About 3500 mya.
Unicellular organisms evolved first; and from them evolved the multicellular organisms. But that leads onto another question as to why multicellular organisms evolved.
The Book of Genesis1: 11 shows that grass, plants, and fruit trees according to their kind was created first. Genesis 1: 20 shows that living creatures in waters then flying creatures according to their kind. Genesis 1: 24,25 shows that domestic animals and creeping animals and wild animals were then created according to their kind. Genesis 1: 26 shows that God then made man in His image, which means that we were created to imitate God's qualities, such as love, joy, peace, patience, kindness, goodness, faith, mildness, self-control, confirmed in Galatians 5: 22,23. So to answer your question, which is what came first plants or animals? The answer is found in the first Book of the Bible, which is a letter from God, and beneficial for our teaching, according to 2 Timothy 3: 16,17. It confirms that plants, creatures living in water then flying creatures, domestic animals,creeping animals,then wild animals, according to their kind were created in that row of order.
unicellular
A unicellular organism is a life form consisting of a single cell.
Bacteria
"Unicellular" refers to life, in which each organism only has a single cell.
It is believed to have taken about 2 billion years for unicellular organisms to evolve into multicellular organisms. The transition from unicellular to multicellular life forms is thought to have occurred around 600 million years ago.
The gametic life cycle exists in which the haploid form is always unicellular as in humans.
The gametic life cycle exists in which the haploid form is always unicellular as in humans.
How unicellular organisms may have given rise to the first animals?
The first scientist to classify unicellular organisms was Antonie van Leeuwenhoek. In the late 17th century, he utilized his own improved microscope to observe and describe a variety of microscopic life forms, including bacteria and protozoa, which he referred to as "animalcules." His detailed observations laid the groundwork for microbiology and the classification of unicellular organisms.
The gametic life cycle exists in which the haploid form is always unicellular as in humans.