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

Population Genetics

Microevolution

Change in the collective genetic material of a population.

Bell Curve

Shows the frequency of a trait in a population.

Gene Pool

Describes the total genetic information available in a population.

Hardy-Weinberg Genetic Equilibrium

Principle based on a set of assumptions about an ideal hypothetical population that is not evolving.

Immigration

Movement of individuals into a population.

Emigration

Movement of individuals out of a population.

Gene Flow

Process of genes moving from one population to another.

Sexual Selection

Tendency of females to choose the males they mate with based on certain traits.

Stabilizing Selection

Individuals with the average form of a trait have the highest fitness.

Disruptive Selection

Individuals with... Continue reading "Population Genetics: An Evolutionary Overview" »

Name the stage of cell division in which paired homologous chromosomes get shortened and thickened?

Ans: Pachytene is the stage of cell division in which paired homologous chromosomes get shortened and thickened.

Which structure of animal cell forms the asters of spindle?

Ans: Centrosome is that structure of animal cell which forms the asters of spindle.

Name the cells in which meiosis occurs?

Ans: Meiosis occurs in the reproductive cells or germ cells.

At which stage of meiosis crossing over of genetic material takes place?

Ans: Pachytene is the stage of meiosis in which crossing over of genetic material takes place.

What is Go phase?

Ans: A stage when cell cycle is arrested during interphase is called Go phase.

Name the cell division concerned with

Understanding Microorganisms and Disease

Viruses (e.g., flu, polio, common cold, AIDS, Ebola, chickenpox, measles, rubella, smallpox, mumps) are microscopic, measured in nanometers. Bacteria (e.g., tuberculosis, botulism, meningitis, tonsillitis, bronchitis, cystitis) are visible with an optical microscope, typically 1-5 micrometers. Fungi (e.g., athlete's foot, thrush, ringworm, candidiasis) are visible with an optical microscope, around 50 micrometers. Protozoa (e.g., malaria, dysentery) are also visible with an optical microscope, around 50 micrometers.

These microorganisms cause infectious diseases, which are illnesses that can spread to other people. Diseases not caused by pathogens are known as non-infectious diseases.

Vectors and Lifestyle

Digestive System Organs

Esophagus

• Tube approximately 25 cm long.
• Located behind the trachea and in front of the spinal cord.
• Drives the food bolus from the pharynx to the stomach.
• Its muscles produce peristaltic movements to ensure food reaches the stomach.
• Produces mucus, which favors food transit.

Pylorus

• A sphincter that communicates with the small intestine (duodenum).

Shared & Digestive System Components

Pharynx

• A duct located behind the mouth.
• Contains lumps called tonsils.
• Communicates the mouth with:
  • Esophagus
  • Back of the nostrils
  • Larynx
  • Middle ear

Epiglottis

• A flap located in the lower part of the pharynx.
• Closes the entrance to the larynx during swallowing.
• Prevents food from entering the respiratory tract.

Cardia (Cardiac Sphincter)

• A sphincter that

vitamin a : fish liver oils, animal liver. Function: required for normal immune system function and for production of cells in retina of eye. 

Microorganisms: Bacteria and Viruses

Bacteria: Key Characteristics

Bacteria are single-celled, prokaryotic microorganisms. They possess ribosomes, typically around 1000nm in size.

Viruses: Key Characteristics

Viruses are non-cellular genetic elements that are obligate intracellular parasites, meaning they must use living cells to reproduce. Their size ranges from approximately 20-300nm.

Viral Structure Explained

A typical viral structure includes:

• Nucleic Acid (Genome): This is the genetic material, which can be either DNA or RNA.
• Capsomeres: Protein subunits that assemble to form the capsid.
• Viral Nucleocapsid: The combined structure of the nucleic acid and its surrounding protein capsid.
• Core Wall (Capsid/Envelope): A protective shell, often referred

• Ecology is the scientific study of the interactions between organisms and the living and nonliving components of their environment.
• Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges.
• A population is a group of individuals of the same species living in an area.
• Population ecology focuses on factors affecting population size over time.
• A community is a group of populations of different species in an area.
• Community ecology examines the effect of interspecific interactions on community structure and organization.
• An ecosystem is the community of organisms in an area and the physical factors with which they interact.
• Ecosystem ecology emphasizes energy flow and chemical cycling

DNA Deoxyribonucleic Acid Forming Chromosomes

Stores genetic info DNA wounded to histones which becomes nucleosome loops onto chromatin

Codes for protein twisted into chromatid looped and packed into chromosome

Nucleotide Chromatin fibers are coiled and condensed to form chromosomes

consisting of a nitrogen-containing base Histones are proteins that help package and organize DNA in the nucleus of

(a, g, t, c.) or uracil in RNA eukaryotic cells by forming nucleosomes around which DNA is wrapped.

- phosphate group nucleosome is a basic unit of DNA packaging in eukaryotic cells

- sugar chromatid is one of the two identical copies of a replicated chromosome

Homologous Chromosomes chromosome is a long, coiled-up strand of DNA that contains genetic information

chromosomes... Continue reading "Understanding DNA, Chromosomes, and Genetic Variation" »

Understanding Pathogens: Viruses and Bacteria

Infectious diseases are caused by various pathogens, primarily viruses and bacteria, affecting different systems of the human body. Below is a summary of common diseases, their classification, and typical symptoms.

Common Viral Infections

• Influenza (Flu)

  System Affected: Respiratory System

  Classification: Virus

  Symptoms: Fever, body aches, tiredness, and cough.

• Herpes Simplex Virus (HSV)

  Classification: Virus (DNA)

  After the initial infection, the virus remains inactive in the human body and later reactivates under certain circumstances, such as stress, menstruation, or temperature changes. Symptoms are highly variable, and herpes lesions can appear anywhere on the body.

• Human Immunodeficiency Virus (HIV)