Lesson plan

Evidence for evolution

Summary
Show how fossil discovery, comparison of living things on different land masses, and the artificial selection of crops and animals, provide evidence for evolution by natural selection.
Science content
Biology: Evolution, Natural Selection (7)
Activities in this lesson
Materials
Procedure

We know that evolution is true and happens by natural selection from many different pieces of evidence.

1. We find fossils which show us that living things have gradually changed over long periods of time.
Do the sedimentary uplifting activity to show how fossils are formed and discovered.
By measuring the age of rock layers that fossils are found in, we can determine when each of the fossils was alive. The fossils we have discovered show a gradual change of how living things look through time, over millions of years.
Fossils have shown how life moved onto land (for example, the Tetrapods) and how whales evolved from land mammals. As more and more fossils have been discovered, intermediate life forms between groups of living things (previously called "missing links") have filled in more and more gaps in the evolutionary history of living things, for example, Archaeopteryx is an intermediate between dinosaurs and birds, and Tiktaalik (found in Nunavut) is an intermediate between fish and Tetrapods.

2. We find that as living things become separated, by being on an island for example, or when the continents were formed, living things that are separated from each other start to look different over time.
Show this with the lego evolution activity.
We see this in both fossils and living things that are alive today.
Many islands have plants and animals that do not live anywhere else e.g. Madagascar, Australia and the Galapagos. They have been separated from the mainland long enough for their own populations to evolve in their unique environment.
On different continents different animals all eat ants (armadillos in North America, anteaters in South America, aardvarks and pangolins in Africa, echidnas in Australia). They have evolved separately as they are on different continents, but all have evolved features that allow them to eat ants.
This evidence shows that natural selection, in different environments, leads to different features evolving.

3. We know that human beings have selected for plants and animals to look certain ways ("artificial selection").
Show students images of all the vegetables that we have made from the wild mustard plant (Brassica), and all the dog breeds we have made from the wild wolf.
We made these vegetables and dogs (and many other plants and animals with certain features) by breeding together individuals with the most prominent features that we like. Their offspring are then again chosen for those with the most desirable feature and bred together. Over several generations, the selected features become more and more prominent, as the DNA sequences responsible for these features are selected for.
Artificial selection shows that there is variation in individuals, and that certain features can be selected for.
Similarly, in nature, the variation is also present, but is is the natural environment that does the selecting - hence it is called "natural selection": living things with features that are more able to survive in the environment become more common in the population.

4. We know that all living things are related by looking at their DNA sequences as well as their embryonic forms.
There are common DNA sequences and developmental stages between living things. More closely-related individuals have more DNA sequences and embryology in common. Through comparisons, we can build up an evolutionary tree of all life on Earth. We are related to every living thing on Earth.

Grades taught
Gr 1
Gr 2
Gr 3
Gr 4
Gr 5
Gr 6
Gr 7
Teaching Site
Tyee Elementary