Notes, abstracts, papers, exams and problems of Biology

Abiogenesis

Process through which life appeared from non-living matter, such as simple organic molecules.

Cyanobacteria

Photosynthetic organisms responsible for the existence of oxygen in the atmosphere.

Homologous Organs

Organs that share an evolutionary origin and structure, but may have different functions. They evidence divergent evolution. Examples: whale and bat extremities.

Analogous Organs

Organs with the same function but different evolutionary origins. They evidence convergent evolution. Examples: insect and bird wings.

Vestigial Organs

Organs that are disappearing because they are no longer useful. Examples: kiwi and cassowary wings.

Evolutionary Lineage

Fossils show progressive transformations, providing evidence of evolution and allowing... Continue reading "Key Concepts in Evolutionary Biology" »

Lymph Nodes and Nephrons

Lymph Nodes

Lymph nodes are made of lymphatic tissue located in specific areas of some lymphatic vessels. They make lymphocytes and release lymph plasma.

Nephrons

Nephrons are the structural and functional units of the kidneys. They are tubes with one closed end and are surrounded by blood capillaries. Nephrons are responsible for filtering blood and forming urine, regulating water and mineral content.

• Bowman's Capsule: Initial zone
• Convoluted Tube: Long twisted tube with two main parts, proximal and distal
• Loop of Henle: Section located between the proximal convoluted tube and the distal zone

Urinary System

Ureters

Ureters are thin tubes that start from each kidney and end in the bladder, an elastic bag in which urine accumulates.... Continue reading "Human Body Systems and Health" »

Su,Aalo Iyo Jawabo biology 

• 1. a) i) Define transport

• Movement of substances from one part of the body to another

  ii) Explain the necessity of transport in plants and animals

• make nutrients move from one point to another

• movement of respiratory gases i.e. oxygen and carbon IV oxide

• elimination of metabolic wastes

• movement of hormones

• movement of water

• movement of salts

• movement of enzymes

  b) i) Describe the structure and function of root hair

• root hairs are found near the root tip

• they are cells with elongated finger-like projections which are in contact with soil particles

• they are permeable to water and mineral salts hence are used to absorb Water and mineral salts

• There large number offers a large surface area for absorption of water and mineral salts.

Charles Darwin and the Discovery of Natural Selection

Charles Darwin made the groundbreaking discovery of natural selection. He observed that organisms with favorable traits are more likely to survive and reproduce, passing on those traits to future generations.

Artificial Selection: Shaping Outcomes through Human Intervention

Artificial selection involves deliberately pairing two organisms to produce desired traits in their offspring.

Gene Flow: The Transfer of Genes between Populations

Gene flow occurs when genes are transferred from one population to another through migration and mating.

Genetic Drift: Changes in Gene Frequency within a Population

Genetic drift refers to the random change in the frequency of a gene within a population. Over time,... Continue reading "Understanding the Mechanisms of Evolution: Natural Selection and More" »

Mendelian Principles of Inheritance

Gregor Mendel

• In the 19th century, he studied inheritance: the passing of characteristics from parents to offspring.
• His work was based on the study of the crossing of different varieties of plants.
• The species chosen was the pea (Pisum sativum).

Method

• Characteristic selection
• Obtaining pure-bred individuals for those characteristics

Parental generation (P)

• Crossing two different pure breeds to obtain descendants

First filial generation (F1)

• Crossing F1 individuals and studying their descendants

Second filial generation (F2)

Complete Inheritance

In the heterozygote, the dominant phenotype is manifested.

Special Cases in Genetics

Complete Inheritance

In the heterozygote, the dominant phenotype is manifested.

Intermediate Inheritance

The... Continue reading "Mendelian Genetics: Principles of Inheritance" »

Early Chordates and the Rise of Tetrapods

The earliest known chordate, Myllokunmingia, is found in the Chengjiang fauna. One of the major challenges for early tetrapods was supporting their bodies on land, along with reproductive and sensory adaptations. Tetrapod limbs consist of three segments: the stylopod (humerus/femur), zeugopod (ulna/radius, tibia/fibula), and autopod (wrist/fingers, ankle/toes). Tiktaalik represents a key transitional fossil between fish and tetrapods.

Amphibians and Amniotes

Amphibians, with over 4,000 living species, represent a halfway point in the transition to land. They still rely on water for breeding and maintaining water balance. Amniotes, including reptiles, birds, and mammals, evolved a semipermeable shell made... Continue reading "Evolution of Life: From Early Chordates to Modern Biodiversity" »

The structural organization of eukaryotic cells is remarkably complex and compartmentalized, reflecting the diverse functions these cells perform. Eukaryotes encompass a wide array of organisms, including plants, animals, fungi, and protists. Below is a detailed exploration of the structural components of eukaryotic cells:

1. Cell Membrane (Plasma Membrane)

• Composition: The cell's outer boundary is formed by a phospholipid bilayer with embedded proteins and other molecules.
• Function: It regulates the passage of substances into and out of the cell, acting as a selective barrier.

2. Cell Wall (in some cells)

• Present in: Plant cells, fungal cells, and some protists.
• Composition: A rigid structure made of cellulose in plants and chitin in fungi.
• Function:

Understanding Kidney Function

As capillaries exit organs, they converge into larger blood vessels, veins, which eventually return the blood to the heart at the right atrium.

Abnormal Kidney Function:

An individual's kidneys are unable to remove waste, the medical treatment known as hemodialysis. Use a dialysis machine 'artificial kidney' is only temporary, until the patient recovers normal kidney function or receives a kidney transplant. Blood is put in close contact with a special solution similar to blood plasma. The semipermeable membrane allows urea and other waste materials to exit the blood and prevents the escape of blood cells.

Painful Stones:

The substances transported in the urine can trigger the formation of crystals, commonly referred... Continue reading "Understanding Kidney Function, Stones, and Blood Disorders" »

The Central Dogma of Molecular Biology

Replication - General Characteristics:

• DNA replication is semiconservative: each strand in the DNA double helix acts as a template for the synthesis of a new, complementary strand. The new two daughter molecules of DNA have a new strand and an old one.
• DNA polymerase III: is the enzyme that adds nucleotides to the growing DNA chain, incorporating only those that are complementary to the template. DNA polymerase III has the following characteristics:
  • It can only read a template in 3’-----5’ direction so the new strand grows in 5’----3’ direction.
  • It needs a pre-existing strand of nucleotides called a primer which provides a 3’-OH end to bind new nucleotides.
  • It is able to repair the mistakes by removing

Arthritis: Inflammation of the Joints

Arthritis is a condition where the joints become inflamed, swollen, and warm to the touch. It can also cause decreased mobility and joint deformities.

Osteoarthritis: A Common Type of Arthritis

Osteoarthritis is a chronic, non-inflammatory condition characterized by progressive degeneration of the cartilage and joints.

Gout: Painful Inflammation of Joints

Gout is a type of arthritis that involves painful inflammation of the joints. It usually begins abruptly and is accompanied by redness and swelling.

Rheumatism: Similar to Osteoarthritis

Rheumatism is similar to osteoarthritis but typically occurs in individuals between the ages of 25 and 55.

Osteoporosis: Decrease in Bone Mass

Osteoporosis is a condition characterized... Continue reading "Common Types of Arthritis and Other Joint Conditions" »