Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

Digestive System

Initial Stage: Stomach

The first stage of digestion occurs in the stomach. Here, digestive substances break down food. The stomach cavity is wider than the intestinal walls and secretes gastric juices. This section also includes glands like the liver, which secrete substances that convert food molecules into smaller ones.

Second Stage: Small Intestine

In the second stage, nutrients are absorbed in the small intestine. This organ's extensive length and folded inner walls maximize absorption surface area.

Final Stage: Large Intestine

The last stage takes place in the large intestine (colon), where water is absorbed. This section is wider than the small intestine and lacks the folds of the previous section.

Transport of Nutrients

Blood

Understanding Living Organisms: Core Concepts

Origin and Development of Life

• Animals born from eggs are called oviparous.
• Those that arise from the mother's body are called viviparous.
• Plants may arise from seeds or spores.
• Fungi are always born from spores.

Nutrition: How Organisms Obtain Energy

Plants are living beings that possess chlorophyll, which enables them to make simple substances like water, carbon dioxide, and some minerals. This process is called photosynthesis and is performed using solar light.

Organisms obtain food in various ways:

• Herbivores eat plants.
• Carnivores eat animals.
• Omnivores eat both plants and animals.

Respiration

All living organisms breathe to sustain life processes.

Reproduction Strategies

The primary form of reproduction...

Internal Environment: The Body's Inner Sea

The internal environment refers to the set of fluids that surround the cells of an organism. From these fluids, cells extract the nutrients and oxygen they need.

Key Components of the Internal Environment

• Interstitial Fluid: This fluid, also known as tissue fluid, performs defensive and nutritive functions, remaining between the cells.
• Blood: Responsible for the transport of substances, blood circulates through blood vessels.
• Lymph: A fluid formed from plasma and interstitial fluid, lymph flows through lymphatic vessels.

The Blood Circulatory System

The blood circulatory system distributes nutrients and oxygen throughout the body while collecting waste products of cell metabolism.

Blood Vessels: Pathways of

Health and Disease Definitions

Health: The state of complete physical, mental, and social well-being.
Disease: A disturbance in the body's health, manifested by specific symptoms.

Types of Diseases

• Infectious: Caused by microbes (e.g., influenza).
• Deficiency: Lack of essential nutrients (e.g., rickets).
• Degenerative: Deterioration of organs or tissues (e.g., Parkinson's disease).
• Congenital: Present at birth (e.g., Down syndrome).
• Mental: Affects thought and personality (e.g., anorexia).

Factors Influencing Health

• Environmental: External characteristics such as pollution.
• Genetic Endowment: Inherited genes that may predispose individuals to diseases.
• Consumption and Habits: Personal lifestyle choices.
• Health System: Accessibility and quality of medical

Habitat and Environmental Conditions

A habitat is the environmental conditions in the place where a species lives.

Environmental Factors

Abiotic factors are the biotype and temperature. Biotic factors define the biocoenosis.

Each species is accustomed to living under certain environmental conditions. The term tolerance refers to the range of a factor that a species can withstand.

Limiting Factors in Terrestrial Environments

In the terrestrial environment, the main limiting factors for life are temperature and humidity.

Temperature

The air is cooled or heated quickly, according to the solar radiation it receives. This depends on latitude, altitude, seasons, and day and night.

Terrestrial beings adapt to temperature changes by following habits and adapting...

The Human Circulatory System

The circulatory system transports and distributes nutrients and other substances dissolved in the blood throughout the body, collecting waste products to be expelled.

Blood Vessels

Blood vessels are the conduits where blood flows. They include:

• Arteries: Vessels that carry blood *away* from the heart. They have thick, slightly elastic walls to withstand high pressure.
• Veins: Vessels that carry blood *toward* the heart. They possess thin walls and one-way valves to prevent the backflow of blood.
• Capillaries: Tiny blood vessels with very thin walls, facilitating the exchange of substances between blood and cells.

The Heart

The heart is the organ responsible for pumping blood rhythmically to every cell in the body. It's made...

Cell Theory: The Foundation of Life

The cell is the fundamental structural and anatomical unit of all organisms; all living things are formed by one or more cells. The cell is the physiological and functional unit; any cell can sustain itself. Cells originate from pre-existing cells.

Common Characteristics of Cells

All cells share fundamental characteristics:

• An outer membrane that separates the cell from its external environment.
• A set of internal structures, called organelles, where vital cellular processes are performed.
• Genetic material (DNA) that transmits cellular processes and commands to offspring.

Cell Types Based on Genetic Material

Prokaryotic Cells

These are simple and primitive cells, such as bacteria. Their genetic material is dispersed...

Cellular Organization and Biological Systems

Living beings are formed by microscopic subunits called cells. These cells associate to form tissues that perform specific functions, unite to create organs, and finally form systems that constitute a living being.

The Cell Theory

The fundamental principles of this theory are:

• Every living being is composed of one or more cells.
• The cell is the anatomical and functional unit of life.
• Every cell originates from another pre-existing cell.

Types of Cells

• Prokaryotic Cells: Lack a membrane surrounding the nuclear material and do not contain membrane-bound organelles.
• Eukaryotic Cells: Possess a defined nucleus and membrane-bound organelles. These cells constitute multicellular and unicellular organisms, categorized

Ribosomes and Protein Synthesis

The primary function of ribosomes is to synthesize proteins.

Rough Endoplasmic Reticulum (RER)

The RER consists of a set of flattened saccules, tubules, and cisterns arranged concentrically near the nucleus. Its functions include:

• Protein Storage: Proteins formed in the ribosomes are introduced into this organelle and transported through tubules.
• Glycosylation: Enzymes and proteins remain inactive until specific sugars are added.
• Nuclear Membrane Formation: The double nuclear membrane is reformed after cell division from this organelle.
• Chemical Storage: It serves as a storage site for various cellular substances.

Smooth Endoplasmic Reticulum (SER)

The SER has a structure similar to the RER but lacks ribosomes and is...

Biological Foundations

Photosynthesis: Energy Capture

Photosynthesis is a vital process that enables plants to convert light energy into chemical energy. This fundamental process, crucial for life, relies on the presence of leaves and pigments to capture solar energy.

Cellular Structures & Nutrient Transport

Unicellular vs. Multicellular Organisms

Unicellular organisms are in direct contact with their external environment. In contrast, multicellular organisms do not have all their cells in direct contact with the outside world, facing challenges in spreading nutrients across individual cells.

Therefore, multicellular organisms require internal transport systems (like 'pipes' or circulatory systems) to distribute nutrients to all cells not in...