Evolution, Disease, and Immunity: Key Concepts in Biology

Posted on Feb 20, 2025 in Biology

Evolutionary Biology and Prehistoric Humans

Prebiotic Synthesis

Prebiotic synthesis: The process involves:

  1. Formation of simple organic molecules.
  2. Formation of complex organic molecules.
  3. Formation of coacervates.

Theories of Evolution

Fixism

Fixism: The belief that all species were created as they exist today. It was characterized by:

  • An anthropocentric view of the world.
  • The idea of a 6000-year-old Earth.
  • False evidence based on common sense. (Advocate of fixism: Georges Cuvier)

Lamarckism

Lamarck: Basic ideas:

  • Organisms change over time.
  • Changes in environmental conditions lead to changes in species’ habits and needs.
  • The use or disuse of organs determines their development or atrophy.
  • Acquired changes are transmitted to offspring.

Darwinism

Darwinism: Basic ideas of Darwin’s evolutionary theory:

  • More individuals are born than can survive.
  • Heritable variations or differences exist among individuals of any species.
  • Natural selection occurs.
  • Populations gradually change.

Natural Selection

Natural Selection: For Lamarck: The environment induces the most appropriate changes. Evolution is teleological, i.e., has a specific objective. For Darwin: The environment selects the most advantageous traits from the existing variability. It is not a voluntary act of organisms, nor is it induced by the environment.

Neo-Darwinism or Synthetic Theory of Evolution

The unit of evolution is the population, not the individual or the environment. Variability arises from mutations, which are sudden changes in DNA. (Mutations are heritable.)

Evolution is Not Always Gradual

Darwin’s theories are synthetic and gradualist, arguing that evolutionary changes occur through the slow and gradual accumulation of small changes.

Origins of New Species

  • Two populations of the same species become separated (geographic isolation).
  • The two populations evolve independently.
  • The accumulation of differences and natural selection eventually lead to two distinct species.

Prehistory: Human Evolution

PREHISTORY: Homo habilis – Homo ergaster – Homo erectus – Homo antecessor – Homo neanderthalensis. The changes have affected different anatomical and functional characteristics, from standing upright to the acquisition of articulate speech, including an increase in brain volume.

Infectious Diseases and Immune Response

Deadly Diseases

Deadly diseases:

  • Emerging: Germs are transmitted in previously unknown ways. Some germs remain confined to their place of origin before abruptly coming into contact with people. Other cases involve mutated organisms.
  • Re-emerging diseases: Cholera, tuberculosis, dengue, malaria.

Germ Theory

Germ theory: Each disease is caused by a specific microorganism, and each organism produces a different disease.

Infectious Agents

INFECTIOUS AGENTS: Pathogenic microorganisms produce disease and are infectious. Infectious agents are parasites that invade the body of a living being (the host), causing symptoms in their tissues. A group of symptoms is called a syndrome.

  • Virus: Cellular parasites that need to enter cells to reproduce.
  • Bacteria: Prokaryotic cell organisms that can reproduce without invading cells.
  • Protozoa and Fungi: Protozoa are unicellular eukaryotes, and fungi can be unicellular or multicellular. If infectious, they are called parasites.

Agency Response to Infection

Germs can pass from the source of infection in two ways:

  • Direct or contagion: Occurs through direct contact between the sick and the healthy, either physically or through inhalation of particles.
  • Transmission: Germs pass to the environment (e.g., water or food) and are transmitted to a healthy person.

Immune Response

RESP. IMMUNE: Skin, tears, and acid secretions of our digestive system inhibit the entry of germs. If infectious agents overcome these barriers, they still must face the immune system. Sometimes the immune response can eliminate germs that cause disease, and the illness is overcome in a few days (e.g., common cold).

Antibiotics and Antivirals

Antibiotics are chemicals that kill bacteria or prevent their multiplication. The first known antibiotic was penicillin. ANTIVIRALS: Act on other infectious agents such as viruses, fungi, and protozoa.

Drug Resistance

RESIST. DRUG: Bacteria acquire resistance to an antibiotic in two ways: by mutation or gene exchange.

Influenza Virus

AS IS AND HOW TO MULTIPLY THE FLU:

  1. The genetic information is distributed into 8 small RNA molecules.
  2. The envelope carries two types of anchored molecules that define the different types of viruses.