To be a bit confused about DD's science homework?

[Nibledbyducks]

DD has just started year 6 and came home with science homeork on classification. One of the fill in the blank questions ended up as "mammals give birth to live young but birds lay eggs". Ok I know they start with the basics but why not "mammals give milk to their young"? what about sharks? and monotremes? surely it's best to be accurate from the get go?

[sycamore54321]

It depends on the context of the question. If it is intended to be a direct comparison between birds and mammals, then yes it makes sense. But if each is intended to cite the defining characteristic of birds or mammals, then you are right that it is not fully accurate. Can you help her see that it is the former rather than the latter?

[steff13]

How old are kids in year six? 6th grade here is 11/12, I'd expect a kid that age to already have those basics down.

[Nibledbyducks]

We ended up explaining the whole system of classification of living things, including going over how it had been done in class, I just don't quite see how giving incorrect information is better than correct information, or how the right information could be worse. I suppose it's a bugbear of mine with science, every time you learn something new you get told to ignore stuff you've learnt before. I never used valencies in Chemistry A level but did at GCSE, why not just learn about electron shells and bonding to start with?
Not all mammals give birth to live young, why teach that they do?

[Nibledbyducks]

Year 6 here is 10-11 year olds.

[OwlinaTree]

A shark is not a mammal or a bird though. Problem is there are probably exceptions to any statement.

[AverageGayLadAtChristmas]

What about a platypus?

[Buggeritimgettingup]

Surely mammals are called mammals because they have mammary glands?

[OwlinaTree]

I've never heard the term monotreme, nice words though, I'm looking forward to a chance to use it. Do you think you might be over complicating this homework?!

I'm guessing you are a scientist?

[contortionist]

But electron shells isn't a correct quantum
mechanical description either. You have to start somewhere!

[Igneococcus]

I never used valencies in Chemistry A level but did at GCSE, why not just learn about electron shells and bonding to start with?
How do you do chemistry without valancies?
I remember a thread on a different site where someone asked a question about something her child learned at school and it seemed they were still being taught the five kingdom system of life, nobody besides me thought this to be a problem.

[KeyserSophie]

Wait till they get onto the blue eye, brown eye thing, OP, you'll be inconsolable

[contortionist]

The statement in your DDs homework isn't wrong, although it isn't the definition of either a bird or a mammal. The most general statement would be "vivaporous animals give birth to live young; oviparous animals lay eggs" (although that still doesn't cover all sharks ) - but that then becomes a empirical-content-free definition.

[Igneococcus]

I think with some concepts you need to start with a broader, less detailed picture and then add on. Like you couldn't teach photosynthesis in its full and fascinating detail without knowing a hell of a lot of chemistry, physical chemistry, biochemistry, physics but you need to know what photosynthesis is and roughly how it works long before you have that knowledge.

[topcat2014]

I think the phrase is necessary but not sufficient.
ie - all mammals give birth to live young (true)

whilst

all animals that give birth to live young are mammals (false).

I remember struggling with electron shells at GSCE - my scientist parents were no help, as they started from the fact that the whole premise wasn't really true. - Didn't help me though :)

[sixandoot]

ie - all mammals give birth to live young (true)
Yeah, but that's not true.

[Tezza1]

Surely mammals are called mammals because they have mammary glands?
At a zoo excursion (Sydney's Taronga Zoological Park) my class was told that one of the defining things for a mammal is fur at some stage in their existence, even if it was pre-birth. This was in an exercise in categorising vertebrates, and used the body covering as a criteria. Saying that mammals give milk to their young is accurate, but eggs to categorise birds doesn't take into account monotremes (which lay are mammals that lay eggs and are covered with fur and also produce milk) like the platyus and echidna.

This was a fair while ago, and methods of categorising may well have changed since then.

[titchy]

I wouldn't swear it - scientists don't use that classification system anyway. It's about 100 years out of date!

[titchy]

Sweat it...

[RhiWrites]

one of the defining things for a mammal is fur at some stage in their existence, even if it was pre-birth.

Surely not. Dolphins don't ever have fur.

[Tezza1]

Surely not. Dolphins don't ever have fur.
Apparently baby dolphins are born with whiskers which fall out soon after birth. So, they do fit that type of categorisation, which, as I said, may well be out of date.

[valencyrules]

Yes YABU and this is why some of the most brilliant science graduates make terrible teachers. They pick holes in everything and just can't bring themselves to simplify concepts to allow 'less gifted' minds to access their subject.

Some - actually many - in that class will never have a hope in hell of understanding the intricacies of chemical bonding etc, but by learning a simple set of valency rules and applying them they may be able to write and interpret the meaning of chemical formulae. They won't get A* in GCSE Chemistry or even consider A level.

It's sometimes worth telling more able students that some explanations are just a construct or simplification, but your viewpoint is elitist and a little offensive IMO.

I really hope you're not a teacher.

[acasualobserver]

It's possible to take too much interest in your child's homework.

[BestZebbie]

valency: teaching that all mammals give birth to live young isn't just a simple version though, it is factually inaccurate, as it erases a whole branch of mammals (including the duck-billed platypus, which is famous enough for most children to have heard of it, often in the context of animal fact books which say that it lays eggs).
I agree that also seems a bit strange to use that example instead of milk or hair, which are actually unique characteristics of mammals (though I guess they were just trying to distinguish birds from other everyday animals)

[babybythesea]

I teach classification in my job (teach educational groups visiting a relevant institution so cover all ages from nursery to uni groups).

I've done this job for almost 20 years and have played around with both curriculum requirements but also the best way to introduce and expand on these things across the age ranges (allowing for the fact that I only see the kids as a one-off, so while I teach year 1 and year 6 classification it's not the same kids progressing through, if that makes sense, so there is some variation in background understanding).

Vertebrate classification is Year 1.
I do it on the basis of visible characteristics, asking 'What is this animal covered in?'
We do it through first hand experience - touch the fur, describe it, compare it to the snake skin etc. As a classification system it's not perfect but it's a start. If the class asks about animals that don't seem to fit, we can explore that, or if their understanding is good enough. But we also cover why we do this - it's as important to get a handle on why classification is important as it is on how to do it.

Bit later on and we do invertebrates vs vertebrates - and look inside a tortoise shell to see the spine, look at a bat x-Ray, look at and handle mini beasts. And then relate it back to what they already know - how does this fit with the bird reptile mammal thing you already know? Can you remember how to do that bit? Let's refresh and go a bit further with how we group those animals.

The trouble is, any statement used to define a group of animals can almost always be undermined with exceptions. Almost any statement in science in fact. So how do you teach it? This is important and these are the rules but they don't work? So you start with broad statements and ideas and as kids get their heads around it you develop the ideas further. Mammals have fur. Fact. Let's let everybody think about that, experience it, take it in, it's broadly true a d they can broadly speaking see it for themselves so apply it in every day life (that dog has fur, it's a mammal). Now, let's look at a dolphin, no fur - how do we explain this being a mammal? By the end you can be saying 'mammals tend to...' Rather than 'all mammals have.... ' But it's a gradual process.

It's easy as an adult who did science at a high level to see your way through apparent contradictions but lots of kids struggle and then switch off if you start with the the 'I'm telling you how complicated this is' approach right from the start.

Does that make sense?

[Tezza1]

Now, let's look at a dolphin, no fur - how do we explain this being a mammal? By the end you can be saying 'mammals tend to...' Rather than 'all mammals have.... '
As I mentioned earlier, the lesson in classification that my class was given at the zoo (8 year olds), was that mammals have hair or fur at some stage in their life, even if it's only before birth.