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 20m
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 52m
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 57m
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

1. Introduction to Biology

Experimental Design

General Biology

1. Introduction to Biology

Experimental Design

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1:43 minutes

Problem 6`

Textbook Question

A controlled experiment is one that
a. Proceeds slowly enough that a scientist can make careful records of the results.
b. Keeps all variables constant.
c. Is repeated many times to make sure the results are accurate.
d. Tests experimental and control groups in parallel.

Verified step by step guidance

Understand the definition of a controlled experiment: A controlled experiment is a scientific test where the researcher manipulates one variable (independent variable) while keeping all other variables constant to observe its effect on the dependent variable.

Identify the key components of a controlled experiment: It involves an experimental group (where the independent variable is altered) and a control group (where the independent variable is not altered). These groups are tested in parallel to compare results.

Analyze the options provided in the question: Option (a) refers to the speed of the experiment, which is not a defining feature of a controlled experiment. Option (b) suggests keeping all variables constant, which is incorrect because the independent variable is intentionally changed. Option (c) refers to repetition for accuracy, which is a good practice but not specific to controlled experiments. Option (d) correctly describes the parallel testing of experimental and control groups.

Eliminate incorrect options based on the analysis: Options (a), (b), and (c) do not align with the definition of a controlled experiment, leaving option (d) as the correct choice.

Conclude that the correct answer is option (d), as it accurately describes the testing of experimental and control groups in parallel, which is a hallmark of a controlled experiment.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Controlled Experiment

A controlled experiment is a scientific test that aims to isolate the effect of a single variable by keeping all other variables constant. This allows researchers to determine the causal relationship between the independent variable (the one being tested) and the dependent variable (the one being measured). By controlling extraneous factors, scientists can draw more reliable conclusions from their data.

Variables in Experiments

In the context of experiments, variables are elements that can change or be manipulated. The independent variable is the factor that is altered to observe its effect, while the dependent variable is the outcome that is measured. Control variables are those that are kept constant to ensure that any changes in the dependent variable are solely due to the manipulation of the independent variable.

Experimental and Control Groups

In a controlled experiment, the experimental group receives the treatment or condition being tested, while the control group does not. This comparison allows researchers to assess the effect of the independent variable by observing differences in outcomes between the two groups. Testing both groups in parallel ensures that results are not influenced by external factors, enhancing the validity of the findings.