Notes, abstracts, papers, exams and problems of Biology

Puberty: Hormonal Changes

Boys: Sperm production, increased bone thickness and muscle mass, voice deepening, beard growth, and the appearance of pubic and axillary hair.

Girls: First menstruation, breast growth, widened hips, and the appearance of pubic and axillary hair.

Female Reproductive System

Ovaries, Fallopian tubes, uterus, vagina, clitoris, labia majora, and labia minora.

Male Reproductive System

Testes, prostate, urethra, epididymis, vas deferens, seminal vesicles, penis, and scrotum.

Key Definitions in Human Development

• Embryo: The second phase of zygote development occurs when it attaches to the endometrium.
• Fetus: The third stage of embryonic development, starting in the second trimester.
• Nidation: The moment when the zygote attaches to

Muscular System

Muscle Characteristics

Involuntary. Located in the heart. Striated fibers are present inside longitudinal filaments called myofibrils. Muscle cells are made of two proteins: actin and myosin. Some form rhabdomyosarcoma.

Types of Muscles

• Long or Fusiform: (spindle-shaped)
• Flat or Planar: (e.g., diaphragm)
• Orbicular: (round body, e.g., orbicularis oculi)

Tendons join muscles to bones. Two muscles are involved in any movement: agonist (contracts) and antagonist (relaxes).

Skeletal System

3.2 - Bones

Functions

• Support the body and give it shape.
• Allow movement of various body parts.
• Protect internal organs (brain, lungs, etc.).
• Serve as the main repository of minerals (calcium, potassium, etc.).
• Some bones act as organs of blood cell production.

Common Illnesses and Their Causes

Illnesses Caused by Viruses

Viruses are responsible for a variety of illnesses, some of which are highly contagious. Here are a few examples:

• The Common Cold: A highly contagious illness that causes mild discomfort, increased nasal secretions, congestion, and sneezing. It typically does not cause fever. Transmission occurs through direct contact, but the virus can also spread through the air. Frequent handwashing is crucial for prevention.
• Flu (Influenza): Often confused with the common cold due to its prevalence in winter and similar transmission methods. However, the flu generally causes greater discomfort, including joint pain, and is a more serious illness.
• AIDS (Acquired Immunodeficiency Syndrome): A serious

Cellular Functions

Cellular functions are basic units of life and conduct nutrition, relationships, and reproduction. Unicellular cells perform all these functions within a single cell, while multicellular organisms have specialized cells.

• Nutrition: Molecular intake from the external environment provides energy to renew cellular structures. This process inside the cell is known as metabolism.
• Relationships: Cells communicate with the outside environment, adapting to changes and maintaining stability.
• Reproduction: New cells are formed from existing ones. In unicellular organisms, this leads to a new being. In multicellular organisms, it replaces dying cells and increases cell numbers during growth. Cells pass their genetic material to their daughter

Item 14. Physical Agents: Thermal Environment

Introduction

Thermal environment refers to environmental conditions including:

• Temperature
• Humidity
• Physical activity

Homeotherms

Homeotherms maintain internal temperature within very narrow ranges.

• Danger: Heat stress
• Heat discomfort
• Comfort
• Discomfort from cold
• Danger: Hypothermia

Thermal Equilibrium

Thermal equilibrium between body and environment involves mechanisms of thermoregulation.

Mechanisms of Thermoregulation

Q = M ± R ± C - E

• Q: Heat generated or heat buildup
• M: Metabolic activity
• R: Radiation exchange
• C: Exchange by convection
• E: Heat lost by evaporation

Radiation Exchange (R)

Heat exchange that originates between two solid bodies in proximity.

Exchange by Convection (C)

Mechanism by which the body exchanges... Continue reading "Thermal Environment: Effects, Regulation, and Comfort" »

Soma Cells: These cells comprise the whole body, excluding the germ cells.

Germ Line: Specialized cells in reproductive organs responsible for producing gametes.

Karyogamy: The fusion of cell nuclei.

Sexual Dimorphism: Morphological differences between males and females of a species.

Fecundity: The ability to produce offspring.

Withers: When two hermaphroditic individuals mate and fertilize each other.

Parthenogenesis: A phenomenon where an unfertilized egg develops into a normal adult.

Receptaculum Seminis: A storage location for sperm after mating.

Spermatophores: Packets containing sperm that are transferred to females.

Segmentation: A series of rapid cell divisions during early embryonic development.

Morula: A solid ball of cells in the early embryo.... Continue reading "Key Concepts in Reproduction and Embryonic Development" »

Mendel's Laws

Mendel explained the observations made during years of crossing different types of peas in the gardens of a monastery. He collected the general laws of inheritance that later became known as Mendel's laws.

Double Helix DNA

DNA carries the genetic information. DNA is a molecule composed of four simple units, repeated often and combined in different ways (called nucleotides). There are four types of DNA nucleotides: cytosine, guanine, thymine, and adenine. A single DNA molecule is formed by two chains of nucleotides linked and facing each other, with a structure that forms a spiral staircase: a double helix.

Replication of DNA

DNA contains genetic information. When the cell divides, it is capable of making an exact copy of the entire... Continue reading "Mendel's Laws, DNA, Genes, and the Genetic Code" »

Biomolecules and Genetic Information

Biomolecules form long chains, such as in genetic information storage. These chains consist of repeating nucleotides. A nucleotide is composed of a nitrogenous base, a pentose sugar (like am5C), and a phosphate group. A nucleoside is simply a base plus a pentose sugar.

Nitrogenous bases include adenine (A), thymine (T), uracil (U), and guanine (G). Purine bases (A and G) have a two-ring structure, while pyrimidine bases (C, T, and U) have a single-ring structure. These bases contain the genetic code necessary for protein synthesis. Approximately 3000 base pairs are needed to code for a single protein. The human genome contains 46 chromosomes (23 pairs), with 22 pairs being autosomes and one pair being sex... Continue reading "Biomolecules, Genetics, and Chromosomal Variations" »

DNA Replication

DNA replication begins with the double helix unwinding, separating like a zipper. Each strand serves as a template for creating a new complementary strand. DNA polymerase enzymes add nucleotides one by one, matching adenine with thymine and guanine with cytosine. This process creates two identical DNA molecules, each with one original and one new strand. Errors during replication can lead to mutations, which can be harmless, cause diseases, or contribute to evolution.

The Importance of Base Complementarity

Base complementarity is crucial for accurate DNA replication, ensuring that genetic information is passed correctly from parent to daughter cells. It also forms the basis of many molecular biology techniques.

Gene Expression:

1. Health and Disease

1.1. Definitions

Health: A state of complete physical, mental, and social well-being, not merely the absence of disease.

Disease: A change in health status, i.e., a temporary or permanent loss of physical, mental, and social well-being.

Quality of Life: The comfort level, happiness, and satisfaction in a person that allows them to act and feel positively about their lives. This depends on their physical and mental health, their level of independence, and social relationships. One of the main indicators is life expectancy at birth.

1.3. Genes, Lifestyle, and Health

There are genetic diseases due to alterations in the genome (e.g., Down syndrome, hemophilia, or certain types of diabetes).

In other cases, the genotype determines... Continue reading "Health, Disease, and Infectious Diseases: A Comprehensive Overview" »