9.4 Reproduction in plants

Paradigm shift—more than 85% of the world’s 250,000 species of flowering plant depend on pollinators for reproduction. This knowledge has led to protecting entire ecosystems rather than individual species.

Albert Einstein is claimed to have said: “If the bee disappears from the surface of the earth, man would have no more than four years to live.” (Quote Investigator). While it appears he did not actually ever say this, it is a remarkably prescient observation about the role that pollinators play in continuing the survival of plants.

While wind, water and explosive propulsion do work for some flowering species, the majority rely on animal pollinators. The co-evolution of pollinators with the plants they pollinate means that, in many cases, species may be pollinated by only a select few animals.  Should the animals decline in population, so will the plants.

A recent example in New Zealand reminds us of this (Biello). The endemic flowering shrub Rhabdothamnus solandri, or New Zealand gloxinia, relies primarily on the bellbird (Anothornis melanura) and stitchbird (Notiomystis cincta) to pollinate its flowers.  These birds have long beaks and tongues to access the long, tubular flowers of the shrub.  However, the bellbird and stitchbird have recently become extinct on New Zealand’s North island. To investigate this impact on the flower, researchers conducted a study on three smaller offshore islands, where the birds were still present. The results were alarming – in the absence of the two birds on the North island, just 22% of of flowers produced fruit and had only 37 seeds per flower. This compares to the the islands that still have the birds, where they produced 232 seeds per flower and 58% produced fruit. In order to save this flower, we must also save the birds.

rhabdothamnus_solandri___taurepo__new_zealand_gloxinia-006

New Zealand Gloxinia – Rhabdothamnus solandri. 

 

A paradigm shift represents a radical change in thinking based on new evidence.  Understanding that protecting birds, for example, will also protect plants, is an important change in thinking from purely looking at the conservation of single species. Conservation methods that focus on ecosystems as a holistic unit reflect our increased understanding of the way animals and plants in particular are inter-related.

Sources:

Biello, David. “For Want Of A Pollinator, A Flower May Be Lost–Or A Forest”. Scientific American. N. p., 2016. Web. 13 Oct. 2016.

“If The Bee Disappeared Off The Face Of The Earth, Man Would Only Have Four Years Left To Live | Quote Investigator”. Quoteinvestigator.com. N. p., 2013. Web. 13 Oct. 2016.

“T.E.R:R.A.I.N – Taranaki Educational Resource: Research, Analysis And Information Network – Rhabdothamnus Solandri (Taurepo) “. Terrain.net.nz. N. p., 2016. Web. 14 Oct. 2016.

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5.4 Cladistics

Falsification of theories with one theory being superseded by another—plant families have been reclassified as a result of evidence from cladistics.

The use of DNA sequences to classify organisms has been an important breakthrough in classification. Previously, species were classified primarily on morphology (physical characteristics), which works some of the time but is less useful in other situations. Thus seemingly unrelated organisms have been grouped more closely together and those that were thought to be very closely related have been found to be more distant.  Carl Woese used gene sequencing to not only overturn the existing dogma of the 5-Kingdom system, but to also propose that Archaea are more closely related to humans (eukaryotes) than to other prokaryotic bacteria. This was a major paradigm shift  in microbiology and has since been recognised as “…one of the 20th century’s landmark achievements in biology…” by Dr. Nigel Goldenfeld (“Carl Woese | Carl R. Woese Institute For Genomic Biology”).

In another example, the Figwort family of flowering plants, underwent a dramatic recent reclassification.   The figworts were a large family classified under the family Scrophulariaceae and included the popular snapdragons and foxgloves. Using three genes found in the chloroplast, researchers were able to determine that there were significant differences in lineage and so an entire family had to be reclassified into six families. See Olmstead et al. (2001), full text available online, for the full scientific story.

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Cladogram representing changes to the classification of the snapdragons. Olmstead et al. (2001).

Sources:

n.a. ” Carl Woese | Carl R. Woese Institute For Genomic Biology”. Igb.illinois.edu. University of Illinois, 2016. Web. 25 Apr. 2016.

Essig, F. “Whatever Became of the Snapdragon Family?”. BotanyProfessor. Botanyprofessor.blogspot.  April 5, 2012. Web. April 25, 2016.

Olmstead, Richard G., Claude W. dePamphilis, Andrea D. Wolfe, Nelson D. Young, Wayne J. Elisons, and Patrick A. Reeves. Disintegration of the Scrophulariaceae.
Am. J. Bot. February 2001 88:348-361. Web. Accessed April 25, 2016.

8.2 Cell Respiration

Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics.

Paradigm shifts are something we see from time to time in biology but we also discuss them in TOK – they represent a way of looking at a problem from a completely new angle (van de Lagemaat).  In doing so, paradigm shifts can often be controversial and may take several years, or even decades, before they are accepted by the scientific community.

In 1961 Peter Mitchell proposed the chemiosmotic coupling theory to account for the production of ATP in oxidative phosphorylation. This theory went against the prevailing view that there were “energy-rich” chemical intermediates that explained the resulting ATP formation. As he writes in his landmark publication, from 1966,

“the study of the question of the coupling mechanism has continued to be ruled by the well-trodden and familiar tenets of the chemical coupling conception, no matter how fantastic the resulting tissue of hypothesis.” (Mitchell,1507)

Terms like “well-trodden” and “familiar” refer to the accepted theory that, despite results to the contrary, remains the only accepted explanation.  A paradigm shift must counter such ingrained views, which is why it can take time for the new explanation to become accepted.  Mitchell was awarded the Nobel Prize in Chemistry in 1978.  Part of his acceptance speech illustrates the challenges for the scientist trying to overturn entrenched theory:

 “…the originator of a theory may have a very lonely time, especially if his colleagues find his views of nature unfamiliar, and difficult to appreciate.” (“Peter Mitchell – Banquet Speech”)

There are many examples of paradigm shifts in biology – they make useful reference points for TOK discussion and analysis. Key terms to consider include bias, justification, subjective, objective and verification.

Sources

Mitchell, Peter. “Chemiosmotic coupling in oxidative and photosynthetic phosphorylation”.  Biochimica et Biophysica Acta (BBA) – Bioenergetics, Volume 1807, Issue 12, December 2011, Pages 1507-1538. Web. 19 April, 2016.

“Peter Mitchell – Banquet Speech”. Nobelprize.org. Nobel Media AB 2014. Web. 19 Apr 2016.

van de Lagemaat, R. Theory of Knowledge for the IB Diploma. Cambridge, Cambridge University Press. 2011. Print.