Introduction to Living Organisms – Study Notes (Biology 2E Chapter 1)

Hierarchy of Life

The different levels of organization in biology, from the smallest (atomic) to the largest (biosphere), which helps in selecting a research focus.

Three Domains of Life

The primary taxonomic framework classifying life into Bacteria, Archaea, and Eukarya, reflecting differences in cellular structure, metabolism, and genetics.

Energy (Characteristic of Life)

All organisms acquire and use energy to power metabolism, growth, movement, and maintain order.

Cells (Characteristic of Life)

All organisms are made up of membrane-bound cells, which are the fundamental structural units of life.

Replication (Characteristic of Life)

All organisms are capable of reproduction, either sexually or asexually, to pass on genetic information.

Evolution (Characteristic of Life)

Populations continually evolve through natural selection in response to changing environmental conditions, leading to adaptation and diversity.

Information (Characteristic of Life)

Organisms use hereditary information encoded in genes (DNA/RNA sequences) and respond to environmental information via receptors and sensors.

Virus

Acellular particles that do not have cells, consisting of a genome (RNA or DNA) and a protein coat (capsid), and require host cells to replicate.

Mitosis

A type of cell division producing two genetically identical daughter cells, typically used in asexual growth.

Meiosis

A type of cell division producing haploid gametes (egg/sperm) for sexual reproduction.

Natural Selection

A process where environmental conditions drive differential survival and reproduction based on genetic diversity, increasing advantageous traits in a population over generations.

Cell Theory

A unifying idea stating that the cell is the fundamental structural unit of life and all cells arise from pre-existing cells.

Theory of Evolution

A unifying idea stating that all species are related by common ancestry and change over time in response to natural selection and other evolutionary forces.

Chromosome Theory of Inheritance

A unifying idea stating that cells store hereditary information on chromosomes (regions of DNA called genes) which encode information for specific traits passed to offspring.