Year 11 Biology: Natural Selection, Variation, and Evolution

Understanding Natural Selection

Natural selection is a process that explains how species change over time. It was proposed by Charles Darwin. Here’s how it works:

Key Concepts of Natural Selection

1. Variation: In any group of living things, there are differences. For example, some rabbits may be brown, while others are white. This is called variation.
2. Competition: Living things compete for resources like food, water, and shelter. Not all individuals will survive.
3. Survival of the Fittest: The individuals with traits that are better suited to their environment are more likely to survive and reproduce. This doesn’t always mean the strongest; sometimes it’s just the best adapted.
4. Reproduction: The individuals that survive will pass on their traits to their offspring. Over time, these traits become more common in the population.
5. Evolution: This process of change can lead to new species forming over a long time.

Example of Natural Selection

Let’s say we have a population of beetles. Some are green, and some are brown. If they live in a forest where the ground is brown, the brown beetles will be less visible to predators. As a result, more brown beetles will survive and reproduce. Over many generations, the population will have more brown beetles because they are better suited to their environment.

Understanding Variation

Variation is important because it provides the raw material for natural selection to act upon. Without variation, all individuals would be the same, and if the environment changed, the entire population could be at risk.

Types of Variation

1. Genetic Variation: This comes from differences in genes. For example, some dogs may be big, while others are small due to their genetic makeup.
2. Environmental Variation: This is caused by differences in the environment. For example, plants in sunny areas may grow taller than those in shady areas.

Tips and Tricks to Remember

• Think of a garden: Imagine a garden with flowers of different colours. Some colours might attract more bees, helping those flowers reproduce better.
• Remember the phrase “survival of the fittest”: This doesn’t just mean strength. It’s about being the best fit for the environment.
• Use real-life examples: Look at animals and plants around you. Notice their differences and think about how these might help them survive.

Questions to Test Your Understanding

Easy Level (1-20)

1. What is natural selection?
2. Who proposed the theory of natural selection?
3. What does variation mean?
4. Give an example of variation in animals.
5. What do living things compete for?
6. What phrase describes how the best-adapted individuals survive?
7. What happens to traits that help survival?
8. What is evolution?
9. Can you name one factor that causes environmental variation?
10. Why is variation important for natural selection?
11. What colour of beetle might survive better in a brown environment?
12. How do traits get passed on to offspring?
13. What is genetic variation?
14. What is one example of competition in nature?
15. How might a change in environment affect a population?
16. Why do some flowers attract more bees?
17. What is meant by “survival of the fittest”?
18. How does natural selection lead to evolution?
19. Give an example of a trait that might help an animal survive.
20. Why don’t all individuals in a population look the same?

Medium Level (21-40)

21. Describe a situation where environmental variation could occur.
22. Explain how natural selection can lead to speciation.
23. What role do predators play in natural selection?
24. How does genetic variation arise?
25. Can natural selection occur in human populations? Give an example.
26. What is the difference between artificial and natural selection?
27. Give an example of a species that has evolved due to natural selection.
28. How do mutations affect variation?
29. What is adaptation?
30. Why is it important for a species to adapt to its environment?
31. How can climate change impact natural selection?
32. What are some traits that might be advantageous in a cold environment?
33. Explain how competition can lead to changes in a population over time.
34. How does the concept of “fitness” relate to natural selection?
35. Can you think of an example of a trait that is not beneficial in a certain environment?
36. How might a drought affect the natural selection of plants in an area?
37. What is the role of reproduction in natural selection?
38. How might overpopulation affect natural selection?
39. Describe how a new predator could affect a population of prey.
40. How does human activity influence natural selection?

Hard Level (41-60)

41. Discuss how the Galapagos finches are an example of natural selection.
42. Explain the concept of “survival of the fittest” in more detail.
43. What evidence do scientists use to support the theory of evolution?
44. How does genetic drift differ from natural selection?
45. What is the significance of the fossil record in understanding evolution?
46. Describe the process of speciation.
47. How can isolation lead to evolution?
48. Explain how sexual selection is a form of natural selection.
49. What impact do invasive species have on local ecosystems?
50. How do scientists study natural selection in real-time?
51. Discuss the role of environmental changes in the process of evolution.
52. How do ecosystems demonstrate natural selection?
53. What is co-evolution, and can you give an example?
54. How does the concept of niche relate to natural selection?
55. Explain how antibiotic resistance in bacteria is an example of natural selection.
56. Describe how human influence can disrupt natural selection.
57. Why is genetic diversity important for the survival of a species?
58. Discuss the role of phenotypes in natural selection.
59. Explain the importance of biodiversity in ecosystems.
60. How might future changes in the environment affect human evolution?

Answers and Explanations

Easy Level Answers

1. Natural selection is the process where organisms better adapted to their environment tend to survive and produce more offspring.
2. Charles Darwin proposed the theory of natural selection.
3. Variation means differences among individuals in a population.
4. Example: Some rabbits are brown, and some are white.
5. They compete for food, water, and shelter.
6. “Survival of the fittest.”
7. They become more common in the population.
8. Evolution is the change in the inherited characteristics of a population over time.
9. Weather, food availability, or space.
10. It allows for better adaptations to changing environments.
11. Brown beetles would survive better in a brown environment.
12. Through reproduction, traits are passed on to offspring.
13. Genetic variation comes from differences in genes among individuals.
14. Animals competing for food.
15. It can lead to some individuals dying off or thriving.
16. Because certain colours might be more attractive to bees.
17. It means being best suited to the environment, not just being strong.
18. Over time, advantageous traits increase in frequency in the population.
19. Example: A thick fur coat in cold weather.
20. Because of genetic differences.

Medium Level Answers

21. Changes in rainfall can lead to different plant growth patterns.
22. It can lead to speciation when populations become so different that they can’t interbreed.
23. They help control population sizes and affect survival.
24. Through mutations and sexual reproduction.
25. Yes, for example, lactose tolerance in some human populations.
26. Artificial selection is when humans choose traits, whereas natural selection is based on environmental pressures.
27. Example: The peppered moth during the Industrial Revolution.
28. Mutations can create new traits that increase variation.
29. Adaptation is a trait that helps an organism survive in its environment.
30. It helps the species survive environmental changes.
31. It can change which traits are advantageous.
32. Thick fur or fat layers may be advantageous.
33. It can lead to the decline of less competitive individuals.
34. “Fitness” relates to how well an organism can survive and reproduce.
35. Example: Bright colours in a predator-rich environment.
36. It could lead to the death of plants that can’t survive without water.
37. Reproduction allows advantageous traits to spread.
38. It can lead to more competition and resource depletion.
39. It could lead to the decline of certain prey species.
40. Human activities like habitat destruction can change selection pressures.

Hard Level Answers

41. The finches adapted their beak shapes to different food sources on the islands.
42. It means that the individuals that are best suited to their environment are more likely to survive and reproduce.
43. Fossils, genetic studies, and observed changes in species.
44. Genetic drift is random changes in allele frequencies, while natural selection is based on advantageous traits.
45. It shows how species have changed over time and can provide links to common ancestors.
46. Speciation is the formation of new and distinct species in the course of evolution.
47. Isolation can lead to different adaptations in different environments.
48. It occurs when certain traits are favored in mate selection.
49. They can outcompete local species for resources.
50. By observing changes in populations over generations.
51. Environmental changes can create new challenges and selective pressures.
52. Ecosystems show how species interact and adapt to their environment.
53. Co-evolution is where two species influence each other’s evolution, like flowers and their pollinators.
54. A niche is the role a species plays in its environment, which can affect its survival.
55. Bacteria that survive antibiotic treatment can pass on resistance to their offspring.
56. It can lead to loss of natural selection pressures.
57. It helps populations adapt to changing environments and resist diseases.
58. Phenotypes are the expressed traits that are subject to natural selection.
59. Biodiversity improves ecosystem resilience and function.
60. Changes could lead to new adaptations or survival challenges for humans.

By understanding these concepts, you will gain a clearer picture of how life on Earth changes and adapts over time!