Characteristics and Classification of Living Things

“Characteristics of Living Things

• Movement: An action that changes position.

• Respiration: Chemical reactions releasing energy from nutrient molecules.

• Sensitivity: Detecting and responding to environmental changes.

• Growth: Permanent increase in size and dry mass.

• Reproduction: Producing more organisms of the same kind.

• Excretion: Removal of toxic waste.

• Nutrition: Feeding on or making food.

Classification of Living Things

• Sorting organisms by common features for identification, grouping, and naming.

• Based on similarities in:

  • Physiology (body parts)

  • Morphology (structural features)

  • Ecology

  • Genetics (DNA + RNA)

• Classification hierarchy:

  • Domain

  • Kingdom

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species

• Mnemonic: Katy Perry Came Over For Good Songs

Kingdoms

• Animal

• Plant

• Bacteria

• Fungus

• Protista (Algae and Protozoa)

Cells

• The smallest unit of life performing essential processes.

• Made of organelles.

• Characteristics vary by kingdom.

• Combine to form different body parts (e.g., heart muscle cell forming heart tissue).

Common Features in All Cells

• Cell membrane: Controls entry and exit of substances.

• Cytoplasm: Contains organelles.

• Genetic material (RNA/DNA): Contains organism information.

• Ribosomes: Make proteins.

Examples of Typical Cells

• Animal cell: Contains centrioles, cell membrane, vacuole, ribosomes, endoplasmic reticulum, mitochondrion, nucleus, nucleolus, chromosomes.

• Plant cell: Contains vacuole, chloroplast, ribosomes, cell wall, plasma membrane, plasmodesma.

• Bacteria cell (bacillus type): Contains cytoplasm, cell wall, chromosome, ribosomes, 11cell wall, plasma membrane, pili, capsule, mesosome, flagella.

Bi-Nominal Nomenclature

• Scientific naming in Latin to avoid confusion and show neutrality.

• Format:

  • Genus (capitalized) + species (not capitalized)

  • Italicized when written

  • Example: Cannis lupus (dog)

Examples

• Tiger: Panthera tigris

• Lion: Panthera leo

Closeness of Living Things

• Scientific names indicate relatedness.

• Organisms in the same genus are closely related and likely share a common ancestor.

Domains

• Broadest classification.

Eukaryotes

• Cells with a nucleus.

Prokaryotes

• Cells without a nucleus.

Prokaryotic Cell

• Contains nucleoid, cytoplasm, cell wall, plasma membrane, flagella.

Eukaryotic Cell

• Contains nucleus, cytoskeleton, plasma membrane, nucleolus, endoplasmic reticulum, Golgi apparatus, vesicle.

Kingdom Bacteria

• Single-celled microorganisms found everywhere.

• Prokaryotic.

Structure

• Cell Wall: Made of peptidoglycan (glycogen and sugars).

• Cell Membrane: Protects from bursting and provides shape.

• Cytoplasm: Contains chromosomes and stores materials.

• Nucleic acid: Single DNA strand (no nucleus).

• Flagellum: For movement (not always present).

• Ribosomes: For protein synthesis.

Kingdom Protista (Eukaryote)

• Simple eukaryotic organisms.

• Mostly unicellular, some multicellular (algae).

• Have membrane-bound nucleus and endomembrane systems.

• Mitochondria for respiration, chloroplasts for photosynthesis (algae).

Characteristics

• Movement: Flagella or cilia.

• Respiration: Primarily aerobic, some anaerobic.

• Nutrition: Heterotrophic (eats other organisms) or autotrophic (makes own food).

Protist Cells

• Algae (plant-like): Autotrophic, contains chloroplast, nucleus, nucleolus, flagellum, photoreceptor, contractile vacuole, polysaccharides.

• Protozoa (animal-like): Heterotrophic, contains nucleus, food particle, flagellum, cytoplasm, pellicle, mitochondrion, endoplasmic reticulum.

Kingdom Fungi

• Multicellular (except yeast).

• Made of hyphae (microscopic threads).

Types of Hyphae

• Reproductive hyphae: Form spores for reproduction.

• Feeding hyphae: Form mycelium network.

• Mainly decomposers.

• Cell walls made of chitin.

Hyphae

• Tube-like, contains cytoplasm, glycogen granules, and nuclei.

• Lacks chloroplasts and starch granules.

• Surrounded by a chitin wall.

• Mycelium: Branching network of hyphae.

How Fungi Eat

• Hyphae secrete enzymes to digest organic matter, then absorb the nutrients.

Kingdom Animalia

• Multicellular.

• Heterotrophic (consume food).

• Typically reproduce sexually.

• Cells lack cell walls.

• Capable of motion.

• Respond to external stimuli (nerve cells, muscle tissue).

Animal Cell

• Contains nucleus, DNA, mitochondrion, Golgi complex, endoplasmic reticulum, lysosome, cytoplasm, ribosome, vacuole, peroxisome, cell membrane, centriole.

Animal Phylum

• Vertebrate (backbone)

• Invertebrates (no backbone)

Classes of Vertebrates

• Fish

• Amphibia

• Reptiles

• Birds

• Mammals

Characteristics Table:

Warm Blooded Animals

• Maintain constant body temperature by generating or releasing heat.

• Convert food into energy to generate heat.

Cold Blooded Animals

• Body temperature matches the environment.

• Activity levels depend on environmental temperature.

Arthropods (Invertebrates)

• Exoskeleton, segmented bodies, bilateral symmetry, and jointed legs.

• Includes Crustaceans, Arachnids, Myriapods, and Insects (C.A.M.I).

Features of Arthropods

Kingdom Plantae

• Multicellular organisms.

• Photosynthesis: Making sugars from water and carbon dioxide using sunlight.

• Contain chlorophyll (green pigment).

• Autotrophic (make own food).

• Plant cells contain a large vacuol 1e, a nucleus, chloroplasts, and a cellulose cell wall.

Plant Cell

• Contains endoplasmic reticulum, nucleus, Golgi apparatus, mitochondrion, cytosol, chloroplast, cell wall, cell membrane, tonoplast, vacuole, cell sap.

Kingdom Characteristics Table

The Virus

• Not classified into a kingdom because it is not considered a living organism as they cannot reproduce on their own.

• Very small (measured in nanometers).

• Visible only with an electron microscope.

• Has a protein coat and genetic material (RNA or DNA).

Why Viruses Are Not Considered Living

• Lack most of the seven characteristics of life, except reproduction (inside a host cell).

• Have DNA and a protein coat instead of a cell wall/membrane.

Virus Structure

• Contains nuclear envelope, protein coat/capsid, DNA/RNA

Cladistics

• Modern evolutionists compare nitrogenous bases within organisms to determine evolutionary relationships.

• Represented by a cladogram.

• Distance indicates DNA difference (less distance = closer relationship).

Example: Evolution of Modern Elephants

• Timeline: Eocene (~56-34 mya), Oligocene (~34-23 mya), Miocene (~23-5.3 mya), Pliocene (~5.3-2.6 mya), Pleistocene (2.6 million-11,700 years ago), Holocene (11,700 years ago to present).

• Species: Gomphotherium, woolly mammoth (Mammuthus primigenius), Asian elephant (Elephas maximus), African savanna elephant (Loxodonta africana), American mastodon (Mammut americanum), African forest elephant (Loxodonta cyclotis).