Module 2 Bio

Biology is the science that studies life.
Defining life is complex due to certain entities like viruses that exhibit some characteristics of living organisms but not others.
Virology is the study of viruses, which can reproduce, infect, and cause diseases but do not fulfill all criteria of life.
Molecular biologists may study the early evolution of life, which is not strictly biological.
Three foundational questions of biology:

All living organisms share eight key characteristics:
Order: Structured organization; organisms are composed of cells. Examples include tissues, organs, and organ systems.
Sensitivity or Response to Stimuli: Organisms respond to their environment. E.g., plants bending toward light (phototropism) and bacteria moving by chemotaxis.
Reproduction: Organisms reproduce by passing DNA, containing genes, to offspring. Single-celled organisms divide, whereas multicellular organisms produce specialized reproductive cells (gametes).
Adaptation: Organisms exhibit traits suited to their environment, evolving through natural selection. E.g., heat-resistant Archaea and nectar-feeding moths.
Growth and Development: Organisms grow and develop based on genetic instructions, ensuring young inherit traits from parents.
Regulation/Homeostasis: Organisms maintain a stable internal environment (homeostasis) despite external changes, performing necessary regulatory functions.
Energy Processing: Organisms utilize energy from food, either through photosynthesis or by consuming other organisms.
Evolution: The diversity of life arises from mutations over time, enhancing reproductive success in adaptable organisms.

The broad scope of biology stems from the diverse forms of life due to evolution.
Phylogenetic Trees: Diagrams illustrating the evolutionary relationships among species based on shared genetic or physical traits.
- Nodes: Points where species diverge from ancestors.
- Branches: Represent evolutionary paths, sometimes proportional to time since divergence.
Carl Woese's work led to the classification of life into three domains: Bacteria, Archaea, and Eukarya based on genetic relationships through rRNA sequencing.
- Bacteria: Prokaryotic organisms, typically single-celled, lacking a membrane-bound nucleus and organelles. Widespread in various environments.
- Archaea: Also prokaryotic, often found in extreme environments (extremophiles), and genetically distinct from bacteria, sharing some similarities with eukaryotes.
- Eukarya: Includes all organisms with eukaryotic cells, characterized by a membrane-bound nucleus and various organelles; can be single-celled or multicellular.

Biology encompasses diverse subdisciplines including but not limited to:
Molecular Biology: Studies biological processes at the molecular level (DNA, RNA, proteins).
Microbiology: Focuses on single-celled organisms, including subfields like microbial physiology and ecology.
Forensic Science: Applies biology to legal contexts, analyzing biological evidence from crime scenes (e.g., DNA evidence).
Neurobiology: Examines the biology of the nervous system, often interdisciplinary.
Paleontology: Uses fossils to study historical life forms.
Zoology and Botany: The study of animals and plants, respectively.
Other areas include biotechnology, ecology, and physiology.

Taxonomy: The classification science organizing organisms into a structured system (Carl Linnaeus's hierarchical model).
Levels of classification: Domain \rightarrow Kingdom \rightarrow Phylum \rightarrow Class \rightarrow Order \rightarrow Family \rightarrow Genus \rightarrow Species.
Example with the common dog (Canis lupus familiaris):
- Scientific name: Canis lupus.
- Taxonomically detailed as: Eukarya \rightarrow Animalia \rightarrow Chordata \rightarrow Mammalia \rightarrow Carnivora \rightarrow Canidae \rightarrow Canis \rightarrow lupus.

While organisms may be visually similar, evolutionary relationships can be misleading (e.g., lizards vs. rabbits).
The branching in phylogenetic trees indicates evolutionary order, not time elapsed unless specified.
Phylogenetic trees are revised continuously as new discoveries are made and new data is analyzed.

Biology reflects an ongoing inquiry into life and provides insights into various phenomena from genetics to ecology, ensuring its relevance in contemporary discussions regarding new species, genetic diversity, and environmental concerns.