Evolution

Use the Earth Clock Worksheet to follow which non-human life forms appeared when and which life forms evolved in different eras. Fill in the timeline of Earth and discover your distant relatives! Upload your Earth Clock timeline to the gallery!

Epic events marked the dawn of new stages of life on Earth. While learning more about evolution, geologists, or scientists who study the structure and history of the earth, divided history into eons, eras, periods, and ages. They created a calendar of creation by examining the rocks and layers of past life found in the ground. Read about the different periods shared in this Britannica chart. For each period, record the timeframe and what kinds of species existed. Create a vertical or horizontal Evolution Timeline and upload it to the gallery.

Charles Darwin was a naturalist and biologist who lived from 1809 to 1882. He spent a five-year journey worldwide to study different life forms. In 1859, he published his famous book, Origin of Species using Natural Selection, proposing a unified theory of evolution. Back then, people thought all life appeared at the world’s beginning or over time. Darwin’s research showed that birds, plants, and fossils existed in similar species worldwide but adapted differently to their environments. Many people once believed that remarkable adaptations were evidence of “design” by a creator. Some species evolved and thrived, while others died off. One way to understand natural selection is to study form and function. How is an organism structured, and how does its structure allow its function? Review the Form and Function Exercise to understand the relationship between form and function better. He called this process Natural Selection of Variations. Pick and draw an organism; could you suggest how its forms connect with its function and upload it to the gallery?

Now we know that natural selection is the mechanism responsible even for the most impressive adaptations, such as the complex human eye. However, natural selection is not the only factor shaping evolutionary paths. In addition to natural selection, random factors can affect much of what happens in the evolution of a lineage. Living things evolve. They grow, mature, adapt, live, and then die. It is part of life. The changes plants, animals, insects, and humans make pass down to the next generation’s DNA, continuing to change in response to the environment and genetic evolution. Over time, Natural Selection helps some versions of these living things to survive while others disappear. Natural selection is a process where some individuals with better traits or genes stick around while those with less valuable characteristics don’t. This process helps species evolve—over many years, new helpful characteristics show up, and these traits get passed down to their offspring, changing the species over time. Research an example of a species that has evolved. (How about the first maritime creature that developed legs to walk on land?) Make a drawing and write about how marine species developed into land species!

Darwin’s data reveals that all organisms come from a common ancestor. Today, categories of species, genera, families, and even individuals like you and your friends connect through complex relationships that date back billions of years. Recently, scientists discovered patterns of molecular similarity to support this. Draw a Tree of Life Diagram to show how all living organisms are connected.

Genetic mutations (spontaneous changes in DNA sequence or organization) occur randomly throughout an organism’s life. These mutations will only have a noticeable effect on the future of the population if they increase or decrease the organism’s chance of survival. Which mutations pass on to future generations depends not only on natural selection but also on random events. The effects of these random events are known as Genetic Drift. For example, specific phenotypes and genotypes may be more common on an oceanic island because they are the ones that, by chance (not because of their particular characteristics), happened to colonize the island or to survive a highly destructive storm. Under many circumstances, the effects of Genetic Drift may overwhelm natural selection. Genetic Drift can happen more often in populations or cases when natural selection favors certain traits slightly over others. Scientists continue to learn about evolutionary processes today, continually opening up more questions.

Because evolution occurs on such a massive timescale, we have yet to determine where evolution might take us next. However, climate change guarantees that animals must adapt to new climates and ecosystems. What do you think your favorite animal will look like in 100 years? 1000 years? 1,000,000 years? Sketch it out!