Concepts of Life Science

What is Life

  • 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.

Emergent Properties

  • 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.

Characteristics of Living Organisms

  • 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).

Metabolic Activities

  • 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.

Environmental Adaptation

  • 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.

Classification of Life

  • 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.

The Origins of Life

  • 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.

Cell Structure and Function

  • 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).

DNA Structure and Function

  • 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.