HS-LS2-8: Evaluating Evidence That Group Behavior Affects Survival
In plain English: HS-LS2-8 is the NGSS high school performance expectation that asks students to evaluate the evidence that group behaviors such as flocking, schooling, herding, cooperative hunting, migrating and swarming change an individual's chance to survive and reproduce, and a species' chance to persist. Students weigh data, spot weak evidence and build arguments. It is usually taught in Biology.
Evaluate the evidence for the role of group behavior on individual and species' chances to survive and reproduce.
Clarification Statement: Emphasis is on: (1) distinguishing between group and individual behavior, (2) identifying evidence supporting the outcomes of group behavior, and (3) developing logical and reasonable arguments based on evidence. Examples of group behaviors could include flocking, schooling, herding, and cooperative behaviors such as hunting, migrating, and swarming.
Next Generation Science Standards · Disciplinary Core Idea: Ecosystems: Interactions, Energy, and Dynamics · Official standard
Students evaluate evidence, which is the practice at the center of this performance expectation. They look at invented but realistic data sets on flocking birds, schooling fish, herding mammals, wolves that hunt together, birds that migrate in formation and honeybee swarms, and they ask three questions each time: Is this a group behavior or an individual behavior? What outcome was measured, and does it show a change in survival or reproduction? How strong is the evidence (sample size, comparison group, other explanations)? Students then separate two levels of effect: an individual's chance to survive and reproduce, and a species' chance, which depends on whether enough individuals in enough groups survive and breed for populations to persist.
The NGSS Clarification Statement says: "Emphasis is on: (1) distinguishing between group and individual behavior, (2) identifying evidence supporting the outcomes of group behavior, and (3) developing logical and reasonable arguments based on evidence. Examples of group behaviors could include flocking, schooling, herding, and cooperative behaviors such as hunting, migrating, and swarming." HS-LS2-8 has no Assessment Boundary. How these behaviors evolved by natural selection belongs to HS-LS4 and is beyond this standard, so the lesson stays with the evidence for their effects. Every data set on this page is invented for teaching and labeled as invented; it follows patterns that biologists have described, but the numbers are not taken from any study.
Learning Objectives
By the end of this lesson, students will be able to:
Distinguish a group behavior from an individual behavior in a described situation
Calculate and compare survival or success rates from data on flocking, schooling, herding and cooperative hunting
Evaluate the strength of evidence by checking sample size, comparison groups and other possible explanations
Explain how a group behavior can change an individual's chances and a species' chances to survive and reproduce
Construct an argument from evidence that weighs both the benefits and the costs of living in groups
Prior Knowledge Required
Students should already be comfortable with:
Using evidence to explain how animal behaviors affect the probability of successful reproduction MS-LS1-4
Predator-prey and competitive interactions in ecosystems MS-LS2-2
Show a short video or photo of a large flock of starlings or a school of fish turning together. Then ask:
Warm-Up Prompt
"A hawk is hunting. Would you rather be a small bird feeding alone or a small bird in a flock of 200? Give one reason the flock helps you and one reason it could hurt you. What data would you need to decide?"
List reasons on the board as benefits (more eyes, harder to single out, safety in numbers) and costs (competition for food, disease, easier to spot from far away). Keep the "what data would you need" answers: they become the evidence checklist for the lesson.
Direct Instruction15-20 minutes
Group or individual behavior? A group behavior is one that depends on several animals coordinating: birds turning together in a flock, fish swimming as a school, a herd bunching when a predator appears, wolves surrounding prey. An individual behavior is done by one animal on its own, even when others are nearby: a bird preening, a single wolf caching food. How group behavior can help: more eyes detect predators sooner; each individual's risk is diluted when a predator can take only one; predators are confused by many similar moving targets; cooperative hunters can take larger prey; flying in formation can save energy. Costs: competition for food, faster spread of parasites and disease, and large groups that predators find easily.
Two levels. An individual's chance is the probability that one animal survives and produces young. A species' chance depends on how many individuals, across all groups, survive and reproduce: when group behavior raises survival and breeding across a population, the population is more likely to persist, and when groups become too small to work, fewer young survive and the population can shrink further. Evaluating evidence: Is there a comparison group? How many animals or trials? Was the outcome survival or reproduction, or only a behavior? Could something else explain the pattern?
Flocking: hawk attacks and flock size
Invented observations of a hawk attacking pigeons in farm fields: 28 of 40 attacks on lone birds caught a bird, 27 of 60 attacks on flocks of 2-10, 16 of 80 attacks on flocks of 11-50, and 4 of 50 attacks on flocks over 50 (Diagram 1).
Result: Success rates: 70%, 45%, 20% and 8%. Each attack on a large flock was far less likely to catch anyone, and a bird in that flock also shares the risk with many others. The evidence supports a benefit of flocking to the individual, and it rests on 230 attacks, a reasonable sample.
Schooling: risk per fish
Invented data from a lake: a lone fish is attacked 0.10 times per hour and half of those attacks succeed. A school of 50 fish is attacked 1.0 time per hour, and 20% of those attacks catch one fish.
Result: Lone fish: 0.10 × 0.50 = 0.05 captures per hour, a 5% risk each hour. School: 1.0 × 0.20 = 0.2 fish caught per hour, shared by 50 fish, or 0.004 (0.4%) per fish per hour. The school is attacked ten times as often, yet each member's risk is 12.5 times lower.
Herding: calves that stay with the herd
Invented data: in one season, 180 of 200 calves that stayed with their herd survived their first month, while 12 of 40 calves that straggled behind survived.
Result: Survival: 90% in the herd against 30% for stragglers. Staying with the herd is the group behavior; straggling is one calf's position. Before claiming the herd caused the difference, ask whether stragglers were already weaker or sick, which would also lower their survival.
Cooperative hunting: food per wolf
An invented model of wolf packs that hunt 3 times a week, get 150 kg of meat from each successful hunt and share it equally. The success rate per hunt rises with pack size: 0.10 for 2 wolves, 0.32 for 4, 0.50 for 6, 0.56 for 8 and 0.60 for 10 (Diagram 2).
Result: Meat per wolf per week = 3 × success × 150 ÷ pack size: 22.5, 36, 37.5, 31.5 and 27 kg. Food per wolf peaks at 6 wolves. Bigger packs catch more in total, but each wolf gets less, so food alone does not explain why some packs grow large.
Migrating: flying in formation
Invented measurements from pelicans fitted with small data loggers on migration: birds flying alone flapped 2.3 times per second, while birds in the middle of a V formation flapped 2.0 times per second at the same speed.
Result: (2.3 - 2.0) ÷ 2.3 ≈ 13% fewer wingbeats in formation. Fewer wingbeats at the same speed suggests the birds save energy, which can leave more reserves for survival and breeding. The lead bird gets no saving, so the benefit to an individual depends on how often birds take turns in front.
After each example, ask: "Is this group or individual behavior? What was measured? Does the measurement show survival or reproduction, or something that only leads to it? What is one weakness of the evidence?"
Guided Practice15 minutes
Pairs evaluate a claim about why flocking helps, using more invented data from the same hawk study. Claim: "Larger flocks spot the hawk earlier because there are more eyes watching."
Guided practice data: distance at which the flock took off as the hawk approached (invented)
Flock size
Attacks watched
Mean take-off distance (m)
alone
40
12
2-10
60
21
11-50
80
34
over 50
50
47
Describe the pattern: take-off distance rises with every step up in flock size, from 12 m to 47 m.
Explain how earlier take-off could produce the lower success rates in Diagram 1.
The observers note that every flock over 50 birds was feeding in open fields, while lone birds were often near hedges. Explain why this is a problem for the "more eyes" claim: a hawk crossing an open field can be seen from farther away whatever the flock size.
Propose a better comparison (for example, flocks of different sizes in the same kind of field) and write one sentence that says how strong the evidence is now.
Independent Practice10-15 minutes
Each student evaluates invented data modeled on a cooperative mongoose that lives in groups, where adults take turns as sentinels and help feed pups. Groups of 2-5 adults raised 11 of 40 pups to 3 months (27.5%), groups of 6-10 raised 39 of 60 (65%), and groups of 11-20 raised 54 of 75 (72%). In groups of 2-5, a sentinel was on watch during 30% of foraging time; in larger groups, during 80%.
Students (1) identify the group behaviors in the data, (2) compute and compare pup survival, (3) explain what the data say about an individual adult's chance to reproduce successfully, and (4) explain what could happen to the whole population if disease made many groups smaller than 6, using the idea that small groups raise fewer young, so the groups stay small.
Closure10 minutes
Exit ticket: "Name one group behavior from today, the outcome it changed, and one question you would ask before trusting the evidence." Return to the warm-up list and ask students which benefit and which cost now have evidence behind them.
Differentiation Strategies
For Struggling Students
Give a three-question evidence checklist card: What behavior? What outcome? How strong is the evidence?
Provide data tables with a percent column already set up so students compute one rate before comparing
Offer sentence frames: "The data show that ___ in groups had a ___% chance of ___, compared with ___% for ___."
For Advanced Students
Ask students to design an observation study that separates the "more eyes" effect from the effect of habitat, with a sample size they can justify
Have students compute per-individual risk when both the attack rate and the success rate change with group size, and find the group size where the benefit levels off
Ask students to argue whether a behavior that lowers one individual's survival (a sentinel on watch) can still raise the group's success, using data
Assessment Guidance
What to Look For
Strong work names the behavior and says why it is a group behavior, computes rates correctly from counts, and compares groups instead of reporting one number. Evaluations mention sample size, a comparison group and at least one other explanation. Arguments separate an individual's chances from a species' chances and weigh costs as well as benefits. Watch for students who treat any animals seen together as a group behavior, who confuse the success rate of attacks on a group with the risk to each member, and who conclude "groups are always better" from one data set.
02
Classroom Activities
3 Activities
1
Tabletop Predator Model: Can You Track One in a Crowd?
20 minPairs
This model tests the confusion effect: a predator may find it harder to keep track of one target among many similar moving prey. One partner is the "prey mover" and the other the "predator". The predator watches one marked counter, the mover shuffles the counters, and the predator tries to pick out the marked one.
Procedure and Safety
Work seated at a desk. Use flat plastic counters only: no food items, which can cause allergic reactions and attract pests, and nothing small enough to roll off the desk and be stepped on.
The mover places 1, 4, 8 or 16 counters in the middle of the desk, including the marked one (sticker on the underside, so it looks the same as the others). The predator watches the marked counter as it is placed.
The mover slides the counters around with flat hands for 5 seconds. The predator then taps one counter, and the mover flips it to check.
Run 20 trials for each group size, swap roles halfway, and record the number of successful picks.
Sample Data (invented)
Successful picks out of 20 trials: group of 1, 20; group of 4, 17; group of 8, 12; group of 16, 7. The success rate falls at every step up in group size, from 100% to 35%.
Discussion Questions
The success rate falls at every step up in group size. Is this evidence about survival? What does the model measure, and what does it leave out?
With 16 counters a random guess would succeed 1 time in 16, about 6%. The sample predator succeeded 35% of the time. What does that tell you about how well "predators" can still track prey in a group?
Real predators often pick the odd one out. Predict what would happen if the marked counter were a different color, and test it.
Modification for Distance Learning
Students play an online shell-game style tracking task with 1, 4, 8 and 16 identical moving dots (or analyze the sample data above), graph success against group size and post a claim with one limitation of the model.
2
Evidence Stations: How Strong Is the Evidence?
25 minGroups of 3-4
Six stations each give a claim about a group behavior and an invented data set. Groups rotate every 4 minutes, compute what they need, and rate the evidence as strong, moderate or weak, with one reason. Each station also asks whether the evidence is about an individual's chances, a species' chances, or both.
Station Cards (all data invented)
1, Flocking: Claim: flocking lets each shorebird spend more time feeding. Birds alone scanned for predators 45% of the time, birds in flocks of 5 scanned 25% and birds in flocks of 20 scanned 12% (80 birds watched).
2, Schooling: Claim: schooling protects fish. In 2 aquarium trials with a model predator, a lone fish was touched in 1 trial, and in schools of 8 one fish was touched in 1 trial.
3, Herding: Claim: forming a defensive ring protects calves. Herds that formed a ring lost calves in 2 of 15 wolf encounters; herds that ran lost calves in 9 of 12.
4, Cooperative hunting: Claim: lions in larger groups keep more of their kills. Pairs lost 40% of carcasses to hyenas, and groups of 5 or more lost 10% (150 kills observed).
5, Migrating: Claim: migration raises calf survival. A migrating herd had 70% calf survival and a herd that stayed in one area had 45%, but the resident herd's area also had more lions.
6, Swarming: Claim: a honeybee swarm chooses a good nest site as a group. In 10 trials with 5 nest boxes of different quality, scout bees led the swarm to the best box in 8.
Discussion Questions
Station 2 is the weakest: with only 2 trials, one touched fish more or less changes the result completely. What would make it stronger?
At Station 3, calves were lost in about 13% of encounters when herds formed a ring and 75% when herds ran. Is that enough to say the ring causes the difference?
Station 5 has a second explanation built in. What is it, and how would you design a fairer comparison?
Which stations measured survival or reproduction directly, and which measured something that only leads to it?
Modification for Distance Learning
Post each station as a slide with its card. Groups work in breakout rooms and fill in one shared evidence-rating table, then compare ratings with another group.
3
Argument Builder: Is Group Living Always Better?
25 minGroups of 4 (two pairs)
One pair argues that group behavior raises an animal's chances to survive and reproduce, and the other pair argues that the costs can outweigh the benefits. Both use the same four evidence cards and Diagram 2. After both sides present, the pairs switch sides and then write one balanced conclusion together.
Evidence Cards (invented)
Card A, wolf packs: the food-per-wolf model in Diagram 2.
Card B, finches at feeders: aggressive encounters per bird per hour were 2 in flocks of 4, 7 in flocks of 12 and 15 in flocks of 30.
Card C, fish schools: in tank tests, schools of 20 reacted to a model predator when it was 1.8 m away on average; lone fish reacted at 0.6 m.
Card D, herd calves: calves that stayed with the herd survived their first month far more often than calves that straggled (the herding example in the lesson).
Procedure
Each pair writes a claim, cites at least two cards as evidence with numbers, and gives reasoning that links the evidence to survival or reproduction.
Each pair presents in 2 minutes; the other pair asks one question about the strength of the evidence.
Switch sides and repeat with the other claim.
Together, write a conclusion that begins: "Group behavior helps an individual survive and reproduce when ___, but it can lower its chances when ___."
Discussion Questions
Card B shows aggressive encounters rising with flock size, and Card C shows schools reacting to a predator 3 times as far away as lone fish. How can both be true for animals living in groups?
Card A says food per wolf is highest at 6 wolves. Name one benefit of a larger pack that the model does not include.
Which card is about an individual's chances, and how would you extend it to a species' chances?
Challenge Variation
Groups find the group size in Card A where the benefit of adding one more wolf turns into a cost, and explain what other data they would need to predict the pack size real wolves settle at.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Hawk Attack Success Against Flock Size
Invented field observations of 230 hawk attacks on pigeons, drawn to scale. The share of attacks that caught a bird falls from 70% for lone birds to 8% for flocks of more than 50. This is evidence that flocking lowers an individual bird's risk, but it does not by itself show why.
Diagram 2: Meat per Wolf Against Pack Size in a Simple Model
An invented model, drawn to scale: packs hunt 3 times a week and share 150 kg of meat from each successful hunt. Success per hunt rises with pack size, but the meat is split among more wolves, so the amount per wolf peaks at 6 wolves (37.5 kg per week) and then falls.
04
Homework Assignment
~30 min
HS-LS2-8 Homework: Weighing the Evidence on Group Behavior
Directions: All data sets are invented for practice. Show each calculation. For every problem, say whether the behavior is a group or an individual behavior, and end with a claim that names your evidence and one weakness of it.
Part 1: Schooling and Herding (Problems 1-2)
In a coral reef survey, a lone fish is attacked 0.2 times per hour and 40% of those attacks succeed. A school of 25 fish is attacked 0.8 times per hour, and 25% of those attacks catch one fish. (a) Find the risk per hour for the lone fish and for one fish in the school. (b) How many times lower is the risk in the school? (c) The school is attacked more often. Explain why each member is still safer.
A herd of 300 grazing animals has 90 animals on the outer edge and 210 in the center. Over one season, predators killed 24 edge animals and 8 center animals. (a) Find the risk for an edge animal and for a center animal. (b) What share of the kills were edge animals, and what share of the herd was on the edge? (c) Use the data to explain why an individual's position in the herd matters, and why the herd as a whole may still protect its members.
Part 2: Swarming and Cooperative Hunting (Problems 3-4)
Honeybee colonies reproduce by swarming: part of the colony leaves with a queen and chooses a new nest site together. In a study, 20 swarms moved into cavities they chose themselves, and 17 survived their first winter. Another 20 swarms were placed by beekeepers in small boxes they had not chosen, and 6 survived. (a) Find both survival rates. (b) Evaluate the claim "The swarm's group decision raises the new colony's chance to survive." Name one other difference between the two sets of swarms that could matter. (c) Explain why swarm survival matters for the species, not only for one colony.
A student claims: "Lions hunt in groups because each lion gets more food." Invented data: a lone lion makes 4 hunts a week with 15% success, a pair makes 4 hunts with 30% success, and a group of 4 makes 4 hunts with 45% success. Each kill provides 100 kg of meat, shared equally. Hyenas steal 30% of a lone lion's kills, 15% of a pair's and 5% of a group of 4's. (a) Find the meat per lion per week for each group size, before and after losses to hyenas. (b) Do the data support the student's claim? (c) Suggest one other benefit of group living for lions that you would collect data on.
Part 3: Migrating Herds and Colonies (Problems 5-6)
Caribou give birth in large groups on their calving grounds, and most calves are born within the same week. Invented data: of 400 calves born in the peak week, 328 survived their first month; of 60 calves born two or more weeks late, 30 survived. (a) Find both survival rates. (b) One explanation is that predators cannot eat more than a fixed number of calves when so many are born at once. Give a second explanation for the difference. (c) Describe data that would help you decide between the two explanations.
Invented data on birds that nest in colonies: in small colonies (up to 10 nests), nestlings carried 5 fleas on average, predators destroyed 40% of nests, and 48% of eggs produced fledglings. In medium colonies (11-100 nests) the numbers were 20 fleas, 20% and 60%. In large colonies (over 100 nests) they were 60 fleas, 8% and 58%. (a) Which colony size had the highest fledging success? (b) Write a claim, evidence and reasoning paragraph on whether nesting in larger colonies raises a bird's chance to reproduce, using both a benefit and a cost from the data. (c) Explain one way colony nesting could affect the species' chances if many colonies shrank.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Group or Individual Behavior
Correctly identifies the behavior and explains why it depends on several animals
Identifies the behavior without an explanation, or mixes up group and individual
Calculations
Correct rates and comparisons from the counts for every data set
Correct method with one calculation error
Evaluating Evidence
Names a comparison, sample size or other explanation that affects how strong the evidence is
Accepts or rejects the evidence without a reason
Argument
Claim cites numbers, weighs a benefit and a cost, and separates individual and species chances
Claim is supported by general statements rather than the data
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data sets are invented for practice. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
Which of these is a group behavior?
Answer: B
Turning together depends on many fish coordinating, so it is a group behavior. Choice D is a common trap: the rest of the herd is nearby, but scratching is something the cow does alone for itself, so it is an individual behavior. Choices A and C are also done by one animal alone.
Question 2 of 20 · Multiple Choice
Invented data: a falcon made 30 attacks on small flocks and caught a bird in 12, and 30 attacks on large flocks and caught a bird in 3. Which conclusion do the data best support?
Answer: C
Success was 12 ÷ 30 = 40% for small flocks and 3 ÷ 30 = 10% for large flocks. Choices A and B are not supported, because both groups received the same number of attacks. Choice D goes beyond the data, which measured attack success, not lifespan.
Question 3 of 20 · Multiple Choice
A heron made 72 attacks on groups of minnows and caught a fish in 18 of them. What was its success rate?
Answer: A
18 ÷ 72 = 0.25 = 25%. Choice B reads the count as a percent. Choice C divides 72 by 18 and reads the ratio 4 as 4%. Choice D is the share of attacks that failed.
Question 4 of 20 · Multiple Choice
A school of 40 fish is attacked 2 times per hour. Half the attacks succeed, and each successful attack catches one fish. What is the risk per hour for one fish in the school?
Answer: D
Fish caught per hour = 2 × 0.5 = 1, shared among 40 fish: 1 ÷ 40 = 0.025 = 2.5%. Choice A is the success rate of an attack, not the risk to one fish. Choice B divides 2 attacks by 40 and ignores that only half succeed, and choice C divides the success rate by 40 and ignores that there are 2 attacks.
Question 5 of 20 · Multiple Choice
A zebra herd bunches tightly when lions appear. Which observation would be the best evidence that bunching lowers an individual zebra's risk of being caught?
Answer: B
The claim is about the outcome of bunching, so the evidence must compare outcomes (catches) with and without the behavior, over many hunts. Choice A describes when the behavior happens, not its effect. Choice C, if anything, is a possible cost of bunching, and choice D says nothing about bunching at all.
Question 6 of 20 · Multiple Choice
Invented data on African wild dog packs: meat per dog per day was 2.0 kg in packs of 3, 3.1 kg in packs of 6, 3.4 kg in packs of 9 and 2.6 kg in packs of 12. Which statement is supported?
Answer: B
Per dog, 3.4 kg (packs of 9) is the highest. Total meat per day is 6.0, 18.6, 30.6 and 31.2 kg, so packs of 12 caught the most overall while each dog got less. Choice A ignores the drop at 12, and choice C mixes up per-dog and total amounts.
Question 7 of 20 · Multiple Choice
When a honeybee swarm looks for a new home, scout bees inspect possible cavities and dance to advertise them, and the whole swarm flies off only after many scouts favor the same site. Why is choosing the site a group behavior?
Answer: A
No single bee decides: the site is chosen when many scouts favor it, and then thousands of bees fly there together. Choice B describes what one scout does, an individual part of the process. Choice C is a common misconception: the queen does not choose the site. Choice D does not explain anything about the behavior.
Question 8 of 20 · Multiple Choice
A scientist claims that geese save energy by flying in a V formation. Which evidence would test this claim most directly?
Answer: D
Comparing the same birds, at the same speed, alone and in formation measures the energy cost directly with a fair comparison. Choice A shows the behavior exists but not its effect, and choices B and C have no comparison group.
Question 9 of 20 · Multiple Choice
Two invented studies test whether herding protects calves. Study 1 followed 3 herds for one season. Study 2 followed 40 herds for 5 seasons in several regions. Why is Study 2 stronger evidence?
Answer: B
More herds across more years and places reduce the chance that a result comes from one odd case. Choice D is false: a longer study can find a smaller effect, or none.
Question 10 of 20 · Multiple Choice
In an invented study, minnows in large schools were caught by pike less often than lone minnows. But the schools were all watched in the morning, soon after the pike had fed, and most lone minnows were watched in the evening, when the pike were hungry. What is the best evaluation?
Answer: D
School size and time of day changed together, so either could explain the lower catch rate. Watching schools and lone minnows at the same times of day would separate them. Choice A claims proof where there is a second explanation, and choice B goes beyond the data, which show pike did hunt schools in the morning.
Question 11 of 20 · Multiple Choice
Which statement is about a species' chance to survive and reproduce rather than one individual's?
Answer: C
The species level is about whether enough individuals, across the population, survive and breed. Choices A, B and D each describe the chances of one animal in a particular position or group.
Question 12 of 20 · Multiple Choice
In an invented study, a flea-borne disease spread between burrows faster in large prairie dog towns than in small ones. How should this be used in an argument about group behavior?
Answer: A
Disease can kill prairie dogs, so faster spread in large towns is a cost of living in big groups. It has to be weighed against the benefits before drawing a conclusion. Choice B draws a conclusion from one cost, choice C reverses the data, and choice D ignores that disease affects survival.
Question 13 of 20 · Multiple Choice
Invented data: 136 of 160 calves that stayed with their herd survived their first month, and 10 of 40 calves that were separated survived. What is the difference in survival rate?
Answer: C
136 ÷ 160 = 85% and 10 ÷ 40 = 25%, so the difference is 85 - 25 = 60 percentage points. Choice B subtracts the counts, which cannot be compared because the groups have different sizes. Choices A and D are the two rates themselves.
Question 14 of 20 · Multiple Choice
A student says: "Schooling protects fish, because I saw a school and no fish got eaten." Which additional data would best strengthen the claim?
Answer: C
The claim needs a comparison group and repeated trials. One observation of a school with no losses has neither. Choices A, B and D add details but not a comparison of outcomes.
Question 15 of 20 · Short Answer
Meerkats in a group take turns as a sentinel: one stands on a mound and gives an alarm call when a predator appears, while the others dig for food. One meerkat is also seen digging alone for insects. Which behavior is a group behavior, which is individual, and why?
Group behavior: the sentinel system, because it depends on several meerkats coordinating (taking turns, and the others responding to alarm calls). Individual behavior: digging for insects, which one meerkat does for itself even when others are nearby. A strong answer names the coordination that makes a behavior a group behavior.
Question 16 of 20 · Short Answer
Invented data: a lone gazelle is attacked 0.02 times per day, and 60% of attacks succeed. A herd of 100 gazelles is attacked 0.5 times per day, and 40% of attacks catch one gazelle. Find the daily risk for a lone gazelle and for one gazelle in the herd, and compare them.
Lone: 0.02 × 0.60 = 0.012 per day (1.2%). Herd: 0.5 × 0.40 = 0.2 gazelles caught per day, shared by 100, so 0.002 per day (0.2%) each. The herd member's risk is 0.012 ÷ 0.002 = 6 times lower, even though the herd is attacked 25 times as often.
Question 17 of 20 · Short Answer
Mayflies in a river emerge as adults in huge swarms on a few nights. Invented data: on a peak night 50,000 emerged and birds ate about 1,000; on an off-peak night 2,000 emerged and birds ate about 400. Evaluate the evidence that emerging together helps each mayfly survive.
Risk on the peak night: 1,000 ÷ 50,000 = 2%. Off-peak: 400 ÷ 2,000 = 20%. Each mayfly was 10 times less likely to be eaten on the peak night, which supports predator swamping: birds can only eat so many. The evidence is limited to two nights, and weather or the number of birds might differ, so more nights should be compared.
Question 18 of 20 · Short Answer
A report says: "Wolf packs with more members raise more surviving pups, so large packs help pups survive." The larger packs in the study also lived in territories with more elk. Evaluate the argument.
The pattern supports the claim, but it is not strong evidence that pack size causes pup survival, because territory quality changed along with pack size: more elk could explain both larger packs and more surviving pups. A stronger study would compare packs of different sizes in territories with similar prey, or follow packs as their size changes. The claim should be stated as a possible link, not a proven cause.
Question 19 of 20 · Short Answer
Invented data: geese flying alone flapped 3.2 times per second, and geese in the middle of a V formation flapped 2.8 times per second at the same speed. Find the percent reduction, and explain what this is evidence for and what it does not show by itself.
(3.2 - 2.8) ÷ 3.2 = 0.4 ÷ 3.2 = 12.5% fewer wingbeats. It is evidence that flying in formation lowers the effort of flight. By itself it does not show higher survival or more offspring: that would need data linking the energy saved to body condition, survival on migration or breeding success.
Question 20 of 20 · Short Answer
Using the idea of costs and benefits, write a short argument (claim, evidence, reasoning) on the question "Does living in a group always raise an animal's chance to survive and reproduce?" Use at least two pieces of evidence from the lesson's examples, diagrams or activities.
Sample answer. Claim: Group living often raises an animal's chances, but not always, because it also has costs. Evidence: hawk attacks caught a bird in 70% of attacks on lone pigeons but only 8% of attacks on flocks over 50 (Diagram 1), and 90% of calves that stayed with the herd survived against 30% of stragglers. But in the wolf model each wolf gets less meat once packs grow past 6 (Diagram 2), and finches in flocks of 30 had 15 aggressive encounters per hour against 2 in flocks of 4. Reasoning: whether a group helps depends on whether benefits such as dilution of risk outweigh costs such as sharing food and spreading parasites, so the answer depends on the species and the group size.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-LS2-8 mean?
HS-LS2-8 asks high school students to evaluate the evidence that group behavior affects an individual's and a species' chances to survive and reproduce.
The code reads: HS (high school), LS2 (the life science core idea Ecosystems: Interactions, Energy, and Dynamics), performance expectation 8. The practice is evaluating evidence, so students judge data and arguments rather than only listing behaviors.
What group behaviors does HS-LS2-8 cover?
The Clarification Statement gives flocking, schooling, herding, and cooperative behaviors such as hunting, migrating and swarming as examples.
Other coordinated behaviors, such as colonial nesting or huddling for warmth, fit too. This lesson uses all of the official examples with invented data sets.
What is the difference between group behavior and individual behavior?
A group behavior depends on several animals coordinating; an individual behavior is done by one animal on its own.
A flock turning together or wolves surrounding prey are group behaviors. A bird preening among other birds is still an individual behavior. Distinguishing the two is the first emphasis of the Clarification Statement.
Is HS-LS2-8 taught in biology?
Yes, it is usually taught in high school Biology, in the ecosystems unit.
It often follows lessons on population interactions and ecosystem stability, and it leads into evolution (HS-LS4), where students explain how such behaviors can become common through natural selection.
How do you evaluate evidence about animal behavior?
Check what was measured, what it was compared with, how large the sample was, and whether something else could explain the result.
Strong evidence compares animals in groups with animals alone (or groups of different sizes) under the same conditions, measures survival or reproduction, and repeats the observation. A single observation with no comparison is weak.
How does group behavior affect a species, not just one animal?
A species' chance depends on how many individuals across its populations survive and reproduce.
If group behavior raises survival and breeding in most groups, populations are more likely to persist. If groups become too small to raise young, fewer young survive and the groups stay small, so the population can decline.
Is living in a group always better for animals?
No. Group living has benefits and costs, and the balance depends on the species and the group size.
Benefits include earlier warning, diluted risk and cooperative hunting. Costs include competition for food, faster spread of parasites and disease, and sharing each catch. HS-LS2-8 asks students to weigh both with evidence.
Does HS-LS2-8 have an assessment boundary?
No. The NGSS gives no Assessment Boundary for HS-LS2-8.
Assessments usually give students data or a described study and ask them to identify the group behavior, judge the evidence and build an argument. The math stays at rates, percentages and simple comparisons.
What mistakes do students make on HS-LS2-8?
A frequent mistake is treating the success rate of attacks on a group as the risk to each member.
Others include calling any animals seen together a group behavior, drawing conclusions from one observation, ignoring a second explanation such as habitat, and concluding that groups are always better from a single data set.
Is there a safe hands-on activity for HS-LS2-8?
Yes. A seated tabletop model with flat plastic counters lets students test whether a "predator" can track one target in a moving group.
It needs no food items and no running games, so there is no allergy risk and little risk of falls. Students then evaluate what the model shows and what it leaves out.
07
Related Standards
5 standards
These standards connect to HS-LS2-8: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-LS1-4Prerequisite
Argue from evidence how animal behaviors affect the chance of successful reproduction
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