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

The Sense of Hearing and Balance

The sense of hearing is located inside the ears. Sounds are vibrations of the air, received by the eardrum. The eardrum transfers these vibrations to the cochlea, where mechanoreceptors transform them into nerve impulses. These impulses then travel to the brain through the auditory nerve. The sense of balance is also located inside the ear and is closely related to the sense of hearing.

The Organization of the Nervous System

The nervous system is composed of two main divisions: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Central Nervous System (CNS)

• The Central Nervous System (CNS) comprises the brain and the spinal cord. This is where all stimuli are evaluated, and responses are generated.

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" »

Human Reproduction: Process of Creating New Life

The process by which humans create new beings involves several complex stages.

Key Aspects of Sexual Reproduction

• Sexual Reproduction: Fusion of the ovum (female gamete) and the sperm (male gamete) to form the Zygote.
• Genetic Material: A mixture of the parents' genetic material.
• Internal Fertilization: Occurs inside the female reproductive system.
• Viviparous: Embryonic development occurs inside the female’s reproductive system.

Stages of Human Development

• Childhood: Birth to Adolescence

  Changes include great motor (control over the body), physical (size), emotional, and cognitive (speaking, reading, writing skills) development. Primary sex characteristics of the male and female reproductive systems

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" »

Composition of Blood

Blood is made up of cells suspended in a liquid called blood plasma. Blood plasma is a yellowish substance made up of water containing various dissolved molecules: minerals, nutrients, waste products, proteins and hormones.

Three types of blood cell:

• Red blood cells: These are the most common type of blood cell. They contain hemoglobin and have no nucleus.
• White blood cells: There are different types: neutrophils, eosinophils, basophils, lymphocytes and monocytes; these cells help to protect the body from infections.
• Platelets: These are not true cells; they contain substances that allow the blood to coagulate, which prevents hemorrhages.

Functions of Blood

• It transports nutrients and oxygen to cells.
• It collects waste products.

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" »