Which two reproductive barriers are at play in mule reproduction?

A mule is produced when male donkey (jack) mates with a female horse (mare).

Explanation:1.Horse have 32 pairs of chromosomes while a donkey has only 31pairs. Hence, their offspring inherit 32 horse chromosomes and 31 donkey chromosomes leaving a chromosome that is not paired up this makes them infertile and inability to produce embryo.

2. Horse and donkey chromosomes are not similar unlike in human hence mules and can rarely produce the cells critical for reproduction i.e eggs and sperm.

really dont know just need some points

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.