Forever fungi

 Lycoperdon excipuliforme

Fungi are not autotrophs like plants. They do not make their own food.  No, fungi are heterotrophs, which means their food has to be digested and absorbed (like in animals, although, clearly, only in this respect!).  Fungi perform Extracellular digestion.  Their enzymes are secreted outside of their body. The enzymes digest the large and insoluble organic molecules (eg wood) into small and soluble ones like glucose.  This can be absorbed into the body and assimilated into more complex materials for growth such as proteins.  Hence fungi are found growing through their food source, eg a tree stump.

Phallus impudicus, the common Stinkhorn

Phallus impudicus was named by the father of taxonomy, Carl Linnaeus, himself.  The common Stinkhorn can be both seen and smelt in the woodland at this time of year.  It is said that Darwin's granddaughter, Etty Darwin, was so upset by them that she attacked them with a cudgel at dawn.

A ten minute walk in the woods on my way home from work yielded a great array of fungi.  I highly recommend getting out and about to observe the vast number of species of every shape, form and colour that pop up in the autumn.

Conkers bonkers

When I was a kid,  nothing could be more thrilling than finding conkers under a horse-chestnut tree in autumn.  The nut, up to 4 cm in diameter, is shiny and smooth, with a scar on one side.   The spiky fruit opens as if it has been scored with a knife, so straight is the cut,  and the conker tumbles out of the fruit, usually one but sometimes two or three.

The horse-chestnut tree is a huge beast.  Massive boughs, five to seven sprigged gigantic leaves, large white  towers of flowers with small pink dots on the petals, and of course, a big scent.  Wrongly called a chestnut, though might be poisonous to horses. The conker does contain toxic saponins.  However, whether there is any truth to the belief that they keep away spiders is not known.

Aesculus hippocastanum

Dissection Club; the Locust

We dissect all sorts at this club, and today it was the turn of the Locust, a fairly large representative of the class Insecta.

Insects are Arthropods with jointed legs, segmented bodies and an exoskeleton made of chitin.

They have three body regions; the head, thorax and abdomen.

The main reason for dissecting insects for A level Biologists is to observe the Gas Exchange system.  Locusts cannot get enough oxygen to their cells by diffusion alone.  (Only fairly small organisms with a relatively large surface area to volume ratio can get enough oxygen through their surface) . 

Insects have a simple tubular system  in which oxygen can enter the body through holes called Spiracles, and can move down a concentration gradient through tubules called tracheoles to the respiring tissues.

Compression of the body brought about by the movements of the legs can aid gas exchange.

Geo-caching challenge

At this time of year, the grey squirrel is incredibly busy, running up and down trees, running madly around woodland, risking life and limb crossing busy roads, all in a frenzy to collect as many nuts as possible as they rain from the skies.  Autumn is indeed bounteous on the nut front, and squirrels behave as if they are on Supermarket Sweep.
What to do with so much food?  Evidence of them eating as many as possible is everywhere, with half eaten nuts strewing the paths.

But they can also be seeing hiding them in caches.  Squirrels do not hibernate but they may sleep for long periods in the winter.  When they wake up, they will be hungry, and their well-developed spatial memory, as well as their excellent sense of smell, will lead them straight to breakfast.

Sexual Selection: how the female mind works

I spent a lovely afternoon at Gwydir Castle in North Wales last weekend.  Gracing the beautiful gardens were a number of peacocks and peahens.
Peacocks (the males) are well known for displaying their magnificent long tail feathers in a fan.  The brown feathers have shimmering tips of blue and green and a pattern that resembles an eye.  It is not difficult to see why a peahen would be impressed by that tail.

In evolutionary biology terms, the dimorphism of the peacock/peahen is because of a form of sexual selection.  Sexual selection is when the female gets to select her mate and the father of her offspring.  Obviously she will choose the one that is the most fit; big, strong, healthy, so that he can pass these genes on to her offspring and make them successful.

How does the elaborate peacock tail indicate his fitness as a father?  The theory is rather bizarre.  Peacocks are native to the rainforest, and to be honest a very long brightly coloured tail could be considered a hindrance; it makes you very conspicuous to predators, and it really hampers your movement through dense vegetation. 

And that is just it! Any individual who survives in spite of this handicap must have good genes, and therefore will make a good father!

It's raining Slugs....

Arion rufus

Not many people like Slugs! Ugly, and slimy, and resembling doggy doo! But like all organisms, they have their role in the ecosystem, and somebody has to do the dirty work; the decomposition.  Slugs are omnivores, consuming a large variety of organisms.  Their exceptional suite of digestive enzymes is testament to this: not just amylase and invert awe, to digest starch and sugar respectively, but also proteases (protein), chitinases (the material of insect exoskeletons), and xylemases and ligninases to digest the woody stems of plants.

The other interesting thing about slugs that everybody knows is that they are hermaphrodite.  But did you know how intricate and beautiful the reproductive organs of a slug or snail are?  Best thing I ever dissected at university, and so I think we must introduce this to Dissection Club. Watch this space...