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

• In the case of partial injuries, some sensation and movement may be retained below the level of the injury.

• In complete injuries, there is a loss of sensation and total muscular paralysis below the level of the injury

• Depression is a mental illness that often takes the form of low mood and an inability to lead a normal life

Functions of the Blood

Transports nutrients and oxygen to all the cells and collects waste products produced by cell metabolism. Contributes to the regulation of body temperature. Plays a role in the fight against infections.

Cardiovascular System

Shares nutrients and oxygen between cells and collects waste products that cells produce during metabolism.

Menstrual Cycle

Pre-menstrual phase: the lining of the uterus begins to break down, progesterone decreases. Menstruation: the endometrium is detached, loss of blood and it is caused by progesterone. Usually it lasts 4 days. Repair phase: the lining of the uterus starts to thicken and becomes more stable. Increase in the concentration of estrogen. Ovulation: occurs around day 14, the ovum is released, there is a peak of estrogen and they are the most fertilized days. Receptive phase: the lining of the uterus is well developed if the ovum has been fertilized it implants itself in the tissue. Hormones: FSH: stimulates the follicle (brain) LH: produces ovulation (brain). Estrogen: creates new endometrium (ovary). Progesterone: makes the endometrium...

Human reproduction is sexual. Two individuals from different sexes are needed. Each produces a type of gamete (reproductive cell).

Embryo development: Zygote undergoes cell division until it becomes an embryo that continues development up to being a fetus.

Childbirth: Baby is born, alive and fully formed

Development: The baby grows until maturity is reached (adulthood)

Changes leading to sexual maturity

• Primary sex characteristics: The reproductive organs
• Puberty: Stage from the ages 10-16, when majority occurs
• Adolescence: From puberty to adulthood, physical maturity and physiological and social changes, sexual desire appears
• Sex

Understanding Biological Adaptation

Adaptation is the evolutionary process where organisms develop traits enabling them to survive and thrive in specific environments.

Types of Adaptations

• Morphological: Involves a change in the body structure or form.
• Behavioral: Involves changes in habits or actions. For example, some animals are nocturnal, others hibernate, and some migrate in search of areas where food is more abundant.

Animal Adaptations to Water Scarcity

• Nocturnal Behavior: Many desert animals are active at night to avoid the sun and extreme heat.
• Efficient Water Retention: Their bodies extract most water from their urine, passing thick uric acid, and their droppings are almost completely dry.
• Thick Skin: Reptiles often have thick skin that does

Inorganic biomolecules

Essential for non-living things.

• Water: The most abundant substance found in living things. It makes up about 65% of the human body.
• Mineral salts: Substances that can be found in living things in the form of dissolved ions, such as sodium ion.

Organic biomolecules

Unique to living things. Structures made up of carbon.

• Carbohydrates: Made of carbon and water.
• Lipids: Fats, phospholipids, and cholesterol.
• Proteins: Chains of amino acids.
• Nucleic acids: Groups of nucleotides.

The cell: Functions

• Structural
• Functional
• Basic
• Biological

Prokaryotic cell

• No nucleus
• Organelles: Ribosomes
• Bacteria are prokaryotes
• Membranes: Cell membrane, cell wall, and bacterial capsule (not always)
• Flagella and Fimbriae

Eukaryotic cell

• Nucleus
• Cell membrane: two

Proteins are composed of 20 amino acids.

Functional groups influence reactivity.

Nonpolar side chains are green.

Polar side chains are pink.

Electrically charged side chains:

• Acidic: red
• Basic: blue

Condensation reactions form a peptide bond by bonding the carboxyl group of one amino acid to the amino group of another. Multiple peptide bonds create a polypeptide. Polypeptides containing more than 50 amino acids are called proteins.

Protein Structure

Primary structure: The unique sequence of amino acids.

Secondary structure: Hydrogen bonds between the carbonyl group of one amino acid and the amino group of another form a protein's secondary structure.

Secondary structure depends on the primary structure.

Tertiary structure: Results from interactions between...

Question 1:

Group the following as nitrogenous bases and nucleosides:

• Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Answer

Nitrogenous bases present in the list are adenine, thymine, uracil, and cytosine.

Nucleosides present in the list are cytidine and guanosine.

Question 2:

If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Answer

According to Chargaff’s rule, the DNA molecule should have an equal ratio of pyrimidine (cytosine and thymine) and purine (adenine and guanine). It means that the number of adenine molecules is equal to thymine molecules and the number of guanine molecules is equal to cytosine molecules.

% A = % T and % G = % C

If dsDNA has 20% of cytosine, then according to...

1. Body Fluids

Our body is composed of approximately 60% water, distributed as follows:

• Intracellular fluids: 40%
• Extracellular fluids: 20%

Interstitial Fluid

All cells in our body are surrounded by fluid to obtain nutrients and expel waste. Interstitial fluids are essential for this process.

2. The Circulatory System

The circulatory system is responsible for transporting nutrients and waste, regulating temperature, and maintaining homeostasis. It consists of:

• Liquid: Blood
• Conduits: Arteries, veins, and capillaries
• Pump: The heart

2.a Blood

Blood is the liquid component of the circulatory system, composed of water, cells, and dissolved substances.

• Blood Plasma: Composed of 92% water, plus nutrients, gases, and waste.

2.b Capillaries

These are tiny vessels...