Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 40m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 12m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

21. Evolution

Introduction to Evolution and Natural Selection

General Biology

21. Evolution

Introduction to Evolution and Natural Selection

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Multiple Choice

What is the best explanation for the change in green anoles' toe pads over time?

Mutations in toe pad genes always result in larger toe pads, regardless of environmental conditions.

Green anoles intentionally changed their toe pads in response to environmental challenges.

Natural selection favored individuals with larger toe pads, allowing them to better grip smooth surfaces and survive in their environment.

Genetic drift randomly increased the frequency of larger toe pads in the population, regardless of environmental pressures.

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Verified step by step guidance

Step 1: Begin by understanding the concept of natural selection. Natural selection is a process where individuals with traits that provide a survival or reproductive advantage are more likely to pass those traits to the next generation. Over time, this leads to the prevalence of advantageous traits in a population.

Step 2: Analyze the environmental challenge faced by green anoles. In this case, smooth surfaces in their environment may have made it difficult for individuals with smaller toe pads to grip effectively, reducing their chances of survival and reproduction.

Step 3: Consider the role of genetic variation. Within the population of green anoles, there would have been individuals with varying toe pad sizes due to genetic differences. Those with larger toe pads had a better ability to grip smooth surfaces, giving them a survival advantage.

Step 4: Understand how natural selection acts on these variations. Over generations, individuals with larger toe pads were more likely to survive and reproduce, passing the genes for larger toe pads to their offspring. This led to an increase in the frequency of larger toe pads in the population.

Step 5: Compare natural selection to other mechanisms like genetic drift or intentional change. Genetic drift is a random process and does not depend on environmental pressures, while intentional change is not biologically possible. Natural selection is the most plausible explanation for the observed change in toe pads, as it directly relates to the environmental challenge and survival advantage.