1

Cells, Microbes & Viruses / Re: How can I find tardigrades?

« on: 04/04/2022 23:39:37 »

they seem to prefer drying out occasionally so don’t choose moss that’s damp all the time

There are many soft and squishy critters that would thrive in an environment that is damp all the time. But when it dries up, they tend to die.
- Tardigrades enter a form of suspended animation (a "tun" stage) when conditions get too harsh (eg lack of water). They reanimate when water becomes available. They can thrive in an erratic environment that would kill many other animals their size.

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Cells, Microbes & Viruses / Re: How can I find tardigrades?

« on: 04/04/2022 08:31:21 »

Perhaps the moss I have been examining has been to dry.

They can become dormant and difficult to see if too dry. Try soaking the moss overnight then look at it with a hand lens - best with top or side lighting (try both) against a dark background.
Although they like damp moss, they seem to prefer drying out occasionally so don’t choose moss that’s damp all the time.
When you are looking under the microscope try spacing the cover slip by putting 2 others underneath on either side, it leaves a small gap between slide and cover slip.
Best of luck

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Cells, Microbes & Viruses / Re: How can I find tardigrades?

« on: 03/04/2022 08:15:28 »

They are small: Up to 0.5mm, so you need to look for them under a microscope
They are fairly transparent, so they will be hard to see
I suggest getting some damp moss, and break it apart under a microscope.
https://en.wikipedia.org/wiki/Tardigrade

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Cells, Microbes & Viruses / Re: Affordable microscope?

« on: 06/04/2021 00:31:01 »

Obviously things have moved on since I last used a microscope, with the traditional lenses.

I suppose that's progress.  I was inclined to complain. But the sharp full-colour image taken by Colin, above, with mobile phone,  has silenced my complaint.

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Cells, Microbes & Viruses / Re: Affordable microscope?

« on: 05/04/2021 23:30:06 »

Tardigrades are quite big, from a microscope point of view. You will need between 20x and 50x magnification and direct top lighting rather than the through lighting that you see in a traditional microscope.
The type @evan_au mentions should be adequate, but make sure you have really good lighting eg led desk lamp.
If you really get into it and want a ‘proper’ microscope I would recommend a secondhand dissecting microscope

This was taken with iphone + adapter but many usb ones are just as good and real cheap.


4B5EDF7C-09EA-4978-91E7-EA3055B026BB.png (100.72 kB . 306x298 - viewed 4422 times)

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Cells, Microbes & Viruses / Re: Affordable microscope?

« on: 05/04/2021 22:15:15 »

These days, you can get quite cheap and portable microscope attachments which:
- Clip onto the camera of your mobile phone, to provide an optical close-up lens
- Plug into the USB port of your computer. These sometimes have built-in illumination of the subject
- Both of these allow you to take photos and videos, without an expensive camera attachment required by "traditional" desktop microscopes.

Holding the device steady, at the right distance from the subject is a real challenge. Look for one with a built-in spacer (which doesn't block the light).

7

Cells, Microbes & Viruses / Re: Are any antibodies all-powerful?

« on: 06/06/2020 15:24:52 »

Rabies viruses escape the immune system by progressing along the nervous system. They are not detected by the Antigen Presenting Cells (macrophages, dendritic cells) that trigger the immune response. But these viruses may be destroyed by antibodies when they are present because of treatment with rabies serum or because they were previously vaccinated.

Antibodies are immunoglobulins. There are different types. Immunoglobulins M (IgM) are predominant during the primary adaptative response of the immune system. They are less effective at neutralizing pathogens than immunoglobulins G (IgG) that characterize the secondary response.

Immunoglobulins A are transmitted by the mother to the fetus or the newborn via the milk.

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Cells, Microbes & Viruses / Re: Are any antibodies all-powerful?

« on: 08/05/2020 01:44:35 »

Camel antibodies also seem to be more flexible than other mammals...

Here is a story published in Cell journal, reporting work done in Llamas (part of the camel family) using Llama antibodies to attack COVID-19.
See: https://thenewdaily.com.au/news/good-news/2020/05/07/llamas-coronavirus-fight-science/

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COVID-19 / Re: What test were Chinese officials applying to the forehead to diagnose Covid?

« on: 14/04/2020 16:15:46 »

... and, given that most people are infections for a considerable time before they are ill, measuring temperatures is a pretty unreliable measure.
Unfortunately it may be the best we can do at the moment.

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COVID-19 / Re: What test were Chinese officials applying to the forehead to diagnose Covid?

« on: 14/04/2020 16:08:18 »

I think they were infrared thermometers looking for people with fevers. A cheap and quick test that identifies people in need of more testing (many causes of fever), or at least greater extent of isolation/restriction based on being more likely to be infected/infectious.

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COVID-19 / Re: What test were Chinese officials applying to the forehead to diagnose Covid?

« on: 14/04/2020 16:07:06 »

Could be a thermometer, or a political publicity stunt.
Or, give this, it could be a colourimeter.
http://www.rfi.fr/en/international/20200411-africans-targeted-in-southern-china-s-second-largest-city-as-covid-19-spreads

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Cells, Microbes & Viruses / Re: Are all of the body's different cell types nonetheless eukaryotic cells?

« on: 28/10/2019 09:40:45 »

It's very hard to definitively say "WHY" in biology, but there is no shortage of guesses...
- Red blood cells and platelets have to be very small, so a nucleus is just wasted space
- Red blood cells have to carry oxygen and carbon dioxide. DNA doesn't do this, so it's just wasted space
- DNA, ribosomes and mitochondria are a few of the complex cell components involved in a cell that is continually maintained, and actively responding to its environment; all this consumes energy. But if the required functions of a red blood cell (or a platelet) can be done just with proteins using much less energy, then why not make the red blood cell (and platelets) disposable?

Liver cells have to deal with toxins from the digestive system. As such, they are likely to suffer mutations and become cancerous. One way of avoiding cancer is to have multiple copies of a gene, so if one copy is damaged, other copies still continue making the required proteins. One way of having multiple copies of every gene is to have multiple copies of the DNA.
See: https://en.wikipedia.org/wiki/Hepatocyte#Microanatomy

Egg & sperm cells have half the number of chromosomes, so that when they meet, they can form a zygote with a full set of chromosomes (half from the mother, and half from the father).
See: https://en.wikipedia.org/wiki/Meiosis

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Cells, Microbes & Viruses / Re: Are all of the body's different cell types nonetheless eukaryotic cells?

« on: 27/10/2019 09:37:12 »

Are (my) red blood cells Eukaryotes ?

Yes, in mammals, red blood cells start off as eukaryotes, with a nucleus.
But in the process of blood cell production, the daughter red blood cells end up without a nucleus (like platelets, another type of blood cell).

However, in birds and reptiles, red blood cells in circulation still have a nucleus.

See: How Red Blood Cells Nuke Their Nuclei

There are a few other specialised cell types in the human body with odd DNA - for example, liver cells have multiple copies of their DNA, and egg/sperm cells have a half-set of DNA.

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Cells, Microbes & Viruses / Re: Are all of the body's different cell types nonetheless eukaryotic cells?

« on: 25/10/2019 22:13:10 »

Human cells are all eukaryotes: cells where the DNA is enclosed in a special membrane.
- Some cells like hair, tonenails and skin cells are produced as living cells by the human body, but they act as a protective barrier. The cells die and are eventually shed, but they do contain DNA in a membrane when they form. Often human DNA can be recovered from hair on a hairbrush, for example.

See: https://en.wikipedia.org/wiki/Eukaryote

There are some cells in the human body which are prokaryotes, and have all their internal DNA and organelles floating around together. This is the bacteria and archaea which form part of our microbiome, living in our gut, for example.
See: https://en.wikipedia.org/wiki/Prokaryote

15

Chemistry / Re: (CONFUSED) Water fuelled car engine possible?

« on: 11/08/2019 17:33:29 »

You can get net energy by reacting chemicals like lithium or fluorine with water, but it wouldn't be worth the trouble. Unlike an air-breathing engine, you'd have to carry those extra chemicals in the car and you wouldn't get nearly as much range as you would burning gasoline. Then there is the hazardous nature of lithium and fluorine to consider...

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Physics, Astronomy & Cosmology / Re: Rainbows on Venus?

« on: 04/04/2019 18:54:50 »

To human eyes, it is pitch-black on Venus, due to the effect of very deep clouds.
What little light reaches the ground is reflected many times, and comes from all directions. A good rainbow requires light from a single direction.
So even if there were a dispersive medium in the atmosphere of Venus, you wouldn't be able to see a rainbow.

To be fair, rainbows are relatively rare on Earth.
They need a "lucky" arrangement of the Sun, clouds and rain.
It's possible that such an arrangement might exist on Venus.

But I'd not waste much time looking for it.

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Physics, Astronomy & Cosmology / Re: Rainbows on Venus?

« on: 04/04/2019 03:22:41 »

To human eyes, it is pitch-black on Venus, due to the effect of very deep clouds.
What little light reaches the ground is reflected many times, and comes from all directions. A good rainbow requires light from a single direction.
So even if there were a dispersive medium in the atmosphere of Venus, you wouldn't be able to see a rainbow.

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Plant Sciences, Zoology & Evolution / Re: Fishy humans?

« on: 23/11/2017 07:32:33 »

This is a really interesting question; thanks for asking it.

As @Kryptid points out, the observation that the genes present in humans (and many other animals) are close matches with those found in fish and, for that matter, right across the trees of life including plants and bacteria, is the strongest evidence we have for the existence of a universal common ancestor (UCA) for all life on Earth.

The fact that you can take a gene from any life-form, be it human, plant, or jellyfish, and insert it into the DNA of E.coli bacteria - where it will be interpreted correctly and the recipe that it encodes expressed as functioning protein - is proof that the code evolved once, and probably over 3.5 billion years ago.

On this basis, it's impossibly unlikely that the same genetic code, and genetic rules that govern the interpretation of that code, evolved identically, multiple times in parallel during evolution.

Therefore, we are related not just to the fish in the sea but also to the grass on your lawn, the algae on your front step and the bacteria living in your bowels. Quite a big extended family when you think about it!