Well, you can always question any statement anyone makes, but is it a reasonable question? If you don't want to take science's estimate of the number of species on earth
"As of 2009 the estimated number of total species is ~11,327,630
However the total number of species for some taxa may be much higher.
10-30 million insects;
5-10 million bacteria;
1.5 million fungi;
~1 million mites
~1 million protists
source
[The number of possible chordates: mammals, fish, birds etc, is ~80,500]
then so be it. However, the rest of us do. So you can either stick to your doubts and excuse yourself from the discussion (if you can't accept the premise then what else do you have to contribute?), or play along with what science says and remain a participant.
Not at all. Wolves,
Canis lupus, and coyotes
Canis latrans, two different species, have often interbred to produce fertile offspring. Then there's the grapefruit, which is a cross between two species, a sweet orange,
Citrus sinesis and a pomelo,
Citrus maxima.
In fact, animals from different genera have been known to interbreed and produce fertile offspring, such as cattle,
Bos taurus and bison
Bison bison, which produce beefalo.
Of course you must, because if you don't it makes explaining all the animals
and plants Noah had to take aboard all the more difficult. (The number of identified plants is 326,175)
.