From school, I remember that for something to be considered life, it must be able to reproduce. With the creation of seedless fruits (such as watermelon), would this be considered life as they don't have seeds so they can't reproduce?
Definition of life
The definition of what is alive and what is not is not a matter of biology but a matter of philosophy. Most definitions are based on:
- Existence of a metabolism
- Ability to reproduce and have heritable traits
- Ability to respond to the environment
There are plenty of possible definitions of "life". Note also that behind the complexity of defining what is alive there is the issue of defining the unit (the individuality if you want) on which the concept of life applies.
Your definition of life
You suggest a quick and simple definition so let's consider it.
to be considered life, it must be able to reproduce
If you talk about the watermelon tree
If this is your definition, then Citrullus lanatus is definitely alive as it is able to reproduce (otherwise we would not be able to cultivate them).
If you talk about the watermelon fruit
Now you may ask is the fruit itself alive. Then, using your definition again, I suppose the answer is no because a given seedless watermelon will not be able to give birth to other seedless watermelons (even via the make-up of a watermelon tree).
Note that following the same logic one could argue that one's head is not alive either as one's head does not reproduce. Only your gonads do. Your dog might not be considered alive either. A castrato (singer) would not be alive either. A woman, after menopause, cannot reproduce either! Arguably, a cloud replicates or a fire replicates and could eventually be considered alive following your definition. So really, as you can see your simple definition hardly fit your intuition of what should be called alive.
My opinion on your definition
Personally, I am not a big fan of your definition but again it is nothing but a matter of preferences. I don't like that your definition is unclear because there are plenty of limit cases and because there are plenty of cases we would want to call alive that we can't anymore (like a woman after menopause for example!) Every definition of life would eave limit cases but with your definition, it really easy to find these limit cases.
Is this question about Biology?
No, it is not. It is a question of philosophy.
Other interesting post on Biology.Stack
You might want to have a look at why isn't a virus alive.
Yes, they are considered life
Seedless fruits can develop in one of two ways: either the fruit develops without fertilization (parthenocarpy), or pollination triggers fruit development, but the ovules or embryos abort without producing mature seeds (stenospermocarpy). Seedless banana and watermelon fruits are produced on triploid plants, whose three sets of chromosomes make it very unlikely for meiosis to produce fertile gametes. This is because one of the three copies of each chromosome can't pair with another appropriate chromosome before separating into daughter cells, so these extra third copies end up randomly distributed between the two daughter cells from meiosis 1, resulting in the (usually) swiftly lethal aneuploidy condition. Such plants can arise by spontaneous mutation or by hybridization between diploid and tetraploid individuals of the same or different species. Some species, such as tomato, pineapple, and cucumber, produce seedless fruit if not pollinated, but do produce seeded fruit if pollination occurs.
They fulfill all processes which are required for anything to be considered as life
- Sensitivity (responding to stimuli like gravity and sunlight)
- Excretion (getting rid of CO2)
According to Wiki:
Life is a characteristic distinguishing physical entities having biological processes (such as signaling and self-sustaining processes) from those that do not, either because such functions have ceased (death), or because they lack such functions and are classified as inanimate.
If we consider, let say, infertile animal, it has signal system and that maintain homeostasis so we can definitely say that is life, but it's life.
I understand, that the question is about species, but if we can say, that such plants can arise by spontaneous mutation or hybridization between diploid and tetraploid individuals of the same or different species, how can we deny mutations that occur in our life in a natural way and state that it is not life?
In my opinion, when someone says that something is not life, it's inanimate. But that is out of the question, i guess.