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

Energy and Matter in Ecosystems

How Does Energy Flow?

Ecosystems maintain an open flow of energy because producers, like plants, transform solar energy into chemical energy through photosynthesis. This energy is then used and degraded as it passes through the trophic levels of consumers (herbivores, carnivores) and decomposers (bacteria, fungi). Ultimately, the activities of all living organisms in the ecosystem generate thermal energy as heat, which dissipates into the environment.

This energy flow is unidirectional because the solar energy entering the ecosystem is transformed into chemical energy within living organisms and eventually lost as heat.

Key Points:

• Typically, no more than 10% of the energy from one trophic level is transferred to

Cellular Components and Their Functions

Lysosome

Features: Lysosomes are vesicles containing substances that digest nutrients.

Function: They break down more complex substances into simpler ones.

Centrosomes

Features: Centrosomes are located near the nucleus and consist of two perpendicular cylinders formed by proteins.

Function: They are involved in cell division and the formation of cilia and flagella.

Understanding Health and Disease

Disease

Definition: A disease occurs when a part of the body is altered and can no longer perform its function properly, leading to dysfunction.

Health

Definition: The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being, not merely the absence of disease.

Symptoms

When... Continue reading "Cellular Biology and Human Health: Diseases and Prevention" »

Cell Structure and Function

Key Components of the Cell

The cell is the basic unit of life, and it is composed of several essential components:

• Cell Membrane: A thin layer surrounding the cell, forming the boundary between the cell and its surrounding environment, the extracellular medium.
• Cytoplasm: The substance of the cell, excluding the nucleus. It is formed by a water-rich solution in which a variety of structures, called organelles, are dispersed. These organelles are responsible for carrying out the different functions of the cell.
• Cellular Nucleus: A structure that is usually spherical and located in the center of the cell. It contains the genetic material with the necessary information to direct and control cellular functions.
• Mitochondria:

Organism Response to Stimuli

Organisms have systems that allow them to collect information from within and outside their bodies and respond to changes that occur.

Key Concepts

• Stimulus: Any factor capable of triggering a response in an organism. This can be physical or chemical.
• Response: The action an organism performs as a reaction to the stimulus received.
• Sensation: The ability to receive stimuli (e.g., sight, hearing, touch, smell, and taste).
• Perception: A function that requires the interpretation of a stimulus by the brain and the elaboration of complex responses.

Sense Organs and Receptors

Sense organs are responsible for receiving environmental stimuli. Receptors are cells within these organs that capture and transmit the stimulus to the brain... Continue reading "Organism Response to Stimuli & Coordination" »

1. Functions of the Digestive System

Digestion and absorption of nutrients.

2. Elements Forming the Small Intestine

Duodenum, jejunum, and ileum.

3. Valves of the Stomach

The stomach has the pyloric valve, and the duodenum connects with the esophagus via the cardia.

4. Portions of the Large Intestine

The large intestine is divided into the following parts:

• The first portion consists of a blind sac.
• The second part is called the ascending colon.
• The third portion is the transverse colon.
• The fourth part is the descending colon.
• Finally, the sigmoid colon, rectum, and anus.

5. Intestinal Loops

Intestinal loops are folds that form the small intestine to adapt to the available space in the abdomen.

6. Gastrointestinal Annexes

These include the parotid salivary... Continue reading "Digestive System: Functions, Organs, and Common Conditions" »

Vertebrate Circulatory Systems

Simple Closed Circulation (Single Circuit)

Fishes

The heart in fishes has one atrium and one ventricle. From the ventricle, deoxygenated blood is pumped to the branchial artery, which branches into arteries supplying the gill lamellae. In the gills, blood becomes oxygenated. This oxygenated blood is then collected by efferent gill arteries that converge into the aortic root and then the dorsal aorta, which distributes it to the body tissues. This is a single-circuit system.

Closed Double Incomplete Circulation

Amphibians

The heart is composed of two atria and one ventricle. The two atria are separated by an interatrial septum. The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated... Continue reading "Animal Circulatory Systems: Vertebrates & Invertebrates" »

DNA and Chromosomes

DNA (deoxyribonucleic acid) is the biomolecule containing the genetic instructions for building proteins. Proteins, especially enzymes, regulate all life processes, including growth, tissue repair, and reproduction. DNA resides in the nucleus of eukaryotic cells as part of the chromosomes.

Chromosomes are composed of chromatin, a complex of DNA and proteins. When a cell is at rest, chromatin is dispersed within the nucleus, making chromosomes invisible. Before cell division, DNA replicates, and chromatin condenses into shorter, thicker fibers, forming visible chromosomes. Due to DNA replication, each chromosome comprises two identical arms called chromatids, joined by a centromere.

Karyotype

The number, shape, and size of chromosomes... Continue reading "DNA, Chromosomes, Genes, and Cell Division" »

Nutrition Basics

Nutrition involves how our bodies obtain, process, and utilize essential nutrients from food. These nutrients, vital for cell function and survival, include:

Types of Nutrients

• Carbohydrates: The primary energy source. Glucose provides quick energy, while complex carbohydrates (starch, glycogen) require longer digestion. Cellulose, a plant fiber, aids digestion.
• Lipids (Fats): Store energy and form reserves in adipose tissue. Phospholipids are crucial components of cell membranes.
• Proteins: Essential for cell structure and regulatory functions.
• Water: The most abundant component, vital for cooling, transporting substances, waste elimination, and facilitating chemical reactions.
• Minerals: Play structural and regulatory roles in various

Arteriosclerosis vs. Atherosclerosis

These terms are similar, but distinct. Arteriosclerosis is a general term for hardening and loss of arterial elasticity. Atherosclerosis is hardening specifically caused by atherosclerotic plaques.

Heart Conditions

Heart Murmurs

Heart murmurs are pathological noises heard during auscultation, caused by increased flow through normal valves, valve alterations, intracardiac abnormalities, or extracardiac issues. They can be systolic, diastolic, or continuous.

Tachycardia

Tachycardia is an increased heart rate, specifically above one hundred beats per minute at rest.

Leukemia

Leukemia is a group of malignant bone marrow diseases causing an uncontrolled increase in white blood cells (WBC), often appearing in peripheral... Continue reading "Understanding Cardiovascular Diseases and Related Conditions" »

Endocrine Glands and Hormones

What are Exocrine Glands?

Exocrine glands are specialized structures with specific functions, releasing chemicals to regulate life processes.

Types of Exocrine Glands

Major exocrine glands in the human body include the pituitary, thyroid, parathyroid, adrenals, testes, and ovaries.

What are Hormones?

Hormones are complex substances produced by endocrine glands, released directly into the bloodstream to regulate various cells and organs.

The Pituitary Gland

The pituitary gland is a small mass of cells located at the base of the brain, in the sella turcica of the sphenoid bone.

The Sex Glands

• Testes: The male sex glands, located in the scrotum beneath the penis.
• Ovaries: The female sex glands, located in the lower abdomen.

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