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

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" »

What is a Plasma Membrane, and Do All Cells Have One?

The plasma membrane encloses the cytoplasm and the cell's genetic material. It regulates what enters and exits the cell. Yes, all cells have a plasma membrane.

What Are the Two Central Tenets of Cell Theory?

• All organisms are composed of cells.
• Cells come only from preexisting cells.

What Are the Two Main Types of Cells?

• Prokaryotic cells lack a membrane-bound nucleus.
• Eukaryotic cells have a nucleus that houses DNA.

Where Do Prokaryotic Cells Store Their Genetic Material?

In the nucleoid.

What Domains Do Prokaryotic Cells Belong To?

Archaea and Bacteria.

What Are Three Characteristics of Prokaryotic Cells?

• They are much smaller and simpler than eukaryotic cells.
• They reproduce very quickly and effectively

Passive Transport Mechanisms

Diffusion: Movement Down the Concentration Gradient

Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration, aiming to equalize solute concentration. Diffusion occurs naturally because more particles move from the region of higher concentration toward the region of lower concentration.

Simple Diffusion

Simple diffusion enables substances to passively cross cell membranes from a region of higher concentration to a region of lower concentration without using metabolic energy (ATP). Once the concentration of the substance is equal on both sides of the cell membrane, a state of equilibrium is reached.

Facilitated Diffusion

Large, charged, hydrophilic, and polar substances... Continue reading "Cell Transport Mechanisms: Passive vs. Active Movement" »

Essential Medical Concepts

Key Definitions in Health and Immunity

What is Health?

Health is a combination of physical, mental, and social well-being, indicating a state where an individual is not suffering from a disease.

Understanding Antigens

An antigen is a substance that is perceived by lymphocytes and triggers a specific immune response.

Phagocytes: Immune System Defenders

A phagocyte is a specific type of white blood cell that activates when a pathogen crosses the first line of defense.

The Body's Defense Mechanisms

Understanding Immunity and Protection

Non-Specific Immune Response

When a pathogen crosses the first line of defense, the second line of defense is activated. This non-specific response is carried out by specific white blood cells, such... Continue reading "Human Body Defenses and Therapeutic Interventions" »

Characteristics of Living Organisms

Movement

A change of position or place.

Respiration

A chemical process in which oxygen is used to release energy from sugar molecules. Most of it happens in the mitochondrion.

Sensitivity

The ability to detect or sense changes in the environment (stimuli) and to make responses.

Growth

A permanent increase in size by increasing cell number, cell size, or both.

Reproduction

The process that makes more of the same kind of organism.

Excretion

The removal of toxic materials, waste products, and excess substances from an organism.

Nutrition

The process in which nutrients are taken into the body and converted into simpler substances used for energy, growth, and tissue repair.

Cell Structure and Organization

Cells can be classified... Continue reading "Fundamental Concepts of Biology: Cells & Life Processes" »