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Minds on

MINDS ON

Survival of the Fittest

This is an image of two dogs on a white background. The dog on the left is a large, black and white coloured Great Dane looking down at the dog on the left. The dog on the right is a much smaller tan-coloured puppy. The puppy is sitting, while the Great Dane is standing and looking down at the puppy.

You have most likely heard the phrase, ‘survival of the fittest,' but what does it actually mean?

This is the Portfolio icon. Survival of the Fittest

Without doing a search to see the true definition, jot down a few ideas of what you think the phrase ‘survival of the fittest’ means. 

 

Bill Shape Matters

This is a photoshopped image of a bear with a long scoop bill. The bear is standing at the top of a small water wall in a river. A salmon has jumped out of the water and the bear stretches its neck to reach the fish. The photoshopped bill is just about to clamp down on the fish.

Have you ever thought about why you see certain animals in one area and not in another? The climate is basically the same across your region, yet you expect to see different organisms in different environments within that region. What makes one habitat perfect for one animal but not another? Maybe it isn’t the habitat at all, and it is the animal, itself, that is perfect for that environment.

Imagine that there is a family of three birds in an area. Due to genetic variation, each bird was born with a different shaped bill (yep, they have a few other noticeable differences as well!) One has a ‘spoon’ bill, another has a ‘tweezer’ bill, and the third has a ‘flat’ bill.

This is an image of a white bird with tufts of feathers on its head and long, pink legs. The bird’s bill is long and flattened at the end like a spoon. The bill is grey in colour with a red border. The background is blurred brown and grey stones.
Spoon Bill

This is an image of a white bird on a black background. Its orange bill is long and tweezer-like.
Tweezer Bill

This is an image of a duck with white and light-brown feathers. Only the head of the duck is in the image. Its black bill is a classic long and flat duckbill. The background is blurred, green leaves.
Flat Bill

Who is the Fittest?

This is an image of a man struggling to open a glass jar of green pickles. The image shows him from the nose down to the waist. He is not wearing a shirt, and he exerting lots of effort to open the jar based on his flexed muscles and bared teeth. The image has a grey background.

Tasks like the one you just tried can give an inaccurate idea of what survival of the fittest truly means. It is easy to think that the best suited individual in an area is the most fit for survival. This does make sense, but there is more to it. Being the strongest, fastest, and most intelligent means little if that individual cannot pass its genetic material on to the next generation.

Survival of the fittest essentially deals with the idea of natural selection. You will soon see that natural selection relies on a number of different aspects, including cooperation among individuals for the good of the population. This isn’t an ‘every organism for itself’ type deal! This is a good time to go back to the survival of the fittest definition you created earlier and make any necessary tweaks to it.

This activity will take you through the processes of natural and artificial selection, and how these selective pressures can help to drive evolution. As you explore the content in the Action section, consider how human activity can influence the traits displayed by certain organisms, as this will play a substantial role in the culminating unit activity. You will see that the biotic and abiotic environment itself plays an important role when it comes to the fitness of the organisms that live in it. After all, changes in the phenotypes of the population are often initiated by changes in the environment.

Action.

ACTION

From Nothing to Something

From the last unit, you know that microscopic organisms such as bacteria and protists can be found almost anywhere. There are some species of Archaebacteria that can live in extreme conditions such as boiling water near undersea hydrovents! What about the more complex multicellular species of plants and animals?  These larger organisms often have more specific needs in terms of habitat and environmental factors. The Selection Activity showed you how the growth of plants can be impacted greatly by a number of different factors within that ecosystem. Because of their role as a food source and habitat for animals, the growth of plants in an ecosystem affects the growth of other species.

For example, you would expect to see a beaver live closer to a stand of alder and poplar trees (which are some of their favourites) rather than living in a pine forest. This helps illustrate that the plants established in an area will have a major impact on the animals that live there.

This is an image of forest with a dirt ground. Ten poplar trees are scattered throughout the image, with some in the foreground and some in the background. Three of the trees are lying on the ground beside their stump. The stumps have been chewed by a beaver and appear as sharpened pencils. Seven other stumps, also chewed by beavers, are scattered throughout the image but the rest of the tree associated with those stumps are not in the image.

Before we start looking at natural selection in terms of genetic processes and heredity, it is important that you understand the influence of the interactions between plants, animals, and the environment on the ‘fitness’ of the animals that live there. As the plants change, so do the other organisms that live there.

Succession

Ecological succession(definition:The process by which the structure of a biological community evolves over time.) is the gradual change of the species that make up a community over time. All ‘land’ on Earth had a beginning. This beginning started with molten magma coming to the surface and solidifying into solid rock. This process of land formation is still happening on our planet. In fact, starting on May 3rd of 2018, lava has been creating new land on the big island of Hawaii. Browse through the following video to see the stunning power of this magma flow.

 

When the magma cools and solidifies, the result will be solid rock. The heat of the magma destroys all life in its path, and the existing soil is covered. Hawaii is a volcanic island, but somehow that bare, barren rock becomes the foundation for lush plant life. How does this happen?

When you start with bare rock, primary succession is the process that takes place. The following interactive goes through the steps of primary succession.

PrimarySuccession

Long Description

 

The succession from bare rock to climax community can take hundreds of years. As the plant life changes, so does the microclimate(definition:The climate in a very small or restricted area.) in that area. Plants will help moderate temperature, wind and moisture levels. The changes in the region mean that a plant that once thrived may not be the most fit for the current conditions. As this happens, new plants take over.

Here is an interesting time lapse video showing the beginning stages of succession after the major Mount St. Helens eruption in 1980 in the Western United States:

 

As the vegetation and the climate changes, different animal species will be attracted to the area. Insects will start to find shelter and food in the beginning stages of succession, and then larger animals such as mice and birds will start to move in. As the shrubs and bushes establish themselves, there will be more shelter for larger animals. The diversity of life continues to increase as the area heads toward its climax community.

The change in biodiversity(definition:The variety of life in the world or in a particular habitat or ecosystem.) in the plant communities will drive change in the animal communities, as well. As the habitat changes, so do the resources in that area. An animal that was best suited for a grassland may not be the best fit for a habitat dominated by forest trees. As resources change, so too do the animal species who will dwell in that area.

Secondary Succession

This is an image of a small plant growing out of a crack in a paved parking lot. The plant is growing beside a yellow pole and a yellow line is painted on the pavement running from the bottom-left to the upper-right corner of the image.

Secondary succession is similar to primary succession, only this occurs after an established area has been disturbed by an event such as fire, flood, or human activity. The major difference between the two types of succession is the starting point. Unlike primary succession that starts with bare rocks, secondary succession starts with the soil and organic material that is left after the disturbance. This means plants can root soon after the disturbance as compared to waiting until soil is produced from bare rock.

If there is no human intervention in the secondary succession, it is possible that the climax community that forms may not be the same as the one that was established before the disturbance. Competition between plants and animals that move in during the succession process can have a large impact on the climax community that forms.

Take a few minutes to view the following video that shows some before and after images of succession. It is interesting to see the progression from one stage to the next. At the start of the video, an area after a forest fire is mentioned. Based on what you see, would the process that takes place after the fire be primary or secondary succession? Where do the (pioneer) organisms come from in the examples described in the video?

 

The habitat, and its position in the succession process, can help determine how successful an individual organism will be in terms of its survival. The environment has an impact on the fitness of an organism, but can other factors, such as human interaction increase or decrease its fitness?

Winds of Change: Evolution of Species

This is an image of five dandelions that are in seed mode and look like puff-balls. The plants are lined up horizontally, with only the seed ball and the top of the stem in the image. Each seed ball is a different colour. Moving from left to right, the colours are white, yellow, blue, green, and purple. The background is blurred, with green leaves.

The last section illustrated how changes in plant biodiversity within an area or ecosystem impact the animals that live there, but what about changes that occur within a species, itself?

In Unit 1, you saw how important is was for classification systems to be dynamic, as well as adjustable to allow for new information. Not only are we finding more new species all the time (and unfortunately, losing them, as well), the species that we do know are changing. These changes don’t happen overnight, and they aren't changes in a specific individual species. Instead, these changes happen to a population over generations. Simply put, species change, or evolve, over time.

It is important to understand that evolution(definition:Change in the heritable characteristics of populations over successive generations.) takes time, and involves a number of factors. In the Minds On section, you looked at birds that had different shaped bills, and the impact this variation would have based on available food resources. This type of variation can drive evolution, but it may not lead to evolution unless that trait is passed on to the next generation and beyond.

Not all evolution is based on useful adaptations that will help that species to survive. In fact, evolution is often based on errors that force change within a population (beneficial or not). We will learn more about these errors later on in this activity, but to see an example of an evolutionary change that was not beneficial, take a look at this article about the Antarctic icefish.

In the past unit, you looked at how sexual reproduction results in genetic variation. In the last few activities, you saw how the process of meiosis generates variation in gametes and how offspring inherit traits from both parents. It is these traits that can make individuals more fit or less fit for the environment in which they live. Are those the only processes that push evolution in a population from one generation to the next? Nope!

What Drives Evolution?

This is an image of a black cell phone being held by a hand coming in from the right-bottom of the image. The thumb is positioned over the screen about to touch a white tab at the bottom of the phone screen. On the screen is the word ‘UBER.' The background of the image is grey with shadowed corners.

Evolution is not only about the mechanics of transferring DNA and its associated characteristics to offspring. There is much more to it.

Before we look more deeply into evolution, it is important to remember that it is the theory of evolution that we will be exploring. This means that a number of plausible and scientifically accepted ideas have been used to explain evolution. Although these ideas have been well-substantiated and based on evidence, theories are subject to change as scientists learn more and more about a subject. Evolution is one of those subjects that is hotly debated (especially on the Internet!), and it is important to keep an open mind and give each theory a chance.

There are many misconceptions about evolution, many of which are caused by images like this:

This is an image showing four silhouettes arranged horizontally on a white background. The left-most image is an ape walking on all fours. The next ape-like figure to the right is walking on two feet but is still hunched over. The next figure to the right is more human-like, but still slightly hunched. The final figure on the right is a modern man standing upright on two feet.

People did not evolve directly from apes. Instead, there is evidence that humans share a common ancestor with modern apes that existed five to eight million years ago. It is believed that two separate lineages diverged from that common ancestor, with one evolving into apes, and the other into humans. This next image shows how species are related based on those common ancestors.

This is a diagram showing how species are related to a common ancestor. Across the top of the image are depictions of nine animals, each with a label beneath them. Starting at the left is a white and black lemur with the label ‘Lemurs, Lorises and Pottos'. The next over is a grey tarsier grasping a tree labelled ‘Tarsiers.' The next is a brown monkey with a white face labelled ‘New World Monkeys.' The next is a grey monkey with a pink face labelled ‘Old World Monkeys.' The next animal to the right is a black gibbon labelled ‘Gibbons.' Next over is an orangish-brown orangutan labelled ‘Orangutans.' The next to the right is a black ape labelled ‘Gorillas.' The next to the right is a black chimp with a pink face labelled ‘Chimpanzees,' and the last image on the right is a nude human labelled ‘Humans.' A square bracket about the lemur and tarsiers is labelled ‘Prosimians.' Another square bracket encompasses the rest of the animals and is labelled ‘Anthropoids.' Below the images is a graph, with the animals making up the x-axis and the y-axis on the left labelled as ‘Millions of Years ago’ and there is a scale from 0 down to 60. Square brackets below the images show the lineage and the date at which they split. These brackets are nested starting from the right. Chimpanzees and Humans share a bracket that indicates the split at 5 on the graph. Moving left, the next bracket connects Gorillas to the last bracket at 7 on the scale. The next connects Orangutans to the last bracket at 9. The next bracket to the left connects Gibbons to the last bracket at 15. Old World Monkeys are then connected to the last bracket at 26 on the scale. The next bracket to the left connects New World Monkeys to the last bracket at 45. The next over connects Tarsiers to the last bracket at 50. The last bracket to the left connects Lemurs, Lorises and Pottos to the last bracket at 55 on the scale. A line extends down from that last bracket to a yellow box that reads ‘Ancestral Primate’ at the 60 on the scale.
Different lineages diverged from a common ancestor.

This video tries to dispel some of the common misconceptions about evolution.

 

Mechanisms of Evolution

There are a number of mechanisms that drive evolution, but the main five are mutations, natural selection, sexual selection, genetic drift, and gene flow. You will look at each one of these mechanisms below.

Mutations

This is an image of an x-ray on a black background. The image on the x-ray is a hand coming up from the bottom with the fingers curled in a fist. Between each finger is a long blade-like extension, indicating that this is an x-ray of the X-men’s Wolverine.

In the last activity, you looked at traits being passed from one generation to the next. Through your study of meiosis, you understand how crossing over and independent assortment result in variation between the gametes produced. But wait...why are there different alleles for the same characteristic in the first place? Why is it that one person can roll her/his tongue while another can’t? If all humans are the same species, shouldn’t we all have the exact same genes and express the exact same traits?

Although the process of DNA replication and cell division is amazingly robust and involves its own system of proofreading, some errors can still occur. It is these errors, or mutations, that produce the different alleles for a characteristic.

Some mutations only affect the individual, while others can be passed onto the next generation through the inheritance patterns you just explored in the last activity. It is these heritable mutations(definition:A mutation that can be passed from parent to offspring.) that have an impact on a species as a whole.

The word mutation is often associated with harmful defects, but that is not always the case at all. When talking about evolution, you need to determine what the impact that the mutation has on the chances of that individual passing on its genetic material to the next generation. After all, that is what success is all about.

A majority of mutations that occur don’t have any impact on an organism's ability to pass on DNA to its offspring; that is to say that the change does not create an advantage of disadvantage in terms of reproductive success. This type of mutation is referred to as a neutral mutation.(definition:A mutation that does not increase the reproductive success of an individual.)

There are also harmful and beneficial mutations. Again, the harm or benefit is based on the impact it has on reproductive success. If it is a deleterious,(definition:A mutation that reduces the reproductive success of an individual.) or harmful, mutation, then the organism’s ability to pass on genetic material is decreased. If the mutation is a beneficial mutation,(definition:A mutation that increases the reproductive success of an individual.) the ability to pass on the traits to the next generation is increased.  

What effects do these different types of mutations have on evolution?

This is the question/answer icon. Challenge!

Neutral mutations have no real impact at all, but neither do some harmful, or deleterious, mutations. How can that be? Why do you think that some harmful mutations wouldn’t have an impact on the population in the next generation and beyond?
Answer

If a mutation is harmful, it may prevent the organism from reaching sexual maturity or from successfully finding a mate. This means that the organism will not be able to pass on the mutation to the next generation. Less harmful mutations may still be passed on if they don’t have a catastrophic impact on the organism.

 

Remember, harmful mutations decrease the chance of passing on genetic material. If that individual does not produce offspring, then the mutation will not be passed onto the next generation.

On the other hand, beneficial mutations increase the chances of reproductive success, in that the mutation makes the individual more fit for the current environment in which it lives. This means that these mutations, if heritable, will be passed on and can shape the population in the future generations.

See if you can determine if the mutations in this interactive are neutral, beneficial, or harmful. Drag the mutation’s description to the type of mutation you think it most likely falls under to see if you are correct.

Mutations

Long Description

 

Being able to pass your genetic information and traits to the next generation is the main biological goal of life. This is where the idea of survival of the fittest comes into play. Based on the current conditions, the fittest individuals are the ones that are able to survive and pass on their DNA to their offspring. Being the strongest or fastest doesn’t mean much in terms of evolution unless those traits are passed onto the next generation. This is the basis of natural selection.(definition:The process in nature by which only the organisms best adapted to their environment tend to survive and pass on their genes to the next generation.)

Evolving Ideas

Discussions about evolution almost always revolve around the theories of Charles Darwin. You will soon see that this course isn’t much different! The contributions that Darwin made to our understanding of evolution cannot be underestimated, but it is important to realize that many other scientists also had a hand in the development of these theories. To this day, there are scientists studying evolution and what drives it. The following interactive shows you some of the ideas that have been proposed before and after Darwin’s theories. As you explore this interactive, notice how earlier ideas are used with new evidence to further scientific understanding. This is the same process you are using in the investigations in this unit.

Theories

Long Description

 

Natural Selection

This is an image of a statue of Charles Darwin in white marble. The image shows the statue from the chest up. He is wearing an overcoat, has a long beard, and is bald on the top of his head. The background is a tiled wall in a mosaic pattern. The tiles are blue, grey, and brown.
A statue of Charles Darwin at the Natural History Museum in London.

This activity has so far shown how certain individuals have traits that make them better suited or have a better ‘fit’ for the conditions in which they exist. These organisms then have a better chance to pass on their genetic information to the next generation.

Charles Darwin, an English naturalist, geologist, and biologist, published a book in 1859 titled On the Origin of Species.  It detailed the theory of natural selection. After studying the differences in populations of similar species in different environments, Darwin saw how nature favoured the reproductive success of certain individuals. In essence, nature ‘selected’ which organisms would pass on their genetic information. Evolution was therefore a result of this natural selection over generations.

Darwin theorized that different groups of a single species could evolve into distinct species as a result of their environment. This allopatric speciation(definition:Speciation, or species formation, that occurs when biological populations of the same species are isolated from each other due to geographic barriers.) occurs when groups of the same species are separated by geographic barriers such as great distances or mountain ranges and not allowed to interbreed.

This video will give you a nice overview of Darwin’s travels and how his observations led to his theories. As you watch the video, see if you can identify some of the geographic barriers Darwin observed between similar species on the Galapagos Islands.

 

Darwin based his theory on observations that he made while studying various populations. Pay close attention to how Darwin recorded his observations, made inferences(definition:A conclusion reached on the basis of evidence and reasoning.) about what the observations represented, and then produced a theory based on those inferences. This is the process that you should go through whenever you participate in an inquiry. You have been thinking about hypotheses throughout this unit. You will have the opportunity to analyse population data in the Consolidation section. ‘Be like Darwin!'

This is an image of a flow chart that has three columns. The left column is labelled ‘Observations’ on the top, and consists of five orange rectangles. Moving from top to bottom, the contents of the rectangles are ‘In each generation, populations produce more offspring than there are adults’, ‘Populations do not continue to grow in size’, ‘Food and many other resources are limited’, ‘Individuals within all populations vary’, and ‘Many variations are heritable.' The middle column is labelled at the top as ‘Inferences’ and consists of two green rectangles. The top three rectangles from the first column have lines coming from them that flow right and lead to the top rectangle in the middle column, which contains ‘Individuals within a population compete for resources.’ The bottom two rectangles in the left column have lines coming from them that flow right and lead to the bottom rectangle in the middle column, which contains ‘Some individuals will inherit characteristics that give them a better chance of surviving and reproducing.’ Each rectangle in the middle row has a line coming from it that meets up and flows to the right to connect with the only rectangle in the right-most column. The column has the label ‘Theory of natural Selection’ above it. The blue rectangle contains ‘Over time the population changes as advantageous heritable characteristics become more common generation after generation.'
The development of Darwin's theory.

This video does an excellent job of showing how natural selection can change the makeup of a population over generations. As you watch the video, see how the phenotype frequency(definition:The number of individuals in a population that have a specific observable trait or phenotype.) of different traits in a population changes over generations.

This is an image of a screenshot for the Vimeo natural selection video.
Click the image to view the video!

Evolution doesn’t mean that species are always gaining new traits. It can also mean that certain traits are being lost as they are no longer needed. Remember, evolution is change over time, so any change fits the definition.

Take a look at this interesting video to see some of the human traits that have been lost over generations, and how we still hang on to slight remnants of these traits, called vestigial features.(definition:A non-functioning or marginally functioning structure that is similar to a fully functional feature in closely related species.)

 

It is quite easy to see the advantages of natural selection. Survival of the fittest means that the best genes of a population will be passed on to the next generation, resulting in a better chance of survival in certain conditions. As those conditions change over time, so do the genetic traits of the species. You will have a chance to look at a specific example of this in the Consolidation section.

Types of Natural Selection

Natural selection can be categorized by the impact it has on an allele frequency(definition:The proportion of individuals in a population carrying the same allele.) within a population. Certain traits may be selected against, as you saw in the video above, while others are selected for. The following interactive will demonstrate the differences between the main types of natural selection: stabilizing selection, directional selection, and disruptive selection.

Selection

Long Description

 

Selection Pressures

Why does a change in the environment in which an organism live have an impact on its fitness? With a change in environment, comes a change in the selection pressures(definition:The set of all the environmental factors which define whether an organism will be more or less successful at surviving and reproducing.) with which the organism must deal.

Pressures such as competition with other species, resource availability, and disease all play a role when it comes to an organism's fitness in a given environment.

To remember the main selection pressures that species must deal with, think about a panda paw. How does a panda paw have anything to do with selection pressure you ask? Click on the panda below to find out!

This is an image of a cartoon panda. It is standing on its hind legs and is holding up its right arm, showing a pink paw and three ‘fingers.'
Click me!
 

Mechanisms of Evolution Continued

The final three mechanisms of evolution you will look at - sexual selection, genetic drift, and gene flow - are presented in the following carousel.

 
 

The five main mechanisms of evolution described above can be remembered by looking at your hand. This is explained in the video below. It is important to note that there are multiple names for each mechanism. While you watch this video, make sure you can relate each mechanism to what has been discussed in this activity. Whenever you see an example of evolution, try to determine which of the five mechanisms were involved.

Also, pay particular attention to the ideas of microevolution(definition:Evolutionary change within a species or small group of organisms, especially over a short period.) and macroevolution(definition:Large scale evolutionary changes including the formation of new species.) that are presented at the end of the video. 

 
 

When Nature Just Isn’t Enough...

Natural evolution has a way to make sure that populations can survive and continue on generation after generation even as the environment in which they live changes.

Now, you know that humans can’t resist getting involved! In fact, human interaction with this natural process has been going on for thousands of years. From the domestication(definition:To convert or tame animals and plants to live in close association with humans.) of animals to the cultivation of specialized crops, humans have had an effect on the evolution of a vast number of species. The question is whether this interaction has had a positive or a negative impact on the genetic diversity of this planet.

...Humans Interfere

This is an image of an incredibly large bull standing in a field with a wire fence and trees in the background. A man wearing blue jeans and a blue shirt is holding on to the bull’s harness. The bull has a white coat, but has been shaved down to pink skin in certain areas to show off its bulging muscles.
A Belgian Blue with the ‘double muscle’ mutation that farmers selected.

Natural selection is just that...natural. This means that nature decides which individuals will have a better chance at reproducing and passing on their genetic material to the next generation.  

Remember being introduced to animals like the liger and tigon in the last unit? What do you think the chances are that those animals would be a natural occurrence? Think about it in terms of natural selection. Since lions and tigers do not live in the same geographical location, the chances of a pairing between these two animals would be impossible. In addition, there would be no reproductive advantage to the survival of either species of cat due to the creation of these hybrids. This alone goes against the theory of natural selection.

Ligers have actually occurred by accident with lions and tigers in captivity, but the captive environment in not natural, so it was human interference that initiated the creation of this hybrid animal.

This is an image of a liger lying on a rock platform. In the background are the zoo cage bars and there is a dark rock wall to the right of the image. The liger has its head up and is looking forward with the mouth slightly open.
A liger is a cross between a male lion and a female tiger.

Artificial Selection

This is an image of a zoo enclosure with a sand floor and rock walls. In the background is a brown material canopy with a tortoise under it. In the centre of the image is a woman in beige shorts and a blue short-sleeve shirt with blond hair in a bun and wearing sunglasses. She is holding a shell of a tortoise to steady it as it climbs on top of another tortoise to mate.
Zoo breeding programs can help restore dwindling populations.

After being hunters and gatherers for generations, humans realized that life would be much easier if they could stay in one place. To do that, they would need to domesticate plants and animals and find some control over their life cycles. Human manipulation can be as simple as trying to get a plant to survive in an area in which it naturally wouldn’t. When humans, rather than nature, decide which traits are the most desirable and then control breeding to manipulate those traits, this is called artificial selection.(definition:Selective breeding of plants and animals to produce desirable traits.)

Domestication of crops and livestock has been a huge advantage to our species, and has allowed us to create powerful civilizations. Evidence of humans picking and choosing traits that we find beneficial as a species and breeding those traits into the next generation has been found throughout history. Prior to the arrival of Europeans, the Indigenous peoples of the lower Great Lakes and St Lawrence regions planted two types of maize, squash and beans, and practised seed selection by choosing the seeds from only the best produce. This artificial selection helped ensure robust crops with the most desirable traits.  

In addition to emphasizing the most important aspects of what we farm, we have been able to create new varieties of plants and animals. Each new variety has some advantage to us over the others in areas such as, higher meat and milk yield, better drought and pest resistance, and increased nutritional value. Almost every single food product we eat today is made from ingredients that were produced by artificial selection.

 

The Great Manipulation

This is an image of a wild cabbage plant growing in dry, brown soil surrounded by rocks. In the background is a side of a hill sparsely covered with low, green shrubs. The plant has long green leaves at the base and long stalks coming up through the centre topped with small, yellow flowers.
Brassica oleracea or wild cabbage.

Wild cabbage is easy to grow, and can survive in dry conditions. It produces thick leaves that stores water and nutrients such as Vitamin C. This plant has been domesticated for thousands of years, and has been an important food staple for many civilizations.

Having been domesticated for so long, it isn’t hard to imagine that artificial selection has produced a wide variety of plants from this original species. The interactive below shows you some of the varieties of vegetables that have come from the original wild cabbage, and the traits that each variety accentuates. Each vegetable is a variety, or cultivar,(definition:A plant variety that has been produced in cultivation by selective breeding.) of the same species Brassica oleracea. Try your hand at matching the cultivar to the trait that it was selected for.

Cabbage

Long Description

 

Now that you have explored both natural and artificial selection, it is time for you to look at the advantages and disadvantages of both.

 

What Does it All Mean?

Although genetic diversity is a product of sexual reproduction, there are many factors at play when it comes to evolution. The process starts with mutations creating new versions of alleles. These new traits can then make some individuals better suited for the environment, giving them a better chance at reproductive success. Passing on these new traits to the next generation through natural selection can increase the allele frequency within a population. This, along with other factors, such as gene flow, genetic drift, and sexual selection, can be the drive behind evolutionary change over the generations.

In addition to this natural selection, humans have made an impact on various populations based on artificial selection. In this process, we often override the natural ‘survival of the fittest’ progression and influence the next generation based on traits that we feel are the most beneficial. There is debate as to whether or not our interactions with the natural evolutionary process are a help or a hindrance to the genetic diversity of our planet..

Consolidation

CONSOLIDATION

Artificial Enhancement

This is an image of a dog’s head superimposed on top of an image of a person wearing a grey suit and brown tie. The suit can be seen from the waist up. The dog is brown with long, fluffy ears. The background is a blurred field with water and hills in the distance.
Humans use artificial selection to enhance traits that ‘suit’ our needs.

Human interactions with the natural world are nothing new. We often look for traits that we find desirable and suit our own purposes. These traits may not increase the fitness of an animal or plant in its local environment, but these organisms are not really meant to live on their own in the wild. Unfortunately, these artificially selected organisms do get out into the natural environment and can impact the allele frequencies in those populations. Almost without exception, the organisms that we help create or modify have an influence in our natural world.

 

Evolutionary Biology

Evolutionary biology is the subfield of biology that studies the process of evolution and how it contributes to the diversity of life on Earth. Take a look at this short video to get a feel for some of the research involving an evolutionary biologist.

 

In this next task, you will assume the role of an evolutionary biologist and follow in the steps of Darwin and his work with finches on the Galapagos Islands. You already know a bit about Darwin’s voyages from earlier in this activity, but take a few minutes to learn about his discoveries based on finches. The first video shows the traits of this species of bird. The second video will give you a better look at the different beak shapes found on Galapagos finches, based on the food source available to them:

 

 

This is the dropbox icon. The Speed of Change

This is an image of two people, a man and a woman, standing side by side and looking at the camera and smiling. They are both wearing white buttoned shirts and a backpack with black straps. Both have grey hair, and the man on the left has a grey beard. The background is trees with a red-brick building in the distance. A concrete staircase runs up behind the woman on the right of the image.
Peter and Rosemary Grant.

From 1973 to 2012, British evolutionary biologists Peter and Rosemary Grant spent six months capturing and tagging finches on Daphne Major and Santa Cruz in the Galapagos Islands.

Listen to Peter and Rosemary explain how the understanding of evolution has changed in their lifetimes.

 

Evolution was thought to take many generations to become apparent, but the Grants were able to show that evolution responds much more quickly to environmental conditions such as drought. This selective pressure is one of the “panda paws” you learned about earlier.

Much of their work focused on the connection between the beak shape of finches and natural selection, as mentioned earlier in this activity. Think back to your understanding of the meaning of 'survival of the fittest.' Your task is to analyse some raw data about the beak depth of parents and offspring to investigate the influence that environmental conditions and location have on the traits found within populations.

This is an image of a black finch with a brown beak. Only the head of the bird is shown, and it is looking to the right. A horizontal white line is drawn on the image just above the beak and one just below. There is a vertical arrow with an arrow head on both ends and the label ‘Beak depth’ to the right of the arrow.
How beak depth is measured.

This is the question/answer icon. Challenge

Do the studies conducted by the Grants on the Galapagos Islands look at microevolution or macroevolution?
Answer

The changes in the finch beaks over short periods of time is an example of microevolution, as it is happening on a small scale and within a single population.

 


 

 

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