Biology: Taxonomy and Classification Overview

Classification of Life's Diversity

• Species are groups of organisms that interbreed, producing fertile and viable offspring.
• Interbreeding means two organisms of the same type mate and produce offspring.
• Fertile offspring can also breed.
• Viable offspring are able to live and grow.
• Morphological classification measures similar characteristics of living things (simple and commonly used, especially for plants). It can be challenging to determine how much physical variation constitutes too much variation.
• Biological classification identifies similar characteristics to classify organisms in the same species. It can't be used to classify species that are physically separated or asexually reproducing, or for fossils.
• Phylogenetic classification focuses on the evolutionary relationships of living things. Analyzing DNA is useful to determine these relationships; this method can also be used for extinct species. Evolutionary history is mostly unknown.
• Binomial Nomenclature is a scientific two-name system (genus and species) for specifying organisms. Names are based on characteristics. The first name (genus) represents the group the organism belongs to, and the second name (species) represents the specific group of organisms.

Hierarchical Classification

• Taxonomy divides organisms into different levels of hierarchy based on similar characteristics or traits.
• The top level is Domains, followed by Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• The domain is the largest group of organisms.
• Levels can have subgroups for a more descriptive classification of organisms with many subgroups.
• Taxonomy classifies and names organisms.

Other Features of Classification of Life's Diversity

• Anatomy: The structure of organisms (internal structures).
• Physiology: How living organisms function.
• Proteins and Genes: Similarities in proteins and genes can be compared to relate organisms to others.
• Phylogenetic Tree: Shows how species are related.
  • Roots represent the oldest common ancestor.
  • Branches end at present-day species..
  • Forks are points where species split or evolved.
• Primitive and Derived Characteristics: Primitive characteristics are traits all species share from a common ancestor. Derived characteristics are new traits that appear as a species evolves.
• Time Scale and Relationship. More recently evolved species will be located closer together on the tree than species that diverged from one another a long time ago.
• Importance of Classification in Medicine: Studying related species can discover similar chemical compounds or proteins, which support disease control by understanding the spread of diseases, crop improvement that leads to high yields and disease resistance, and controlling pests via biological control.
• Species Protection and Prevention: Classification helps to protect newly identified species from poaching and harmful invasive species.

Seven Characteristics of Living Things

• Movement
• Respiration
• Sensation
• Growth
• Reproduction
• Excretion
• Nutrition

Prokaryotes and Eukaryotes

• Prokaryotes: Organisms without a nucleus.
  • Unicellular organisms.
  • Lack a nuclear membrane.
  • Small.
  • Simple internal structure.
• Eukaryotes: Organisms with a nucleus.
  • Can be single or multicellular organisms.
  • Have a nuclear membrane.
  • Larger than prokaryotes
  • Complex internal structure.
• Three Domains: Bacteria, Archaea, and Eukarya. Eukaryotes are grouped into the Eukarya domain. The Archaea and Bacteria domains are made up of prokaryotes. Bacteria and Archaea became separate domains due to major differences in their characteristics.

Dichotomous Keys

• Tools for identifying organisms using two-part statements of characteristics.
• 'Dichotomy' means divided into two parts.
• The user is led through a series of yes/no questions, until the species is identified when the path stops at a specific classification. 'Key' refers to the tool used for identification.

Types of Biodiversity

• Species Diversity: Variety of species in a given area.
• Genetic Diversity: Variety of inherited characteristics (genes) within a species, making individuals unique. Genetic diversity leads to greater resistance to diseases.
• Ecosystem Diversity: Variety of ecosystems and how different ecosystems interact. Biotic (living interactions) and Abiotic (non-living factors) elements contribute to ecosystem diversity.

Viruses and Prions

• Viruses: Non-living entities that cannot survive without hosts to replicate. Viruses rely on their host for reproduction.
• Viruses have a protein coat and nucleic acid (DNA or RNA). The effectiveness is dependent on this nucleic acid and protein coat abilities.
• Prions: Abnormal misfolded proteins that can cause diseases by influencing others to misfold.
• Can cause neurodegenerative diseases like encephalopathy.
• No DNA or RNA.
• Usually present, but misfolding changes shape and therefore function.

Viral Replication

• Lytic Cycle: a virus infects a host cell to replicate genetic material, making new virus particles, and eventually bursting and releasing new viruses.
• Lysogenic Cycle: the virus inserts its genetic material into the host's DNA, so as the cell divides the virus genetic material is replicated and carried in the new cells.

HIV

• HIV is a retrovirus that weakens the immune system by infecting certain cells, such as T4 helper T cells. Reverse transcriptase converts viral RNA to DNA. The viral DNA will insert into the host cell's DNA chain. This virus forms a provirus and will remain there until the cell divides and the virus is replicated, causing more damage to the host cell.

Bacteriophages

• Viruses specific for bacteria (bacteriophages) enter bacteria cells and can either destroy them (lytic cycle) or exist within cells' genetic material before destruction of the cell (lysogenic cycle).

Neurodegenerative Diseases

• Rare diseases where the illness is inactive in the body for a long time, and after the exposure to radiation, the disease does not get destroyed. Prions are hard to get rid of. These prions are abnormal misfolded proteins that cause diseases. Prion diseases can spread by getting contaminated tissue.

How Viruses Affect Plants and Humans

• Plants: Viruses affecting plants cause diseases and reduce crop yields/food shortages and cause crop diseases.
• Humans: Viruses affect human health via various diseases.

Biotechnology

• Gene Cloning: Insertion of genes into host cells for replication.
• Gene Therapy: Altered viruses deliver healthy genes to treat genetic disorders.

Comparing Bacteria and Archaea

• Both are prokaryotic (without cell nuclei), but their structures and functions differ.
• Bacteria cell walls contain peptidoglycan and archaea do not.
• Gram staining distinguishes bacteria based on cell wall thickness. Bacteria can be Gram-positive or Gram-negative.
• Bacteria Shapes include spheres (cocci), rods (bacilli), and spirals.
• Bacteria reproduce through binary fission, which is a rapid asexual reproduction where each cell splits into two identical cells.
• Bacteria and archaea both can reproduce, have genetic material exchange or conjugation, plasmids, endospores, and different morphologies, but in their specific form and features.

Endosymbiosis

• Eukaryotic cells evolved from prokaryotic cells through endosymbiosis, which is the process where one cell engulfs another cell and they form a mutually beneficial relationship.
• Mitochondria evolved from aerobic bacteria, and chloroplasts evolved from photosynthetic bacteria.
• These organelles have their own DNA and ribosomes.