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

The Internal Environment

• Refers to the fluids that surround the cells.
• Temperature and composition must be stable for the correct working of cells.
• This internal environment is maintained by the organ systems of the body.
• Interstitial fluid (plasma): Surrounds and bathes the cells.
• Blood and lymph: Collect and distribute substances for the cells (O2, nutrients) and remove waste.

The Circulatory System

• Carries nutrients and oxygen throughout the body and collects waste (blood): Blood Circulatory System.
• Returns excess interstitial fluid to the blood.
• Transports fat to the blood.
• Defends the immune system (lymph): Lymphatic System.

The Lymphatic System

• Lymph capillaries:
  • Thin vessels closed at one end.
  • Collect excess interstitial fluid.
• Lymphatic vessels:

Basic Nutrients

The human body is two-thirds water. Water is an essential nutrient that is involved in every function of the body. Water helps transport nutrients and waste products in and out of cells. Water is necessary for all digestive, absorption, circulatory, and excretory functions. Water is needed for the utilization of the water-soluble vitamins. It is needed for the maintenance of proper body temperature. It is recommended that you drink at least eight 8 glasses of water each day.

Dietary Recommendations

Carbohydrates

• It is recommended that about 60 percent of your total daily calories come from carbohydrates.
• If much of your diet consists of healthy complex carbohydrates, you should easily fulfill the recommended daily minimum of 25 grams

The Endocrine System Explained

The endocrine system consists of a coordinated group of glands known as endocrine glands. They are termed endocrine (endo meaning internal) because they release hormones directly into the bloodstream.

Hormones are organic molecules responsible for the regulation, control, and coordination of organs to ensure they function correctly as a unified system. Although all hormones reach all body tissues, each hormone acts only on specific cells, known as target cells.

Nervous System vs. Endocrine System

• Nervous System: Information is transmitted via nerve impulses (electrical signals). The action is fast and short-lived.
• Endocrine System: Information is transmitted via chemical substances. The action is slower but lasts longer.

Abiotic Levels of Organization

Subatomic Level

Composed of different particles (protons, neutrons, and electrons) that form atoms.

Atomic Level

Consists of atoms of the chemical elements from which living matter is formed. The different types of atoms are represented in the periodic table according to their number of protons within their nucleus. For example:

• Nitrogen
• Carbon
• Hydrogen
• Oxygen
• Phosphorus
• Sulfur

Molecular Level

Molecules are formed by the joining of two or more atoms. This level includes both inorganic and organic molecules.

Inorganic Molecules

• Water
• Gases
• Mineral salts

Organic Molecules

• Simple sugars
• Lipids
• Nucleotides
• Amino acids

Macromolecular Level

Macromolecules are formed when molecules join together. For example, proteins are formed when amino...

When a cell is not in a state of division and is in the phase known as interphase, its nucleus is more or less spherical and located in the center or near the periphery. During the interphase, we can distinguish the following structures:

• Nuclear membrane: This is a covering formed by two membranes covered in ribosomes. The membranes have perforations called nuclear pores, which allow substances to be exchanged between the nucleus and the cytoplasm.
• Nucleoplasm: This is the liquid in the nucleus.
• Nucleolus: This is a rounded structure that is darker than the rest of the nucleus. It is where the components of the ribosomes are created.
• Chromatin: This is made up of DNA filaments and proteins. During cell division, it condenses and forms chromosomes.

Natural Selection:

Some variations are inherited (passed on from parents) and some are acquired (developed during life). Only inherited variation is passed on to the next generation.
Animals and plants produced by sexual reproduction will show variation from their parents, for example, in the size of the muscles in the legs of lions.
When new organisms are produced, not all of them are likely to survive because of competition for resources such as food, water, and shelter. The same is true for plants (they compete for resources such as nutrients, light, water, and space).
The individuals with the most favorable characteristics are most likely to survive.

The process of natural selection...

Fungi and Plant Kingdom Characteristics

Characteristics of Fungi (Four Points)

• Most fungi grow as tubular filaments called hyphae.
• The walls of hyphae are often strengthened with chitin.
• Fungi disperse themselves by releasing spores.
• Fungi are heterotrophic.

Characteristics of the Plant Kingdom (Four Points)

• Most plants are eukaryotic and chlorophyll-containing organisms.
• Cell walls of plant cells are comprised of cellulose.
• They have an ability to grow by cell division.
• In the life cycle of plants, interchanges occur from the embryos and are supported by other tissues for self-production.

Ecosystem Energy Flow and Cycles

Photosynthesis Equation and Components

The equation for photosynthesis is: 6CO₂ + 6H₂O + solar energy → 6O₂ + C₆H₁₂O₆

• CO₂: Carbon Dioxide
• H₂O:

Cellular Energy Production

Cells use energy for all their reactions and processes. These vital processes include:

• Movement
• Making new substances from small molecules
• Growth and repair
• Active transport
• Nerve impulses
• Heat production

Aerobic Respiration: Energy with Oxygen

Aerobic respiration is the release of energy using oxygen. Oxygen is carried by the blood in red blood cells within hemoglobin and diffuses into cells. Glucose also travels to the cells in the blood.

In the cytoplasm of cells, there are specific organelles called mitochondria. Oxygen diffuses into the mitochondria and is used to react with glucose to produce carbon dioxide and water. The chemical energy is transferred to a substance called ATP, which stores a small amount of energy.

The...

Understanding Our Senses

What do all the senses have in common?

The eye, the ear, the nostrils, and the tongue are organs adapted to capturing specific stimuli. They have a high concentration of specialized receptors.

The Ear

Outer ear: flap, external ear canal. Middle ear: eardrum, ossicles (small bones). Inner ear: semicircular canals, cochlea, Eustachian tube.

Why Avoid Loud Noises?

Loud noises can eventually cause hearing problems and, in extreme cases, a perforated eardrum.

How Do We Perceive Colors?

Inside our eyes are cells that function as sensors in the retina, called rods and cones.

Rods and Cones

• Rods: Activated in darkness, allowing us to distinguish black, white, and shades of gray. They enable us to perceive contrast.
• Cones: Work during

The Human Excretory System

The excretory system comprises the urinary system and various other organs that facilitate the removal of waste products from the body.

Key Excretory Organs and Systems

• Respiratory system: Removes CO2 from the blood and expels it from the body.
• Sweat glands: Located in the skin; produce sweat that evaporates to cool the body.
• Liver: Eliminates waste products resulting from the breakdown of hemoglobin in old red blood cells.
• Urinary system: The primary component of the excretory system, responsible for eliminating waste as urine.

Components of the Urinary System

• Kidneys: A pair of organs that filter waste substances from the blood to produce urine.
• Ureters: Two tubes that transport urine away from the kidneys.
• Bladder: The organ