Acetabularia in the news links DP Biology topics
Monday 31 October 2022
It's always good when Biology makes the news but it's rare that the news matches the DP Biology curriculum so closely as it did today in this article from The Guardian. I've recently been thinking of how best to make links between topics and while broad overlying themes and concepts like, "Form and function" can be used to form links, I realise now that so can current affairs.
The article, written by Helen Scales who is a marine biologist, touches on several biological concepts from the DP Biology course as well as highlighting this fascinating exception to Cell Theory, Acetabularia made up of one giant cell.
Lets hop through the article in a few quotes.
Binomial nomeclature from 5.3 Evolution:
When species are discovered they are given scientific names using the binomial system. |
Prof Felix Bast from the Central University of Punjab, with four others, published a paper naming them Acetabularia jalakanyakae. (Bast et al, 2021) He was inspired by Hans Christian Andersen’s classic tale, The Little Mermaid, to give this new species a mythical twist. “I first thought to name it syreni, which is Latin for mermaid,” says Bast. “Then I changed my mind. Why go with Latin? This is from India, and I am Indian.” So he landed instead on the Sanskrit word for mermaid, jalakanyakae.
Cladistics from 5.4 Evolution:
Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein. |
At first glance, the algae looked like a common species, Acetabularia acetabulum. However, Bast realised the shape of the circular caps wasn’t quite right. He took some back to his lab in a Ziploc bag, and with DNA sequencing showed this is indeed a distinct species, the fifth Acetabularia from India.
mRNA from 2.7 DNA replication
The amino acid sequence of polypeptides is determined by mRNA according to the genetic code. |
“If you chop off one cap, it can regrow,” says Bast. In the root, there’s a single, giant nucleus, housing the algae’s DNA. In the 1930s, the German scientist Joachim Hämmerling conducted groundbreaking experiments with Acetabularia and showed for the first time that a cell’s nucleus controls how an organism grows. He cut off the root of one Acetabularia species, grafted it to the stem of another, and the cap grew back in the shape of the root species. Instructions for growth were evidently coming from the root. Thanks to Acetabularia, Hämmerling anticipated – by several decades – the discovery of messenger RNA
Sexual life cycle from 3.3 Meiosis
The halving of the chromosome number allows a sexual life cycle with fusion of gametes. |
Individual mermaid’s wineglass alga are either male or female. To reproduce, the giant nucleus splits into multiple copies which drift up the stem to the cap and burst into the sea as tiny gametes. The gametes are mobile
Sensitivity from 1.1 Introduction to cells
Organisms consisting of only one cell carry out all functions of life in that cell. |
The gametes are mobile and they have light-sensitive eyespots. “Just like a human eye,” says Bast. They swim towards the light and the sea surface where they’re more likely to encounter a gamete of the opposite sex.
Hydrogen carbonate ions from 4.3 Carbon Cycling
In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions. |
Finally, Acidification of oceans in 4.4 Climate change
Threats to coral reefs from increasing concentrations of dissolved carbon dioxide. |
The ocean is absorbing more anthropogenic carbon from the atmosphere and consequently becoming more acidic, which puts species like the mermaid’s wineglass algae at risk. As Bast explains, more than half of the dry weight of this algae is calcium carbonate, which melts in acidified seawater.
“Any organism, be it animal or a plant, with calcium carbonate is highly prone to ocean acidification,” says Bast. “So, that will be having a tremendous impact on species like Acetabularia because the calcium carbonate will simply dissolve into the acid.”
I might use this article in the beginning of a revision session next term, I'll get students to match the syllabus points to the article, in the hope that they will realise for themselves some of the connections between the topics, but also simply because it will make revising more interesting.