Georgia Milestones Biology EOC, Classification and Phylogeny (SB4): a complete overview of the cell cycle, interacting body systems, classification, cladograms, and viruses

What the Classification and Phylogeny domain demands

Classification and Phylogeny (SB4) is about how life is organized and grouped: how the systems of a body work together, how organisms are sorted into a classification scheme, how branching diagrams show their relationships, and where viruses sit. It is the smallest domain at about 13 percent of the Georgia Milestones Biology EOC, but it links cells, body systems, and evolution. This library also places the cell cycle and mitosis here, as the cellular-reproduction element of SB1.b.

This guide ties together the matching topic pages, each with its own practice questions: the cell cycle and mitosis, interacting body systems and homeostasis, classification and taxonomy, cladograms and phylogeny, and viruses and the criteria for life.

The cell cycle and mitosis

The cell cycle is mostly interphase (growth, and DNA copying in the S phase), then mitosis and cytokinesis. Mitosis divides the nucleus in four phases, PMAT (prophase, metaphase, anaphase, telophase), producing two genetically identical cells with the full chromosome number, for growth, repair, and asexual reproduction. Prokaryotes divide by the simpler binary fission. The cycle is regulated at checkpoints; a mutation that disables them causes uncontrolled division, a tumor, and possibly cancer.

Interacting body systems

Multicellular bodies are organized in levels: cell, tissue, organ, organ system, organism. The organ systems interact, for example the respiratory system takes in oxygen and the circulatory system transports it to cells. The body holds a stable internal environment, homeostasis, mainly through negative feedback, where a response opposes a change to return a variable to its set point (sweating cools, shivering warms, insulin lowers blood sugar). Recognizing the feedback loop (stimulus, sensor, response, return to set point) is the key skill.

Classification and taxonomy

Life is sorted into a nested hierarchy. The broadest groups are the three domains, Bacteria, Archaea (both prokaryotes), and Eukarya (all eukaryotes). The taxonomic levels from broadest to most specific are domain, kingdom, phylum, class, order, family, genus, species, with lower levels sharing more characteristics. Every species has a two-part scientific name: the genus (capitalized) then the species (lowercase), italicized, like Canis lupus. Modern grouping reflects common ancestry, which connects to phylogeny.

Cladograms and phylogeny

A cladogram (phylogenetic tree) is a branching diagram showing evolutionary relationships. Each branch point (node) is a common ancestor; organisms are grouped by shared derived characteristics (a backbone groups vertebrates). The key reading rule: organisms that share a more recent common ancestor (a closer branch point) are more closely related. The trees are built from evidence including comparative anatomy, embryology, and DNA and protein similarity, tying SB4 to the evidence for evolution in SB6.

Viruses

A virus is genetic material (DNA or RNA) in a protein coat, not made of cells, with no metabolism of its own. It can only reproduce by infecting a host cell and using its machinery. Against the characteristics of living things (cellular, metabolism, growth, response, reproduction, homeostasis), a virus fails the key ones, so it is generally classified as nonliving, though it contains genetic material and can evolve. This is an "evaluate" standard: name the criteria, show which a virus meets and fails, then conclude.

Check your knowledge

A mix of recall and reasoning questions covering the Classification and Phylogeny domain. Attempt them under timed conditions, then check against the solutions.

1. List the four phases of mitosis in order. (2 marks)
2. State the main purpose of mitosis. (1 mark)
3. Explain how a mutation can lead to cancer. (2 marks)
4. List the levels of organization from cell to organism. (2 marks)
5. A person sweats to cool down when too hot. Name the type of feedback. (1 mark)
6. List the taxonomic levels from broadest to most specific. (2 marks)
7. In the name Canis lupus, state the genus and the species. (2 marks)
8. State what a branch point (node) on a cladogram represents. (1 mark)
9. State the two main parts of a virus. (2 marks)
10. State one reason a virus is generally not considered alive. (1 mark)