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

Endocrine Coordination and the Hormonal System

Endocrine coordination is a mechanism which regulates the action of many of the body’s organs in a slow way over a long period of time.

It is carried out by the endocrine system, which is made up of a network of endocrine glands specialized in manufacturing and secreting hormones into the blood. Blood transports hormones all around the body, but the hormones only affect certain organs or cells called target cells.

The Role of the Pituitary Gland

The pituitary gland is located at the base of the brain. It is the most important gland, since some of the hormones that it manufactures control secretion by the rest of the glands.

Other Key Endocrine Glands

Other endocrine glands include:

• Thyroid gland
• Parathyroid

Neo-Darwinism and the Synthetic Theory

Neo-Darwinism, also known as the synthetic theory, is a revised version of the theory of natural selection, enriched by contributions from studies made in fields such as genetics, paleontology, and taxonomy after Darwin's time.

Punctuated Equilibrium

Punctuated Equilibrium (Punctualism) suggests that there are certain periods of intense speciation which interrupt, or punctuate, the equilibrium of the normal process of adaptation through natural selection.

Biodiversity and Biological Adaptation

Biodiversity refers to the quantity and variety of organisms that exist or have existed in the past, and the adaptation of organisms to different habitats.

Adaptation is the accumulation of changes in the characteristics...

1. Interaction and Coordination

The basic path of a nerve impulse from stimulus to response is:

1. A stimulus occurs.
2. Sensory receptors detect the stimulus.
3. Sensory neurons receive the information and transmit it to the central nervous system (CNS).
4. The CNS receives the information and a response is decided.
5. Motor neurons transmit the response to the effectors.
6. Effectors carry out the response. An effector can be a muscle or a gland.
7. The response is given. There are two types: motor responses, which are carried out by muscles, and secretory responses, which are carried out by glands.

Coordination Systems

• Nervous system: Receives and transmits information rapidly via electrical impulses through sensory neurons and processes them in the CNS. Responses are

Biogeographical Evidence

Isolated groups evolved in different ways.

Molecular Evidence

The higher the molecular similarities, the closer their evolutionary relationship.

Coevolution

Coevolution is the process by which two species mutually influence each other during their evolution.

Lamarckism

Lamarckism is the theory of inheritance of acquired traits, explaining that animals develop the structures and organs they need in order to adapt to the environment they live in, and these new characteristics are transmitted to offspring.

Darwinism

Darwinism posits that there is competition between the individuals of a species, known as the struggle for existence. Individuals whose characteristics help their survival are favored over those who are poorly adapted...

Stages of Cell Division

Prophase: The first stage of cell division, before metaphase, during which the chromosomes become visible as paired chromatids and the nuclear envelope disappears. The first prophase of meiosis includes the reduction division.

Metaphase: The second stage of cell division, between prophase and anaphase, during which the chromosomes become attached to the spindle fibers.

Anaphase: The stage of meiotic or mitotic cell division in which the chromosomes move away from one another to opposite poles of the spindle.

Telophase: The final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.

Cytokinesis: The cytoplasmic division of...

Key Characteristics of Birds

Birds are terrestrial vertebrates with feathered bodies. They are descended from reptiles, but they are considered to be more evolved as they have a more developed nervous system. Some of their main characteristics are the following:

• They have a fusiform or spindle-shaped body which is covered by feathers, except the legs which are covered by scales.
• Two of their limbs are wings, which in the majority of cases allow them to fly.
• They have a beak, but no teeth.
• They have a highly developed sense of sight.
• They are homeotherm or warm-blooded animals, which means that their internal temperature stays at around 42 ºC regardless of the temperature around them.

The Body of Birds

The body of birds has a very characteristic shape...

Bohr Shift

In the cytoplasm of red blood cells, the enzyme carbonic anhydrase catalyzes the following reaction: CO₂ + H₂O ⇌ H₂CO₃ (carbonic acid). The carbonic acid then dissociates: H₂CO₃ ⇌ H⁺ + HCO₃^-. Hemoglobin readily combines with the hydrogen ions, forming haemoglobinic acid (HHb), which releases the oxygen it is carrying.

The Cardiac Cycle

• 1. Atrial systole: Both atria contract. Pressure forces the atrioventricular valves open, and blood flows from the atria into the ventricles.
• 2. Ventricular systole: The ventricles contract. Atrioventricular valves are pulled shut as ventricular pressure exceeds atrial pressure. Semilunar valves are forced open, and blood rushes into the arteries.
• 3. Ventricular diastole: The heart muscle relaxes. Semilunar

Cellular Interaction and Responses

Cellular interaction is the capacity of cells to detect changes in their environment and respond to them correctly.

Types of Cellular Responses

Static Response

In a static response, there is no movement produced. Rather, the cell responds in a different way, for example, by secreting a substance.

Dynamic Response (Taxis)

In a dynamic response, the cell responds by moving. These movements are collectively called taxis (plural: taxa). They are considered:

• Positive: If the cell moves towards the stimulus.
• Negative: If the cell moves away from the stimulus.

Mechanisms of Cellular Movement

Flagellar and Ciliary Movement

This type of movement is produced in cells that have cilia (many tiny structures) or flagella (longer than...

The Endocrine System

The endocrine system is a set of organs and tissues responsible for secreting hormones. It is distributed throughout the body, similar to the nervous system. However, the endocrine system uses chemical substances instead of nerve impulses.

Types of Hormones and Glands

• Pituitary: Located in the head.
  • Growth hormone: Stimulates the growth of all body tissues, especially the skeleton.
  • Thyroid-stimulating hormone: Regulates the production of thyroid hormones.
• Testes: Male gonads.
  • Testosterone: Stimulates the production of sperm and the development of secondary sexual characteristics.
• Thyroid: Located in the neck, in front of the trachea.
  • T3 and T4: Increase cell metabolism, oxygen consumption, protein synthesis, and glucose utilization.

The Lymphatic System

The lymphatic system is a network of vessels and structures distributed throughout the body.

• Lymph capillaries: They collect excess interstitial fluid.
• Lymphatic vessels: They return excess lymph to the circulatory system.
• Lymph nodes: They contain defense cells that locate and fight microorganisms that could cause infection.

Composition and Function of Blood

Blood is a thick red liquid that flows inside the blood vessels.

• Blood plasma: A yellowish liquid that makes up 55% of blood.
• Blood cells: Red blood cells, white blood cells, and platelets make up the remaining 45% of blood.
• White blood cells (leukocytes): Protect the body against infection and foreign substances.
• Red blood cells (erythrocytes): Transport oxygen and pick up