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.