What real evidence do scientists have that living things have changed over time?

Answer 1

The first living things that we know of were prokaryotes (single celled organisms without a cell nucleus), and they appeared about 3.8 billion years ago. About 3 billion years ago, the first prokaryotes evolved the ability to make food using sunlight, air, and water (photosynthesis). About 2 billion years ago, the first eukaryotes (organisms with a cell nucleus) evolved, and the first multicellular organisms evolved 1 billion years later. Approximately 500 million years ago, the Cambrian explosion occurred, and within only 140 million years of that (360 million years ago), plants, amphibians, insects, and fish lived on Earth, along with most other major invertebrate groups. Amphibians evolved into reptiles about 300 million years ago (mya), and reptiles diversified into mammals (about 200 mya), dinosaurs (225+ mya), crocodillians, and a variety of other groups that are now extinct. Dinosaurs evolved into birds about 150 mya.

Meanwhile, the simple, seedless plants from 300 mya evolved into conifers , cycads (less than 300 mya) and ginkgos (199 mya), and then flowering plants appeared about 130 million years ago, one group of which was the Magnolids.

After the K-T extinction 65.5 mya that wiped out the non-avian dinosaurs, the tiny mammals quickly evolved into larger and more diverse forms, and finally into the mammals that are alive today.

Answer 2

The remains of the plants and animals. Millions of years of history is contained within the earth. Scientists have the evidence of the development of man, animals, and how the earth has changed through finding bones, items from past civilizations, core samples of the earth and ice samples showing the difference and changes in environment. Tree rings also give evidence of fire, drought, and diseases that trees have lived through.

Answer 3

I'll take it that by 'changed over time' you are referring to evolution. There are various forms of evidence that support Darwin's theory of evolution.

One of such forms of evidence is homologous structures. Homologous structures are structures that have the same structure but perform different functions in different organisms. An example of this is the pentadactyl limb, which is a limb with five digits. This bone structure is present in the human hand, the flippers of a whale and the wings of a bat. This supports the theory of evolution as it suggests that these organisms all evolved from one common ancestor with a pentadactyl limb.

More modern methods use DNA analysis. A technique called DNA hybridisation is used where the DNA of two organisms is extracted and compared. The greater the degree of similarity between the base sequences, the more closely related the organisms are. The proteins of different species can also be compared.

Hope this helps!