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

Key Ecological Concepts

Ecology is the science that studies the relationships between living beings, and also between them and their surrounding environment.

• Population: A group of individuals of the same species living together in a given area.
• Community: A group of populations living together in a specific area.
• Biotope: The physical environment or habitat occupied by a community.
• Ecosystem: The combination of the community and the biotope in which they live, including the ways in which individuals interact with one another and with their surrounding environment to reproduce and form a stable system.

Environmental Factors

The environment is influenced by various factors:

• Biotic factors: Factors that result from the presence and activities of other

Polymerase Chain Reaction (PCR)

Continuous replication is a fragment of DNA containing a gene or genes of our interest. In this way, we obtain a large number of copies that make it possible to study without worrying about the amount of the sample.

At first, it was a cumbersome technique. Due to the different temperatures used during the process, some of them very high, we were forced to replace the polymerase at each change in temperature. This problem was solved by the DNA polymerase of a thermophilic bacterium: Thermus aquaticus (Taq polymerase).

The method is deceptively simple and involves replication in a medium rich in triphosphate nucleotides, the DNA strand of interest, to which we add small pieces of RNA and Taq polymerase.

A cyclic temperature

Eukaryotic Cell Organelles and Functions

Eukaryotic cells, found in animals, plants, fungi, and protists, contain specialized structures called organelles that perform essential life functions. Below is a detailed look at the key components found in animal and plant cells.

Animal Cell Organelles

Nucleus: The Control Center

• Nickname: The Control Center
• Function: Holds the DNA (genetic material).
• Parts: The Nucleolus is the dark spot within the nucleus that helps manufacture ribosomes.

Ribosomes

• Function: Responsible for protein synthesis (making proteins).
• Note: Ribosomes are found in all cells, both Prokaryotic and Eukaryotic.

Endoplasmic Reticulum (ER): The Roads

• Nickname: Roads (Internal Delivery System)
• Function: Serves as the internal delivery system

Epithelial Tissue: Simple Layers

• Simple Squamous Epithelium (Protection + Filtration)
  • Locations: Blood vessels, lymph vessels, Bowman's capsule, inner surface of the tympanic membrane, endocardium, pulmonary alveoli.
• Simple Cuboidal Epithelium (Secretion + Absorption)
  • Locations: Ovarian surface, posterior surface of the lens, renal tubules.
• Simple Columnar Epithelium
  • Non-ciliated: Digestive tract (stomach to anus), microvilli, ducts of mucous glands.
  • Ciliated: Upper respiratory tract, Fallopian tubes, ependyma, paranasal sinuses.
  • Function: Performs and receives stimuli, movement (cilia), cough, and sneezing.

Epithelial Tissue: Stratified Layers

• Stratified Squamous Epithelium
  • Keratinized: Skin.
  • Non-keratinized: Mouth, esophagus, epiglottis.
• Stratified

Human Digestive and Circulatory Systems

Nutrition is the process by which a living being obtains the matter and energy needed to sustain life.

Components of Digestive Function:

• Taste: Involves eating food, breaking it down, and transporting it.
• Reduce: Food is broken down into simple molecules that cells can use.
• Absorb: Simple molecules are absorbed and passed into the bloodstream for circulation to all body tissues.
• Remove: Undigestible remains are eliminated.

Digestive Tract Components:

The Pharynx

A short part of the digestive tract, also part of the respiratory system, extending from the oral cavity to the top of the esophagus.

The Esophagus

The conduit between the pharynx and the stomach.

The Stomach

An enlarged, bag-shaped part of the digestive tube,... Continue reading "Human Digestive and Circulatory Systems: Functions and Components" »

The Digestive Process

There are three phases in food processing: digestion, absorption, and the expulsion of waste. The movement of food through the digestive tract is known as peristaltic movements. These consist of the narrowing of the tube through the contraction of the muscles of the walls. The muscles contract successively.

Digestion

Types of Digestion

• Mechanical digestion consists of cutting, crushing, moving, and diluting foods.
• Chemical digestion is done through the action of various substances, which attack the foods and bring about chemical changes.

Stages of Food Digestion

• Digestion in the mouth is a result of mastication and salivation. Mastication cuts and crushes the food. Saliva is a liquid produced by the salivary glands in the mouth.

Skeletal System Fundamentals

During vertebrate embryonic development, the notochord develops, which is the precursor of the adult skeleton. (The lamprey retains its notochord in adulthood, while in other groups it is replaced by the spine).

Spine Composition

The spine includes articulated parts and is enlarged in its anterior section, forming the skull. The skeleton may be composed of cartilage (e.g., sharks and rays) or bone (e.g., other vertebrates). Bone is harder and more resistant.

Human Skeletal Development

The human skeleton in embryonic stages consists of cartilage that is later replaced by bone. Ossification begins in the sixth week of embryonic life and continues until adulthood is reached.

The human skeleton is divided into two main parts:... Continue reading "Vertebrate Skeletal System Structure and Development" »

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

Mechanisms of Defense: The Immune System

The immune system consists of a set of organs, cells, and molecules dispersed throughout the body that is responsible for its defense. This defense system operates through internal and external defenses.

External Defenses

They consist of physical and chemical barriers and are the first line of defense to prevent the entry of pathogens. These barriers are mainly the skin and mucous membranes.

Internal Defenses

In the interior of the body, we can distinguish two types of defenses:

• Nonspecific Defenses

  Are so called because they do not depend on the nature of the pathogen. The most important are the inflammatory reaction and the nonspecific cellular defense:

  • Inflammatory reaction. It is a local reaction involving

Stress and the Nervous System

In alarming situations, the nervous and hormonal systems trigger a series of processes that provoke reactions such as increased heart rate, elevated blood pressure, and heightened tension. This tension typically subsides when the alarming situation ends. However, if the situation persists, it can lead to anxiety, distress, depression, and insomnia.

To reduce these effects, consider the following:

• Adequate sleep
• Regular exercise
• Balanced diet
• Avoid consumption of tranquilizers, drugs, and sleep aids

Hormonal Coordination: The Endocrine System

The endocrine system is a set of glands formed by specialized cells that secrete hormones. Glands are classified as:

• Endocrine: Release hormones into the bloodstream.
• Exocrine: Discharge