Life on Earth
Life on Earth started around 3.8 billion years ago and has since evolved and diversified through the process of natural selection to be adapted to almost every environment possible. There are currently an estimated 1.9 million animals, plants, and other forms of life on Earth. Life can be found in every nook and cranny/niche of the globe, from the extreme environments of deep sea hydrothermal vents and the freezing conditions of the Polar Regions to the lush habitats found at the equator. Looking back through time, by means of the fossil and phylogenetic record, we can see that the Earth has been home to many more species than are alive today. Taking a historical perspective shows that life is constantly evolving, with the success and dominance of different groups waxing and waning over time. The diversity of life is truly amazing, but all living organisms do share certain similarities. All living organisms can replicate, and the replicator molecule is DNA. As well, all living organisms contain some means of converting the information stored in DNA into products used to build cellular machinery from fats, proteins, and carbohydrates
Complete the sentences. Choose no more than three words and / or a number from the passage for each answer.
1. The world developed changed by ...............for over 3.8 billion years.
2. The past history of the species that used to exist on earth can be found through the............... record.
3. The coming and going of specific groups and species can illustrate to us that life isforever ...............
4. Without ...................., life forms would not be able to replicate.