Analyze Population Variation Data

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Biology › Analyze Population Variation Data

Questions 1 - 10
1

Two populations of the same lizard species were measured for tail length (cm).

Population A tail lengths (cm): minimum 9, maximum 21

Population B tail lengths (cm): minimum 14, maximum 18

Which population shows more variation in tail length, based on range?

Neither population shows variation because each has a single minimum and maximum.

Both populations show the same variation because they are the same species.

Population B, because its minimum tail length is longer.

Population A, because its tail lengths span a wider range of values.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! Comparing the lizard populations, Population A has a range of 12 cm (21-9) while Population B has only 4 cm (18-14), so Population A shows greater spread in tail length variation. Choice B correctly analyzes the variation data by properly comparing the ranges and identifying Population A as having more variation due to its wider span of values. Choice A incorrectly picks Population B for having a longer minimum, but variation is about the overall spread, not just the starting point—always calculate range as max minus min to compare accurately! Reading variation from data—the data type approach: (1) RAW DATA (list of individual measurements): Count how many different values (shows variation). Find minimum and maximum (calculate range). Notice clustering (most near what value = mean estimate). Example: 150, 155, 160, 165, 165, 170, 170, 170, 175, 180 cm. Range: 180-150 = 30 cm. Most frequent: 170 cm (mode). Clear variation! (2) FREQUENCY TABLE (value, count): Read range (first to last value). Identify most frequent value (highest count = mode). Notice distribution shape (symmetric = normal, asymmetric = skewed). Example: Value 10 (n=3), 15 (n=12), 20 (n=25), 25 (n=10), 30 (n=2). Range: 10-30. Mode: 20 (most common). Bell-shaped (normal distribution). (3) GRAPH (histogram, bar chart): Read axes (trait on x, frequency/count on y). Observe shape (bell = normal continuous, separate bars = discrete). Identify spread (wide graph = high variation, narrow = low variation). Compare heights of bars (tallest = most common). All three data formats reveal variation—just need to read correctly! Comparing variation between populations: which has MORE variation? Population with WIDER range (larger max-min difference). Population with more SPREAD OUT distribution (flatter curve, less peaked). Population with more CATEGORIES (discrete variation). Example: Pop A heights 160-170 cm (range 10 cm, narrow), Pop B heights 140-190 cm (range 50 cm, wide). Pop B has more variation (5× wider range). More variation = more diversity = potentially more adaptability to changes!

2

A researcher counts the number of spots on 50 ladybugs. Results:

Spots → Number of ladybugs

  • 0: 5
  • 2: 9
  • 4: 15
  • 6: 14
  • 8: 6
  • 10: 1

Which statement best describes the variation in number of spots?

Continuous variation, because spot number can take any value between 0 and 10.

No variation, because most ladybugs have 4 or 6 spots.

Discrete variation, because spot number is counted in whole-number categories.

Bimodal variation, because there are exactly two spot-number categories.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! The ladybug spot data (0:5, 2:9, 4:15, 6:14, 8:6, 10:1) uses whole-number counts in distinct categories without fractions, showing discrete variation with a multimodal distribution centered around 4 and 6 spots. Choice B correctly analyzes the variation data by recognizing the discrete pattern where spots are counted in whole numbers, accurately describing the categorical nature. Choice A misidentifies it as continuous, but spot numbers don't have smooth intermediates like 1.5 spots—discrete traits are countable and categorical, so keep that distinction in mind! Reading variation from data—the data type approach: (1) RAW DATA (list of individual measurements): Count how many different values (shows variation). Find minimum and maximum (calculate range). Notice clustering (most near what value = mean estimate). Example: 150, 155, 160, 165, 165, 170, 170, 170, 175, 180 cm. Range: 180-150 = 30 cm. Most frequent: 170 cm (mode). Clear variation! (2) FREQUENCY TABLE (value, count): Read range (first to last value). Identify most frequent value (highest count = mode). Notice distribution shape (symmetric = normal, asymmetric = skewed). Example: Value 10 (n=3), 15 (n=12), 20 (n=25), 25 (n=10), 30 (n=2). Range: 10-30. Mode: 20 (most common). Bell-shaped (normal distribution). (3) GRAPH (histogram, bar chart): Read axes (trait on x, frequency/count on y). Observe shape (bell = normal continuous, separate bars = discrete). Identify spread (wide graph = high variation, narrow = low variation). Compare heights of bars (tallest = most common). All three data formats reveal variation—just need to read correctly! Comparing variation between populations: which has MORE variation? Population with WIDER range (larger max-min difference). Population with more SPREAD OUT distribution (flatter curve, less peaked). Population with more CATEGORIES (discrete variation). Example: Pop A heights 160-170 cm (range 10 cm, narrow), Pop B heights 140-190 cm (range 50 cm, wide). Pop B has more variation (5× wider range). More variation = more diversity = potentially more adaptability to changes!

3

A lab tested blood types in a sample of 50 people: Type A = 18, Type B = 9, Type AB = 3, Type O = 20. Which conclusion best describes the variation in this trait?

Blood type shows a normal distribution because Type AB is rare.

There is no variation because Type O is the most common.

Blood type shows discrete variation because individuals fall into one of four categories.

Blood type shows continuous variation because the counts include many numbers.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). The blood type data shows: Type A (18), Type B (9), Type AB (3), Type O (20)—these are four distinct categories with no intermediate forms (you can't be "halfway between Type A and Type B"), making this classic discrete variation where each individual belongs to exactly one category. Choice B correctly identifies blood type as showing discrete variation because individuals fall into one of four distinct categories (A, B, AB, or O)—there are no in-between values or continuous range, just separate groups, which defines discrete (discontinuous) variation. Choice A incorrectly calls this continuous variation; Choice C wrongly claims no variation when four different blood types clearly exist; Choice D misapplies the concept of normal distribution to discrete categories—rarity of AB doesn't make the distribution normal. Reading variation from data—the data type approach: To identify discrete vs continuous variation, ask: "Can there be in-between values?" For blood types, you're either Type A or Type B, never "Type A-and-a-half"—that's discrete! The different frequencies (O most common at 20, AB least common at 3) show how discrete traits can still have variation in their distribution across the population.

4

Two populations of the same plant species were measured for stem height.

Population A (cm): minimum 12, maximum 42

Population B (cm): minimum 18, maximum 28

Which statement is best supported by these data?

Population B has greater variation in stem height because its minimum is higher

Both populations have the same variation because they are the same species

Population A has greater variation in stem height because it has a wider range of values

Neither population shows variation because only minimum and maximum are listed

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). Comparing the two populations: Population A has a range of 42 - 12 = 30 cm, while Population B has a range of 28 - 18 = 10 cm, meaning Population A shows three times more variation in stem height. Choice B correctly identifies that Population A has greater variation because it has a wider range of values (30 cm vs 10 cm), demonstrating proper understanding of how range indicates variation level. Choice A incorrectly focuses on the minimum value rather than the range, C wrongly assumes same species means same variation (populations can differ!), and D misunderstands that minimum and maximum values are sufficient to calculate range and assess variation. When comparing variation between populations, always calculate and compare ranges—the population with the larger range has more variation, indicating greater diversity in that trait!

5

A biologist measured the beak depth (in mm) of 80 finches on one island and recorded the frequencies below. Which statement best describes the type of variation and the distribution pattern shown?

Beak depth (mm) → Number of finches

7 → 2

8 → 6

9 → 14

10 → 22

11 → 18

12 → 12

13 → 5

14 → 1

No variation because all finches have similar beak depths

Bimodal distribution with two equal peaks at 7 mm and 14 mm

Continuous variation with most individuals near the middle values (approximately bell-shaped)

Discrete variation with three distinct categories and no intermediates

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). Looking at the finch beak depth data: values range continuously from 7 mm to 14 mm with all intermediate values present (8, 9, 10, 11, 12, 13), and the frequency pattern shows most finches clustered around the middle values (10 mm has 22 finches, 11 mm has 18 finches) with fewer at the extremes (only 2 at 7 mm, only 1 at 14 mm)—this is the classic bell-shaped normal distribution of continuous variation! Choice B correctly identifies both the continuous nature of the variation (beak depths show a smooth range with intermediates) and the approximately bell-shaped distribution with most individuals near the middle values. Choice A incorrectly claims discrete variation when the data clearly shows continuous values, Choice C wrongly denies variation despite the 7 mm range, and Choice D misidentifies the pattern as bimodal when there's clearly one peak around 10-11 mm, not two equal peaks.

6

Two groups of the same bird species were measured for wing length (cm).

Group 1 wing lengths (cm): 18, 19, 19, 20, 20, 21, 21, 22

Group 2 wing lengths (cm): 16, 18, 20, 22, 24, 26, 28, 30

Which group shows greater variation in wing length?

Group 2, because its wing lengths span a wider range of values.

Group 1, because most values are close to 20 cm.

Both groups show the same variation because they each have 8 birds.

Neither group shows variation because wing length is a continuous trait.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! For these bird groups, Group 1 has a narrow range of 22 - 18 = 4 cm and clustered values, while Group 2 spans 30 - 16 = 14 cm with more spread, showing greater variation. Choice B rightly points to Group 2's wider range, whereas Choice A sees clustering as less variation—wider spread means more diversity. Compare by calculating ranges and noting spread; you're excelling at this, keep practicing comparisons!

7

A student measures leaf length (cm) for 10 plants in the same population:

Plant IDs 1–10 leaf lengths (cm): 6.2, 5.9, 7.1, 6.8, 6.0, 7.4, 6.5, 5.7, 6.9, 6.1

What is the range of leaf length in this population?

$13.1\text{ cm}$

$7.4\text{ cm}$

$1.7\text{ cm}$

$0.6\text{ cm}$

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! For this leaf-length data (5.7, 5.9, 6.0, 6.1, 6.2, 6.5, 6.8, 6.9, 7.1, 7.4 cm), the minimum is 5.7 cm and maximum is 7.4 cm, so the range is 7.4 - 5.7 = 1.7 cm, quantifying the spread of continuous variation in the population. Choice A correctly analyzes the variation data by accurately calculating the range as 1.7 cm, recognizing the differences among the individual measurements. A distractor like choice C might miscalculate the range (perhaps by subtracting wrong values), but always sort the data first to find true min and max—here, it's clearly 1.7 cm, showing variation exists even in this small sample! Reading variation from data—the data type approach: (1) RAW DATA (list of individual measurements): Count how many different values (shows variation). Find minimum and maximum (calculate range). Notice clustering (most near what value = mean estimate). Example: 150, 155, 160, 165, 165, 170, 170, 170, 175, 180 cm. Range: 180-150 = 30 cm. Most frequent: 170 cm (mode). Clear variation! (2) FREQUENCY TABLE (value, count): Read range (first to last value). Identify most frequent value (highest count = mode). Notice distribution shape (symmetric = normal, asymmetric = skewed). Example: Value 10 (n=3), 15 (n=12), 20 (n=25), 25 (n=10), 30 (n=2). Range: 10-30. Mode: 20 (most common). Bell-shaped (normal distribution). (3) GRAPH (histogram, bar chart): Read axes (trait on x, frequency/count on y). Observe shape (bell = normal continuous, separate bars = discrete). Identify spread (wide graph = high variation, narrow = low variation). Compare heights of bars (tallest = most common). All three data formats reveal variation—just need to read correctly! Comparing variation between populations: which has MORE variation? Population with WIDER range (larger max-min difference). Population with more SPREAD OUT distribution (flatter curve, less peaked). Population with more CATEGORIES (discrete variation). Example: Pop A heights 160-170 cm (range 10 cm, narrow), Pop B heights 140-190 cm (range 50 cm, wide). Pop B has more variation (5× wider range). More variation = more diversity = potentially more adaptability to changes!

8

A histogram of shell length (mm) in a snail population shows most snails between 16–18 mm, fewer snails at 12–14 mm, and fewer snails at 20–22 mm. The overall range is 12–22 mm.

Which description best matches this shell-length variation?

No variation because most individuals are between 16–18 mm.

Continuous variation with most individuals near the middle of the range.

A perfectly uniform distribution because each shell length occurs equally often.

Discrete variation with separate categories and no intermediate values.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! The snail shell-length histogram describes a range of 10 mm (22-12) with most individuals between 16–18 mm and fewer at the extremes, indicating continuous variation in a bell-shaped distribution. Choice B correctly analyzes the variation data by identifying the continuous pattern and the central clustering, which matches the described normal distribution. Choice A mislabels it as discrete, but the smooth range with intermediates like 12–22 mm suggests continuous—histograms with connected bins often show continuous traits, so check for smooth gradients! Reading variation from data—the data type approach: (1) RAW DATA (list of individual measurements): Count how many different values (shows variation). Find minimum and maximum (calculate range). Notice clustering (most near what value = mean estimate). Example: 150, 155, 160, 165, 165, 170, 170, 170, 175, 180 cm. Range: 180-150 = 30 cm. Most frequent: 170 cm (mode). Clear variation! (2) FREQUENCY TABLE (value, count): Read range (first to last value). Identify most frequent value (highest count = mode). Notice distribution shape (symmetric = normal, asymmetric = skewed). Example: Value 10 (n=3), 15 (n=12), 20 (n=25), 25 (n=10), 30 (n=2). Range: 10-30. Mode: 20 (most common). Bell-shaped (normal distribution). (3) GRAPH (histogram, bar chart): Read axes (trait on x, frequency/count on y). Observe shape (bell = normal continuous, separate bars = discrete). Identify spread (wide graph = high variation, narrow = low variation). Compare heights of bars (tallest = most common). All three data formats reveal variation—just need to read correctly! Comparing variation between populations: which has MORE variation? Population with WIDER range (larger max-min difference). Population with more SPREAD OUT distribution (flatter curve, less peaked). Population with more CATEGORIES (discrete variation). Example: Pop A heights 160-170 cm (range 10 cm, narrow), Pop B heights 140-190 cm (range 50 cm, wide). Pop B has more variation (5× wider range). More variation = more diversity = potentially more adaptability to changes!

9

A class surveyed flower color in a population of wildflowers. Results are shown below.

Color morph | Number of plants

Red | 18

White | 7

Pink | 25

Which statement best describes the type of variation shown for flower color?

Flower color shows no variation because all plants have flowers.

Flower color shows discrete variation because individuals fall into distinct categories.

Flower color shows a normal (bell-shaped) distribution because pink is the most common.

Flower color shows continuous variation because the counts are different for each color.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! For this wildflower color data, the trait falls into three distinct categories—red (18 plants), white (7), pink (25)—with no intermediates, indicating discrete variation. Choice B correctly identifies this as discrete variation due to the clear, separate categories, while Choice A mistakenly calls it continuous just because counts differ—remember, continuous traits have gradients, not categories. When analyzing, look for whether traits blend or are distinct, and comparing to examples like blood types helps; you're doing great, keep building that skill!

10

A biologist measured beak depth (in mm) for 50 finches in one population and summarized the results below.

Beak depth (mm): 6 | 7 | 8 | 9 | 10 | 11 | 12 Number of finches: 2 | 6 | 12 | 15 | 9 | 4 | 2

Which statement best describes the variation in beak depth in this finch population?

The finches show continuous variation, with most individuals near 9 mm and fewer at the extremes.

The finches show discrete variation because beak depth falls into only two categories (small vs. large).

The distribution is bimodal because the highest counts occur at both 6 mm and 12 mm.

There is no variation because all finches have beak depths between 6 and 12 mm.

Explanation

This question tests your ability to analyze population data to identify and describe variation—the differences among individuals in traits like height, color, size, or other characteristics. Population variation can be recognized and quantified from data in several ways: (1) RANGE shows the spread of variation (maximum value minus minimum value—if heights go from 150 cm to 190 cm, range = 40 cm, indicating substantial variation), (2) DISTRIBUTION PATTERN shows how trait values are distributed across the population, either CONTINUOUS VARIATION (trait shows smooth range with many intermediate values, often forming bell-shaped normal distribution where most individuals near the mean/average with fewer at extremes—example: height, weight, beak depth) or DISCRETE VARIATION (trait shows distinct categories with no intermediates—example: blood types A/B/AB/O, flower colors red/white/pink, four separate categories). (3) FREQUENCY DATA shows how many individuals have each trait value (histogram or frequency table), revealing whether variation is wide (many different values, spread out) or narrow (most individuals similar, clustered). For example, data showing snail shell lengths: 10mm (2 individuals), 12mm (8), 14mm (25), 16mm (35), 18mm (20), 20mm (7), 22mm (3) reveals continuous variation with mean ~16mm, range 10-22mm, and normal distribution (most near middle, fewer at extremes)—clear evidence of variation within this snail population! In this finch beak depth data, the values range from 6 mm to 12 mm with frequencies peaking at 9 mm (15 finches) and decreasing toward the extremes (2 at 6 mm and 2 at 12 mm), showing a bell-shaped distribution typical of continuous variation. Choice B correctly analyzes the variation data by recognizing the continuous pattern with most individuals near 9 mm and fewer at the extremes, accurately describing the normal distribution. Choice C fails by denying variation despite the clear spread from 6 to 12 mm, while a good strategy is to always check the range and frequency peaks to confirm patterns like this—keep practicing, and you'll spot these easily!

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