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Park Walk in Evolution 2.0
Natalia Omelchenko
Created on September 21, 2025
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Transcript
Park Walk in Evolution
bIO lab Simulation
Start
Click for sound
Dr.O
Hi Alex! Want to join us for a walk? As long as you do not mind that vicious Missy is going to lick you all over.
Alex
Vicious? She’s a Boston terrier! Wolves are vicious. I know dogs are related to wolves, but this one looks nothing like them.
AiAi
Biologists used to agree with you, Alex. Back in 1758, Linnaeus named dogs Canis familiaris and wolves Canis lupus, treating them as separate species. But in 1993, after genetic studies, dogs were reclassified as Canis lupus familiaris — a subspecies of the wolf.
Dr.O
Of course, if scientists used other definitions — like the morphological or ecological species concepts — we could count hundreds of different ‘dog species,’ each based on looks or jobs. But most of those forms wouldn’t survive in the wild.
Alex
Yeah, Missy might be fierce with kisses, but I can’t imagine her hunting elk.
AiAi
Artificial selection also limits the genetic variety that populations need to stay healthy. More alleles mean better health. That’s why so many artificially selected animals and plants struggle with inherited issues.
Alex
Is it avoidable?
AiAi
Loaded question... Let’s run a model and see what happens when we let artificial selection shape a population.
Click to change the population size
Population size
Progress Toward Goal
10-100s
Selection Intensity
Population Health
Dr.O
Two key factors can be controlled in selection. The first is population size: small groups (10–100) are easier to manage and preserve traits, large groups (10,000+) may lose them through competition for resources, and medium groups (~1,000) fall in between. Breeders often reduce offspring (e.g., limiting seeds or spawn) to improve the chances that desired traits survive.
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Dr.O
Two key factors can be controlled in selection. The first is population size: small groups (10–100) are easier to manage and preserve traits, large groups (10,000+) may lose them through competition for resources, and medium groups (~1,000) fall in between. Breeders often reduce offspring (e.g., limiting seeds or spawn) to improve the chances that desired traits survive.
Population size
Progress Toward Goal
10,000s (or more)
Selection Intensity
Population Health
Dr.O
Two key factors can be controlled in selection. The first is population size: small groups (10–100) are easier to manage and preserve traits, large groups (10,000+) may lose them through competition for resources, and medium groups (~1,000) fall in between. Breeders often reduce offspring (e.g., limiting seeds or spawn) to improve the chances that desired traits survive.
Population size
Progress Toward Goal
Selection Intensity
Population Health
Top 50% (weak)
Dr.O
The second control is selection intensity. It only works on traits with a genetic basis. Strong selection (top 10%) shifts traits quickly but reduces diversity. Weak selection (top 50%) keeps variation but slows change. Moderate selection (top 30%) shows steady progress.
Population size
Progress Toward Goal
Selection Intensity
Population Health
Top 30% (moderate)
Dr.O
The second control is selection intensity. It only works on traits with a genetic basis. Strong selection (top 10%) shifts traits quickly but reduces diversity. Weak selection (top 50%) keeps variation but slows change. Moderate selection (top 30%) shows steady progress.
Population size
Progress Toward Goal
Selection Intensity
Population Health
Top 10% (strong)
Dr.O
The second control is selection intensity. It only works on traits with a genetic basis. Strong selection (top 10%) shifts traits quickly but reduces diversity. Weak selection (top 50%) keeps variation but slows change. Moderate selection (top 30%) shows steady progress.
Dr.O
These are only general guidelines. Choosing specific breeding strategies actually requires deep knowledge of the biology of each species. And for most organisms, a single human lifetime is rarely enough to establish a stable line.
AiAi
The American Kennel Club officially recognized the Boston Terrier in 1893. So Missy is the product of just over 200 years of selection — a relatively young breed. Some other dog breeds, like the Greyhound or Mastiff, have histories stretching back more than 800 years.
Dr.O
Finally, remember — traits are shuffled by the laws of probability. Chance always plays a part, and sometimes luck is what separates success from failure. Want to try a breeding model?
What should we look at first?
👉 Choice 1: Goldfish
👉 Choice 2: Corn
Alex
Do I want a challenge that takes knowledge, patience, and maybe a little luck — with no promise of success? Absolutely. Count me in!
Dr.O
All modern goldfish are a variety of a carp. Average lifespan: about 10–15 years. Each spawn: hundreds to thousands of fry. You notice a cool new color variety. Question is — how turn that into a stable new breed?
Progress Toward Goal
Population size
10-100s
Population Health
Selection Intensity
Top 50% (weak)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
10-100s
Minimal
Selection Intensity
Population Health
Compromized
Top 50% (weak)
Dr.O
When selection pressure is too weak, the health bar barely changes — but you’re not moving toward your goal either. In small groups, chance events can still shuffle traits unpredictably, often in the wrong direction. That random effect is called genetic drift.
Progress Toward Goal
Population size
10-100s
Population Health
Selection Intensity
Top 30% (moderate)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
10-100s
Moderate
Selection Intensity
Population Health
Compromized
Top 30% (moderate)
Dr.O
The health meter shows compromised health as variation is lost. You’ll see some progress, but not enough to reach the goal within a reasonable time.
Population size
Progress Toward Goal
10-100s
Selection Intensity
Population Health
Top 10% (strong)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
Achived
10-100s
Population Health
Selection Intensity
Poor
Top 10% (strong)
Dr.O
It likely took 15–30 years, but you achieved your goal! This is the new fish variety — congratulations! Click the chevron on the right to finish the activity. 👉
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Top 50% (weak)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Top 30% (moderate)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Top 10% (strong)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 50% (weak)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 30% (moderate)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 10% (strong)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Dr.O
In real fish breeding, even a few hundred breeders is considered a large population. Talking about thousands of individuals for goldfish experiments is unrealistic. Scale it down and try again.
Why is this new fish breed unhealthy?
👉 Too much food
👉 Loss of genetic variety
👉 Improper care
👉 all of the above
Alex
Well... Funny, but sad. Let’s see if you followed along.
Why is this new fish breed unhealthy?
👉 Too much food
✅ Loss of genetic variety
👉 Improper care
👉 all of the above
Alex
Yes — the result of lost genetic variety. Reduced allele diversity weakens overall health.
Why is this new fish breed unhealthy?
👉 Too much food
✅ Loss of genetic variety
👉 Improper care
👉 all of the above
Alex
No. It is the result of lost genetic variety. Reduced allele diversity weakens overall health.
AiAi
Goldfish new traits can appear in just a few generations, but making a stable variety takes decades. Some famous types took centuries of selective breeding — and most came with health costs compared to their wild-type ancestors. Unfortunately the same applies to specific dog breeds like Missy.
Dr.O
The modern corn you know today is related to a wild grass called teosinte. What would it take to establish a new sort of corn? Think about population size, selection intensity, and the time required for traits to become stable.
Progress Toward Goal
Population size
10-100s
Population Health
Selection Intensity
Top 50% (weak)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10-100s
Population Health
Selection Intensity
Top 30% (moderate)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
10-100s
Selection Intensity
Population Health
Top 10% (strong)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Top 50% (weak)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Top 30% (moderate)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Population size
Progress Toward Goal
1000s
Selection Intensity
Population Health
Top 10% (strong)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Dr.O
In real corn breeding, talking about just hundreds or a few thousand plants is far too small. A typical selection starts with tens of thousands of plants in a field. That’s the scale where meaningful patterns show up. Scale it up and try again.
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 50% (weak)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 50% (weak)
Dr.O
The health meter stays high — the corn is vigorous and resilient. But progress crawls. With so much variation left in play, the new trait never locks in. The price of perfect health is that you don’t reach your goal.
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 30% (moderate)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 30% (moderate)
Dr.O
Congratulations — you reached your goal! With moderate pressure, you kept the line healthy. The health meter stayed steady because diversity wasn’t shaved away too fast. Now sit back and enjoy your popcorn!
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 10% (strong)
Dr.O
Set the population size and breeding intensity sliders in the top left, then click the chevron on the right to check your guess. Keep experimenting with different combinations until you reach the goal. 👉
Progress Toward Goal
Population size
10,000s (or more)
Population Health
Selection Intensity
Top 10% (strong)
Dr.O
The health meter crashes as genetic diversity is stripped away. Plants may look uniform at first, but yield and resilience collapse. Pests or drought hit harder, and the line can’t survive long-term.
Why did corn breeders choose moderate selection intensity?
👉 Because popcorn tastes better that way.
👉 To keep some variation in the population.
👉 Because fields look nicer when they’re full.
👉 To reduce the population size.
Alex
So this is how popcorn popped into existence—literally. Let’s see if you followed along.
Why did corn breeders choose moderate selection intensity?
👉 Because popcorn tastes better that way.
✅ To keep some variation in the population.
👉 Because fields look nicer when they’re full.
👉 To reduce the population size.
Alex
Yes—removing all variation would harm the population.
Why did corn breeders choose moderate selection intensity?
👉 Because popcorn tastes better that way.
✅ To keep some variation in the population.
👉 Because fields look nicer when they’re full.
👉 To reduce the population size.
Alex
Nope—removing all variation would harm the population.
AiAi
Corn was domesticated over thousands of years, with wild teosinte transformed into today’s high-yield plant that depends on humans for survival. In domesticated corn, new traits can appear in a single season, but stable varieties require many rounds of selection.
Click to return to selection models.
👉 Choice 1: Goldfish
👉 Choice 2: Corn
Dr.O
You’ve done great work today. You learned about the artificial selection— the evolution in action. There’s always so much more to explore—every example, sample, every slide can reveal something new if you look closely enough.
Alex
I understand now that artificial selection is always a compromise—balancing population health, the breeder’s goal, and the speed of progress. And every species brings its own biological twists. As for avoiding negative health impacts? Well… that was indeed a loaded question.
Dr.O
There’s also the factor of time. Slow, natural change allows mutations to add new alleles and helps populations stay healthy. In artificial selection, health depends far more on the breeder’s choices — though random mutations still accumulate in the background.
AiAi
In dogs, each pup gets about 100 new mutations. In rice, it’s closer to 150. That’s tiny compared to the whole genome — roughly 1 change in every 1 to 10 million nucleotides. Still, even these small changes matter, and over time they add up.
Dr.O
Artificial selection powerfully supports evolutionary theory—the mechanisms are the same, the only difference is who makes the choices: nature or breeders.
Alex
And nature’s had millions of years to create variety. So are 200 new dog species just a matter of time — or does macroevolution need something more?
Dr.O
We often separate the formation of varieties — microevolution — from the splitting of species — macroevolution. But nature doesn’t draw that line; the two are deeply interconnected. Add reproductive isolation to the mix, and with enough time, speciation follows.
AiAi
And the time really depends on the species. In many plants and animals, new species can arise in about 2 million years. In primates, it’s more like 1–4 million. Short-generation organisms can do it much faster.
Alex
Thanks for breaking it down for me. My head’s kind of spinning, but in a good way. I can see now how it all fits into one bigger process — macroevolution… and little Missy, evolution’s most dangerous kisser.
Dr.O
And that’s the beauty of evolution — whether in nature or shaped by humans, it’s all one process.
Click here to get my notes
Notes
(Don't forget to return when you'are done.)
AiAi
And I saved today’s notes for you to download.