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

Biological Reproduction: A Vital Function

Reproduction is a vital function that allows living things to produce offspring similar to themselves.

Types of Reproduction

• Asexual Reproduction: A simple process where a single progenitor copies identical DNA, common in unicellular organisms.
• Sexual Reproduction: A complex process involving two progenitors that produce specialized sex cells, or gametes.

Asexual Reproduction in Plants

• Spore Formation: Cells are formed in specialized organs and expelled; when ripe, they germinate to produce a new being (e.g., mosses and ferns).
• Fragmentation: The formation of new plants from fragments of a leaf or stem (e.g., roses, geraniums).
• Budding: Groups of cells (buds) detach from the parent plant to create new individuals.

Central Nervous System

The brain is divided into two hemispheres and contains convolutions. It controls all voluntary movement.

Cerebellum: Divided into two hemispheres, it controls and coordinates voluntary muscle movements, ensuring accuracy and maintaining equilibrium.

Medulla Oblongata: Connects the brain to the spinal cord and is responsible for controlling pulmonary ventilation and cardiac rates.

Spinal Cord: Located inside the vertebral column and surrounded by meninges. It is formed by a nervous cord with two main functions: communication and the elaboration of responses.

Peripheral Nervous System

Cranial Nerves: There are 12 pairs that originate from the encephalon and travel to various parts of the body.

Spinal Nerves: There are 31 pairs...

Plasma Membrane

A lipid bilayer containing various types of proteins. It controls the passage of substances between the inside and outside of the cell and isolates it from the environment.

Cell Wall

A rigid layer consisting of cellulose and other sugars, exclusive to plant cells. It provides support, confers protection, and gives shape to the cells.

Chromosomes

Composed of DNA and proteins. When a cell is at rest, they appear as a mass called chromatin while maintaining their individuality. The number of chromosomes is characteristic of each species and is best observed during cell division. DNA acts as the carrier of genetic information and controls cellular activities.

Nucleolus

A mass of RNA, proteins, and a small proportion of DNA. There may be...

Iron Metabolism

The body contains a total of approximately 4.5 grams of iron. Of this total:

• 4% corresponds to Hemoglobin (Hb).
• 15–30% is stored in the reticuloendothelial system, primarily as myoglobin.

White Blood Cells (Leukocytes)

Leukocytes are mobile units of the systemic organism. They provide protection and form part of the bone marrow and lymphatic tissue.

Normal count ranges between 4,000 to 11,000 leukocytes per microliter. Granulocytes are the most common type (ca. 65%), including neutrophils, eosinophils, and basophils.

Principal Functions of Leukocytes

1. Granulocytes and Monocytes: Protect the body from invading microorganisms (MO) through phagocytosis.
2. Lymphocytes and Plasma Cells: Generally act within the immune system.

Eosinophils

Eosinophils...

Microorganisms and Their Characteristics

Micro-organisms are life forms that have small main characteristics: they can only be seen through a microscope, are abundant in nature, can multiply quickly, and can be either beneficial or harmful.

Types of Microorganisms

• Eukaryotes: These include fungi (such as mushrooms).
• Prokaryotes: These include cyanobacteria and algae.
• Viruses: These have a subcellular organization.

Bacteria vs. Viruses

Bacteria have a cellular organization including ribosomes, genetic material, and a cell wall. They can be autotrophs or live on organic substances. While some cause disease, many are beneficial, such as intestinal bacteria. In contrast, viruses have a subcellular organization consisting of genetic material and a protein...

The Human Digestive Process

There are three phases in the processing of food: digestion, absorption, and expulsion of waste. This process, driven by peristaltic movements, involves several key steps:

1. Mouth: Digestion begins in the mouth as a result of mastication (chewing) and salivation. Saliva is a liquid produced by the salivary glands in the mouth.
2. Stomach: After swallowing, the food reaches the stomach where gastric digestion begins, and chyme is produced.
3. Small Intestine: The duodenum continues the chemical digestion of the food. Chyme is mixed there with intestinal juices, resulting in chyle, which is then absorbed.

Respiration and Blood Composition

The Respiratory Cycle

During inspiration, the air enters the lungs. During expiration, the air...

Inorganic Nutrients: Water and Minerals

Water: This is a vital component, making up 60% to 80% of body weight. Its primary functions include providing the environment where metabolic reactions occur, transporting substances, and regulating body temperature. It is obtained habitually through the consumption of food and liquids.

Minerals: These are nutrients formed by non-metallic elements (such as phosphorus and carbon) attached to metallic elements (such as iron and sodium). They play a regulatory role by intervening in metabolic processes and performing structural functions, such as forming bones and teeth.

Organic Nutrients: Carbohydrates, Lipids, and Proteins

Carbohydrates: These nutrients are most abundant in foods of plant origin. Their primary...

The Endocrine System: Glands and Functions

Endocrine glands are ductless glands that produce hormones, which are released directly into the bloodstream and distributed throughout the body. Key endocrine glands include:

• Pituitary Gland: A small, round gland located below the brain, attached by the pituitary stalk.
• Thyroid Gland: Located in front of the thyroid cartilage of the larynx.
• Parathyroid Glands: Four small glands situated on the dorsal region of the thyroid.
• Adrenal Glands: Two pyramid-shaped glands located on top of the kidneys.
• Pancreas: A digestive organ containing endocrine tissue known as the islets of Langerhans.
• Gonads: Reproductive organs that produce sex cells; testes (male) produce sperm, and ovaries (female) produce eggs.

Pituitary

Human Gametes and Fertilization

The gametes of women and men are called ovules and sperm. Their union is called a zygote. Fertilization is internal; when the two cells join, they grow to eventually be born alive, as we are viviparous.

The Reproductive Process

The reproductive process involves several stages:

• 1. Production of gametes: Occurs in specialized organs of the reproductive apparatus.
• 2. Fertilization: The union of both gametes where the zygote forms.
• 3. Development: The process of the zygote becoming an embryo and then a fetus.
• 4. Birth: When a baby or child is fully formed and delivered.
• 5. Development to Maturity: The organs mature until the individual is able to reproduce.

Sexual Characteristics and Adolescence

Primary Sexual Characteristics

In...

Characteristics of Vertebrate Animals

All vertebrates have a characteristic in common: their bones and spine. There are five types of vertebrates:

Fish

• Spindle-shaped body.
• Skin covered with scales.
• Poikilotherms (cold-blooded).
• Breathing through gills.
• There are carnivores and others that are herbivores that feed on plankton.
• They reproduce sexually with external fertilization. Fertilization takes place in water. Eggs hatch into several small larvae called fingerlings.

Amphibians

• They have four limbs as legs.
• They have bare skin and need to be constantly wet.
• They are poikilotherms (their body temperature varies with the temperature outside). So, when they go into cold lethargy, it is a kind of deep sleep.
• Adults breathe through lungs and skin.
• Adults are