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

Elastic Fibers

Elastic fibers maintain the position of alveoli and bronchioles. When fibers recoil during exhalation, they reduce the size of alveoli and push air out.

Pneumocyte Type I

Pneumocyte type I cells are squamous epithelial cells that are unusually thin, providing an ideal site for gas diffusion.

Pneumocyte Type II

Pneumocyte type II cells are scattered among the squamous cells and produce surfactant.

Breathing

Deep breathing, also known as diaphragmatic breathing, involves the contraction of the diaphragm to change the volume of the lungs, allowing air to be exhaled passively. Shallow breathing, or costal breathing, occurs when the rib cage alters its shape, changing the thoracic volume.

Dalton's Law

Dalton's Law states that the partial pressure... Continue reading "Elastic Fibers and Gas Exchange in the Respiratory System" »

Unit 1: Cellular Metabolism and Cell Types

Catabolism and Anabolism

Catabolism refers to all chemical reactions where substances are broken down into simpler ones, releasing energy.

• Cellular respiration: C₆H₁₂O₆ + 6O₂ (glucose) → 6CO₂ + 6H₂O + Energy (ATP)

Anabolism refers to all the chemical reactions where simple substances are joined together to form more complex ones.

• Photosynthesis: H₂O + CO₂ + Sunlight → C₆H₁₂O₆ + 6O₂

Heterotrophic Nutrition

Heterotrophic nutrition: Heterotrophic organisms cannot synthesize organic compounds from inorganic compounds. They incorporate organic matter which has been made by other organisms.

1. Some glucose molecules are used in cellular respiration and others are used in other processes.
2. Cellular respiration takes

Respiratory System: Nutrients and O2

The respiratory system captures oxygen from the air and transfers it into the blood. Cells use oxygen and nutrients to produce energy. Blood removes carbon dioxide (CO2), which is expelled from the body along with water vapor.

Respiratory system function: Gas exchange with the atmosphere.

Nasal Cavity

The nasal cavity is divided into two chambers. Each chamber has an external opening (nostril) and an internal opening to the pharynx (choana). A partition called the nasal septum separates the chambers. The nasal cavity is the entry point for air.

Characteristics

• Abundant capillaries with circulating blood.
• Abundant nooks that allow the air to travel further and remain inside longer, heating the air.
• Internally covered

Spontaneous Generation

The idea that life can appear from inanimate objects is known as spontaneous generation.

• In Ancient Egypt, people believed that the Sun's heat created life.
• During the Middle Ages, people created recipes to generate living things from materials.
• In the 17th century, scientists proved that spontaneous generation was not possible.
  • In 1668, Redi demonstrated that larvae found in rotten meat came from fly eggs.
  • In the 19th century, Pasteur demonstrated that microorganisms did not come from spontaneous generation, and this theory was finally rejected.

Origin of Life

Chemical Evolution

Chemical evolution is the process that formed the molecules that make up living things and their organization into membranes.

1. The first biomolecules to

All cells in an organism require nutrients for growth and function. Heterotrophic organisms cannot produce their own nutrients; they obtain these essential substances from food. Multicellular organisms possess numerous organs, which are grouped into different systems that perform diverse functions.

Five important systems work together to maintain bodily function:

• Digestive System
• Respiratory System
• Circulatory System
• Excretory System
• Lymphatic System

Digestion: Obtaining Nutrients

The Digestive Process

Like all animals, human beings obtain sugars, fats, and proteins from food. This process is carried out by the digestive system and involves three main phases:

1. Digestion (breaking down food)
2. Absorption (taking nutrients into the body)
3. Expulsion of waste

Food... Continue reading "The Human Digestive System: Function and Processes" »

Lamarck: The Evolution of Giraffes

1. The ancestors of giraffes had shorter necks and legs than nowadays.
2. As giraffes tried to reach the leaves on the top branches of the trees, their necks and legs grew.
3. Offspring inherited these characteristics.

Darwin: Natural Selection and Giraffe Evolution

1. Giraffes originally had some variation in the length of their necks and legs.
2. Natural selection favored the giraffes with longer necks and legs, leading to increased offspring.
3. As a result, the number of giraffes with long necks and legs increased.

Amniocentesis: Prenatal Genetic Anomaly Detection

Amniocentesis is a technique used in prenatal diagnosis to search for possible genetic anomalies. It involves extracting a sample of amniotic fluid and studying the fetal... Continue reading "Evolution of Giraffes and Human Ancestors: Lamarck vs Darwin" »

Accessory Digestive Glands

Salivary Glands

These glands secrete saliva into the mouth:

• Parotid: Located in front of and below the ears.
• Submaxillary (Submandibular): Located against the inner face of the lower jaw.
• Sublingual: Located on the floor of the mouth.

Pancreas: A Mixed Gland

The pancreas is an elongated, spongy gland located underneath and behind the stomach. It performs both exocrine and endocrine functions:

• Exocrine Function (Digestion): It secretes pancreatic juice into the small intestine (duodenum) through the Ampulla of Vater.
• Endocrine Function (Hormone Secretion): Secretes hormones into the blood. Example: Insulin regulates the transport of glucose inside the cells.

Liver: The Body's Largest Gland

Location: Right side of the stomach... Continue reading "Human Digestive System: Glands, Stages, and Nutrient Absorption" »

Polygenic Inheritance vs. Monogenic Inheritance

Polygenic inheritance refers to the kind of inheritance in which a trait is produced from the cumulative effects of many genes. This is in contrast to monogenic inheritance, wherein a trait results from the expression of one gene (or one gene pair). In humans, height, weight, and skin color are examples of polygenic inheritance, which does not follow a Mendelian pattern of inheritance.

Linkage Groups, Sex Chromosomes, and Autosomal Chromosomes

• Linkage group: A pair or set of genes on a chromosome that tend to be inherited together.
• Sex chromosomes are the ones that determine your gender. These are X and Y (XX in females, XY in males).
• Autosomal chromosomes are the remaining chromosomes that are not

Key Plant Cell Terms: A Comprehensive Glossary

Amyloplast

Amyloplasts are non-pigmented organelles found in some plant cells. They are responsible for the synthesis and storage of starch granules through the polymerization of glucose. Amyloplasts also convert this starch back into sugar when the plant needs energy.

Cell Wall

The cell wall is a tough, usually flexible but sometimes fairly rigid layer that surrounds certain types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, in addition to acting as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell.

Nucleus

The nucleus is a membrane-enclosed... Continue reading "Key Plant Cell Terms: A Comprehensive Glossary" »

Amylase begins the digestive process by breaking down starch when you chew your food, converting it into a smaller carbohydrate. Pepsin helps digest the proteins in food because amylase is at the mouth and the pepsin at the stomach.

Chyle

Is a body fluid in the small intestine. It is turbid and milky due to the presence of emulsified fats. Is formed from the chyme during the digestion of fatty foods.

Intestinal Flora

Is the symbiotic bacteria occurring naturally in the gut.

Defecation

Is the final action of digestion, by which organisms eliminate solid, semisolid, or liquid waste material from the digestive tract via the anus.

Mechanical Digestion

This is the enzymatic breakdown of large, complex molecules found in food into smaller, simpler, more... Continue reading "Understanding Digestion, Blood Composition, and the Endocrine System" »