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

A gene is the carrier of an inherited feature that is passed from generation to generation.

Alleles are possible alternatives for a character. Alleles stand at the same site on two chromosomes in an individual, one from each parent. Alleles are equal when it is said that the individual is homozygous or pure-bred for the character. If different, they are heterozygous or hybrid.

A dominant allele is the character that is always represented (capital letters).

A recessive character emerges only in homozygous individuals (lowercase).

Genotype is the joint of the genes, half from one progenitor and the other half from the other.

Phenotype is the set of characters that manifests externally. This is particular, but the genotype influences the environment.... Continue reading "Understanding Genes, Alleles, and Inheritance" »

Understanding the Nervous System

The nervous system is responsible for processing received information and generating appropriate responses. It connects with sensory receptors that receive stimuli and effector organs that execute the response.

Sensory Receptors

Receptors are specialized cells that capture stimuli and translate them into nerve impulses. Neurons are somewhat modified or non-nerve cells that connect chemically or electrically with other neurons.

Types of Receptors:

• Exteroceptors: Detect external stimuli.
• Interoceptors: Detect internal stimuli.
• Proprioceptors: Detect body position and movement.

Types of Neurons

Neurons can be classified in several ways:

By Number of Extensions:

• Monopolar: One extension.
• Bipolar: Two extensions.
• Multipolar:

Digestive System Processes

Ingestion

Seizure of food by the digestive system through the mouth.

Chewing

Spraying of food through chewing movements and mixing with saliva.

Swallowing

Movement of food from the mouth to the stomach.

Digestion

Mechanical and chemical breakdown of food into absorbable molecules.

Absorption

Passage of monomers of food molecules through the mucous membranes of the intestine into the bloodstream.

Peristalsis

Waves of rhythmic contractions that propel food along the digestive tract.

Elimination (Clarification)

Discarding of indigestible waste, called feces, which contains water, dead cells, dead bacteria, mucus, and gas.

Digestive System Phases

• Propulsion: Movement of food along the digestive tract.
• Secretion: Release of digestive juices.

What are Tissues?

A tissue consists of a group of specialized cells. Often, in addition to the cells themselves, tissues also contain substances created by the cells. These are called extracellular substances or the extracellular matrix. A set of cells that work together to perform the same function is called a tissue. In most cases, tissues are made up of cells of the same type.

Types of Tissue

There are four main types of tissue in the human body:

Epithelial Tissue

Epithelial tissue covers the external surface of the body and lines the internal and external surfaces of organs. There are two main types:

• Covering or Lining Epithelium: This type may be made up of one or several layers of cells. Its primary function is protection.
• Glandular Epithelium:

Meiosis: Cell Division for Reproduction

Meiosis is a type of cell division involved in sexual reproduction. Its purpose is to produce reproductive cells called gametes, which have half the number of chromosomes as normal somatic cells (they are haploid). Meiosis consists of two consecutive divisions. Starting with a single diploid cell, four haploid daughter cells are obtained. These daughter cells are genetically different due to the exchange of information between homologous chromosomes. Meiosis occurs in the reproductive organs or gonads: ovaries and testes in animals, and ovaries and anthers in plants.

Meiosis I

Prophase I

Meiosis begins with steps similar to mitosis. The main difference is that homologous chromosomes pair up and become fully... Continue reading "Meiosis Cell Division: Stages and Purpose" »

Tissues represent an organizational level above the cellular level. They are a set of similar cells that specialize in a particular function and are classified into four basic groups: epithelial, connective, muscular, and nervous.

1. Epithelial Tissue

Formed by epithelia, epithelial tissue has two main types based on its features:

• Epithelial tissue lining: Lines the body's surface and internal body cavities. This is further divided into two types:
  • Simple: Just one layer of cells.
  • Stratified: Many layers of cells.
• Glandular epithelial tissue: Builds secreting cells that are exchanged or clustered epithelial cells to form glands.

Examples of Epithelial Tissue:

• Simple squamous epithelium: Flattened cells, wider than they are high. Lines the heart and

Understanding Nutrition

Nutrition is the set of processes that allows organisms to use and transform nutrients to stay alive. Food is the process by which these nutrients are obtained from the external environment. Food contains nutrients, which are essentially the biomolecules that make up our body.

Essential Nutrients

These include:

• Carbohydrates (Carbs): Energetic substances.
  • Simple Carbohydrates (Sugars): Sweet, crystalline, and water-soluble.
  • Complex Carbohydrates: Not crystalline, do not dissolve, and are formed by the bonding of many simple carbohydrate molecules.
• Lipids: A very diverse set of substances characterized by being insoluble in water and having an oily appearance.
  • Fats: Highly energetic molecules. Depending on their chemical composition,

Digestive System

Function

The digestive system is responsible for processing food, absorbing molecules, and eliminating waste.

Types of Digestion

There are two main types of digestion: mechanical and chemical.

System Interactions

The digestive system interacts with the nervous, endocrine, and circulatory systems.

Functional Structure

1. Mouth: Digestion begins in the mouth.
2. Esophagus: Food travels down the esophagus.
3. Stomach: Gastric digestion occurs in the stomach.
4. Small Intestine: Intestinal digestion and absorption take place.
5. Large Intestine: Final absorption and waste processing.

Excretory System Structure

The excretory system plays a crucial role in waste removal.

• Cecum: Follows the ileocecal valve.
• Colon: Divided into ascending, transverse, and descending

Virus Characteristics

Viruses are unique pathogens, not classified as living organisms. A virus particle, a submicroscopic infectious agent, has a single nucleic acid type (DNA or RNA) within a protein coat called the viral capsid, forming the nucleocapsid.

Some viruses have a lipid-protein envelope. The capsid's protein organization determines the virus's shape, usually helical or polyhedral. Viruses are genetic elements in transit, switching between extracellular and intracellular states.

Extracellular Phase (Virion)

In the extracellular phase, the virion is metabolically inert. It carries viral genetic material from one cell to another.

Intracellular Phase

Inside a cell, the virus replicates, using the cell's machinery to synthesize new viral... Continue reading "Virus Structure, Classification, and Replication Cycles" »

1. Bacterial Antibodies

Which individual component of a bacterium should be injected into rabbits to generate effective antibodies against subsequent exposure to the same bacteria?
c. Bacterial chromosome DNA fragments

2. Lymphocytes

The lymphocyte, a type of leukocyte, is characterized by:
II. Providing long-term or short-term immunity to the body

3. Acquired Immunity

Acquired immunity, whether natural or artificial, is achieved by:
I. Suffering from an illness
II. Vaccination with an attenuated microbe
III. Administration of antibodies produced by another source

4. Natural Immunity

The term "natural immunity" refers to:
I. Immunity that develops during an individual's life as a result of the body's response to a pathogen
II. Immunity that is activated