Exponential Growth: When reproduction makes populations explode!

• Positive Feedback: More babies = More individuals to make even more babies!
• Real-World Fun Fact: It's like when you buy one ice cream and they give you an extra scoop, and then another extra for that extra, and so on... Yummy, but chaos!

But, wait! Most populations can't grow forever.

• Density-Dependent Factors: As populations get denser, these factors (like food scarcity) kick in and slow down growth.
• Like when you invite too many friends to a party and suddenly, there's not enough pizza for everyone. 🍕

Exception Time!

• When a species enters a new place where everything's abundant, it's party time!
  • No enemies? Check! 🚫🦠
  • Lots of resources? Check! 🌿🍖
• Real-World Example: Eurasian collared dove in Europe during the 20th century. From Asia to European gardens, these doves were living the dream. But then, as with all good things, the population growth had to chill.

Changing Curves 📉📈

• Exponential (J-shape) can't last forever.
• It often turns S-shaped (sigmoid) because of resource limits or other factors.
• It's like trying to stuff infinite clothes in a finite closet. At some point, the door just won't close!

Boom and Bust

• Some populations go through wild rides - big increases and then massive decreases.
• Think of it as the ultimate roller coaster for species. Wee!

Backstory

• 1911: US Gov introduces reindeer to the Pribilof Islands.
• Setting: Tree-less grassland and taiga. Main winter food? Slow-growing lichens. Predators? Nope!

Reindeer Party 🎉

• Between 1911-1938, reindeer numbers soared.
• But, was this growth exponential? Hmm 🤔

The Big Dip 📉

• 1939-1950: From 1800 reindeers to just 8! That's a 99.56% decrease! 😱
• Reasons? Maybe super cold winters, hunting by humans, or not enough yummy lichens.

Density What? 🤨

• Factors affecting population can be:
  • Density-Dependent: Things that become an issue due to population size, like food scarcity.
  • Density-Independent: Things that affect populations no matter their size, like cold winters.
• So, are our reasons dependent or independent? Let's investigate!

Reindeer Aftermath

• Lichens are still sparse, but the reindeer provide meat for humans.
• Some want to introduce reindeer to parts of Canada. Good idea or not?