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

ACTIVITIES

Trasplant: is a surgical procedure in which diseased or injured organs, tissues, cells are replaced with healthy one from a donor.

|The donor can be another person, the same person or an animal|

Types of transplant:

-Autotrasplant: the recipient and donor are the same person

-Allogeneic transplant:  the donor is another person

-Xenotrasplant: the donor is an animal

Organ donation: is voluntary. Donors must be in good health, free from mental health problems, of legal age, not receive money in exchange for their organs, and give written consent

Types of donation:

-Cells:... Continue reading "A body is placed in a certain airstream" »

The Skeletal System: The Internal Framework of the Body

The skeletal system is the internal framework (structure) of the body. It is made up of 206 bones and tissue.

Support

Bones hold our body and give us shape. For example, the spinal cord provides support.

Protection

The skeleton protects our vital organs. For instance, the skull protects the brain, and the ribs protect our heart and lungs.

Movement

Bones allow us to move as a whole body or as individual parts.

Blood Production

Certain bones in the skeleton contain red bone marrow, which produces red blood cells, white blood cells, and platelets.

Storage

Our bones can store different minerals, such as calcium.

Endocrine Regulation

Endocrine glands produce hormones, and the skeletal system helps regulate... Continue reading "The Importance of the Skeletal System in the Human Body" »

The Human Eye

Structure and Function

The Retina

The retina is a structure at the back of the eye that contains light-sensitive cells called rods and cones.

• Rods: Detect different light intensities, see in black and white, sensitive to low light levels, used to see in dim light.
• Cones: Different types sensitive to different colors (especially primary colors), need bright light to work, cannot see in dim light.

The central part of the retina has a lot of cone cells and no rod cells. The outer part of the retina has no cone cells and a lot of rod cells.

Blind Spot

The blind spot is the point where the optic nerve leaves the eye. There are no receptor cells in this area.

Cornea

The cornea is the transparent front part of the eye. It protects the eye and... Continue reading "The Human Eye: Structure, Function, and Vision" »

The Nervous System

The nervous system receives information from the receptors, processes and coordinates it, and generates orders to the effectors.

Central Nervous System (CNS)

The central nervous system coordinates all the body's functions. It is formed by the encephalon and the spinal cord.

The Encephalon

The encephalon is protected by the skull or cranium and by three membranes, the meninges, between which a liquid called the cerebrospinal fluid circulates. This liquid protects the encephalon from knocks and blows. The encephalon is divided into three parts: the brain, the cerebellum, and the brainstem.

• The brain is divided into two hemispheres, separated by a fissure. Its surface, called the cerebral cortex, is rough and full of folds and furrows,

Understanding Cnidarians: Phylum Characteristics

The phylum Cnidaria represents one of the more primitive animal phyla. It encompasses diverse aquatic organisms such as jellyfish, sea anemones, corals, and hydras. While most cnidarians are marine, a few species, like the familiar hydra, inhabit freshwater environments.

A defining characteristic of all cnidarians is their **radially symmetric body plan**, a contrast to the bilaterally symmetric body plans found in most other animal phyla. Though more advanced than sponges (Phylum Porifera) due to their distinct tissue layers, cnidarians lack many features of more complex animal phyla, such as true internal organs and central nervous systems. Most cnidarians possess tentacles, and many also feature... Continue reading "Marine Life Essentials: Cnidarians, Coral Symbiosis, and Reef Types" »

Water: Properties and Cycle

Properties of Water

Freshwater: Salinity below 35g/L.

Saltwater (Ocean Water): Salinity over 35g/L.

General Properties: Colorless, odorless, tasteless. Higher density in liquid state than solid state. Universal solvent. High heat capacity. Facilitates many chemical reactions. Exhibits adhesive capacity.

States of Water

• Solid (S)
• Liquid (L)
• Gas (G)

Transitions: S --(fusion)--> L --(vaporization)--> G --(condensation)--> L --(solidification)--> S S --(sublimation)--> G --(inverse sublimation)--> S

Water as a Thermal Regulator

Water's high heat capacity means significant temperature changes require large amounts of energy. This explains why coastal regions experience milder climates compared to inland areas.

The

The Discovery of Cells

a) In 1655, scientist Robert Hooke made an observation while examining a dried section of cork tree with a crude light microscope. He observed small chambers and named them "cells."

What are Cells?

b) The cell is known as the basic structural and functional unit of life, as all organisms are composed of cells.

c) Single-celled organisms are called unicellular (e.g., amoeba), while those having more than one cell are called multicellular.

Functions of Cells

d) All basic chemical and physiological functions of living beings - for example, repair, growth, movement, immunity, communication, and digestion - are carried out inside the cells.

Structure of a Cell

e) Cells are mostly round, spherical, or elongated. Some cells are quite... Continue reading "Exploring the Building Blocks of Life: An Introduction to Cells" »

The Excretory System: Function and Components

The **excretory system** is primarily composed of the kidneys, which play a central role in filtering waste from the blood. While other organs like the large intestine remove waste (feces) from the body, the excretory system specifically handles metabolic waste products dissolved in blood.

What is Excretion?

**Excretion** is the biological process of removing waste products of metabolism and other useless materials from an organism. The **kidney** is the key organ in this process, forming the core of the excretory system.

Key Components of the Excretory System

• Kidneys
• Ureters
• Bladder
• Urethra

Blood Filtration in the Kidneys

Toxin-laden blood reaches the kidneys via the **renal artery**. Within the kidneys,... Continue reading "Human Excretory System: Kidney Function & Waste Removal" »

Water and Salts

Water

More than half of our body is water. Water is used for carrying out chemical reactions and for transporting substances.

Mineral Salts

Make up the hard and solid parts of our bodies.

Glucids

Glucids are bio-molecules made up of carbon, hydrogen, and oxygen.

Types of Glucids

• Monosaccharides: The simplest glucids.
• Disaccharides: The union of two monosaccharides.
• Polysaccharides: Many monosaccharide molecules joined together.

Proteins

Proteins have carbon, hydrogen, nitrogen, oxygen, and a smaller proportion of sulfur.

They are made of the joint of many molecules called amino acids.

Functions of Proteins

• Are an important part of cell structure.
• Defense.
• Transporting substances.

Lipids

Lipids are a group of different substances. Lipids are not... Continue reading "The Building Blocks of Life: Cells, Molecules, and Processes" »

Nuclear Pore Complex (NPC) Structure and Function

NPC as Gatekeepers

Embedded within the nuclear envelope are nuclear pore complexes (NPCs), large protein structures situated in circular openings where the inner and outer nuclear membranes fuse. These aqueous protein channels regulate the transport of proteins and RNA across the nuclear envelope, acting as gatekeepers of the nucleus and facilitating nearly all transport between the nucleoplasm and cytoplasm.

NPC Architecture

The main NPC structure features rings on both the cytoplasmic and nucleoplasmic sides, with a luminal ring (LR) in between, creating twofold symmetry across the nuclear membrane.

Transport Across the Nuclear Envelope

Selective Permeability

While small molecules like metabolites... Continue reading "Nuclear Pore Complex Structure and Transport Mechanism" »