5.5b Cladistics

20/05/2013 § Leave a comment

I can honestly say that I have never seen the word “cladistics” in this section of the textbook. This last blog (of the unit, of the semester, and of the year!) roughly outlines animal classification. Although there are similarities between plants and animals, they’re still different kingdoms with very different characteristics. Embryonic development is different between animals and plants, which is generally what separates them into different kingdoms.

While plants can be classified into just four different phyla, there are more than 30 phyla in the kingdom animalia. Some examples of animal phyla are: porifera, platyhelminths, mollusca (mollusks?!), cnidaria, annelida, and arthropoda (oh God, like insects, spiders, crabs and millipedes, ugh).

And to quickly discuss the classification of humans, on the hierarchy of taxa, we’d be in the order of Primates and the family Hominidae. This means that our closest relatives include the Gorilla gorilla (the gorilla, obviously), the Pan troglodytes (chimps!), and Pan paniscus (the bonobo, a very close relative of the chimp). I’m not sure how other people feel about this but it’s quite controversial as this classification suggests that humans, chimps and gorillas evolved from a common ancestor.


Looks like that’s it.

An entire year’s worth of blogging. I’ll be back in a few months for more biology. IT’S TEST-TAKING, LAB-WRITING, QUESTION-ASKING TIME.







Essay Questions

  1. Outline what is meant by the trophic level of an organism with three examples from one named habitat. (4 max)
  2. Compare the ways in which autotrophic, heterotrophic and saprotrophic organisms obtain energy. (6 max)
  3. Draw a labelled sigmoid population growth curve. 4 marks
  4. Explain the factors that cause a population to follow the sigmoid ( S-shaped) growth curve. (8 max)
  5. Apply the concept of carrying capacity to the struggle for survival resulting from overproduction of offspring. (5 max)
  6. Outline the international system used for naming species of living organisms. (4 max)
  7. Discuss the definition of the term species. (8 max)
  8. Name the levels and the specific taxa in the hierachy of classification using humans as an example. (2 max)
  9. Describe the relationship between the rise in the concentration of atmospheric carbon dioxide and the enhanced greenhouse effect. 5 marks
  10. Outline the consequences of a global temperature rise on arctic ecosystems. 6 marks
  11. Outline the precautionary principle. 5 marks
  12. Outline the structural differences which characterize bryophytes, filicinophytes, coniferophytes and angiospermophytes. 9 marks
  13. List the structural differences between bryophytes and angiospermophytes. 5 marks
  14. Briefly explain Darwin`s theory of evolution. 4 marks
  15. Outline five types of evidence which support the theory of evolution by natural selection. 6 marks
  16. Outline one modern example of observed evolution by natural selection. 2 marks
  17. Explain the evidence from homologous anatomical structures that supports the theory of evolution. 6 marks
  18. Outline how antibiotic resistance in bacteria can arise in response to environmental change. 5 marks
  19. Antibiotic resistance in bacteria is an example of evolution in response to environmental change. Using another example, explain how an environmental change can lead to evolution. 8 marks


Chapter 18 Questions

1. Identify the phylum to which each of the plants shown in Figure 10 belongs, giving reasons for your answer.

  • a – filicinophyte
  • b – angiospermophyte
  • c – filicinophyte
  • d – angiospermophyte
  • e – coniferophyte
  • f – angiospermophyte
  • g – bryophyte
  • h – filicinophyte

2. Quiz alert, quiz alert, this was on a quiz, adsfhalsdkfhalkf.

  • a) State one species that is in a genus with no other species. —> species 1 or species 34
  • b) State the species that are in a family with two genera. —> species 24 – 33
  • c) State the species that are in an order with two families. —> species 1 – 23
  • d) State the species that are in a class with three orders. —> species 1 – 34
  • e) Deduce whether species 8 is more closely related to species 16 or species 6. —> species 8 is more closely related to species 16; though all are in the same order, species 8 and 16 are in the same family and genus, species 6 is in a different family and genus
  • f) Explain why three concentric circles have been drawn around species 34 on the diagram. —> Species three is in the same class but in a different order. All these species are in the same class, phyla, and kingdom, but from the order classification downwards, species 34 is different from the other 33 species.


  • a) Distinguish between Porifera and Mollusca using external recognition figures. —> While a porifera has no mouth or anus, mollusca has both. Mollusca has bilateral symmetry while porifera has no symmetry. Mollusca’s skeleton has a shell made of CaCO3 (whatever) and porifera has skeletal needles, or internal spicules. Porifera has many pores all over its surface used to draw in water for filter feeding, while mollusca does not. Mollusca has a fold in its body wall called the mantle, which secretes the shell, and porifera does not have this. Mollusca feeds with a hard rasping radula.
  • b) Compare the external recognition features of Annelida and Arthropoda. —> Both annelida and arthropoda have a mouth and anus, and both have bilateral symmetry. Annelida’s skeleton consists of an internal cavity with fluid under pressure while Arthropoda has an external skeleton made of plates of chitin. Annelida’s bodies are made of many ring-shaped portions, with bristles (oh, ew), and we can see the blood vessels (whyyyyy). Conversely, arthropoda has segmented bodies and legs with joints in between sections.
  • c) Compare the external recognition features of Cnidaria and Platyhelminths. —> Both cnidaria and platyhelminths have mouths, but platyhelminths only have mouths (cnidaria can have anuses?). The symmetry of cnidaria is radial and the symmetry of platyhelminths is bilateral. Cnidaria’s skeleton is soft but has hard corals that secret CaCO3, like mollusca. The skeleton of platyhelminths is soft with no skeleton, actually. Cnidaria have tentacles arranged in rings around the mouth with stinging cells – think of jellyfish! Platyhelminths have flat and thin bodies in the shape of a ribbon. They have no blood system or gas exchange system.


  • a) State the group that humans are placed in at each of the seven levels in the hierarchy of taxa. —> Kingdom: Animalia, Phyla: Mammalia, Class: Chordata, Order: Primates, Family: Hominidae, Genus: Homo, Species: Sapiens
  • b) Outline the binomial system that is used for naming living organisms. —> There are always two names: the first is the only name capitalized and is the genus. The second is left in lower case and is the species. Example – Homo sapiens. Italics are always used for the binomial system of nomenclature on digital print but on actual print or handwritten, the names are underlined.
  • c) Explain how keys are designed to allow organisms to be identified. —> Keys consist of a series of numbered stages, each of which present a pair (only two!) of characteristics. Some of the choices will lead to another pair of alternatives, but some choices can be the final determination for the identity of the organism. 

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