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

Fundamental Concepts in Genetics and Heredity

Core Genetic Terminology

Genetics

The science that studies hereditary characters and their transmission between parents and offspring.

Genome

The complete set of genes (genetic material) of an organism.

Gene

A fragment of DNA containing the information necessary for a specific character (trait).

Allele

One of the variant forms of a gene.

Locus (Singular) or Loci (Plural)

The specific location of a gene on a chromosome.

Genotype

The complete genetic makeup of an organism.

Phenotype

The external manifestation of the genotype; the set of observable characteristics of an organism.

Organism and Allele Status

• Haploid

  An organism or cell where each gene has only a single copy or set of information.

• Diploid

  An organism

...

Prenatal development is divided into two main periods: the embryonic period, which occurs during the first 2 months, and the fetal period, which follows. The embryonic period begins in the oviduct with the segmentation of the zygote. This involves successive mitotic divisions that produce 2 cells, called blastomeres, approximately 36 hours after fertilization. These cells then divide into 4, then 8, then 16, and so on, forming a morula.

About 5 days after fertilization, the morula transforms into a hollow, spherical structure called the blastocyst. The blastocyst consists of a cavity and two sets of cells: trophoblast cells (or the outer cell mass) and the embryoblast (the inner cell mass). After 7 days, the trophoblast attaches to the endometrium...

General Function

The cardiovascular system transports various substances to and from cells.

Heart Anatomy and Function

The heart is a hollow, muscular organ responsible for pumping blood throughout the cardiovascular system to maintain adequate pressure. It is situated in the thoracic cavity.

Heart Structure

• Dimensions: Conical shape, weighs approximately 250g, and measures 10cm in length.
• Chambers: Composed of four chambers: two upper atria (right and left) and two lower ventricles (right and left).
• Septa: The atria are separated by the interatrial septum, while the ventricles are separated by the interventricular septum.

Valves and Blood Flow

The right atrium communicates with the right ventricle via the tricuspid valve. The left atrium communicates...

Understanding Genetics

DNA is the genetic material that all living things have in their cells. It is transmitted from one generation to the next. Characteristics like blue eyes, hair color, etc., are examples of the diversity and variability that exists within a species.

Hereditary vs. Acquired Traits

Characteristics of an organism that are transmitted from parents to children are called hereditary traits. In contrast, acquired characteristics are those developed during an organism's life, such as a tattoo.

Genetics studies the specific characteristics encoded in DNA, how they are expressed in organisms, and explains how this information is passed to the next generation—that is, their inheritance—and why traits vary from generation to generation....

Mammals

• Females have breasts that produce milk to feed their young.
• The body is covered with hair.
• Body temperature is constant.
• Young are born alive.
• Examples: Prototherians (e.g., the platypus), marsupials (e.g., kangaroos), and eutherians (e.g., insectivores, bats, primates, cetaceans, carnivores, Perissodactyla, and Artiodactyla).
• Temperature: Mammals maintain a constant body temperature, typically between 38 and 40 degrees Celsius, regardless of whether they live in hot or cold climates.
• Reproduction: Mammals reproduce viviparously with internal fertilization. They lay eggs without nutrient reserves, which are implanted and developed in the womb. The placenta provides nourishment and oxygen to the developing fetus and facilitates the excretion

...

The Three Major Types of RNA

Messenger RNA (mRNA)

The Messenger RNA (mRNA) molecule is a long, single strand that contains the codons which will be translated into the amino acid sequence of a protein.

Transfer RNA (tRNA)

Transfer RNA (tRNA) molecules bind to specific amino acids and deliver them to the ribosome, where they are incorporated into growing protein chains. There are many types of tRNA, with at least one type for each amino acid.

Ribosomal RNA (rRNA)

Ribosomal RNA (rRNA) and a large amount of protein constitute ribosomes. Each ribosome consists of two subunits.

Understanding the Genetic Code

The genetic code is often compared to Morse code: a set of symbols (bases in nucleic acids, or dots and dashes in Morse code) can be translated into

...

Mitosis

Interphase: This is the state in which the cell is when it is preparing for division. During this time, the cell duplicates its genetic material, grows, and prepares the structures and proteins needed to carry out mitosis.

Prophase: This is the first phase of mitosis. During this phase, the cell's centrioles duplicate, and each pair moves to opposite poles of the cell. The nuclear membrane disintegrates. Chromosomes condense and become visible as double structures.

Metaphase: This is the second phase of mitosis. During this phase, the chromosomes align along the equatorial plane of the cell. The cytoplasmic spindle appears.

Anaphase: This is the third phase of mitosis. The chromatids separate and are pulled towards the spindle poles by...

Cellular Respiration: Energy Production in Cells

Understanding Cellular Respiration

Cellular respiration is often associated with the exchange of gases. The utilization and disposal of gases occur within the confines of individual cells in animal or plant bodies, or within the single cell of unicellular organisms. This process is known as cellular respiration. During cellular respiration, the breaking of chemical bonds follows a sequence of steps catalyzed by various enzymes, allowing for a gradual release of energy. This energy is not transformed into light; instead, it is partly "packaged" into ATP molecules, while the remainder is dissipated as heat.

Stages of Cellular Respiration

The first stage, Glycolysis, occurs in the cytoplasm's matrix,...

Understanding Metabolism: Energy Exchange in Living Systems

Metabolism refers to the reactions of degradation and synthesis that result in a continuous exchange of matter and energy between a living system and its environment.

Anabolism and Catabolism

• Anabolism: The set of chemical reactions in which complex substances are synthesized from simple substances, requiring energy input.
• Catabolism: Chemical reactions in which molecules are degraded with the release of energy.

The Role of ATP

ATP (Adenosine Triphosphate) is the primary energy carrier in cells. It prevents energy loss during degradation reactions by capturing and delivering energy where it is needed. ATP is a nucleotide consisting of:

• A nitrogenous base (adenine)
• A simple sugar (ribose)
• Three

...

Homeostatic Mechanisms of Plasma Potassium

Dietary potassium intake can vary from 50 mEq/day to 150 mEq/day. To maintain potassium balance, urinary excretion must equal dietary intake. The renal mechanisms that allow this variability are known as the external balance of potassium.

Bladder Dysfunction Following Spinal Injury

A patient with a T12 spinal cord injury presents with paralysis, loss of sensation below T12, and urinary incontinence. Studies show spontaneous contraction of the detrusor muscle during bladder filling.

• Explanation: The parasympathetic system remains active, but the patient lacks voluntary control over the external sphincter.

Glomerular Filtration and Starling Forces

Glomerular ultrafiltration is governed by Starling forces,...