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

1. Viruses

Viruses are not living organisms but very small particles that cause infectious diseases. A virus has an outer coat of protein but no nucleus. It carries genetic information and damages cells while it reproduces.

Reproductive Cycle

• Infection: A single virus attacks a cell and breaks through the cell membrane.
• Replication: The virus reproduces its genetic information inside the host cell.
• Release: The cell bursts, releasing newly made viruses to infect other cells.

2. Three More Kingdoms: Fungi, Prokaryotes, and Protista

Prokaryotes: Bacteria

Bacteria are microorganisms—living cells capable of respiration, movement, growth, feeding, and reproduction. They are unicellular and prokaryotic.

Characteristics

They are surrounded by an outer cell...

Sulfur in Prokaryotes

In prokaryotes, sulfur is most often stored as elemental (S0) granules that can be deposited intracellularly or extracellularly. Sulfur granules are especially common in bacteria that use hydrogen sulfide as an electron source.

DNA Structural Components

Do you know the specific structural setup for the DNA molecule? Bases, phosphate, sugar, etc.

A nucleoside consists of a sugar and a nitrogenous base. A nucleotide consists of a phosphate group, a five-carbon sugar, and a nitrogenous base (purines: adenine and guanine; pyrimidines: cytosine and thymine).

Function of Cellulose

Makes cell walls. Cellulose is the main structural component of plant cell walls and provides rigidity and support.

Translating mRNA Codons

Know how to translate...

Cell Theory and the Nature of Life

The concepts of living matter and the cell are closely linked. Living matter is distinguished from non-living matter by its ability to metabolize and self-perpetuate. Furthermore, the structures that make these two functions possible define what is considered alive.

The cell is the smallest level of organization of matter that possesses the ability to metabolize and self-perpetuate; therefore, it has life and is responsible for the vital characteristics of organisms. Within the cell, all chemical reactions occur that help sustain us as individuals and as a species. These reactions enable the manufacture of new materials to grow, reproduce, repair, and regulate the organism, while also producing the energy necessary...

The Intestines: Structure and Function

The Small Intestine

The main function of the small intestine is the absorption of necessary nutrients for the human body. It is the part of the digestive tract that starts just after the stomach and ends at the cecum of the colon.

Divisions of the Small Intestine

The small intestine is divided into three parts:

• Duodenum
• Jejunum
• Ileum

It measures approximately 3 meters long in a living person, but extends up to about 6.5 meters post-mortem due to the loss of muscle tone. It is located between two sphincters: the pyloric sphincter (connecting to the stomach) and the ileocecal sphincter (communicating with the large intestine).

The Large Intestine (Colon)

The large intestine is the penultimate portion of the digestive...

Embryonic and Fetal Development

Embryonic development is the period of growth and morphogenesis between the formation of a zygote and the birth of a new organism. In humans, this process takes 38 weeks (266 days) from fertilization. This period involves growth, cell differentiation, and morphogenesis—the formation of tissues and organs.

Fetal Development and Maturation

Fetal development focuses on the growth and maturation of organs. During the first two months following fertilization, the human being in formation is an embryo. The concept of the fetus and fetal development applies from the ninth week of gestation until birth.

The Mechanism of Delivery

Delivery is the mechanism by which viviparous animals expel the fetus from the womb. This process...

Female Reproductive Tract: Anatomy and Function

• Oviducts (Fallopian Tubes or Uterine Tubes)

  These are two small tubes with a funnel-shaped opening at the end closest to the ovaries. They are responsible for collecting the eggs released by these organs. Fertilization occurs in the fallopian tubes. The innermost layer of these tubes consists of ciliated cells that enable the movement of the eggs along them. They also secrete a fluid that facilitates the movement of the zygote before it reaches the uterus.

• Uterus

  A conical-shaped cavity into which the fallopian tubes lead. Its wall has a thick muscular layer, the myometrium, and is lined internally by a mucous layer, the uterine lining (endometrium). At its lower end, called the neck or cervix, the

The Organization of the Human Body

Cellular and Tissue Hierarchy

A Cell is the basic structural and functional unit of living things.

• All human cells originate from a single initial cell called the Zygote.
• Although we originate from one cell, we develop several types of specialized cells.
• A group of specialized cells results in a Tissue.

From Tissue to Organism

A Tissue is a set of cells of the same type performing a specific function.

• The combination of various tissues forms an Organ.
• A combination of organs results in an Organ System or Apparatus.

We use the term System when there is only one predominant tissue type (e.g., Nervous System).

The union of all systems and apparatuses results in a Multicellular Organism.

Specific Roles of Human Tissues

Tissues...

Seasonal Isolation

Response:

Species: The name given to each of the groups that divide the sexes, i.e., the limitation of the generic in a particular field of morphology. In biology, a species is the basic unit of biological classification.

Variations: These are the distinctive features that occur in individuals of the same species. These changes or differentials in characteristics of individuals relate to those who show up. Even though their heredity plays an important role in the transmission of hereditary or genetic characteristics, there is no chance, or a very remote one, that there are individuals the same as those around us.

Adaptation: A biological adaptation is an anatomical structure, physiological process, or behavioral trait of an organism...

Animal Nutrition

Performed by the digestive system, this process comprises four phases:

• Ingestion: Taking food from the outside.
• Digestion: Processing food into nutrients.
• Absorption: The passage of nutrients into the blood.
• Egestion: The elimination of undigested waste.

Breathing

Performed by the respiratory system, there are several types of breathing:

• Skin: Gas exchange occurs across the body surface.
• Gill: Carried out through gills, thin extensions of the body surface surrounded by blood vessels.
• Tracheal: Accomplished by tracheae, thin extensions that reach almost all animal cells.
• Pulmonary: Takes place in the lungs, internal cavities with thin, moist walls and blood vessels.

Circulation

The circulatory system performs transport. Types of systems...

Human Heart: Structure and Function

The heart is a vital muscular organ responsible for pumping blood throughout the body. Its walls are primarily composed of a specialized muscle tissue called the myocardium.

Heart Anatomy: Key Components

The heart is divided into four main chambers:

• Two Atria: These are the upper chambers. They have thin, elastic walls and receive blood returning to the heart via veins.
• Two Ventricles: These are the lower chambers. They possess thick, powerful walls, especially the left ventricle, which pumps blood to the entire body. Arteries exit from the ventricles.

The left ventricle is connected to the left atrium, while the right side is separated by a partition (septum). Blood enters the atria from veins and leaves the ventricles...