What is living

Characteristics of Living Organisms

• Living organisms exhibit a complex organization, ranging from atoms to molecules, to organelles, cells, tissues, organs, organ systems, and eventually, the whole organism.
• Living things are composed of one or more cells, the basic unit of life.
• Living organisms are characterized by the ability to reproduce. Reproduction can be asexual (simple cell division) or sexual (fusion of gametes).
• Organisms maintain a relatively stable internal environment despite fluctuations in the external environment (homeostasis).
• Organisms respond to internal and external stimuli (irritability).
• Living organisms obtain and use energy to carry out life processes (metabolism). This includes photosynthesis in plants and cellular respiration in animals.
• Living organisms grow and develop, undergoing changes in size and form as they mature.
• Living organisms adapt to their environments over time through processes like natural selection.

Diversity of Life

• Life on Earth is incredibly diverse, with a vast array of species.
• Organisms can be classified into different taxonomic groups, including domains (e.g., Bacteria, Archaea, Eukarya) and kingdoms (e.g., Animalia, Plantae, Fungi).
• Classification systems are hierarchical, with broader levels encompassing more diverse groups of organisms.
• Species are the basic unit of classification, defined as groups of organisms that are capable of interbreeding and producing fertile offspring.
• Organisms exhibit various adaptations in structure and function that allow them to thrive in specific environments.

Evolutionary Processes

• Evolution is the change in heritable characteristics of biological populations over successive generations.
• Evolution occurs through mechanisms such as natural selection, genetic drift, and gene flow.
• Natural selection is a process where organisms with traits better suited to their environment are more likely to survive and reproduce, passing their advantageous traits to their offspring.
• Mutations are changes in the DNA sequence that can introduce new genetic variations into a population.
• Evolutionary relationships among organisms can be visualized using phylogenetic trees, which depict the evolutionary history of a group of organisms.

Structure and Function

• The structure of an organism's components is closely related to their function.
• Different organisms adopt different strategies to ensure their survival and reproduction.
• Cellular structure varies depending on the specific function of the organism.
• Organs and organ systems perform specific roles in coordinating life processes.
• Example mechanisms include digestion in animals and photosynthesis in plants, which are crucial for obtaining and using energy and materials.

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Organisms live in ecosystems, where biotic (living) components interact with abiotic (non-living) components.
• Ecosystems exhibit complex interactions, including predator-prey relationships, competition for resources, and symbiotic relationships (mutualism, parasitism, commensalism).
• Energy flows through ecosystems via food chains and food webs, with producers (plants), consumers (animals), and decomposers (bacteria and fungi).
• The balance and health of an ecosystem rely on the interaction and resilience of its biotic and abiotic components.

Classification System

• There are different taxonomic ranks, ranging from broadest to narrowest categories: Domain -> Kingdom -> Phylum -> Class -> Order -> Family -> Genus -> Species.
• Latin binomial nomenclature (Genus species) is used to uniquely name each species.
• Modern classification systems are based on evolutionary relationships, using phylogenetic schemes.
• Dichotomous keys are tools used for identifying organisms based on their observable characteristics.

Explore the fundamental characteristics that define living organisms, including their complex organization, cellular composition, ability to reproduce, and maintenance of homeostasis. This quiz also delves into how organisms respond to stimuli, obtain energy, grow, develop, and adapt over time. Test your understanding of what distinguishes life on Earth!