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

Digestive Process

Key Components of the Digestive System

• Epiglottis: A flap of cartilage at the root of the tongue, which is depressed during swallowing to cover the opening of the windpipe.
• Esophagus: The tube that extends from the throat to the stomach.
• Lower Esophageal Sphincter: A bundle of muscles at the low

What Makes a Living Thing ‘Living’?

Non-Living Things

Non-living things are made up of inorganic matter. The most abundant chemical elements that make up inorganic matter are: oxygen (O), silicon (Si), aluminum (Al), and iron (Fe).

Living Things

All living things, also called organisms, are made up of the same chemical elements.

The elements that form part of living matter are known as bioelements.

The six most abundant bioelements are: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S). They make up more than 90% of living matter. The atoms and molecules of bioelements combine with each other through chemical reactions, producing biomolecules. Biomolecules may be:

• Inorganic, such as water and mineral salts.
• Organic

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Key Concepts in Evolution

Species: A set of individuals that can reproduce with each other and create fertile offspring.

Speciation: A process driven by several factors:

• Natural selection: Natural selection favors some individuals over others.
• Genetic isolation: Members of two different populations within the same species can no longer reproduce with the other population.
• Gradual differentiation: After isolation, populations become increasingly different.
• Speciation: Over time, genetic changes produce such significant differences that it's no longer possible for two populations to produce fertile offspring.

Human Ancestors

• Australopithecus (6 million years ago): The first hominid, walked upright.
• Homo habilis (2.5 million years ago): Used rudimentary

Interaction and Homeostasis

Interaction includes a series of processes whose object is to adapt the body to changing conditions in the internal and external environment. It connects and coordinates the different parts of our body so that they work together.

Homeostasis is the process that maintains the body's stability when there are changes in the internal environment. This process works as a feedback device, meaning that when a variation is detected in a particular element, a series of mechanisms in the body start up to make the variation return to its normal state.

Systems Participating in the Interaction Process

• Sensory Organs: Capture the stimulus, which is transformed into a nerve impulse and transmitted to the nervous system.
• Nervous System:

Steroid Hormones

Steroid hormones are a type of hormone consisting of four rings made of carbon atoms. They are derived from cholesterol and have three primary modes of action:

• Binding to membrane receptors
• Binding to and activating proteins in the cytoplasm
• Acting on receptors linked to chromosomes

Sex Hormones

Gonadal steroid hormones are produced by the gonads, which include the ovaries and testes. These hormones include:

• Androgens (e.g., testosterone, dihydrotestosterone)
• Estrogens
• Progesterone

It is important to note that gonads can produce both types of hormones, with the aromatase enzyme mediating conversions between them.

Organizing Effects of Sex Hormones

Organizing effects refer to the hormonal effects on the brain and genitals that occur during... Continue reading "Steroid and Sex Hormones: Organizing and Activating Effects" »

Saturated Fats

Carbon atoms fully saturated with hydrogen atoms. (meats, animal fats, lard, whole milk, butter, cheese, ice cream, coconut oil, palm oil)

Trans Fatty Acids

Solidified fat forms by adding hydrogen to MUFA and PUFA to increase shelf life

Osteoporosis

Condition of softening, deterioration, or loss of bone mineral density that leads to disability, bone fractures, and even death from medical complications

Protein

Classification for nutrients consisting of complex organic compounds containing nitrogen and forms by combinations of amino acids; the main substances used in the body to build and repair tissues

Amino Acids

Chemical compounds that contain nitrogen, carbon, hydrogen and oxygen; the basic building blocks the body uses to build different... Continue reading "Understanding Nutrition: Fats, Proteins, Vitamins, and Minerals" »

1. The Circulatory System

The circulatory system carries substances via the blood, which circulates through the blood vessels and is pumped by the heart.

1.1 Blood

Human blood is a thick, red liquid composed of plasma and blood cells.

Types of Blood Cells:

• Red Blood Cells: Small cells without a nucleus. They are the most numerous in the body and contain iron. This protein helps transport oxygen and carbon dioxide.
• White Blood Cells: Larger and less numerous. They defend our bodies against pathogens and tumor cells.
• Platelets: Are not true cells, but pieces of cytoplasm. They help our bodies to clot.

The Functions of Blood:

• Transport Substances: Transport nutrients and waste substances.
• Regulates Body Temperature: Maintain body temperature by distributing