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

Phonetics and Phonology Basics

Phonetics Defined

Phonetics deals with the material or substance of sound. When we make a sound, it is made with a number, a tone, an intensity...

Physical Qualities of Sound

• Tone: High-intensity musical quality, related to articulatory energy.
• Quantity: Term related to time or duration.
• Resonance: Depends on the volume and sounding board, namely, the oral cavity.

Sounds originate in the speech apparatus. Syllables are also studied in phonetics because they are also sound units. Our sound system consists of 19 consonants and 5 vowels. There are more letters than phonemes because a phoneme may represent several letters.

Phonology Defined

Phonology deals with the study of the characteristics that are relevant in each sound... Continue reading "Phonetics and Phonology Fundamentals" »

Animal Tissues

Epithelial Tissue

Epithelial tissue consists of sheets of densely packed and connected cells that cover internal and external body surfaces.

Simple Epithelia

Simple epithelia are formed by a single layer of cells that can be:

• Flattened, like the endothelial walls of capillaries and the lining of blood vessels, which protect yet allow the exchange of substances.
• Polyhedral (cubic and cylindrical), such as the epithelial lining inside the intestine. Their cells possess microvilli or fingerings on the surface that faces the lumen of the tube.

Stratified Epithelia

Stratified epithelia consist of several layers of cells. Cells in the deepest layer are constantly dividing, and new cells push the older ones upward. The most superficial cells,... Continue reading "Animal Tissues: Epithelial, Muscle, and Nervous Tissues Explained" »

Biotope: The Foundation of Ecosystems

The biotope refers to the main components that determine the presence of living organisms: the medium and environmental (physical and chemical) factors.

The Medium

The medium is the place where living organisms reside and interact within an ecosystem, maintaining constant exchanges of matter and energy. Broadly speaking, we can distinguish two primary types of media:

• Terrestrial Medium: Located on the surface of continents, characterized by direct contact with the atmosphere.
• Aquatic Medium: Consists of water and is characteristic of aquatic ecosystems.

Abiotic Environmental Factors

Abiotic environmental factors encompass all physical and chemical conditions of the biotope. This set of external conditions significantly... Continue reading "Ecosystem Components: Biotope & Biocoenosis Explained" »

Vision Development in Infants

The visual system is designed to capture light effects. The apparatus of global vision allows us to perceive images based on the amount of light reflected. Light enters through the cornea, passes through the pupil to the lens, and is then sent to the retina.

Developmental Milestones

• Newborn: Distinguishes between light and dark (chiaroscuro).
• 1 Month: Can stare at a large object.
• 2 Months: Can accommodate and converge their vision.
• 3 Months: Can follow a moving object by turning their head.
• 4 Months: Has a vertical and horizontal visual field of 180 degrees.
• 6 Months: Acquires eye-hand coordination.
• 8 Months: Examines objects with more detail.
• 12 Months: Acquires adult-like visual acuity.

Vision Disorders

Refractive Errors

• Myopia

1.2. Carbohydrates and Lipids: Concept, Classification, and Functions

Carbohydrates

Carbohydrates are biomolecules formed fundamentally by C, H, and O in the proportion C_nH_2nO_n. Hence, H and O are in the same proportion as in water (H₂O), also called hydrates of carbon. Carbohydrate molecules are chains formed by carbon atoms attached to radical groups and hydroxyl (OH) groups. There may be an alcoholic or a carbonyl group; this group may be an aldehyde (gluc aldose) or a ketone (gluc ketonic). For this reason, they are defined as polyhydroxyaldehydes or polyhydroxyketones.

Classification:

Carbohydrates are classified in two forms:

1. According to the functional group they possess:
   • Ketoses: if they have ketone groups.
   • Aldoses: if they have aldehyde groups.

Mitosis and Cytokinesis

Mitosis

Mitosis (discovered by botanist Eduard Strasburger) is a process of nuclear division exclusive to eukaryotes, ensuring the segregation and equal distribution of sister chromatids between the daughter cells during cell division.

Mitosis is an equational division that ensures the conservation of the genetic and chromosomal makeup of the species. Thus, mitosis of a parent cell yields two daughter cells with the same number of chromosomes and genetic information as the parent cell.

Mitosis can be structured into five phases: prophase, prometaphase, metaphase, anaphase, and telophase.

Prophase

During prophase, the following key changes occur:

• Chromatin Condensation: Chromatin condenses into visible chromosomes, each composed

2. Genetic Engineering: Genetic engineering is defined as the set of technologies to manipulate the genetic material of a living being, i.e., modifying genes. This manipulation consists basically of: introducing new genes into a genome, removing existing genes from a genome, and modifying the information in a particular gene. The new genetic combinations are introduced into organisms capable of transmission to subsequent generations. It is also called recombinant DNA technology because most techniques rely on DNA fragments that recombine.

2.1. Genetic Engineering Tools To obtain new combinations of heritable material, you must use:

• 1. Restriction Enzymes: They are a type of protein that can recognize a specific DNA fragment and cut it. Using

Elements Involved

In order to perform the transcription of DNA into cells, the following elements are required:

• Original DNA to serve as a template to be copied.
• RNA polymerase: synthesizes RNA from a DNA template.
• Ribonucleotide triphosphates to perform the copy.
• Poly-A polymerase, small nuclear ribonucleoprotein, RNA ligase.

Transcription Mechanism

As in replication, there are differences between prokaryotes and eukaryotes. The main differences are the existence of multiple RNA polymerases in eukaryotes and, above all, the need to produce a "mature" form of some RNAs due to the existence of introns. The process is divided into three stages:

• Initiation: The RNA polymerase binds to a region of DNA prior to the DNA that is to be transcribed. It then

The Journey of Childbirth and Lactation

Understanding Childbirth

Stages of Labor and Delivery

Childbirth begins with labor, typically lasting around 12 hours, characterized by frequent uterine contractions that move the fetus towards the dilating cervix. If the amniotic sac ruptures, amniotic fluid exits through the vagina. The baby then passes through the cervix and vagina during birth, after which the umbilical cord is cut. The process concludes with the expulsion of the placenta and other membranes.

Hormonal Regulation of Childbirth

• Progesterone: This hormone remains in the uterus, maintaining pregnancy conditions, particularly by relaxing uterine walls and keeping the cervix closed.
• Estrogens: During pregnancy, estrogens stimulate the growth

Understanding Immune System Components

Lymphoid Organs: Sites of Immune Activity

Lymphoid organs are specialized sites where immune system cells concentrate and function. They are classified into two main types:

• Primary Lymphoid Organs: These are the sites where lymphocytes mature. Stem cell precursors originate in the bone marrow. T lymphocytes mature in the thymus, while B lymphocytes mature in the bone marrow (or the Bursa of Fabricius in birds).
• Secondary Lymphoid Organs: These are the locations where mature lymphocytes accumulate, encounter antigens, and initiate adaptive immune responses. Examples include the spleen (which filters blood), lymph nodes (which filter lymph), and various lymphoepithelial structures (like tonsils and Peyer's patches)