Category Archives: Science Careers

E.O. Wilson’s Letter to Young Scientists [TED Talk]

This is a great motivational address to young scientists the world over. Living legend EO Wilson gives his words of advice to the problem-solvers of tomorrow: you guys.

“The thirst for knowledge is in our genes; it was put there by our distant ancestors and it’s never going to be quenched.” 

EO Wilson

Stephen Fry and the Great American Oil Spill

“This turtle gonna go to rehab, to make its flippers go, go, go…*”

In a recent BBC documentary, Stephen Fry and Mark Carwardine head to the USA to see the damage and recovery from the Deepwater Horizon oilspill:

“Stephen Fry loves Louisiana. Four months after the BP oil spill, dubbed the worst ecological disaster in the history of America, Fry returns to the Deep South together with zoologist Mark Carwardine, to see what the impact has been on the people, the vast wetlands and the species that live there. What they find both surprises and divides the travelling duo.”

From the BBC Website (you might get it in your area)

Two more BBC YouTube clips: Has the oil really gone? and Damage to the deep-sea ecosystem.

 

BBC Special Report: Oil Spill

The BBC has a good set of resources on the BP Oil Spill, as do the Geographical Association and PBS News Hour Extra. More resources can be found at NewsroomAmerica and Associated Content.

The Deepwater Horizon spill would make a great foundation for an interdisciplinary science unit or Group 4 project, looking at ocean chemistry, waves and dispersal, remote sensing technologies, geological resources, ecology, marine biology and food chains, economics, politics, ethics and much more.

*Amy Winehouse, if you didn’t get it.

Read the rest of this entry

NOAA Environmental Visualisation Library

Education Resources, Animations, Videos and Satellite Images

Education Resources, Animations, Videos and Satellite Images

Awesome. NOAA (National Oceanographic and Atmospheric Administration) has revamped its Environmental visualisation libray – bringing new educational materials, visualisations, animations and resources to educators and the public. See the images of the 2008 hurricane season, animations of the ocean damage caused by humans or check out their library of satellite images.

They also have a YouTube channel where you can view and download some of their video resources. In relation to our upcoming Earth Day theme of “Reefs and Oceans“, here’s a clip about the effects of coral bleaching:

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Check out the NOAA image galleries too...

Check out the NOAA image galleries too...

Parthenogenesis – Virgin Births in Nature

Happy (belated) Christmas!

How do you really reproduce without sexual reproduction? Asexual reproduction, of course.  Simple, really… but not for the females of some species.

There are loads of links in this post, so click on them to learn more.

Parthenogenesis

Parthenogenesis

Some plants, insects, shark and lizard species are known to reproduce by parthenogenesis – embryo development is carried out without fertilisation by a male -so called  ‘virgin creations.’

Parthenogenesis can take a range of pathways :

  • Chromosomes in the egg can self-replicate, making up the diploid number and the embryo develops from there.

Other methods include suppression of male genotypes (technically still sexual reproduction?), or eggs cells dividing by meiosis.

The resulting offspring are going to be all the same gender. In some species, the XY system determines gender and parthenogenesis produces all females. In other, the ZW system dictates that they will all be male.

Parthenogenesis is a reproductive strategy that sacrifices the genetic variation (a driving force of evolution) of sexual reproduction for the simple ability to reproduce. Small invertebrates, such as aphids, can use it to produce large numbers of females very quickly.

Komodo Dragons

Komodo Dragons

Larger organisms, such as Komodo dragons (Indonesia link!), have been known to use parthenogenesis in the absence of males, producing an all-male clutch of eggs. It is thought that this might allow them to set up new populations on isolated islands, using just a single female. Here’s a quick video of a Komodo dragon parthenogen hatching:

Some interesting Komodo readers here from Richard Dawkins and Not Exactly Rocket Science.

Parthenogenesis in sharks

Parthenogenesis in sharks

Parthenogenesis has also been observed in captive sharks – the female had no access to males, yet gave birth to live young (though only one, where the normal litter would be larger). Genetic tests confirmed parthenogenesis, rather than the alternative hypothesis of superfecundation (storing sperm for a long period of time). Read the full paper here, and another on hammerheads here. BBC audio explanation here.

So can it work in us?

Let’s let House MD explain:

In short, no. Not naturally.

Generally, we use mitosis to replace and repair damaged cells and tissues and for growth and development – filling in the gaps with copied cells. Along the way, our cells differentiate to their function and we end up with a body full of specialised cells – each cell’s structure and biochemistry reflect its function.

We don’t use mitosis for reproduction, as it narrows genetic variation – one of the driving forces of evolution. Instead, when sperm and eggs are produced, meiosis is used – producing daughter cells with half a set of chromosomes. During meiosis, crossing over occurs, giving some recombinants – or ‘mixed up’ chromosomes – leading to some varation. The greatest variation comes from the process of sexual reproduction itself – the gametes – sperm and egg – meet in fertilisation, combining their chromosomes to  make a new blastocyst, which becomes an embryo, then a fetus and out pops a baby.

All the offspring of organisms that reproduce sexually carry two copies of each chromosome – one from each parent –  and each chromosome carries different alleles – ‘versions’ of each gene. This leads to a great deal of variation and this genetic diversity keeps the the population going.

What about uses in technology?

Funny you should ask that…

Induced parthenogenesis is being pursued as a method for obtaining embryonic stem cells. Read this New Scientist article to learn more.

The disgraced Korean scientist Hwang Woo-Suk, who shot to infamy after faking stem cell results, was actually and inadvertently pivotal in the use of parthenogenesis as a method to produce human embryonic stem cell lines:

Normally these parthenogenic embryos die after a few days, yet researchers are able to harvest them for stem cells for research. Ethically, these are considered engineered eggs, rather than human embryos. How do you feel about that?

Questions to think about:

1. How does parthenogenesis differ from binary fission in bacteria, or vegetative reproduction in some plants?

2. How do the XY and ZW gender systems work?

3. How does sexual reproduction lead to genetic variation?

4. What are the costs of parthenogenesis in terms of evolution or resistance to disease?

5. How would the genetic fingerprint of a parthenogen differ from its parent?

6. How would researchers use genetic fingerprinting to determine whether the offspring were parthenogens or were the product of sexual reproduction?

7. What are the ethical considerations of using parthenogenic human ambryonic stem cells?

References:

Chapman et al. Parthenogenesis in a large-bodied requiem shark, the blacktip <i>Carcharhinus limbatus</i>. Journal of Fish Biology, 2008; 73 (6): 1473 DOI: 10.1111/j.1095-8649.2008.02018.x

Chapman et al. Virgin birth in a hammerhead sharkBiol Lett. 2007 August 22; 3(4): 425–427. Published online 2007 May 22. doi: 10.1098/rsbl.2007.0189.


Microdocs: Stanford’s reef sustainability documentaries

Stanford’s Microdocs project is a well-presented set of video and pdf resources for learning about sustainability and the coral reef ecosystem. Each video is a few minutes long and accompanied by a short article or links to useful sources.

It’s divided into useful topics and easy to navigate (and looks good, too).

And while we’re on the theme of the oceans (again) there’s a brilliant student activity resource centre at the UCLA’s OceanGlobe centre. Everything you could ever need to study marine science.

HHMI Biointeractive: teach ahead of the textbook

The Howard Hughes Medical Institute has produced some great, interactive resources for medicine and genetics, including a virtual ELISA test and a transgenic fly virtual lab. Go and have a look – there’re also plenty of animations, though even Flashcatcher can’t save them.

Download a worksheet for the ELISA here.

For a simple mock HIV test (using potassium iodide, lead nitrate and a bit of imaginitive labeling), visit the IB Biology Lab Bank 

Real-Life CSI: Autopsy

Interesting short clip about the job of a medical examiner.

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