce small vesicles.
• Plasma Membrane: The boundary that surrounds and limits the cell.
• Cytoskeleton: Consists of three types of protein fibers: microfilaments, intermediate filaments, and microtubules. It provides structural support and facilitates movement.
• Mitochondria: The power plants of the cell. They consist of five parts: the matrix,

Biological Reproduction and Development

Reproduction is the function by which progenitor individuals give rise to new individuals, called descendants, which are like them.

Phases of Biological Development

• Reproduction: In this phase, the organisms produce a cell, or group of cells, from which a new individual forms.
• Embryonic development: The cell formed in reproduction, called a zygote, gives rise to a complete individual through a series of divisions.
• Growth: In this phase, there is maturation and an increase in body size.

Asexual Reproduction Methods

• Vegetative Reproduction: Based on the ability of plants to form new individuals from a fragment of them, called a bud.
• Spore Reproduction: From a cell of an individual, whose nucleus divides repeatedly,

Elimination of Cellular Waste Products

Elimination involves removing waste excretions from our cells. Urine has a composition similar to blood plasma, although it has a higher concentration of waste substances such as urea.

Components of the Urinary System

Kidneys

Kidneys: Two bean-shaped organs located on both sides of the spine. They form urine. Three parts can be differentiated within them: the medulla or central mass (divided into pyramid-shaped zones), blood vessels, and the cortex.

Bladder

Bladder: Urine collects here, arriving continuously through the ureters. It is extensible and can contain a varying amount of urine (250 to 500 cm³). When full, it contracts, and the need to urinate arises.

Ureter

Ureter: Two thin tubes that collect the urine...

Fundamentals of Biological Reproduction

Reproduction: The biological method necessary to ensure the survival of species.

Types of Reproduction

• Asexual Reproduction: Requires only one parent; creates exact genetic copies of itself; does not require gametes.

• Sexual Reproduction: Requires two parents who provide the gametes; descendants inherit characteristics from both parents.

Gametes and Gonads

Gamete: Specialized cells formed by meiosis from diploid cells in the gonads.

Reproductive Structures (Gonads)

• Unisexual: Characterized by two distinct types of individuals and gonads (Male and Female). Males and females exhibit traits that differentiate them (sexual dimorphism).

• Hermaphrodite: Individuals possess both male and female gonads.

Key Reproductive

Fundamentals of Neurobiology

Biology is the science that studies living beings and vital phenomena. The Human Nervous System acts as a mechanism of control for bodily functions.

• Nerve Impulse: A physical and chemical phenomenon occurring in the neuron that passes from one neuron to another.
• Reflexes: Automatic and involuntary responses produced by a stimulus.
• Synapse: Functional unions between the terminal branches of the axon of one neuron and the dendrites of another.
• Nerves: A group of fibers that carry sensations and impulses between receptor organs and the brain.
• Learning: The process by which organisms modify their behavior as a result of experience.

Sensory Organs and Perception

• The Eye: Light is processed in the retina through the optic nerve,