Notes, summaries, assignments, exams, and problems for Biology

Invertebrate Excretory Mechanisms

Simplest animals: Excretion occurs by direct diffusion through the skin.

• Protonephridium: Found in Platyhelminthes (flatworms) and annelids. This is a closed system consisting of two highly branched duct systems distributed throughout the body. At the closed ends, waste molecules are taken up by ciliated cells (flame cells); at the open end, they feature a pore (nephridiopore) for waste elimination.
• Metanephridium: Found in annelids and molluscs. This consists of a tube that allows fluid to enter the tubule through a ciliated, funnel-like opening. It is surrounded by blood vessels that reabsorb water, salts, sugars, and amino acids.
• Antennal glands: Found in crustaceans. Located in the ventral part of the head,

Human Skeletal System: Key Structures and Functions

Types of Synovial Joints

• Plane Joints

  Characterized by flat surfaces on one bone meeting with flat surfaces of another, allowing for slipping and gliding movement with no axial rotation. Common examples include the carpal bones of the wrist.

• Hinge Joints

  A cylindrical projection of one bone fits into a trough-shaped surface of another bone. These joints permit flexion and extension, like the elbow joint (specifically, the olecranon process of the ulna).

• Pivot Joints

  A rounded projection of one bone fits into a rounded depression or sleeve of another bone, often held together by ligaments. They allow for uniaxial movement, such as the rotation of the odontoid process of C2 (axis) within the anterior

Prime Mover Muscles and Their Functions

• Iliopsoas: Prime mover of thigh flexion.
• Tibialis Anterior: Prime mover of dorsiflexion.
• Extensor Digitorum Longus: Prime mover of toe extension.
• Tibialis Posterior: Prime mover of foot inversion.
• Pectoralis Major: Primary arm flexor.
• Subscapularis: Prime medial rotator of the humerus.
• Serratus Anterior: Prime mover to protract and hold the scapula against the chest wall.
• Diaphragm: Prime mover of inspiration.
• Erector Spinae: Prime mover of back extension.
• Deltoid: Prime mover of arm abduction.
• Sternocleidomastoid: Prime mover of head flexion.
• Masseter: Prime mover of the jaw.
• Triceps Brachii: Prime forearm extensor.
• Extensor Digitorum Communis: Prime mover of finger extension.

Central Nervous System: The Hypothalamus

Vital

Characteristics of Sexual Reproduction

Human reproduction is sexual. This means that it's necessary for two individuals of different sexes to take part.

1. Each sex produces a different type of sex cell or gamete.
2. Fertilization is internal; it takes place inside the female reproductive system.
3. We are viviparous; the fetus grows in the mother's womb.
4. We are sexually dimorphic. This means that males and females have physical differences. This happens in many species.

Process of Reproduction

1. Gametogenesis: formation of the gametes.
2. Fertilization: joining of the male and female gametes.
3. Embryo Development: cell division and differentiation.
4. Childbirth: birth of the baby.
5. Development: cells increase and mature.

Changes in Adolescence

Adolescence begins with puberty,... Continue reading "Human Reproduction: Characteristics, Process, and Systems" »

Translation

• mRNA (Messenger RNA): Conveys genetic information from DNA to the ribosome.
• tRNA (Transfer RNA): Helps decode the mRNA sequence into a protein.
• rRNA (Ribosomal RNA): The RNA component of the ribosome, essential for protein synthesis.
• Ribosome: Protein builders that connect one amino acid at a time to build long chains.
• Codon: A sequence of three DNA or RNA nucleotides in mRNA.
• Anticodon: Binds with the codon in the ribosome.
• Amino Acid: A simple organic compound.
• Start Codon: The first codon of an mRNA transcript translated by a ribosome.
• Stop Codon: A nucleotide triplet within mRNA that signals the termination of translation.
• Peptide Bond: A covalent chemical bond formed between two amino acid molecules.
• Polypeptide: An organic polymer consisting

Fundamentals of Genetics

In the nucleus of every cell, there are a number of long threads called chromosomes. Each chromosome is made up of a large number of genes coding for the formation of different proteins, which ultimately determine our characteristics or traits.

Defining Key Genetic Components

DNA (Deoxyribonucleic Acid)

A molecule that carries most of the genetic instructions used in the development of living organisms. It serves as the blueprint for all living things.

Chromosome

A very long DNA molecule that carries a large amount of genetic information.

Gene

A section of a DNA molecule that codes for a specific protein or characteristic (e.g., hair color). A part of a DNA molecule coding for one protein is called a gene.

Trait

A notable feature

Trophic Levels in Ecosystems

Producers

Producers are organisms that use photosynthesis to capture energy from sunlight, water, and carbon dioxide to create organic matter (carbohydrates). They also synthesize complex biomolecules such as proteins and lipids. They perform autotrophic nutrition.

Consumers

Consumers are organisms incapable of producing their own basic molecules, requiring them to consume other organisms for nutrition. They perform heterotrophic nutrition and are categorized as follows:

• Primary: Herbivores that consume producers.
• Secondary: Carnivores that consume herbivores.
• Tertiary: Carnivores that consume other carnivores.

Decomposers

Decomposers consume dead plant and animal material, converting it into energy and nutrients for producers.... Continue reading "Ecosystem Energy Flow and Biogeochemical Cycles" »

Main Reasons Why Cell Divides

• Larger cell demands more place for the DNA.
• Larger cells result in less moving nutrients and waste materials across the cell membrane.

Information Overload

Cell grows, information is used to build the molecules needed for cell growth. DNA doesn't increase.

Exchanging Materials

Food, oxygen, water enter by the cell membrane, waste products also go out like that.

Division of the Cell

Forms 2 daughter cells. Cell division: process in which a cell divides into 2 daughter cells.

Asexual Reproduction

1 parent, cell divides by fission, little chances of genetic variation, found in bacteria, 2 offspring.

Sexual Reproduction

2 parents, cell divides by meiosis, genetic variation, found in mammals, 1 offspring.

Both

Forms of reproduction,... Continue reading "Cell Division, Chromosomes, and Cell Differentiation" »