Final answer:
Life on Earth began approximately 3.5 billion years ago. Plants first appeared around 470 million years ago. The first domesticated animals were dogs.
Step-by-step explanation:
1. Life on Earth
Scientific data suggests that life on Earth began approximately 3.5 billion years ago. This was established through the study of fossil records and the discovery of ancient microorganisms in rocks.
2. First Appearance of Plants
Plants first appeared on Earth around 470 million years ago during the Ordovician Period. This is known through the examination of fossil remains, such as spores and pollen, found in rocks from that time period.
3. Why Plants Weren't the First
Plants were not the first form of life to appear on Earth because the early conditions of the planet were not suitable for their growth. The atmosphere lacked oxygen, which is essential for photosynthesis, and the land was barren. Simple microorganisms such as bacteria and archaea were the first life forms to emerge.
4. Abundance of Dinosaurs
Dinosaurs were most abundant during the Mesozoic Era, specifically during the Jurassic and Cretaceous Periods. They dominated the Earth for millions of years before their eventual extinction.
5. Placental Mammals
Placental mammals, which give birth to live young, first appeared on Earth around 65 million years ago during the Paleogene Period. This is known through the analysis of fossil evidence and genetic studies.
6. First Domesticated Animals
The first animals to be domesticated by humans were dogs. They were likely domesticated between 20,000 and 40,000 years ago. Dogs provided companionship, protection, and assistance in hunting, making them valuable allies for early human civilizations.
7. Agency for Small Animal Care
The responsibility for regulating the care and management of small animals varies depending on the country and local jurisdictions. In the United States, for example, organizations such as the Animal and Plant Health Inspection Service (APHIS) and the American Society for the Prevention of Cruelty to Animals (ASPCA) play a role in overseeing the welfare of small animals.
8. Linnaeus and Woese Classification Systems
Carl Linnaeus developed a classification system called Linnaean taxonomy in the 18th century. This system categorizes organisms based on their shared characteristics and arranges them into a hierarchical framework. The Woese system, on the other hand, is a more recent classification system that focuses on evolutionary relationships by examining the genetic code of organisms, specifically the 16S rRNA gene.
Learn more about The origins and development of life on Earth