Characteristics and Classification of Living Organisms.

• Living organisms possess all of these characteristics, distinguishing them from non-living things:

  • Nutrition
  • Respiration
  • Movement
  • Excretion
  • Growth
  • Reproduction
  • Sensitivity
• Classification of living organisms:

  • Hierarchical classification system groups organisms from kingdom to species based on structural similarities
  • Kingdom is the largest group, species is the smallest
  • Features become more specific as you move down the classification hierarchy
  • Species defined as organisms with similar features capable of breeding and producing fertile offspring
• Living things are called organisms
• Classification hierarchy helps scientists in various ways:

  • Sort organisms in order
  • Identify new organisms by finding out which group they fit
  • Easier to study organisms when they are sorted in groups
• Hierarchy of classification system:

  • Kingdom (largest group): prokaryotes, protoctista, fungi, plants, animals
  • Each kingdom is divided into phyla based on shared features
  • Phylum contains organisms without a backbone but with jointed legs and a hard body covering
  • Phylum further subdivided into classes, orders, families, genera, species
  • Various groups in classification are called taxa (singular: taxon)
• Homologous structures:

  • Features of organisms similar in structure but may look different and used for different purposes
  • Example: horse's front leg, human arm, bat's wing
  • Share same number and arrangement of bones, probably evolved from a common ancestor
  • Fly's wing and bat's wing are analogous, not homologous
• Evolutionary relationships in natural classification system:

  • Biologists group structurally similar organisms that share common ancestors
  • Produces branching set of relationships
  • Plants divided into subgroups like mosses, ferns, conifers, flowering plants
  • Subgroups can be further divided based on similarities
• Artificial classification:

  • Can use any grouping
  • Basis for dichotomous keys used to identify organisms
• Binomial system of naming species by Carl Linnaeus:

  • Gives each species a scientific name in Latin
  • Two names in Latin (genus and species)
  • Genus name written first with a capital letter, species name written second with a small letter
  • Scientific names printed in italics when typed and underlined when handwritten
  • Example: Tiger - Panthera tigris
  • Scientific names are universal and understood by biologists worldwide
• Cell walls are found only in plants, fungi, algae, and some bacteria.
• Plant cells have a rigid cell wall that provides support to the plant body.
• The cell wall is made up of polysaccharides, such as cellulose.
• The cell wall provides support and protection to the cell.
• Animal cells do not have a cell wall but instead rely on their cytoskeleton for structure.
• Vacuoles store water, nutrients, waste products, pigments, and enzymes.
• In animals, there is no cell wall present as they do not require it due to their soft bodies.
• The cell wall is made up of cellulose fibres which give strength to the cell.
• Chloroplasts contain chlorophyll, which is necessary for photosynthesis.
• Bacteria also lack a cell wall, except for gram-positive bacteria which have peptidoglycan in their cell wall.
• Vacuoles store water, nutrients, and waste products.
• Some bacteria have a peptidoglycan layer called a cell wall, while others lack this structure.
• Chloroplasts contain chlorophyll, which is responsible for photosynthesis.
• Bacteria may or may not have a cell wall depending on the type of bacterium.
• Ribosomes synthesize proteins.
• Bacteria can be either gram-positive or gram-negative based on their cell wall composition.
• Mitochondria produce energy through aerobic respiration.
• Chloroplasts contain chlorophyll and are responsible for photosynthesis.
• Mitochondria produce energy through respiration.
• Mitochondria are responsible for producing energy through respiration.
• Plant cells are surrounded by a rigid cell wall that gives them shape and protects them from external stressors.