Lecture on Natural Selection and Environmental Influence

Today, we will explore the concept of natural selection through a series of four experiments involving our hypothetical "slime" creatures. Each experiment will build upon the previous one, gradually introducing more complexity into the system. This methodical approach will help us understand how different factors—such as speed, energy, and sensing—affect the survival and evolution of these creatures.

Organisms searching for food

Experiment 1: Basic Survival without Energy Consideration

In our first experiment, we will focus on observing the basic survival mechanics of the slimes without introducing any mutations or evolutionary changes. The goal is to understand how the slimes interact with their environment under fixed conditions. The rules are as follows:

Since there are no mutations in this experiment, the slimes will not adapt or evolve over time. Instead, we are simply observing how these fixed traits influence survival and reproduction based on the available resources and housing. To explore this further, we will run the experiment multiple times with varying amounts of food each day and observe the outcomes over several generations, allowing us to see how these basic rules shape the dynamics of the slime population.

Run the experiment with different daily food amounts and analyse the similarities and differences

Before going in to the experiments have a look at the explanation on experiment window

Experiment Window Tutorial

Experiment 1

Questions:

Reflection and Observation Questions:

  1. What did you observe about the population size over time? How did the number of slimes change from one generation to the next?
  2. How did the availability of food impact the survival and reproduction of the slimes? Did the amount of food available seem to control the population size?
  3. How did the limitation on the number of homes affect the survival of the slimes?
  4. Did all slimes that found food survive? If not, what factors contributed to the death of some slimes despite finding food?

Analysis and Critical Thinking Questions:

  1. How did competition for homes influence which slimes survived? Were there patterns in which slimes were more likely to secure a home?
  2. How did the stability of the slime population differ between runs with 50 daily food pieces and 200 daily food pieces? If you observed a difference, what do you think caused it?
  3. If the number of homes was increased or decreased, how do you think the population would be affected? Predict what would happen to the population size and structure if double the number of homes were available.
  4. Which environmental changes do you think could increase the survival chance of slimes? Consider the placement of food, the number of homes, and other factors in your response.

Application and Hypothetical Scenario Questions:

  1. If you were to design a slime that could survive better in this environment, what traits would you focus on?
  2. How might the outcomes change if the amount of food available each day varied randomly?
  3. If the experiment were to run indefinitely, what do you think would eventually happen to the population of slimes?

Experiment 2: Introducing Speed Mutations

In the second experiment, we introduce the concept of mutations, specifically focusing on the trait of speed. Speed will determine how quickly a slime can move across the environment to find food. The rules remain the same as in the first experiment, but now, every time a slime divides, there’s a chance that its offsprings will have a slightly different speed—either faster or slower than its parent.

The variation in speed introduces a new dynamic. Faster slimes can reach food more quickly, potentially securing more food before others. However, slower slimes might still manage to survive by focusing on nearby food sources.

This experiment not only helps us observe how speed mutations impact the slimes' ability to survive and reproduce but also allows us to explore a crucial concept in evolutionary biology: the role of small changes in traits in driving the evolution of populations.

The Role of Small Trait Changes in Evolution

In evolutionary biology, small changes in traits—like the variations in speed we’re introducing here—can have significant effects on the evolution of populations over time. This principle, known as microevolution, refers to changes in allele frequencies within a population due to mutations, natural selection, genetic drift, and gene flow.

Even minor alterations in traits can give certain individuals an advantage, allowing them to survive, reproduce, and pass those advantageous traits to their offspring. Over many generations, these small changes can accumulate, leading to noticeable evolutionary shifts in the population.

For example, in our experiment, if faster slimes consistently gather more food and thus divide more frequently, the population may evolve to favor higher speed. However, the effect of these small changes is context-dependent—what benefits the population in one environment may not be advantageous in another.

Through this experiment, we can observe how even slight modifications in speed influence the broader evolutionary trajectory of the slime population. It’s a practical demonstration of how microevolution works, providing insight into the processes that shape species over time.

Run the experiment multiple time with different food and starting speeds. How do they effect the evolution of the slime population.

Experiment 2

Questions:

Reflection and Observation Questions:

  1. How did the introduction of speed mutations affect the overall population? Did you observe any significant changes in the number of slimes or their survival rates?
  2. Did certain speeds seem to be more beneficial for the slimes?
  3. What patterns did you notice in how speed evolved over several generations?

Analysis and Critical Thinking Questions:

  1. Why do you think some slimes survived while others did not, even though they had the same access to food?
  2. How did the constant amount of food impact the evolution of speed? Would you expect the population to evolve differently if the amount of food were to change?

Application and Hypothetical Scenario Questions:

  1. What change in the environment make it suddenly favor the slower slimes rather than fast ones?
  2. How did the mutation rate influence the outcome of the experiment? How do you think the results would change if the mutation rate were slower or faster?
  3. Imagine running this experiment with different initial speeds. How do you think starting with very fast or very slow slimes would affect the evolutionary outcome?

Experiment 3: Introducing Movement Energy Costs

In our third experiment, we introduce a critical aspect of natural selection: the energy cost associated with movement. This experiment builds on the previous ones by adding a new layer of complexity that significantly affects the slimes' survival strategies. Here’s how it works:

  1. Slimes will still search for food and return home, but now, moving across the environment consumes energy.
  2. The faster a slime moves, the more energy it uses. While speed offers the advantage of reaching food quickly, it comes at the cost of greater energy consumption.
  3. If a slime’s energy reaches zero before it returns home, the slime will die.

The Role of Energy in Evolutionary Biology:

Energy is a fundamental constraint in biological systems, influencing how organisms interact with their environment and with each other. In nature, energy is often the limiting factor that determines whether an organism can survive, grow, and reproduce. For our slimes, energy is now a crucial resource that they must manage carefully.

This experiment mirrors real-world scenarios where animals must balance the need to move quickly—whether to capture prey, escape predators, or find mates—with the energy they expend to do so. In the wild, many animals face trade-offs between speed and endurance. For example, a cheetah’s incredible speed allows it to catch prey quickly, but it can only maintain that speed for short bursts due to high energy costs. On the other hand, animals like wolves or humans have evolved to balance speed with endurance, allowing them to engage in long pursuits.

Exploring Trade-offs and Optimal Strategies:

With the introduction of energy costs, our slimes must now navigate similar trade-offs. Faster slimes might have the advantage of reaching food first, but they also risk depleting their energy reserves too quickly, especially if food is scarce or far away. Slower slimes, while less likely to win races to food, may be more energy-efficient and better suited for environments where food is more evenly distributed.

This scenario brings us to an important concept in evolutionary biology: optimal foraging theory. This theory suggests that organisms have evolved strategies that maximize their energy intake per unit of effort. For our slimes, the evolution of speed will now be influenced by the balance between the energy costs of movement and the benefits of acquiring food.

Predicting Evolutionary Outcomes:

In this experiment, we can predict that the population will evolve towards an optimal speed—one that balances the need to reach food quickly with the energy costs of moving. This optimal speed may not be the fastest possible speed, but rather the speed that allows slimes to survive and reproduce most efficiently in their environment.

Moreover, we may observe the emergence of different strategies within the population. Some slimes may evolve to be fast and energetic, thriving in environments where food is sparse and competition is high. Others may evolve to be slower and more energy-conservative, better suited for environments where food is abundant but spread out.

Energy Management and Survival:

This experiment also highlights the broader principle of energy management in evolution. In real ecosystems, organisms that manage their energy efficiently are more likely to survive and pass on their genes to the next generation. This concept is evident in behaviors like hibernation, migration, and resource hoarding, all of which are strategies to conserve energy in the face of environmental challenges.

As we observe the slimes over several generations, we’ll gain insight into how energy costs shape evolutionary outcomes. We’ll see how the need to conserve energy influences the evolution of traits like speed, and how different environmental pressures can lead to the development of diverse survival strategies within a population.

Experiment 3

Questions:

Reflection and Observation Questions:

  1. How did the slimes’ behavior change once energy costs were introduced? Were there any noticeable shifts in how slimes moved or how quickly they attempted to find food?
  2. What happened to slimes that moved too quickly or too slowly under the new energy constraints? Did certain speed ranges seem to offer an advantage or disadvantage?

Analysis and Critical Thinking Questions:

  1. How did the trade-off between speed and energy efficiency influence which slimes survived and reproduced?
  2. In what ways did energy constraints create new selective pressures on the slime population? How did these pressures differ from those in the previous experiments without energy costs?

Application and Hypothetical Scenario Questions:

  1. If you were to further increase the energy costs of movement, how do you think the population would respond? Would you expect the average speed to decrease, increase, or remain the same?
  2. Conversely, if you reduced the energy costs associated with movement, what changes might you expect in the population? How might this affect the balance between speed and survival?
  3. Imagine introducing another energy-consuming activity, like digging for food or fighting over resources. How do you think this would influence the evolution of the slimes? Would the population need to adapt in new ways to manage these additional energy demands?
  4. Can you think of any real-world examples where animals face similar trade-offs between speed and energy efficiency?
  5. Based on what you observed, how would you predict the slime population might evolve if movement energy costs were gradually increased over time?
  6. Advanced question: Compare the average speed and the stability of average speed by different amount of daily foods. what do you observe? Why some values leads to more stable average speed than the other values?
  7. Advanced question: If it is known that energy cost per distance is proportional to the speed square, Is it possible to estimate the average speed, with the help of knowledge energy cost of movement, size of the field and amount of daily food

Experiment 4: Introducing Sensing Energy Costs

In our final experiment, we introduce a new layer of complexity by considering the energy costs associated with sensing. Sensing is a crucial trait in many organisms, allowing them to detect food, avoid predators, and navigate their environment. However, like movement, sensing also comes with an energy cost. Here’s how this experiment will work:

  1. As slimes move and search for food, they consume energy not only for movement but also for sensing.
  2. Each slime has a sensory range, and the greater the range, the more energy it costs to maintain.
  3. A slime with a higher sensing ability can detect food from a greater distance, but this increased sensing range requires more energy.
  4. If a slime's energy reaches zero before it returns home, it will die, just as in the previous experiment.

The Importance of Sensing in Evolution:

Sensing is a critical factor in the survival of many species. In nature, organisms that can better sense their environment are often better equipped to find food, escape predators, and locate mates. For instance, predators like eagles have evolved keen eyesight to spot prey from great distances, while prey animals like rabbits have developed acute hearing to detect approaching predators.

The evolution of sensory systems is deeply intertwined with the energy costs associated with maintaining and using these systems. In environments where food is scarce or predators are abundant, the ability to sense effectively can mean the difference between life and death. However, the energy required to maintain these advanced sensory systems can also be a limiting factor.

Predicting Outcomes in the Sensing Experiment:

In this experiment, we might observe several possible outcomes. Slimes that evolve highly sensitive sensory systems may initially have an advantage in detecting food or avoiding threats. However, if the energy costs are too high, these slimes might not be able to sustain themselves in the long run, leading to a shift in the population towards more energy-efficient sensory strategies.

Alternatively, slimes with moderate sensing abilities might strike a balance between detection and energy use, allowing them to survive and reproduce more effectively over time. This could lead to the evolution of a "sweet spot" in sensory capabilities—where the energy costs and benefits are optimally balanced.

Experiment 4

Questions:

Reflection and Observation Questions:

  1. How did the introduction of sensing energy costs affect the overall population? Did you notice any changes in population size, sensing range, or speed distribution?
  2. What happened to slimes with higher sensing abilities once energy costs were introduced? Were they more successful in finding food, or did the energy cost of sensing outweigh the benefits?
  3. How did slimes with different combinations of speed and sensing traits fare in this experiment? Did certain combinations prove to be more advantageous than others?

Analysis and Critical Thinking Questions:

  1. Did you notice any trends in the evolution of sensing and speed over several generations with both energy costs in place? Did the population evolve toward a specific balance between sensing range and speed, or did the traits remain varied?

Application and Hypothetical Scenario Questions:

  1. If you were to further increase the energy costs associated with sensing, how do you think the population would respond? Would you expect a decrease in average sensing ability, or might other traits adapt to balance the energy demands?
  2. Conversely, if you reduced the energy costs for sensing while keeping movement costs high, what changes might you expect in the population? How might this affect the balance between sensing and movement?
  3. How might the introduction of sensing energy costs affect the overall stability and diversity of the population? Did the population size and trait diversity stabilize, fluctuate, or decline after both energy costs were introduced?
  4. Based on what you observed, how would you predict the slime population might evolve if sensing energy costs were gradually increased over time? Would you expect a gradual shift in traits, or might some other evolutionary strategy emerge?
  5. If you make both the energy cost of movement and sensing high, which threat will be more favorable, why?
  6. What changes in the environment would make the sensing tread move favorable than movement speed, even if both have high costs

Conclusion

Through these four experiments, we have progressively introduced more factors that influence the survival and evolution of our slime creatures. Starting with a simple survival model, we explored the impact of speed mutations, the cost of movement energy, and finally, the cost of sensing. Each experiment demonstrated how natural selection operates under different environmental pressures, leading to the evolution of traits that enhance the slimes' ability to survive and reproduce.

In the next sessions, we will continue to explore natural selection by introducing even more complex scenarios and observing how these creatures adapt. Thank you for your attention, and I look forward to seeing you in our next session as we dive deeper into the fascinating world of evolution.