Please select target conditions first by clicking on the 'Breeding target' button.
Animal evolution
Selection pressures:
Mutation type:
Selection type:
Show fitness ranking:
Initial state:
Environment settings
Mottle size:
20
Colouring:
500
Colour A:
Colour B:
Colour C:
Animal options
Colour palette:
Overview
Select the headings at the top of the settings panel to model Evolution or Selective Breeding. You will see how the colouring and patterning of the animals changes over time in response to the environment (evolution) or your decisions (selective breeding).
General instructions
Environment settings: adjust the background colouring and the mottle-size slider.
Initial state: toggle this on to show the initial population and compare against the current one.
Generate animals: click this button to regenerate 10 new animals.
Population fitness (initial and current) is displayed at the top-right of the simulation panel.
Hovering over any animal displays its current genes and overall fitness.
The current generation is displayed at the bottom of the simulation panel.
Evolution instructions
Advance evolution step-by-step by clicking the Step 1 button, or automatically by toggling Auto-evolution mode.
Toggle selection pressures on or off to choose what gets selected for. Toggling both off removes selection pressures and results in genetic drift.
Toggle mutation type between Guided (weights mutations toward matching the background, less accurate but neater for learners) and Random (more accurate but slower).
Toggle selection type between Absolute (four fittest always selected, more children for fitter animals, less realistic but neater) and Probabilistic (fitness improves chance of selection but does not guarantee it, more realistic but slower).
Toggle Show fitness ranking to show or hide each animal's rank.
Selective breeding mode
Manual selective breeding: select the two animals with the most desirable features, click Step 1 to confirm the selection, and continue through the steps until the next round of selection. Repeat for several generations until the desired characteristics are seen.
Auto-breeding mode: click Breeding target to choose the characteristics you want to breed for, then toggle Auto-breeding mode to automate selection of the two individuals whose characteristics most closely match the target.
Evolution
Evolution is the process by which the characteristics of populations of living organisms gradually change over time in response to the conditions they live in. Evolution affects every single aspect of living organisms from their external appearance, to the workings of their cells and organs to the behaviour produced by their brains.
There is no single process for how evolution occurs, but it generally involves the following:
Environmental change - The environment changes in some way that means the organisms are no longer as well adapted (suited) to it as they used to be. This could be a change to the climate, a new predator or disease appearing, a new food source appearing; anything that affects the organism's chances of survival.
Note: Environmental change is not absolutely necessary - competition alone is enough to drive evolutionary changes, but environmental change can speed it up.
The circles represent organisms and the rectangle represents their environment. Their environment used to be red, so they were well camouflaged, but it has changed to blue and now they are very poorly camouflaged. Variation means that none of them are identical, and some are naturally slightly better adapted to the blue background than others.
Variation - No two organisms in a population are identical to each other, they have differences - called "variation" - caused by differences in the number and combination of alleles they inherit from the parents, and from mutations in their DNA. Variation means that some individuals in a population will be better adapted to withstand the challenges caused by the environmental change.
Natural selection
Different aspects of an organism's environment - climate, food, predators, disease etc - influence an organism's chance of survival, favouring some traits over others, this is called a "selection pressure".
Organisms with adaptations best suited to the selection pressures they face are more likely to survive long enough to reproduce and pass on their genes, this is called "natural selection". Natural selection is a game of chance: an organism with poor adaptations may still survive and breed because it gets lucky, whilst one with excellent adaptations may die young because it gets unlucky.
The "bluest" organisms are the least likely to be spotted by predators, and are the most likely to pass on their "bluer" genes to their offspring.
Reproduction and inheritance - The organisms that survive to breed tend to be the ones with the best adaptations, and pass the genes for those adaptations on to their offspring.
Some offspring will contain "mutations" in their genes that introduce new previously unseen variation into the population.
The "bluest" offspring reproduce and pass on their bluer genes to their offspring, some of which receive mutations that make them even bluer.
Many generations - Over many generations, the genes that code for the most successful traits will spread through the population. Over many generations, the small generation-to-generation changes build up so that the population can now be so different from the original one that it is a new species. This process is called "speciation", and is particularly likely to occur when two populations of a species become isolated so their genes cannot mix - for example a new river forms and splits a habitat in two, so the individuals on either side can no longer interbreed.
When the environment stays stable, speciation is less likely to occur, because the selection pressures remain the same, so there is less pressure for populations to change.
Generation 2
Generation 3
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Generation 1000
Note: In reality, evolution is much slower and much less "fixed" than these diagrams show.
Try this in the simulation:
In "Evolution" mode, adjust the values of the "Colour" and "Mottle size" sliders to whatever you like, and note the "Initial" value in the "Population fitness" readout.
Hover the mouse (PC) or tap (mobile) on one of the organisms to see its colour and mottle size genes.
Click the "Natural selection" button; organisms whose genes produce traits that most closely match the background survive, and those that least match their background die.
Click the "Reproduction or death" button; the survivors reproduce, with those with the best adaptations producing more offspring and passing on more of their genes.
Click the "Variation due to mutations" button, you will see that "mutations" happen in the offspring, causing them to look different to their parents. "Note:" this is the least realistic part of the simulation, in reality, mutations are rare, and they occur in the sperm and egg cells rather than the living offspring, but you would not be able to see that in the simulation.
Click the "Next generation" button again to go round the cycle again. You can click "Auto-evolution mode" to cycle through this process automatically.
Try repeating the whole process with one or more of the selection pressures switched off. You will see the genes tend to "drift", with the characteristics of the population changing over time, but not in a way that makes them better match their background.
Advanced - In order to make the simulation work in a small amount of time suitable for the classroom, the "Guided" mutation type nudges the mutations in favour of matching the environment. This is not realistic, and reality mutations are entirely random, with many making organisms less well adapted rather than making them better adapted. Similarly, natural selection has been set to "Deterministic" where the fittest always survive and have the most offspring, whilst in reality, they are simply more likely to. You can toggle both of these features off, and explore the effect on the speed of evolution; it does still work, but takes much longer to get there, accurately reflecting the random nature of evolution.