Unit A Lesson 5: Variations and Species
Completion requirements
Unit A Lesson 5: Variations and Species |
Learning Targets |
Inquiry Question: Is variation among species more than just skin deep?
The variations between species, and individuals within a species, can be the difference between life and death.
The variations between species, and individuals within a species, can be the difference between life and death.
At the end of this inquiry, you should be able to answer the following questions:
- Why does variability occur within species?
- What is interspecies competition?
- What is natural selection?
Pages 21 to 24 in your textbook will help you answer these questions about variations and species.
Introduction
How are the kittens in Figure 1 and the snakes in Figure 2 similar to one another? How are they different? Does variation within a species mean only differences that we can see?
Figure 1 - Kittens are cute, fluffy, and snuggle warmly in your arms.
Figure 2 - Snakes are cute, scaly, and snuggle against you for warmth.
Why is variation within species important?
The stability of an ecosystem relies on the diversity of its communities and species. The ecosystem is like a puzzle where each piece occupies its own niche yet relies on other species for survival. Variation within species (intraspecies variation) is important so genetic differences occur among species members. Not only would the world be a boring place if we all looked exactly alike, but if we were the same genetically, then we would have the potential to be wiped out with one disease (figure 3).
Why is variation between different species important?
To keep our world from being taken over by tigers and zebras, we need to have various organisms of species. Biodiversity is important for the balance of our ecosystems. Variations between species (interspecies variation) ensure that competition keeps any one species from taking over the earth. This is known as interspecies competition (figure 4).
The stability of an ecosystem relies on the diversity of its communities and species. The ecosystem is like a puzzle where each piece occupies its own niche yet relies on other species for survival. Variation within species (intraspecies variation) is important so genetic differences occur among species members. Not only would the world be a boring place if we all looked exactly alike, but if we were the same genetically, then we would have the potential to be wiped out with one disease (figure 3).
Why is variation between different species important?
To keep our world from being taken over by tigers and zebras, we need to have various organisms of species. Biodiversity is important for the balance of our ecosystems. Variations between species (interspecies variation) ensure that competition keeps any one species from taking over the earth. This is known as interspecies competition (figure 4).
Figure 3 - Intraspecies variations help to ensure that a disease does not kill the entire population.
Figure 4 - Interspecies variations help to ensure all niches are filled.
Watch More
The video βWhat are interspecific and intraspecific interactions?β explains the difference between interspecies and intraspecies interactions.
In 1918, an influenza outbreak killed more than 50 000 Canadians and killed 25 million people worldwide. Variability within the human population (intraspecies variation) allowed some humans to remain uninfected and, therefore, the flu did not
wipe out the entire population of humanity. For more information on the Spanish flu and other pandemics, watch the video "How the Spanish Flu Killed More People than World War One".
Figure 5 β This type of Galapagos finch eats insects.
Figure 6 β This type of Galapagos finch eats nuts and seeds.
Natural Selection
Natural Selection also increases variability within species and helps increase survival.
Natural selection is the process by which the environment selects organisms that are more suitable for survival to carry on and have offspring. Over time, the traits that increase the survival rates of species become the dominant traits.
All living things are the result of natural selection. The saying "Survival of the fittest" is a simplified version of how natural selection works because it's not always the strongest that survive; a better saying would be "Survival of those lucky enough to have the characteristics that give them an advantage compared to everyone else".
Natural Selection also increases variability within species and helps increase survival.
Natural selection is the process by which the environment selects organisms that are more suitable for survival to carry on and have offspring. Over time, the traits that increase the survival rates of species become the dominant traits.
All living things are the result of natural selection. The saying "Survival of the fittest" is a simplified version of how natural selection works because it's not always the strongest that survive; a better saying would be "Survival of those lucky enough to have the characteristics that give them an advantage compared to everyone else".
Figure 7 β Darwin's sketches of the Galapagos finches show an understanding of natural selection.
Watch
Check this video of Charles Darwin and his finches to learn how the environment rules out the weaker members within a species.
Interactive
Natural selection is the process we use to explain how living things and their children become better and better adapted to their environments.
Click here
to watch the BrainPOP video "Natural Selection" about Charles Darwin and his idea of natural selection.Check out some of the other interactive activities on this page while you're there.
You will need a username and password to access the video.
You will need a username and password to access the video.
- Username: 0099
- Password: students
Recall the term
speciation
from the first inquiry question. Natural selection over millions of years eventually causes new species of animals to be named, such as Darwinβs finches. If you have forgotten what speciation is, click here to go back to that lesson now.
Try It!
Practice Worksheet: Natural Selection
1. DOWNLOAD this practice worksheet (S9_UA_S1_L5_natural_selection) worksheet. If you prefer to use a Google Drive or PDF version of the worksheet, click here.
2. Click on the image to the right to download and open the "Natural Selection" application and run the simulation of bunnies in the forest. See the note below if you have trouble opening the application. Complete the worksheet.
3. When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below.
Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
1. DOWNLOAD this practice worksheet (S9_UA_S1_L5_natural_selection) worksheet. If you prefer to use a Google Drive or PDF version of the worksheet, click here.
2. Click on the image to the right to download and open the "Natural Selection" application and run the simulation of bunnies in the forest. See the note below if you have trouble opening the application. Complete the worksheet.
3. When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below.
Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
Note: This simulation is a java applet. You may have trouble running it on your computer. If you are unable to activate java on your computer, don't worry, just watch the video below instead, it runs through the
simulation for you.
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5. A true ecosystem may have other predators and different types of food. The bunnies would have to interact with other organisms.
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5. A true ecosystem may have other predators and different types of food. The bunnies would have to interact with other organisms.