Concepts of Life Science

Atoms and Molecules
- All matter is composed of atoms and molecules.
- Difference between living and non-living objects lies in types of atoms/molecules, organization, and interactions.
Chemical Similarity
- While physical appearance may vary, chemical makeup among all living organisms is quite similar.
Biological Instructions
- Biological molecules carry instructions to build complex structures from simpler units.
- Living organisms must gather energy and materials from surroundings to build biological molecules, grow, maintain, repair, and reproduce.
Response to Environment
- Living organisms must adjust their chemistry and activity in response to environmental changes.
Levels of Organization
- Atoms, molecules, and macromolecules alone are not alive; organization into cells is essential for life.
- Cells are the basic unit of life, organized chemical systems enclosed by a membrane, capable of reproduction if they have energy sources and raw materials.

Definition
- Emergent properties arise from the organization of matter into cells; life itself is an emergent property.
Types of Organisms
- Unicellular organisms: single cells (e.g., bacteria, protozoans).
- Multicellular organisms: plants and animals; cannot live independently.
- Higher levels include populations, communities, ecosystems, and biosphere.
- Each level displays emergent properties.

Chemical Instructions
- Organisms contain instructions (DNA) that regulate structure and function.
- DNA is a double-stranded helical molecule constructed from nucleotides (A, T, G, C).
Genome
- All DNA in an organism forms its genome, which carries genetic information unique to each organism.
Genes and Gene Expression
- Genes are segments of DNA that encode instructions for RNA and proteins.
- Gene expression involves two steps: transcription (DNA to mRNA) and translation (mRNA to proteins).

Definition of Metabolism
- The ability of cells to extract energy from surroundings, essential for growth, reproduction, and maintenance.
Energy Flow and Matter Cycles
- Energy from the sun supports most life on Earth; plants convert this energy into chemical energy (photosynthesis).
- Animals are consumers; fungi and bacteria are decomposers that break down organic matter.

Detection and Compensation
- Organisms can detect environmental changes and respond to survive.
Biological Evolution
- Populations change and adapt through inherited traits and genetic variations over generations.

Biodiversity and Classification
- Diversity of organisms; systems developed to track evolutionary relationships.
- Categories include species, genus, family, order, class, phylum, kingdom, domains (Bacteria, Archaea, Eukarya).
Phylogenetic Trees
- Illustrations of evolutionary pathways and relationships.

Geological Evidence
- Earth formed approximately 4.6 billion years ago. Early life (e.g., prokaryotes) existed around 3.5 billion years ago.
Experimental Data
- Protocells may represent the earliest life forms; endosymbiotic theory explains the origin of mitochondria and chloroplasts in eukaryotes.

Introduction of Cells
- All living organisms consist of cells, which are the fundamental unit of life.
Cell Membranes and Organelles
- Organelles perform specific functions essential for survival (e.g., energy production in mitochondria, photosynthesis in chloroplasts).

Discovery and Features
- DNA is composed of nucleotides and exhibits a double helix structure.
Replication
- DNA replication is a semi-conservative process where strands are unwound and new complementary strands are synthesized.