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

Fundamental Concepts in Genetics

Understanding genetics requires familiarity with key terminology related to DNA sequences, inheritance patterns, and individual characteristics.

Defining Genes and Genetic Makeup

• Gene

  A Gene is an entire nucleotide sequence determined along one side of the chromosome ladder. This sequence may code for proteins or be inhibited, depending on the program assigned to the cells bearing the chromosomes.

• Genotype

  The Genotype is the genetic content (specific genome) of an individual in the form of DNA. It can also be defined as the complete set of genes of an organism.

• Phenotype

  The Phenotype is the observable expression of the genotype in a given environment. Phenotypic traits include both physical and behavioral characteristics.

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:

Core Concepts in Classical Genetics

Genetics:

The branch of biology responsible for the transmission of hereditary traits from one generation to the next.

Gene:

A fragment of DNA information that determines a character. It produces a protein responsible for determining a character, such as eye color or hair color.

Alleles:

The different variants of a gene.

Dominant Inheritance:

Occurs when one gene has greater strength to manifest itself than another gene.

Dominant Gene:

The allele that has more power to manifest itself (expressed even in heterozygotes).

Recessive Gene:

The allele that has less force to become apparent (expressed only in homozygotes).

Intermediate Inheritance:

The pattern in which both genes have the same force to manifest themselves, resulting

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

Tabanidae: Horseflies and Deerflies

Life Cycle of Tabanus, Chrysops, and Haematopota

The life cycle of horseflies and deerflies (genera Tabanus, Chrysops, and Haematopota) is closely tied to water and is notably long, typically lasting 1-2 years.

• Oviposition: Females lay eggs on plants or stones located close to water bodies.
• Larval Stage: Upon hatching, the larvae enter the water. They are not swimmers but feed on organic matter and plankton. They undergo several larval stages.
• Pupation: The final larval stage burrows into the mud and transforms into a pupa.
• Adult Emergence: Orthorrhaphous adults emerge from the pupa.

Ecology and Ethology

These flies are commonly found in meadows and woodlands near water collections. Ethologically, they are highly... Continue reading "Horsefly and Deerfly Biology: Life Cycle, Health Impact, and Morphology" »

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