Biology: Cells as Units of Life

Cell: The Unit of Life

• Cells are the basic structural and functional units of all living organisms.
• Cells exhibit a remarkable diversity of forms and functions.
• All cells are enclosed by a plasma membrane.
• The internal organization of a cell is complex, with various organelles carrying out specific tasks.
• Prokaryotic cells lack a membrane-bound nucleus and other organelles, while eukaryotic cells possess a nucleus and various membrane-bound organelles.
• The nucleus is the control center of the cell, containing the genetic material (DNA).
• DNA organization varies between prokaryotes and eukaryotes.
• Cytoplasm is the region between the nucleus and the plasma membrane, containing various organelles.
• Ribosomes are the sites of protein synthesis.
• Endoplasmic reticulum (ER) is a network of membranes involved in protein and lipid synthesis and transport.
• Golgi apparatus processes and packages proteins for secretion or use within the cell.
• Lysosomes are involved in intracellular digestion.
• Mitochondria are the "powerhouses" of the cell, responsible for cellular respiration and generating ATP.
• Chloroplasts are specific to plant and algal cells, where photosynthesis takes place.
• Vacuoles are membrane-bound sacs involved in storage and maintaining turgor pressure.
• The cytoskeleton provides support, shape, and facilitates movement.
• Plant cells have a cell wall for structural support.

Biological Classification

• Organisms are classified into various hierarchical categories.
• Broad categories include Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• Classification systems aim to reflect evolutionary relationships.
• Modern classification emphasizes evolutionary relationships.
• Various methods for classifying living organisms have evolved.
• Early classifications were based on observable characteristics.
• Modern classifications utilize molecular data like DNA and RNA sequences.
• The Three-Domain system (Bacteria, Archaea, Eukarya) is a widely accepted classification.
• Key characteristics that differentiate the different kingdoms (e.g., Monera, Protista, Fungi, Plantae, Animalia)

Human Physiology

• This section covers the human body systems and their functions.
• Digestive System: Breakdown of food for absorption of nutrients; Key organs include the mouth, esophagus, stomach, small and large intestines.
• Respiratory System: Gas exchange (oxygen and carbon dioxide); Key organs are the lungs and associated airways.
• Circulatory System: Transportation of materials throughout the body; Blood, heart, blood vessels.
• Excretory System: Removal of metabolic waste; Key organs include kidneys, ureters, bladder, and urethra.
• Nervous System: Coordination and control of body functions; The brain, spinal cord, and nerves.
• Endocrine System: Regulation of body functions through hormones; Endocrine glands.
• Reproductive System: Production of gametes and offspring.

Reproduction

• Asexual reproduction involves a single parent.
• Sexual reproduction involves two parents.
• Types of asexual reproduction include binary fission, budding, fragmentation, spore formation.
• Sexual reproduction often involves meiosis (gamete formation) and fertilization.
• Key events in sexual reproduction include meiosis, gamete formation, and fertilization.
• Reproductive systems in plants and animals differ greatly.
• Reproductive strategies vary across species and are adapted to environment and life cycle.

Genetics

• Mendel's laws of inheritance (segregation and independent assortment).
• Chromosomes and genes function as the carriers of genetic information.
• DNA structure and its role in gene expression.
• Gene and chromosome mutations.
• Genetic disorders (e.g., sickle cell anemia).
• Heredity and its role in human traits.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is a key driver of evolution.
• Adaptation is the evolutionary adjustment of organisms to their environment, contributing to survival.
• Evidence for evolution is derived from comparative anatomy, embryology, fossil records, and molecular biology.
• Factors contributing to evolution include natural selection, genetic drift, gene flow, mutation.

Ecology

• Ecology studies the relationships between organisms and their environment.
• Levels of organization in ecology include organism, population, community, ecosystem, biome, and biosphere.
• Various ecological interactions exist (predator-prey, competition, symbiosis, etc.).
• Nutrient cycling plays a vital part in ecosystems.
• Biodiversity and its conservation.
• Human impact on the environment.

Biotechnology

• Modern biotechnology uses biological processes, organisms, or systems to develop or make products.
• Applications include genetic engineering, recombinant DNA technology, and cloning.

Human Health and Diseases

• Various factors contribute to human health, including diet, hygiene, and exercise.
• Common diseases, causes and prevention.
• Importance of immunology, vaccination programs and disease control.

Organisms and Processes

• Examples of various organisms and their defining characteristics are considered.
• Study of plant and animal diversity and their adaptation to environments.
• Focus on specific biological processes (e.g., photosynthesis, respiration) and their importance.