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

Core Concepts in Ecology

Defining Ecological Units

• Population: A group of organisms of the same species within a defined area that coexist.
• Biotope: The physical environment or place occupied by a community, characterized by environmental conditions such as light or humidity.
• Ecosystem: A community (including different populations) and the biotope in which it is found, where they relate to each other and the physical environment (MDI).
• Environment (MDI): The surroundings of an organism or species, made up of all the factors or conditions that exist in the place where it lives and influence it.

Environmental Factors

Environmental factors include:

• Biotic Factors: Interactions between living organisms, such as the struggle for food or space, or mutual

Fundamental Ecological Laws

Liebig's Law of the Minimum

Established in 1840, this law states that plant development depends on the minimum quantity of a specific element present (e.g., water, gas).

Shelford's Law of Tolerance

This principle dictates that the existence and prosperity of an organism depend on the deficiency or excess of factors approaching its tolerance limits. Organisms vary in their ability to tolerate environmental conditions.

• Stheno: Organisms with narrow tolerance ranges.
• Eury: Plants and animals with wide tolerance ranges.

Biotic Interactions

Biotic factors include diseases, predation, and parasitism.

Types of Relationships

• Interspecific Relationships: Interactions between different populations.
• Intraspecific Relationships: Interactions

Core Concepts in Biotechnology and Genetics

Genetic Code

The genetic code is the set of rules by which information encoded in messenger RNA (mRNA) sequences is translated into amino acid sequences during protein synthesis. It dictates which amino acids correspond to each codon, allowing them to join together in the correct position to form a protein.

Biotechnology

Biotechnology involves the use of living organisms, or parts of organisms, or modified products derived from them, to improve plants or animals, or to develop microorganisms for specific objectives.

Plasmids

Plasmids are circular DNA molecules, independent of the chromosomal DNA, that often carry genetic information useful to the host organism, typically found in bacteria and yeasts.

Bacteriophage

The Digestive System: Functions and Anatomy

The digestive system is responsible for several key functions:

• Food intake: Consuming food.
• Nutrient preparation: Breaking down nutrients through mechanical and chemical digestion.
• Absorption: Absorbing nutrients into surrounding tissues.
• Elimination: Eliminating undigested waste.

Components of the Digestive System

The digestive system consists of the following organs:

• Mouth
• Pharynx
• Esophagus
• Stomach
• Intestines:
  • Duodenum
  • Jejunum
  • Ileum
  • Large Intestine (Cecum, Appendix, Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum, Anal Canal, Anus)

The entire system is lined with the peritoneum, a serous membrane.

Accessory Glands

Several accessory glands aid in digestion:

• Minor and major salivary glands

Arachnids

Arachnids, such as spiders, scorpions, and mites, are terrestrial animals that typically live in dry regions. Their bodies are divided into two regions: the cephalothorax and the abdomen.

• Anatomy: They possess two chelicerae for feeding, two palps for defense, and four pairs of legs.
• Physiology: They breathe through tracheae and are primarily carnivorous.
• Reproduction: They are equipped with poison glands to capture prey, have separate sexes, and are oviparous or ovoviviparous.

Crustaceans

Crustaceans include lobsters, shrimp, barnacles, and crabs. While most are marine, some species, such as freshwater crabs or terrestrial woodlice, inhabit different environments.

• Body Structure: The body is divided into the head, thorax, and abdomen, though

Endocrine System Fundamentals

What is Endocrinology?

Endocrinology is the science studying the function and pathology of the ductless or endocrine glands, whose secretions are called hormones.

Components of the Endocrine System

The endocrine system is a control system responsible for various bodily functions. It maintains the body's internal environment, participates in growth, sexual differentiation, and reproduction, and intervenes in reactions. Closely related chemically with the nervous system, the endocrine system functions in an integrated way. Endocrine interrelations between glands are most often governed by the hypothalamic-pituitary axis.

The main endocrine glands include the pituitary gland, thyroid gland, endocrine pancreas, parathyroid... Continue reading "Endocrine System and Hormone Function" »

Circulatory System and Blood Components

Blood Cells and Platelets

Red blood cells (RBC): They bind oxygen via hemoglobin and transport it through the bloodstream.

White blood cells (WBC): Defend the body from infectious agents.

Platelets: Involved in blood clotting.

Heart Muscle and Valves

Myocardium: Makes the heart contract and relax.

Mitral and tricuspid valves: Let blood flow from the atria to the corresponding ventricles and prevent backward movement.

Semilunar valves: Prevent backflow of blood into the ventricles.

Capillaries and Circulation Types

Capillaries: Perform exchange of substances between blood and cells.

Pulmonary (minor) circulation: Its function is to facilitate the exchange of respiratory gases.

Systemic (greater) circulation: Transports... Continue reading "Cardiovascular, Respiratory & Excretory System Functions" »

Unit 5: Cell Nutrition

All living beings need food used as follows:

• For growth: it provides the substances needed for making new cells and tissues.
• As a source of energy: required for the chemical reactions which take place in living organisms to keep them alive.
• For replacement: of worn and damaged tissues, for example, red blood cells that break down each day and to replace the skin which is worn away and to repair wounds.

Nutrition can be defined as obtaining organic substances and mineral ions from which organisms obtain their energy and their raw materials for growth and tissue repair. Several systems are involved in cell nutrition: this process is carried out by organ systems which working together allow cells to obtain matter and energy.

• Digestive

DNA, Genetic Code, and Translation

Classical genetics is devoted to studying the mechanisms of heredity. In the 1930s, questions were raised, and geneticists began to explore the nature of the gene. Even earlier, there were no doubts about the existence of genes.

The Discovery of DNA Structure

The first chemical analysis of genetic material showed that the eukaryotic chromosome consists of deoxyribonucleic acid (DNA) and proteins. Both DNA and proteins were good candidates for the molecule that carries the genetic material.

In 1953, James Watson and Francis Crick gathered data from different studies on DNA. They postulated a model for DNA structure and were able to deduce that DNA is a double helix, an intertwined and long structure. An essential... Continue reading "DNA Structure, Replication, and Genetic Code Translation" »

The Rhinencephalon and Limbic System

The rhinencephalon is a structure related to the sense of smell. In humans, it has evolved into an area responsible for instinctive motor activity, autonomic and visceral functions, behavior, emotions, and memory. It forms the beginning of the limbic circuitry, a complex formation that occupies the inner surface of the cerebral hemispheres, with its end at the cingulum.

Klüver-Bucy Syndrome

First described in 1930, Klüver-Bucy syndrome results from a bilateral temporal lobectomy. Its symptoms include:

• Visual agnosia
• Hyperorality
• Hyperphagia
• Hypersexuality
• Flattening of emotions (emotional blunting)

MacLean's Theory on the Limbic System

MacLean's theory suggests that the limbic system is primarily related to the... Continue reading "Functions of the Rhinencephalon, Amygdala, and Hypothalamus" »