Introduction to Biology

Biology is the study of life and living organisms, encompassing all aspects from the smallest molecules to the largest ecosystems.
It's a diverse field, subdivided into numerous branches, including botany, zoology, ecology, genetics, and microbiology.
Key characteristics of living organisms include:
- Organization: Cells are the fundamental unit of life, organizing into tissues, organs, and systems.
- Metabolism: Chemical processes that convert energy and nutrients, essential for growth, repair, and reproduction.
- Growth: Increase in size and complexity.
- Adaptation: Organisms adjusting to environmental changes over time.
- Response to stimuli: Organisms react to internal and external factors.
- Reproduction: Creating new organisms, necessary for species continuation.
- Homeostasis: Maintaining internal stability and balance despite external changes.
- Heredity: Passing traits from parents to offspring.

Cells are the basic structural and functional units of all living organisms.
Two main types of cells: prokaryotic (lack a nucleus) and eukaryotic (contain a nucleus).
Eukaryotic cells are more complex, containing various organelles with specialized functions.
Cell membrane: A selectively permeable barrier controlling what enters and leaves the cell.
Nucleus: Contains the cell's genetic material (DNA).
Mitochondria: Sites of cellular respiration, generating energy (ATP).
Chloroplasts: Found in plants and algae, site of photosynthesis.
Endoplasmic reticulum (ER): Network of membranes involved in protein synthesis and lipid metabolism.
Golgi apparatus: Processes and packages proteins.
Ribosomes: Sites of protein synthesis.
Vacuoles: Storage compartments.
Cytoplasm: The jelly-like substance that fills the cell, holding the organelles in place.

Genetics is the study of heredity and the variation of inherited characteristics.
Genes are segments of DNA that code for specific proteins, ultimately determining traits.
DNA (deoxyribonucleic acid) is the molecule that carries genetic information.
RNA (ribonucleic acid) plays a crucial role in protein synthesis.
Chromosomes are thread-like structures composed of DNA, carrying the genes.
The process of DNA replication allows genetic information to be passed from one generation to the next.
Mutations can lead to changes in genetic information.
Meiosis is the process of sexual reproduction, creating genetically diverse gametes (sperm and egg).

Evolution is the change in the heritable characteristics of biological populations over successive generations.
Natural selection is a key mechanism of evolution, where organisms better adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits.
Genetic drift is a random change in allele frequencies within a population.
Speciation is the process by which new species arise over time.
Fossils provide evidence of past life forms and evolutionary relationships.

Ecology is the study of the interactions between organisms and their environment.
Ecosystems include both living (biotic) and non-living (abiotic) components.
Energy flows through ecosystems via food chains and food webs.
Populations, communities, and ecosystems are complex systems with interconnected relationships.
The biosphere is the global sum of all ecosystems.
Ecological processes influence the distribution and abundance of organisms.

Taxonomy is the science of classifying and naming organisms.
Organisms are grouped into hierarchical categories, from species to domain, based on shared characteristics and evolutionary relationships.
Modern classification systems use genetic data alongside anatomical and morphological traits.

Biochemistry is the study of chemical processes within and relating to living organisms.
Key biomolecules include carbohydrates, lipids, proteins, and nucleic acids.
These molecules carry out essential functions in cells, such as energy storage, structural support, catalysis (enzymes), and information storage.
Metabolic pathways are series of connected chemical reactions responsible for biosynthesis and energy generation.

Physiology is the study of the normal functions of living organisms and their parts.
It encompasses various levels, from cellular processes to whole-organism functions.
Includes organ systems like the nervous, respiratory, circulatory, and digestive systems.
Homeostatic mechanisms regulate the internal environment of organisms.

Microbiology is the study of microscopic organisms, which include bacteria, viruses, fungi, and protists.
These organisms can be beneficial (e.g., in fermentation) or harmful (e.g., causing disease).
Microorganisms play critical roles in ecosystems and human health.