"Biology is the science of exceptions"

Question 1

Why is biology called science of exceptions?

Answer 1

Biology is referred to as the “science of exceptions” because life’s diversity and complexity prevent strict universal rules from applying to all organisms. Evolution, natural selection, and genetic variation lead to unique adaptations in different species, resulting in deviations from general biological principles. These exceptions demonstrate the complexity and variability of life, making biology a field where unique cases challenge generalizations.

Question 2

Red Blood Cells (RBCs) Without Nuclei in Mammals

Answer 2

General Rule: Most cells in an organism contain a nucleus.
Exception: Mammalian red blood cells (RBCs) lack a nucleus when mature. This allows them to carry more hemoglobin and oxygen, increasing their efficiency. In contrast, RBCs in birds, amphibians, and reptiles retain their nuclei.

Question 3

Reproduction in Honeybees

Answer 3

General Rule: Sexual reproduction involves the fusion of sperm and egg cells.
Exception: Male honeybees (drones) develop from unfertilized eggs through a process called parthenogenesis, a form of asexual reproduction. They have only one set of chromosomes (haploid), while female bees (workers and queens) develop from fertilized eggs and are diploid.

Question 4

Heart in Crocodiles

Answer 4

General Rule: Reptiles generally have a three-chambered heart (two atria and one ventricle).
Exception: Crocodiles are reptiles with a four-chambered heart, which is typically found in birds and mammals. This adaptation allows for more efficient separation of oxygenated and deoxygenated blood.

Question 5

DNA as the Genetic Material

Answer 5

General Rule: DNA is the universal genetic material that carries hereditary information in living organisms.
Exception: Some viruses, like retroviruses (e.g., HIV), use RNA as their genetic material instead of DNA. These viruses reverse-transcribe their RNA into DNA using an enzyme called reverse transcriptase when infecting host cells.

Question 6

Respiration in Anaerobic Bacteria

Answer 6

General Rule: Most organisms, especially multicellular ones, rely on oxygen for cellular respiration.
Exception: Anaerobic bacteria can survive and thrive in environments devoid of oxygen by using alternative electron acceptors (like nitrate or sulfate) during respiration. Some, like Clostridium species, even die in the presence of oxygen.

Question 7

Heterotrophic Plants

Answer 7

General Rule: Plants are autotrophic, meaning they make their own food through photosynthesis.
Exception: Some plants, like dodder (Cuscuta) and Venus flytrap, are heterotrophic. Dodder is parasitic and derives nutrients from host plants, while Venus flytraps capture and digest insects for nutrients.