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

Fundamentals of Biological Reproduction

Reproduction: The biological method necessary to ensure the survival of species.

Types of Reproduction

• Asexual Reproduction: Requires only one parent; creates exact genetic copies of itself; does not require gametes.

• Sexual Reproduction: Requires two parents who provide the gametes; descendants inherit characteristics from both parents.

Gametes and Gonads

Gamete: Specialized cells formed by meiosis from diploid cells in the gonads.

Reproductive Structures (Gonads)

• Unisexual: Characterized by two distinct types of individuals and gonads (Male and Female). Males and females exhibit traits that differentiate them (sexual dimorphism).

• Hermaphrodite: Individuals possess both male and female gonads.

Key Reproductive

Kinds of Amino Acids

Amino acids can be classified into several categories:

• Nonpolar:
  • Aliphatic
  • Aromatic
• Polar Uncharged
• Charged:
  • Acidic (Anionic)
  • Basic (Cationic)

Proteins: Building Blocks of Life

Proteins are biopolymers formed by molecular chains of 20 different amino acids, each with its own characteristics.

Protein Structures

Primary Structure

The primary structure is characterized by the specific composition of amino acids and their sequential order within the polypeptide chain.

Secondary Structure

The secondary structure refers to the folding of the primary structure due to the formation of hydrogen bonds between the -C=O group of one peptide bond and the -NH group of another. This results in the side chains (R groups) adopting specific spatial arrangements... Continue reading "Amino Acids and Protein Structures: A Comprehensive Look" »

Ecosystems: Definition and Characteristics

An ecosystem is a system formed by the interaction between a community and a biocenosis, or physical environmental factors. An ecosystem model for the subject is closed but open to energy, being capable of regulating itself and remaining in dynamic equilibrium over time.

Population Dynamics

A population is comprised of a set of individuals of the same species living in a particular location. There are some factors that prevent a population from reaching its full biotic potential. These can be external or internal to the population:

• External Factors: These may be biotic (predators, parasites, or diseases caused by other agencies competing for a given resource) and abiotic (climate change, food shortages,

• In the pyramids of numbers, the lengths of the steps are proportional to the number of individuals of all species in each trophic level per unit area or volume.

  Biomass in the lengths of the steps are proportional to the dry weight of all individuals in each trophic level per unit area or volume.

  These pyramids best describe the trophic relationships of the ecosystem as they indicate the amount of organic matter that can be eaten at each trophic level, but do not express the amount transferred from one level to another.

  Energy in the lengths of the steps are proportional to the energy produced per unit time of all individuals in each trophic level per unit volume or surface.

  These pyramids provide a better overall picture of trophic relationships

Cholera

Pathogen: Vibrio cholerae

Methods of Transmission:

• Foodborne
• Waterborne

Note: 3/4 of infected people may be asymptomatic carriers and pass large numbers of bacteria in their feces.

Global Distribution: Asia, Africa

Incubation Period: 1-5 days

Site of Action: Wall of the small intestine; secretes a toxin called choleragen

Clinical Features:

• Severe diarrhea
• Loss of water and salts
• Weakness

Note: Can be fatal if not treated within 24 hours.

Method of Diagnosis: Microscopic analysis of feces

Annual Incidence Worldwide: 5.5 million

Annual Mortality Worldwide: 120,000

Treatment: Antibiotics

Tuberculosis

Pathogen: Mycobacterium tuberculosis

Transmission:

• Airborne droplets
• Infected meat

Global Distribution: Worldwide

Incubation Period: A few weeks or months

Site of

Infection: Pathogen Penetration and Host Response

Infection is the penetration of a pathogen into the body of an animal or plant, causing changes in organs and their functions. It is essential for the microbe to possess pathogenicity (the ability to cause disturbances in the body), which depends on its invasiveness and toxin production. For an infection to develop, the host organism must be receptive to the microbes (i.e., susceptible to invasion).

Organic Defense Mechanisms: Protecting the Body

Nonspecific Defense (External Barriers)

These are the body's first lines of defense, acting as external barriers:

• Structural: Skin and mucous membranes. These are common entry points for pathogens when compromised.
• Mechanical: Tears, urine, coughing, and

Genetic Mutations

A mutation is an alteration of genetic material. Key characteristics include being detectable and heritable.

Types of Mutations

• Chromosome Mutations

  These are visible under light microscopy and affect large fragments of chromosomes or entire chromosomes, thus involving many genes. They can impact the structure or number of chromosomes.

  • Structural Alterations: Changes in chromosome structure resulting from broken chromosomes and the rejoining of fragments.
  • Numerical Abnormalities: Changes that alter the normal chromosome number of a species.

• Gene Mutations

  These are not observable by light microscopy and typically involve only a few nucleotides.

Genetic Engineering

Genetic engineering encompasses the study and techniques for the manipulation... Continue reading "Genetic Mutations, Engineering, and Biotechnology Applications" »

Understanding Health and Disease

Key Definitions

• Disease: A part of our body that changes and ceases to perform its function well.
• Health: Your mental or physical condition.
• Symptoms: A physical or mental feeling experienced by someone with a disease or illness.
• Diagnose: To study symptoms of an illness or disease and to decide what is wrong with a person.
• Sign: A symptom of a disease or illness that is recognized by others.
• Treatment: Medical care or attention given to a person who is ill (curative or symptomatic).
• Convalescence: The period needed for returning to health after illness.

Factors for Maintaining Good Health and Preventing Diseases

• A Healthy Environment: Free of anything harmful to health.
• Healthy Habits and Lifestyles.
• Personal Characteristics.

Diarrheal Diseases

Diarrheal diseases are among the most serious health problems worldwide. Key diseases in this category include cholera, dysentery, and salmonellosis. These are caused by organisms that reside in the intestines of infected individuals, sometimes without causing apparent symptoms. Regardless of whether the person exhibits symptoms, their feces contain large amounts of pathogenic microorganisms.

The disease spreads via the digestive tract through the consumption of contaminated food or drink. Contamination can occur directly or indirectly, such as through flies, or via contact with the hands or skin of individuals living without proper sanitation. Intense diarrhea is often accompanied by vomiting, leading to significant loss of... Continue reading "Understanding Common Infectious Diseases and Their Management" »