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

Ascending Tracts of the Spinal Cord

Propriospinal: These tracts integrate multiple segments of the spinal cord, surrounding the gray substance.

Fasciculus Gracilis and Cuneatus: Responsible for epicritic sensation. They involve Laminae I and II; pathways are ipsilateral (ascending to the bulb) and contralateral (from the bulb). The sequence involves: 1st node (spinal ganglion), 2nd core (posterior Cordner/column), and 3rd (thalamus).

Anterolateral System (Neospinothalamic): Responsible for protopathic sensation. It involves Laminae III and IV; it crosses contralaterally (within 2 segments). The sequence involves: 1st node, 2nd node at Lamina VII of the posterior horn, and 3rd node (left thalamus, fibers to the reticular formation, midbrain roof/... Continue reading "Spinal Cord Tracts and Brainstem Nuclei Anatomy" »

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

Components and Dynamics of Ecosystems

Defining Ecosystem Components

• Biotope: Encompasses the non-living components of the ecosystem, such as rocks and water, or physical conditions like temperature.
• Biocoenosis: Is made up of all the living organisms that inhabit the biotope.

Interactions in the Ecosystem

• Abiotic Factors: Affect the biocoenosis (e.g., soil and low temperatures).
• Biotic Factors: Affect the biotope (e.g., herbaceous plants increasing the number of herbivores).

Adaptations to the Environment

Adaptation is an adjustment in the body or behavior of an organism to its environment.

1. Anatomical Adaptations: Physical characteristics of living things that enable them to carry out a specific activity.
2. Behavioral Adaptations: Actions that organisms

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