Evolution by Natural Selection

What we’ve learned so far… We began our exploration of biology by observing biodiversity and how it has changed over time. Next, we observed that population sizes of some species have fluctuated and we figured out some causes for that. Is it possible that these two ideas are connected? Can changes in population sizes play a role in species change? TEACHER NOTES: Before we dive into our first learning segment, let’s go back and review what we’ve figured out so far in the first two triangles in MBER-Bio: We started the academic year by observing that biodiversity has changed over time Most recently, we learned that population sizes, such as those of the moose and wolf on Isle Royale, tend to fluctuate due to various factors [list some of the factors students included in their model] Now we begin to explore if and how these two ideas are connected…is it possible that changes in population sizes play a role in species change? At this point, you may want students to come up with some possible answers to these questions. Right or wrong answers do not matter at this point—it’s just a means to get them thinking about what comes next... Sources: https://commons.wikimedia.org/wiki/File:Grey_wolf_P1130270.jpg

https://www.youtube.com/watch?time_continue=9&v=rFxu7NEoKC8

Let’s talk “evolution” first The theory of evolution (decent with modification) by natural selection What’s is a theory?

Misconceptions…

- Acknowledgment that life on Earth has changed - The First Hurdles - Acknowledgment that life on Earth has changed - Dominant religious beliefs stated that life was created at the same time as Earth. Newly discovered species were not at odds with this. The discovery of evidence of extinct species was a problem for this belief system. There was also an issue with time. Common religious belief, taking cues from religious texts, was that the world was in the neighborhood of 4000 years old.

The First Hurdles Georges Cuvier – Catastrophism Sudden geologic catastrophes caused large groups of organisms to go extinct The idea that all species have not remained unchanged was NEW

The First Hurdles Geological time scale Charles Lyell – Uniformitarianism Geological processes that shape the Earth’s surface in the past continue to work today Helped people recognize the long time frame and provided a mechanism for Darwin to explain some of the changes in species

All species have always existed… The First Hurdles… All species have always existed… Jean Baptist Lamarck Use and disuse Inheritance of acquired characters

All species have always existed… The First Hurdles… All species have always existed… Explained changes in life without requiring species to have gone extinct

Jean Baptist Lamark The mechanism for decent with modification (Evolution) is… Inheritance of Acquired Characteristics

Charles Darwin 1809-1882 HMS Beagle 1831 1859 – “On the Origin of Species”

the mechanism for decent with modification (Evolution) Natural Selection is … the mechanism for decent with modification (Evolution)

Misconceptions… Scientist don’t debate “if” they debate “how”

Misconceptions…

Misconceptions…

Natural Selection can only work on traits/structures already present. It is not perfect.

4 Parts of Natural Selection 1. Overproduction 2. Genetic Variation 3. Struggle to Survive 4. Differential Reproduction

Populations Adapt – Individuals Can’t (They acclimatize) Fitness = ability to make a hereditary contribution to the next generation Populations Adapt – Individuals Can’t (They acclimatize)

1. Overproduction

2. Genetic Variation

3. Struggle to Survive

4. Differential Reproduction