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

Chromosomes and DNA

Genes are contained within chromosomes, which are made of DNA and located in the cell nucleus. A chromosome contains thousands of genes. Every normal human contains 23 pairs of chromosomes, a total of 46 chromosomes.

Traits and Alleles

A trait is any gene-determined characteristic, often determined by more than one gene. Gene: A segment of DNA that controls a hereditary trait. Alleles are different versions of a gene that produce distinguishable traits in offspring. Two alleles must be present in order for a trait to appear in the offspring. One allele is provided by each parent to the offspring. When fertilization of sperm and eggs occurs, the new offspring will have 2 alleles for each gene.

Gregor Mendel's Contributions

Gregor...

Anabolic Reactions & Biomolecules

A reaction where two molecules join is anabolic and produces NH₂. Glucose and starch are carbohydrates (CH). Glucose + fructose = sucrose. Unsaturated fats increase HDL levels. An amino acid has an H and R group bonded to a carbon atom, along with NH₂ and COOH. Adenine, cytosine, guanine (thymine in DNA and uracil in RNA). Saponifiable lipids include phospholipids, fats, and waxes.

Factors Affecting Enzyme Activity

• Temperature
• pH levels
• Substrate concentration

Four Main Biomolecule Groups

Carbohydrates, lipids, proteins, and nucleic acids.

Cell Biology Concepts

Schleiden. Kingdoms with cells containing mitochondria: Animalia, Plantae, Fungi, and Protoctista. Organelles of endosymbiotic origin: mitochondria and chloroplasts....

1. Sensory Receptors

Sensory receptors are responsible for perceiving information, which they convert into a nerve impulse. The nerve impulse travels to the brain and produces feeling.

1.1. Types of Sensory Receptors

Sensory receptors can be classified according to the stimuli that they can receive, or by where they are located.

1.1.1. According to the Stimuli

• Photoreceptors: They detect light stimuli and are located in the eye.
• Mechanoreceptors: They are stimulated by mechanical changes such as pressure, contact, or sound waves.
• Chemoreceptors: They respond to chemical changes.
• Thermoreceptors: They detect temperature changes.

1.1.2. According to Their Location

• Internal receptors: They are located in the internal organs where they collect information

Human Reproduction & Sexuality

Human reproduction is sexual and has two key characteristics:

• The new individual is formed from a single cell called a zygote.
• Zygotes result from the union of two gametes (fertilization).

Humans have two types of gametes: sperm (men) and ova (women).

Changes During Reproductive Life

During the reproductive life of a human being, there are three main stages:

• Puberty

  Puberty begins in men with the first ejaculation (spermarche) and in women with the first menstruation (menarche). This is due to the increased secretion of pituitary hormones: Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), which stimulate gamete production.

  Puberty typically begins when girls are 10-13 years old and boys 12-14. It lasts

MICROEVOLUTION

Changes that lead to the appearance of new species and groups that are closely related to each other.

MACROEVOLUTION

Leads to large groups of organisms after drastic change.

PUNCTUATED EQUILIBRIUM

The appearance of major groups of organisms took place as a result of drastic changes and the accumulation of gradual variations.

PHYSIOLOGICAL TREES

Visual representation of the evolutionary history of a group of organisms. A simplified diagram that, using a series of branches, shows the relationship between organisms.

SPECIATION

Two or more distinct species.

GEOGRAPHICAL BARRIERS

Examples are lakes, mountain ranges, and seas.

SEXUAL BARRIERS

Caused by anatomical changes that prevent mating from occurring.

PHYSIOLOGICAL BARRIERS

Incompatibilities...

What Makes a Living Thing ‘Living’?

Non-Living Things

Non-living things are made up of inorganic matter. The most abundant chemical elements that make up inorganic matter are: oxygen (O), silicon (Si), aluminum (Al), and iron (Fe).

Living Things

All living things, also called organisms, are made up of the same chemical elements.

The elements that form part of living matter are known as bioelements.

The six most abundant bioelements are: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S). They make up more than 90% of living matter. The atoms and molecules of bioelements combine with each other through chemical reactions, producing biomolecules. Biomolecules may be:

• Inorganic, such as water and mineral salts.
• Organic

Understanding Cells: Structure, Functions, and Types

The cell is the smallest unit of a living organism that can carry out vital functions: nutrition, interaction, and reproduction.

Essential Cell Components

All cells possess a plasma membrane, cytoplasm, and DNA.

• Plasma Membrane: This is a very thin and stretchy cover that separates a cell from its environment. Its primary function is to regulate the movement of substances in and out of the cell. It also detects environmental stimuli and allows cells to communicate.
• Cytoplasm: This is the substance contained inside the cell, in which the cell organelles are found. Metabolic processes occur within the cytoplasm.
• Genetic Material (DNA): A complex chemical substance that contains the information needed

Water: The Essential Solvent

Water constitutes approximately 80% of the human body and plays a crucial role in biological systems.

Role of Water as a Solvent

Water is an important solvent, a liquid in which substances (or solutes) are dissolved, forming a solution. In a solution, the solvent is typically present in a greater amount than the solute.

Metabolic reactions, which are vital for life, can only take place if the chemicals reacting are dissolved in water.

Other Vital Functions of Water

Water is also essential for other reasons, such as being the primary component of plasma, the liquid part of blood, facilitating transport throughout the body.

Carbohydrates: Energy & Structure

Carbohydrates include starches and sugars, and are composed of...

Special diets:

-Low cholesterol diet

-Low salt diet

-Gluten free diet

-Diabetes diet

-High or low calorie diets

Excretion:Is the process of

eliminating or expelling waste

matter from our bodys.

Excretion of CO2: Carbon

dioxide is produced during

cellular respiration and is

excreted from the body by

the lungs.

Wastes that are solids:The urine

and the sweat.

The urine:This is usually yellow

or transparent , but it can be

opaque when there is a lot of

waste. More or less the 95% is

water and the other 5% are

dissolved substances .The

composition is similar to blood

plasma .Urea is the primary

waste molecule in the urine .

Sweat:Is similar to urine but is

more dilute , approximately 99%

water.

sweat glands.The tiny , tubular

structures within the skin expel

The Cori Cycle: Recycling Lactic Acid

After lactate (often referred to as lactic acid) is produced, it is transported by the blood to the liver. In the liver, most of the lactate is converted back to glucose. During periods of rest, this newly formed glucose is efficiently stored as glycogen through a process known as glycogenesis. Approximately one-sixth of the lactate is oxidized to carbon dioxide.

Essentially, during the Cori Cycle, lactic acid is recycled. It is converted to pyruvate, which can then be used for the future conversion to glucose and subsequently stored as glycogen.

Energy Sources Beyond Carbohydrates

While the primary source of energy during physical activity typically comes from carbohydrates and other glucose sources (like...