Biology Classification and Taxonomy

Classification and Taxonomy

• Classification is the grouping of organisms based on criteria that organize and indicate evolutionary relationships
• Hiarchical system, from most general to specific
• Taxonomy is the practice of classifying organisms

Binomial Nomenclature

• Genus species: two-part scientific name based on Latin or Greek
• Names often reflect characteristics of the organism or honor a scientist

Identifying a Species

• Morphological species concept: focuses on morphology (structure, body shape, size, other features)
• Biological species concept: based on whether species can produce fertile offspring
• Phylogenetic species concept: examines phylogeny (evolutionary history) of species

Taxonomic Categories

• Rank: level in the classification system (8 total)
• Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
• Species is the smallest and most specific rank
• Species can interbreed and produce fertile offspring

Phylogenetic Trees

• Used to show the evolutionary history of a species or group of organisms
• Most ancient species are at the bottom of the tree
• Two main cell types: prokaryote and eukaryote

Cell Types

• Prokaryotic cell (bacteria):
  • No true nucleus
  • DNA is a single, circular strand
  • No organelles larger than a ribosome
  • Cell wall is a target for antibiotics
• Eukaryotic cell (plant, animal, fungi, protists):
  • Membrane-bound nucleus
  • More complex internal structure
  • Can be 1000x larger in size

Dichotomous Key

• A system for narrowing down the identification of a species using two-part choices leading to the correct identification

Domains of Life

• Three domains: Archaea, Bacteria, and Eukarya

Archaea

• Prokaryotic cell in Archaea domain
• Found in extreme environments (extremophiles)
• Examples: halophiles, thermophiles, acidophiles, methanogens

Bacteria

• Kingdom: Eubacteria
• Characteristics:
  • Single-celled
  • Prokaryotes (no internal membranes, single chromosome)
  • Reproduce asexually by binary fission

Viruses

• Lytic cycle: quickly take over host cell, make many copies, break the cell, and infect other cells
• Lysogenic cycle: sneak into host's DNA, stay hidden, and wait
• Retroviruses: type of virus with RNA instead of DNA as genetic material

Plants

• Non-vascular plants (bryophytes):
  • Three phyla: mosses, liverworts, and hornworts
  • No vascular tissue
  • Depend on diffusion and osmosis for nutrient transport
• Seedless vascular plants:
  • Include whisk ferns, club mosses, horsetails, and ferns
• Gymnosperm: vascular plant with non-enclosed seeds
• Angiosperm: vascular plant with seeds enclosed in a protective environment

Fungi

• Characteristics:
  • Kingdom Fungi
  • Cell Organization: some are unicellular (yeast), most are multicellular
  • Energy: Heterotrophs (feed by releasing digestive enzymes into surroundings and absorbing nutrients)
  • Structural Features: made of hyphae, have cell walls made of chitin
• Reproduction:
  • Asexual: fragmentation (pieces of hyphae break off and form new mycelia)
  • Asexual: sporulation (windblown reproductive cells that help fungi disperse)
  • Sexual: not specified

Animal Kingdom

• All animals are Heterotrophs
• Characteristics not specified

Cell Division and Reasons

• Cell division occurs to form tissues, repair damage, facilitate individual growth, transfer information effectively, and prevent cells from becoming too large.
• Cell division involves creating new cells through mitosis, meiosis, or binary division.

Mitosis

• Mitosis is the division of the nucleus, where DNA is separated to make two copies.
• Cytokinesis is the division of the cytoplasm, resulting in two identical cells.

Structures in Mitosis

• Centrioles (centrosomes) are small proteins found in the cytoplasm that form spindle fibers.
• Spindle fibers are protein chains that guide chromosomes during cell division.

Stages of Mitosis

• Interphase: the longest time interval in a cell, where cells grow, make proteins, transport nutrients, and replicate DNA to prepare for mitosis.
• Prophase: chromosomes shorten and thicken, centromeres develop, and the nuclear membrane dissolves.
• Metaphase: chromosomes move to the center of the cell, and spindle fibers attach to centromeres.
• Anaphase: chromosomes move to opposite poles, and centromeres divide.
• Telophase: chromosomes reach opposite poles, the cell lengthens, and the spindle fibers dissolve, and the nuclear membrane forms.
• Cytokinesis: the cytoplasm divides equally in two, and the cell cleaves (in animals) or develops a cell plate (in plants).

Key Concepts of Mitosis

• Mitosis is required for transporting nutrients, cell repair, tissue and organism growth.
• Mitosis occurs in somatic cells.
• Cell division is the combination of mitosis and cytokinesis.
• IPMAT (Interphase, Prophase, Metaphase, Anaphase, Telophase)
• Parent chromosome number is equal to daughter chromosome number.
• All cells are diploid (parent and daughter), and new cells are exactly the same as the original.

Genetics

• Genetics is the study of how genetic information is passed from one generation to the next.
• The cell cycle occurs in somatic cells (body cells).
• Interphase is the stage of growth and intense cell activity (G1) and preparation for division (S and G2).

DNA Structure

• DNA stands for Deoxyribonucleic Acid.
• DNA is the means by which hereditary information is passed on from generation to generation.
• The sequence of DNA determines the composition of proteins made by the cell.
• DNA is composed of sugar, phosphate, and nitrogenous bases.
• Nitrogenous bases pair up as Adenine + Thymine and Guanine + Cytosine.

DNA Replication

• When DNA splits to replicate, DNA polymerase creates a match for the other half strand of DNA to create two complete DNA daughter strands.

Chromosomes and Genes

• Homologous chromosomes are chromosomes that contain the same sequence of genes as another chromosome.
• Genes are parts of a chromosome that govern the expression of a trait and are passed onto offspring.
• Alleles are different forms of the same gene.

Meiosis

• Meiosis occurs in two divisions and produces sex cells as the final product (gametes).
• Meiosis provides genetic diversity in sexual organisms.

Stages of Meiosis

• Prophase 1: chromosomes condense, homologous chromosomes pair up to form tetrads (synapsis), and crossing over occurs, resulting in genetic diversity.
• Metaphase 1: homologous chromosomes line up along the equatorial plate.
• Anaphase 1: spindle fibers pull apart each homologous pair, and chromosomes move to the end of the cell (pole).
• Telophase 1: nuclear membrane reforms, and each cell is now haploid.
• Prophase 2: spindle fibers form and attach to centromeres.
• Metaphase 2: chromosomes line up along the equatorial plate.
• Anaphase 2: spindle fibers pull apart the sister chromatids, separating them from each other.
• Telophase 2: nuclear membrane forms around genetic material, and each haploid daughter cell now contains different combinations of chromosomes.

Fertilization

• Fertilization occurs when 23 chromosomes from the mother are matched by 23 chromosomes from the father to produce homologous chromosomes, resulting in a zygote.

Abnormal Meiosis

• Abnormal meiosis can result in errors in chromosome structure or chromosome number.
• Two types of errors can occur: independent assortment and crossing over.