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

Understanding Digestion: Mechanical & Chemical Processes

Digestion is the complex process by which food is broken down into nutrients the body can use. It involves both mechanical and chemical actions.

Mechanical Digestion

Mechanical digestion is the physical act of breaking down food by non-chemical means. This process begins in the mouth with chewing. The food is then manipulated by the tongue and cheeks to mix with saliva, forming a soft ball called a bolus. While the original text mentions the small intestine and defecation here, these are later stages of the overall digestive process, not specifically mechanical digestion in the initial stages.

Chemical Digestion

Chemical digestion involves breaking down food into simpler nutrients that... Continue reading "Human Body Systems: Digestion, Respiration & Key Organs" »

DNA is the molecule that gives cells and organisms their biological characteristics. Types of Nucleotides: Adenine, Cytosine, Thymine, Guanine. DNA/RNA: DNA has a double helix structure, while RNA does not. In DNA, thymine is present, whereas in RNA, uracil is present. RNA can exit the nucleus, but DNA cannot. Ribose Nucleotide does not contain thymine. Transcription is the process of copying a part of the genetic message from DNA to RNA. Translation is the process in which RNA moves from the nucleus to the cytoplasm. Genetic Code refers to the relationship between the sequence of nitrogenous bases in DNA and the sequences of amino acids that form proteins. Transcription occurs in the nucleus, while translation occurs in the cytoplasm. In prokaryotic... Continue reading "DNA and Genetic Engineering: A Comprehensive Overview" »

Peripheral Nervous System

Consists of nerves and supports it collects info about the body's external and internal environment.

Central Nervous System

Consists of the brain and spinal cord, processes info, and creates a response.

Cell Body

The largest part of the typical neuron.

Dendrites

Short branched extensions that receive impulses from other neurons and carry them to the cell body.

Axon

Long fiber that carries impulses away from the cell body.

Myelin Sheath

Insulating membrane that surrounds a single, long axon.

Resting Potential

Electrical charge across the cell membrane of a resting neuron.

Action Potential

A nerve impulse that charges more negatively charged to more positively charged.

Threshold

The minimum level of a stimulus that is required to cause... Continue reading "Understanding the Nervous System and Sensory Organs" »

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" »

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" »