Notes, summaries, assignments, exams, and problems for Biology

Parasite Life Cycles

Direct (Monoxenic) Cycles

Direct cycles are those that do not require the presence of an intermediate host.

Indirect (Heteroxenic) Cycles

Indirect cycles require an intermediate host to complete their cycle.

Key Features of Parasites

Resistance to the Outside

To cope with climatic factors and chemical agents, eggs, cysts, or larvae are protected with coverings that make them resistant to protein.

Pathogenicity

Pathogenicity is associated with morbidity and mortality.

Auto-infection

Auto-infection is the way for the parasite to remain longer in the host.

It can be:

• Autoexoinfection, which is outside for a very short time
• Autoendoinfection, which multiplies within the host

Recontamination is done on the inside.

Prepatent Period

The prepatent... Continue reading "Understanding Parasite Life Cycles and Survival Strategies" »

Blood Composition and Its Vital Role

Blood is a red liquid that circulates throughout the blood vessels. It plays a crucial role in the body by transporting essential nutrients and oxygen to cells, while also collecting carbon dioxide and other waste products for removal.

Blood primarily consists of two main components: plasma and blood cells.

Plasma: The Liquid Matrix of Blood

Plasma is a yellowish liquid that serves as the transport medium for various vital substances, including nutrients, hormones, enzymes, and waste products throughout the body.

Types of Blood Cells

Blood cells are primarily produced in the bone marrow. There are several distinct types, each with specialized functions:

• Red Blood Cells (Erythrocytes): These cells contain a protein

... Continue reading "The Circulatory System Explained: Blood Components & Flow" »

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

... Continue reading "Nutrition Essentials: Food, Energy, and Health" »

Polymers

A polymer is a macromolecule composed of long chains of repeating molecular units known as monomers. Polymers are typically organic compounds formed by joining monomers containing carbon, hydrogen, and other elements. The properties of a polymer depend on its monomers and its spatial structure, which can be a linear chain, a ring, or other more complex configurations.

Types of Polymers

• Natural Polymers: Found in nature and formed by living organisms. Examples include proteins and cellulose.
• Artificial Polymers: Derived from chemically modified natural polymers. Celluloid was the first artificial polymer. Other examples include cellulose nitrate, rayon, and vulcanized rubber.
• Synthetic Polymers: Designed and synthesized by humans. Examples

... Continue reading "Polymers and New Materials: A Comprehensive Overview" »

Respiratory System Anatomy and Function

The respiratory system is composed of the following key components:

• Nostrils
• Pharynx
• Larynx
• Trachea
• Bronchi and Bronchioles
• Lungs
• Pulmonary Alveoli
• Diaphragm

Nostrils: Air Filtration and Warming

The nostrils are two channels located at the base of the nose, leading to the nasal cavity. The nasal cavity is separated by the septum. Nasal hairs filter the air, trapping dust and particles. The interior is lined by the nasal mucosa, which warms and humidifies the inhaled air. Their primary function is to allow air entry into the body.

Pharynx: The Throat's Passageway

The pharynx, a tube approximately 14 cm long, connects the nasal passages, oral cavity, larynx, esophagus, and middle ear. From the pharynx, air is directed... Continue reading "Human Body Systems: Respiratory and Urinary Functions" »

The Circulatory System

The circulatory system is the anatomical structure that includes both the cardiovascular system (which carries and circulates blood) and the lymphatic system (which carries lymph).

Its main function is to transport nutrients, gases, hormones, and blood cells to the body's cells. It also helps fight disease, stabilize body temperature and pH, and maintain homeostasis.

Basic Structures of the Circulatory System

• Arteries
• Veins
• Blood
• Heart
• Capillaries

The Nervous System

The nervous system is a network of ectodermal tissues found in animals. Its basic unit is the neuron. Its main function is to quickly capture and process signals, exerting control and coordination over other body systems to achieve timely and effective interaction with... Continue reading "Understanding Human Body Systems: Circulatory, Nervous, Locomotor, and Digestive" »

Sperm and Egg Characteristics

Sperm are male gametes, representing highly specialized cells. These cells are small and mobile and consist of three parts:

• Head: The most voluminous part of the sperm. It contains the nucleus, with 23 chromosomes, and the acrosome, a cellular organelle that secretes substances that participate in the fertilization of the egg.
• Tail: Consists of a flagellum, a protein structure that allows the movement of the sperm.
• Neck: Lies between the head and tail. It contains numerous mitochondria around the base of the flagellum; these cellular organelles provide the energy needed to travel to the egg. It also contains a centriole, an organelle responsible for controlling movement.

Eggs have 23 chromosomes and have a very different... Continue reading "Sperm, Egg, Ovaries, and Spermatogenesis" »

How New Species Originate: The Speciation Process

All living things descend from a common ancestor. Evolution explains how a single species can diverge into two or more, leading to the current biodiversity. This process, known as speciation, typically occurs as follows:

• Geographic Isolation: Two populations of the same species become separated by a geographical barrier, such as a sea or a high mountain range.
• Independent Evolution: Both populations then undergo independent evolutionary paths. Mutations occur randomly in each, and since the number of genes is very high, these mutations will differ between the two populations.
• Accumulation of Differences: The accumulation of these genetic differences, combined with the pressures of natural selection,

... Continue reading "Speciation & Evolutionary Evidence: Unpacking Biological Change" »

Part II: The Endocrine System

Endocrine System Function

The endocrine, or hormonal, system is another system of coordination within the body. This system is closely related to the nervous system, and they are dependent on each other. In some cases, the nervous system stimulates or inhibits the secretion of hormones, and in others, the hormones stimulate or inhibit the action of the nervous system.

The endocrine system consists of a series of glands located throughout the body. These glands, called endocrine glands, are not anatomically connected to each other. They pour their secretions directly into the bloodstream.

Endocrine glands are formed by specialized secretory cells that synthesize chemicals called hormones. Once produced, hormones are... Continue reading "Endocrine System: Function, Hormones, and Diseases" »

Mitosis: is a dynamic, continuous and very complex whereby the nuclear material is duplicated and then divided and shared equally between the daughter cells.
Phases of mitosis: interphase, prophase, prometaphase, metaphase, anaphase, telophase.
Chromatic chromosome is a newly formed, still attached by the centromere.
Equatorial plate: the formation is taken as linear chromosomes in the center of the spindle in the metaphase stage of mitosis and meiosis.
Spindle fibers: attract the respective chromosomes toward the centrioles.
Meiosis is a type of reduction division and multiple it is performed by two successive divisions during which four daughter cells are formed, the chromosomes are duplicated so that the number of chromosomes that appear... Continue reading "Mitosis and Meiosis" »